Pacific Centre for Advanced Materials and Microstructures (PCAMM) Annual Meeting (Link)
This year, the 12th Annual Meeting of the Pacific Center for Advanced Materials (PCAMM) will be held at the Univeristy of British Columbia (Fred Kaiser Electrical Engineering Building, Room 2020) on Saturday, December 1st.
The meeting is organized by L. Chrostowski, T. Tiedje, and A. Nojeh, and sponsored by Systems for Research (SFR), and NanotechBC.
Schedule
9:00 Registration and coffee
9:30 - 10:45 Speaker Session 1
10:45 - 11:05 Break
11:05 - 12:00 Speaker Session 2
12:00 - 2:00 Lunch and Poster Session
2:00 - 3:15 Speaker Session 3
3:15 - 3:45 Break
3:45 - 5:00 Speaker Session 4
Invited Presentations
9:30 Carl Hansen (UBC)
"Interrogating dynamic phenotypes using a high-throughput single cell microfluidic platform"
R. James Taylor [1,2], Didier Falconnet [1], Antti Niemisto [1], Stephen Ramsey [2], Ilya Shmulevich [2], Tim Galitski [2], and Carl Hansen [1,2]
1. The University of British Columbia, 2. The Institute for Systems Biology
Elucidating complex biological networks is of central interest for understanding cellular function and the mechanisms of disease. Genetics and chemical biology have emerged as powerful techniques for dissecting cellular circuits through the controlled perturbations of protein function, and traditional studies have been successful in elucidating the roles of core pathway components. However, current experimental techniques generally lack the ability for precise modulation of environmental stimuli and are limited to averaged measurements of large populations of cells. This lack of precise temporal control of the chemical environment limits the ability to interrogate kinetic information processing circuits or cellular response to temporal stimuli, while the ensemble averaging conceals the ever-present heterogeneity in the cellular response.
We have developed microfluidic technology for the dynamic analysis of single cells over time using well defined and highly controlled chemical environments. Our technology allows for the temporal control of the microenvironment, enabling the study of complex biomolecular circuits under time varying stimuli. Such control is necessary for the analysis of signalling dynamics and the uncovering of kinetic phenotypes. Our system is high throughput with 256 different experiments able to be run simultaneously. Each experiment contains on average the analysis 100 live single cells with a sampling rate of 15min, allowing for over a million data points per experiment. We are currently using our platform to interrogate the dynamics of MAPK signaling pathways in yeast. 9:55 Bret Heinrich (SFU)
"Rf spin currents in nanoscale systems"
B. Heinrich, B. Kardasz, and O. Mosendz
Physics Department, Simon Fraser University, Burnaby, BC, Canada
Research interest in magnetic nanostructures and spintronics has shifted increasingly from the static to dynamic properties of magnetic nanostructures. This is motivated by the fact that the switching time of magnetic hybrid multilayers used in mass data storage devices and magnetic random access memories (MRAM) is a real technological issue. The crystalline Fe/Au,Pd/Fe/Au (001) nano-structures were prepared by Molecular Beam Epitaxy (MBE) technique using 4x6 reconstructed GaAs(001) substrates. A gyrating magnetic moment creates a spin current in surrounding normal metal layers and leads to non-local interface spin damping. The precessing magnetization acts as a peristaltic spin pump, which transports the spin momentum and allows one to establish a transfer of information between the magnetic layers separated over thick nonmagnetic metallic spacers with no electric charge. Modified Landau-Lifshitz-Gilbert (LLG) equations of motion are modified by spin pumping and spin sink effects. Time Resolved Magneto-Optical Kerr effect (TRMOKE*) is an ideal tool to investigate propagation of spin currents across nanostructure films. The stroboscopic time-resolved measurements (with the time resolution of 1 ps and sub micron spatial resolution) were carried out using a slotted and co-planar transmission lines and with either repetitive ps magnetic pulses or cw microwave power.
* TRMOKE studies were carried out in cooperation with Prof. Freeman, U.Alberta, and Prof. Ch. Back groups , U.Regensburg 10:20 Titichai Navessin (NRC)
"Hydrogen/Air Fuel Cell: Influence of Material Fabrication on Performance"
T. Navessin*(1), Z. Xie (1), M. Adachi (1,2), X. Zhao (1), Z. Shi (1) and S. Holdcroft (1,2). 1) Institute for Fuel Cell Innovation, National Research Council, 2) Department of Chemistry, SFU
A brief overview of the fuel cell technologies and the existing technical gaps will be presented. Reducing costs and increasing the durability & reliability are the major barriers for successful commercialization. One of the key technical challenges in the catalyst layers is to develop fundamental understanding of the complex relationship between the microstructure, the effective transport properties and the fuel cell performance. This knowledge is essential for mitigation of electrode kinetics and mass transport limitations, and is needed for designing of the next generation technologies. This talk will focus on the influence of fabrication methodology on the microstructure of catalyst layer and the fuel cell performance. The microstructure of the catalyst layer can be controlled by the fabrication parameters, including the precursor ink formulation, the deposition method and the annealing/conditioning steps. The influence of the dispersion media (present in the ink formulation) on the catalyst layer microstructure and fuel cell performance is discussed. The characterization techniques, such as SEM/TEM, porosimetry, particle size analysis, were used to analyze the microstructure of catalyst layers. Fuel cell evaluation and electrochemical diagnostics were performed and the performance limiting factors identified. 11:05 Alan Guest
Announcement: Cascadia Nanotech Symposium 2008, Vancouver 11:10 Reuven Gordon (U Vic)
"Recent Work on Plasmonics and Optofluidics at UVic/SFU"
R. Gordon (ECE - UVic), A. G. Brolo (Chem - UVic), D. Sinton (Mech - UVic), K. L. Kavanagh (Phys - SFU)
I will overview our recent contributions to the areas of plasmonics and optofluidics. In the area of plasmonics, our pioneering experiments on nanoholes will be described, including work on the shape-effect, surface-plasmon resonance, surface-enhanced Raman scattering, enhanced fluorescence, enhanced interactions with quantum dots, double-holes for second-harmonic generation and Raman, diffraction control using quasi-crystals, and plasmonic Bragg reflectors. In particular, progress towards single molecule detection and identification using nanostructured metals will be described. In the area of optofluidics, our recent progress to create an optical trap in an inexpensive and versatile microfluidic environment will be reported. In addition to recent trapping experiments, a comprehensive theoretical model of fiber optical trapping will be presented that agrees with the experiments both qualitatively and quantitatively. 11:35 Gary Leach (SFU)
Organized Organic Monolayers – From Structure and Dynamics to New Materials
We fabricate ordered organic monolayer and multilayer structures via the Langmuir Blodgett (LB) technique and use nonlinear optical spectroscopy and scanning probe microscopy to characterize their orientations, chain morphologies and their degree of crystallinity. Insights into their structure allow us to design new materials that have unique properties that depend on their order and architecture. Examples include highly ordered regioregular, amphiphilic polythiophene-based thin films and MoS2-based nano-inclusion materials. We present data that provides new insight into the structure and stability of supported LB structures, as well as the unique properties of these new materials. 2:00 Peyman Servati (UBC)
"Silicon nanowires for high mobility thin film transistors and efficient solar cells"
One-dimensional (1-D) semiconductor nanowires and nanotubes have exceptional electrical, optical and mechanical properties with significant potential for future nanoscale transistors, high efficiency solar cells and display devices. These properties include 1-D quantum conduction, tunable bandgap and large surface to volume ratio. For instance, high quantum conduction in silicon nanowires is being investigated for fabrication of low power nanoscale transistors with a gate-all-around architecture. The tunable bandgap of nanowires can be employed for efficient conversion of solar energy over a wide spectrum. In particular, by embedding nanowires in a polymer matrix, nanocomposite electronic devices can be deposited on low cost plastic substrates. Embedded nanowires boost current carrying capability of the composite and enhance its light sensitivity. Here, we present methods for growth of silicon nanowires with controlled diameters and morphology (e.g., straight, tapered and chain-like), suitable for nanocomposite materials. We discuss low temperature processes for deposition of nanowire/polymer composite films and explore the use of these films for fabrication of high mobility transistors and efficient solar cells. 2:25 Michael Hochberg (Washington University)
Integrated Nanophotonics in Silicon for Nonlinear Optics
Silicon has recently been used to build chip-scale optical and optoelectronic devices, using the same nanoscale fabrication processes used to make transistor-based electronic chips. Because of the ability to build nanoscale, high-confinement Silicon waveguides, it is possible to greatly enhance nonlinear optical effects and to construct complex, low-power, ultrafast optical devices and systems. Through evanescent coupling to these waveguides, it is possible to take advantage of the properties of high-activity soft optical materials. I will review the state of the field and will present a number of recent results, including electrooptic modulators, and all-optical ultrafast modulators. This talk will cover progress into the use of Silicon and Silicon:Polymer nanostructures to create an integrated platform for nonlinear and ultrafast optics, and will include a discussion of some of the major challenges for building all-optical, ultrafast systems for computation and logic. 2:50 Rodney A. Herring (U Vic)
"Coherence Measurements of Phonon-, Plasmon-, and Ionization-loss Electrons"
Energy-filtered electron holography of diffracted beams has been used to measure the degree of coherence of energy-loss electrons. Since the fast electrons of the primary beam when passing through the material create phonons, plasmons, magnons, etc., the energy-loss electrons retain the coherence properties of these quasi-particles such as their lateral coherence width, which is required for understanding nanoscience and for our development of nanotechnology. Interestingly, the ability to measure the intensity of ionization-loss electrons will enable the creation of a new magnetic microscopy method, as well as, the measurement of the coherence properties of the magnon. This work has also led to a better understanding of the Stobbs factor, which is a contrast mismatch between experimental lattice images and simulated lattice images that is required for the development of high-resolution quantitative lattice imaging where the type and number of atoms making up a lattice image can be determined. A mathematical expression is derived that adequately predicts the Stobbs factor. 3:45 Mike Jackson (Kodak)
"Connecting the Dots - Thermal Imaging in the Printing Industry"
The printing industry touches all our lives through information, like the magazines and books we read, and packaging, which protects and describes the goods we consume. In this talk we will discuss some of the technology developed at Kodak in Vancouver that has revolutionized the printing business. Specifically we will look at thermal laser imaging of printing plates, and how SQUARESpot technology outperforms competing imaging technology to allow customers to print consistent high-quality materials day-in and day-out. 4:10 Alex Wlasenko (U Vic)
"Diffusion-Limited and Pressure-Driven Electrodeposition in a Microfluidic Channel"
Self-terminating electrochemical fabrication has previously been devised to create quantum point contacts with single-atom contacts, but the structure of the growth has been poorly controlled. We have introduced a microfluidic channel with which to apply pressure-driven flow during the formation of the junction between two Au electrodes. Without applied flow, dendritic growth and dense branching morphologies were typically observed at the cathode. The addition of applied pressure-driven flow resulted in a densely packed gold structure that filled the channel. Our computer simulation yielded insight into the regimes where the diffusion, flow and electric field between the electrodes individually dominated growth. Proposals for further sophistication in both experiment and simulation will also be presented. 4:35 Mike Wolf (UBC)
"Hybrid Conjugated Polymer Materials"
Organic conjugated polymers have many useful and interesting electronic and optical properties, which are being widely exploited. We are interested in hybrid materials, where additional components such as metal complexes, photoactive groups or nanoparticles are incorporated. The properties of some of these recently developed hybrid materials will be discussed, along with potential applications in solar energy harvesting and chemical sensing.
Call for Papers
Please submit abstracts for posters or talks by email at pcamm2007@gmail.com. Please include: Title, Authors, Affiliations, and a 200 word abstract.
The deadline for submissions is November 23st, 2007.
Topics: area related to advanced materials, microstructures, and devices. Including: semiconductors, industrial materials and devices, organic materials, surface characterization, biosensors, optoelectronics, magnets, superconductors, microfluidics.
Travel grants
A $40 travel grant is available to students traveling from outside Vancouver.
Location
Fred Kaiser Building, Room 2020
About PCAMM
The Pacific Centre for Advanced Materials and Microstructures (PCAMM) brings together world-class expertise and sophisticated materials research infrastructure at Simon Fraser University (SFU), at the University of British Columbia (UBC), and at the University of Victoria. The depth and breadth of materials scientists in the Vancouver area led to the formation of PCAMM in 1995. This collaborative venture seeks to ensure that developments in materials growth, fabrication, and characterization at the three universities are optimized both in terms of people and resources for the entire region. Exceptional research outcomes are achieved through collaboration among research groups with complementary expertise; this philosophy, which is common in industry and government, has been adopted within PCAMM. PCAMM is currently based on seven complementary laboratories whose directors are committed to maintaining the equipment at the highest levels, both for their own individual research programs and for the research of others. In this way, PCAMM creates a unique centre for materials research that is internationally competitive and capable of addressing some of the most important contemporary materials research issues. More details can be found on the PCAMM web page
Poster Session
- M. Beaudoin, D. Beaton, I.C.W. Chan, M. Elouneg-Jamroz, P. Pitach*, T. Tiedje, M. Whitwick, E.C. Young and J.F. Young (AMPEL, UBC, *Paris-Sud 11,France)
Absorption edge and gap states of GaAsN and GaAsBi films measured by photothermal deflection spectroscopy
semiconductor alloys GaAs:N and GaAs:Bi. In GaAsN, the N electronic core potential and atomic relaxation create a short-range localized potential that is attractive to electrons thus acting as a pseudoacceptor. This leads to the so called giant bandgap bowing. This bandgap reduction has allowed development of photonic devices operating near the technologically important 1300 nm and 1550 nm wavelength ranges by epitaxially growing InGaAsN alloys on GaAs substrates. Despite these successes, (In)GaAsN still suffers from drastic degradation of optical properties and electron mobilities with increasing N content. Moreover, cluster states are also observed below the conduction band minimum. We use the photothermal deflection spectroscopy (PDS) technique to measure the absorption bandedge (Urbach edge) and gap states of GaAsN and GaAsBi films. By fitting the PDS spectra with a 2 layer absorption model, details of the bandedge absorption in dilute GaAs1-xNx and GaAs1-yBiy alloys for x,y <2% are revealed. The optical bandgap of GaAsN follows the same N composition dependence observed in the literature while the Urbach parameter is found to be approximately 3 times that of good crystalline quality GaAs. - Liya Wang and Michael Eikerling, Department of Chemistry, Simon Fraser University
Kinetic Model of Electrocatalytic Activity in Arrays of Supported Catalyst Nanoparticle
In Polymer Electrolyte Membrane Fuel Cells, current conversion proceeds at supported catalyst nanoparticles. Based on a kinetic model for hydrogen evolution at a single supported nanoparticle, we develop a model for exploring kinetic processes and overall electrocatalytic activity at an array of catalyst nanoparticles on a catalytically inactive substrate. In the current version of the model we focus on the hydrogen evolution reaction. The objective is to rationalize effects of catalyst particle sizes and catalyst particle densities on apparent reactivity. We systematically explore hydrogen coverage as a function of position and time and correlate it to the hydrogen turn over rate (TOR) in steady state. In the plot of TOR as a function of particle separation, TOR exhibits a characteristic maximum at an optimum separation distance, which varies mainly with particle size. With the decreasing the particle size, TOR is continually increasing for all particle densities. The model was used to fit experimental current densities for different particle coverages and different electrode potentials. A good agreement between experimental data and calculated results was found. The fits provide parameters of surface processes on the catalyst-support system and help rationalize the role of the so-called spillover effect on the apparent reactivity. - X.D. Chen*, S. Dhar, T. Isaacs-Smith J. R. Williams, L.C. Feldman and P.M. Mooney*, *Department of Physics, Simon Fraser University
Interface states in as-oxidized and nitrided SiO2/n-4H-SiC
The development of 4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs) has been hindered by a high-density of interface states near the conduction band edge of SiO2/4H-SiC. It was recently shown that the interface state density can be reduced by post-oxidation annealing in nitric oxide (NO), however, the mechanism of passivation and the nature of the interface traps are still not fully understood. Here we report the properties of interface states in as-oxidized and post oxidation NO annealed samples determined constant capacitance deep level transient spectroscopy (CCDLTS) measurements.
SiO2/4H-SiC was fabricated by thermal dry oxidation at 1150oC for 8 hours followed by annealing at 1150oC for 30 minutes. Nitridation was then conducted by annealing in NO at 1175oC for 2 hours. MOS structures were fabricated by the evaporation of Au on the backside of the n+ 4H-SiC substrate and 0.5 mm Al dots on the SiO2 surface.
CCDLTS measurements in as-oxidized samples reveal three overlapping distributions of electron traps. The dominant distributions have energy centered at Ec-0.24eV, with capture cross section σ~7x10-19cm2, and at Ec-0.46eV, with σ~4x10-17cm2. The concentration of both distributions is reduced with increasing NO annealing time and they are no longer detected after nitridation for 2 hours. The CCDLTS results are consistent with models in which carbon-related defects at the SiO2/4H-SiC interface are passivated by nitrogen. - He Huang, Simon Watkins (Department of Physics, Simon Fraser University)
Atomic Layer Deposition of ZnO films on sapphire substrates
High quality c-axis oriented single crystal ZnO films have been grown successfully on sapphire substrates by atomic layer deposition (ALD) using a commercial MOCVD reactor. Diethylzinc (DEZ) and N2O were used as reactant gases. The growth of ZnO films has been conducted with different substrate temperatures and layer-by-layer growth has been achieved. The high growth rate of ~ 1 µm/hour at growth temperature of 500ºC is comparable to standard MOCVD technology. The crystal structure and morphology were investigated by XRD and AFM. ZnO films grown by the ALD technique at the optimized substrate temperature of 500 0C showed the smoothest surfaces and highest growth rates compared with films grown at lower or higher temperatures. - Jordan Roszmann (University of Victoria Crystal Growth Laboratory)
Zone Refining - Experimental Study
A numerical and experimental study has been conducted to improve the effectiveness of tellurium and cadmium zone refining. Recently, experimental studies assessed the effect of electromigration in tellurium and the stability of molten zones in the cadmium system. Electromigration failed to improve segregation efficiencies for selenium in tellurium, but forced cooling of the interzonal solids greatly improved performance of the cadmium system. The experimental study was carried out in a zone refiner built at the University of Victoria through a Collaborative Research and Development grant funded by NSERC and 5N Plus Inc. - G. Abadir, A. Mahmoudzadeh, K. Walus, R.F.B. Turner*, and D.L. Pulfrey (Microsystems and Nanotechnology Group (MINA), Electrical and Computer Engineering, *also with Michael Smith Labs, UBC)
Biomolecular Sensing and Possible Sequencing using Electroluminescent Carbon Nanotube FETs
In our research, we seek to directly sense, and possibly sequence, biomolecules using stationary, or mobile, electroluminescence, respectively, from an ambipolar CNFET [1]. The basic idea is illustrated in the figure. The position of the optical emission along the length of the nanotube is controlled by the gate-source voltage. It is anticipated that variations in the spectrum and intensity of the electroluminescence will provide a signature of the biomolecule. If the light spot can be made small enough, and/or if its position can be controlled precisely enough, then the spatial variation may allow identification of different biomolecules of interest and, for large biopolymers (e.g., proteins) perhaps even allow sequencing of the individual amino acids.
Preliminary results using a Schroedinger-Poisson solver show that the existence of nearby partial charges, (representative of those on the atoms of the amino acid), result in noticeable changes in the intensity of the emitted infrared radiation. Furthermore, DFT-NEGF simulations using the Atomistix toolkit [2] show that the existence of a molecule of the amino acid glycine near the surface of a (10,0) carbon nanotube results in a significant local increase of the density of states (DOS). This suggests a corresponding increase in the electroluminescence intensity. - Neil Armour, Dr. Sadik Dost (University of Victoria, Dept. Mechanical Engineering, Crystal Growth Lab)
Silicon Dissolution into Germanium Melt
Silicon germanium, SiGe, is an important emerging compound semiconductor material. To produce quality bulk material by solution or melt techniques, good understanding of the transport behavior is necessary. The dissolution behavior of silicon in a germanium melt has been experimentally investigated. The effect of free surface on mixing was examined. The effect of the direction of gravity was also examined. One set of experiments had the silicon dissolution interface on top the melt and the others the bottom of the melt. The chosen orientation had a profound effect on dissolution. Far more dissolution was realized with the dissolution interface at the bottom of the melt. Silicon transport was aided by its buoyancy in the germanium melt. The gravity aided dissolution experiments were additionally investigated through the application of a static magnetic field. The changed flow structure caused by the field, serves to increase the dissolution of silicon. In addition, the concentration profile of the melt changes with application of the field. - Jeffrey N. Murphy (UBC/SFU), Alan K. Cheng (SFU), Hua-Zhong (Hogan) Yu (SFU), Dan Bizzotto (UBC)
Investigation of Fluorescent Thiol-DNA Monolayers With Fluorescence Imaging
Fluorescence imaging is used in conjunction with electrochemical measurements to study the interactions of fluorescent tagged thiol-DNA monolayers with co-adsorbed mercaptohexanol for the first time. Observations on the specific and nonspecific interactions of DNA on the electrode surface show that nonspecifically adsorbed DNA can constitute a large component of the adsorbed DNA, which may contribute disproportionately in averaged fluorescence measurements. Means to improve the preparation of such monolayers and limit the nonspecific adsorption of DNA are also explored. - Narasimachary P Sudha*, Ata Roudgar, Michael Eikerling (*Department of Chemistry, SFU; NRC Institute for Fuel Cell Innovation)
Ab-initio Study of Interfacial Correlations in Proton-Conducting Polymer Electrolyte Membranes for Fuel Cells
Polymer Electrolyte Membranes (PEMs) are the critical components of Polymer Electrolyte Fuel Cells (PEFCs). Currently utilized PEMs rely on water as the medium for proton conduction. Membrane dehydration leads to the failure of fuel cell operation at elevated temperatures (>100C). Tremendous research work focus on design of advanced PEMs with high proton mobility and thermal stability. This motivates our efforts in understanding structural correlations and molecular mechanisms of proton transport at acid-functionalized interfaces between polymer aggregates and water. Our model consists of a densely packed regular 2D array of proton binding surface groups evaluated under conditions of minimal hydration. Here, we focus on the role of density, length and flexibility of surface groups on interfacial structure formation and 2D correlations in side chains, RxSO3H with Rx=C2F5, C3F7, C3F7O. Transition from highly ordered hydrogen bonded network of surface groups to clustered conformations occurs at a separation, dbcc = 6.7Å. Increasing length and decreasing hydrophobicity of surface groups slightly decreases the formation energy at the most stable conformation, dacc =6.2Å. For longer surface groups, range of 2D correlations extends until higher dcc. This implies under dynamic real membrane situations, it is highly likely to find dissociated protons at all dcc. - David Owen, David Lackner, Oliver Pitts, Simon Watkins and Patricia Mooney (SFU)
In-Place Bonding of Strain-Relaxed In0.08Ga0.92As/GaAs Heterostructures
In-place bonding of dislocation-free strained semiconductor heterostructures is a possible method to use to create relaxed dislocation free layers in III-V materials. In-place bonding has previous only been examined in Si/SiGe heterostructures, this poster reports the initial results of in-place bonding of strain-relaxed GaAs/In0.08Ga0.92As heterostructures. - Usama Al-Atar, Andrew Lewis and Neil Branda (4D Labs, Chemistry, SFU)
Using MRI to Investigate Materials Properties of Calcium Oxalate Monohydrate Kindy Stones
We investigated the porosity of Calcium oxalate monohydrate (COM) stones in an attempt to develop a better understanding of their character. Surgically removed COM kidney stones were examined through a humidity chamber to observe water absorption. Whole and fragmented stones were then analyzed by magnetic resonance imaging (MRI) to observe uptake of free water and navigate its location within the stone. Scanning electron microscopy (SEM) equipped with energy dispersion x-ray (EDX) detector was used to perform elemental analysis on the stones. Stones put through the humidity chamber demonstrated a 3-6% weight increase. When non-fragmented stones were examined by MRI, it was found that free water molecules only penetrated the shell of the stone, the porous layer, but did not travel through its core, the non-porous layer. Surprisingly, even in fragmented stones, free water molecules were still unable to penetrate the core of the stone and only remained in the shell. EDX spectroscopy did not reveal a difference in the elemental composition between porous and non-porous layers, neither did spectral data acquired by X-ray diffraction. The data gives new insights about the porosity of COM stones, sheds light on their mechanical properties and has implications for shockwave lithotripsy. - He Huang, Simon Watkins (Physics, SFU)
Atomic Layer Deposition of ZnO films on sapphire substrates
High quality c-axis oriented single crystal ZnO films have been grown successfully on sapphire substrates by atomic layer deposition (ALD) using a commercial MOCVD reactor. Diethylzinc (DEZ) and N2O were used as reactant gases. The growth of ZnO films has been conducted with different substrate temperatures and layer-by-layer growth has been achieved. The high growth rate of ~ 1 um/hour at growth temperature of 500 C is comparable to standard MOCVD technology. The crystal structure and morphology were investigated by XRD and AFM. ZnO films grown by the ALD technique at the optimized substrate temperature of 500 0C showed the smoothest surfaces and highest growth rates compared with films grown at lower or higher temperatures. - Qing Gu, Kai Wa Chan, Ada Au, Behnam Faraji, Lukas Chrostowski (Microsystems and Nanotechnology Group (MINA), Electrical and Computer Engineering, UBC), W. Hofmann, M.-C. Amann (Walter Schottky Institut, Germany)
Optical Injection Locking of VCSEL with Amplitude Modulated Master
Optical injection locking (OIL) has been actively investigated in various applications in optical communications and microwave photonics in recent years. We have observed the microwave behaviour of an optical injection locked system with an externally amplitude-modulated master laser. We experimentally demonstrated the possibility of constructing a stable local oscillator for homodyne detection using such configuration. We further propose and experimentally demonstrate for the first time a novel communication system scheme with an Optical Injection Locked Vertical Cavity Laser (OIL-VCSEL) acting both as a transmitter and a receiver, under an identical forward-bias condition. We show that an OIL-VCSEL can function as a receiver with a small signal modulation bandwidth of ~20 GHz, and for large signal digital modulation with data rate as high as 12 Gb/s. - Matthew N. Roberts, Jeremy G. Finden*, Neil R. Branda*, Michael O. Wolf (Department of Chemistry, UBC, *Department of Chemistry, SFU)
Platinum Sensitized Dithienylethenes
Multichromophoric compounds are of significant interest for their utility in various applications, particularly chemical sensing, optical applications, and solar energy conversion. Photochromic dithienylethenes (DTEs), are appealing components to incorporate in these systems due their ability to reversibly modulate photobehavior of the overall compound. Platinum terpyridine complexes have garnered attention due to their rich photophysics and most notably, their potential application in solar energy conversion. We report here platinum terpyridine complexes that are attached to DTEs through acetylide linkages of differing lengths. Efficient photocyclization of the DTE occurs upon irradiation into the platinum based MLCT/LLCT transition when a short linker is utilized. The photophysical behavior of this class of complexes will be discussed. - Vincent Lemieux, Neil Branda (4D Labs, SFU)
Photomodulation of the Lewis Acidity of a Boron-containing Dithienylethene Derivative
Tricoordinate organoboron compounds are known to be good Lewis acids and have proven to be of great utility in organic synthesis. They are used commercially as co-catalysts in metallocene-mediated olefin polymerization and as catalysts or reagents for organic transformations such as the Diels-Alder reaction. The ability to regulate the Lewis acidity of a boron centre using an external stimulus would enable the control of chemical processes that are catalyzed by Lewis acids and thus has the potential to impact numerous technologies, including novel materials such as sensors and electron-transporting materials. Herein, a novel approach for the photoregulation of reactivity using dithienylethene-based molecular switches is described. Using light as the trigger, modulation of the Lewis acidity of a boron center has been achieved. Upon irradiation with light of the appropriate wavelength, the molecule toggles between low and high affinity to Lewis bases. Experimental and computational results are presented. - Bryan D. Wood, Valentin Mocanu, and Dr. Byron D. Gates (4D Labs, Chemistry, SFU)
Anisotropic Lithium Niobate Nanostructures by a Solution-Phase Technique
This presentation describes a simple two-component technique to synthesize anisotropic crystalline lithium niobate nanostructures on an appreciable scale. The formation of these unique structures is a direct consequence of employing a coordinating solution approach that is known to offer control of the resulting crystal size and shape. The as-synthesized product is crystalline (space group R3c) with a predominant morphology of rod-like structures as fine as 7 nm and as long as 100 nm. These morphologies are obtained after only 24 h of synthesis using a relatively mild thermal decomposition of metal alkoxides in the presence of a phosphine oxide stabilizing agent. Our in-house production of specific bimetallic alkoxides allows us to tune the decomposition properties of our precursor to produce LiNbO3 and gaseous volatiles exclusively. Relevant dopants to LiNbO3, such as iron and magnesium can be easily integrated in the production of these precursors. This presentation will discuss our recent progress in the synthesis and characterization of these nanostructures, including analysis of composition, growth direction, and surface chemistry. - David Owen, David Lackner, Oliver Pitts, Simon Watkins and Patricia Mooney (SFU)
In-Place Bonding of Strain-Relaxed In0.08Ga0.92As/GaAs Heterostructures
In-place bonding, which has previously been reported only for Si/SiGe heterostructures, is a possible method to create strain-relaxed dislocation-free layers in III-V materials. A pseudomorphic heterostructure consisting of a 50 nm thick sacrificial AlAs layer, followed by a 50 nm GaAs layer, 100 nm In0.08Ga0.92As layer and capped with a 50 nm GaAs layer was grown on an exact GaAs (001) substrate by metal-organic chemical vapour deposition (MOCVD). This sample was then patterned by conventional photolithography to form an array of 10 956 nm photoresist squares with 5 956 nm spaces between them. The structure was then etched down to the AlAs using a selective citric acid/hydrogen peroxide mix to etch the GaAs and In0.08Ga0.92As layers at equal rates. Following this, hydrofluoric acid was used to remove the AlAs layer. During etching, the strained GaAs/In0.08Ga0.92As /GaAs stack relaxes elastically according to the relative thickness of the two materials and attaches to the substrate, presumably via hydrophobic forces. Upon removal from the etch solution the stack remains attached to the substrate by Van der Waals forces. X-ray diffraction (XRD) measurements show that the strain of the In0.08Ga0.92As layer is reduced by 47% of the initial value, which was in good agreement to the expected relaxation of 50% for this structure. Additionally, the presence of thickness fringes on the In0.08Ga0.92As diffraction peak confirms that the strain relaxation is elastic. - Sabrina Lorenz, Dan Bizzotto (UBC)
The Electrochemical Nature of A Mixed Monolayer of Octadecanol and BODIPY Adsorbed on an Au(111) Electrode
The adsorption and desorption of a monolayer of octadecanol (C18OH) on a Au(111) electrode is consistently obtained as determined by cyclic voltammetry (CV) and differential capacity (DC) measurements. The addition of the fluorescent dye BODIPY FL C12 at 1, 3 and 5% mol/mol has resulted in the mixing of the two components as evident by the reproducible CV and DC curves obtained. Compression isotherms have yielded mean molecular areas of each system. The next step is the imaging of the octadecanol/BODIPY system as the potential is scanned from the potential of adsorption to the potential of desorption repeatedly, giving information on the dependence of the adsorption/desorption process on the applied potential. The aggregation state of the BODIPY molecules can be used as an indicator of the arrangement of octadecanol near the electrode surface after desorption, as well as an indicator of adsorption based on fluorescence quenching by the gold electrode. By incorporating the dye, the movement of a monolayer of octadecanol on a Au(111) surface can be monitored. The goal of this project is to provide controlled, directed delivery of agents into a single living cell by a combined electrodesorption/electroporation technique and as such, the ability to monitor the adsorption and desorption of a species on a Au(111) electrode via fluorescence is the first step in the achievement of this goal. - Thomas P. Johansson, Claire McCague, and Gary W. Leach (Department of Chemistry, Simon Fraser University)
Ice Confined within Langmuir Blodgett Films
Temperature studies on Langmuir Blodgett films have revealed the presence of confined ice within these films. Through a series of experiments involving deuterated subphases, multi-layered films, and deuterated multi-layered films it has been shown that the water within the system originates due to the Langmuir Blodgett deposition process. At 155 K the water within the film undergoes a phase transition from disordered water to ordered crystalline ice. A second phase transition was observed at 100 K, where the hydrogen bonding network within the system is strengthened. - Charles Foell and Jeff Young (Physics, UBC)
Spontaneous emission rates of dipoles in photonic crystal microcavities
We investigate the spontaneous emission rate (SER) modification of a dipole in a silicon-based photonic crystal microcavity, with the dipole placed in the central air hole. The SER is extracted from the Green function tensor, which is calculated from FDTD simulations. SER modification due to the Purcell effect as calculated by others is confirmed for calibration purposes and we further determine the SER modification attributable to the conductive properties of the photonic crystal host material. - K. Mukherjee and M. Militzer (The Centre for Metallurgical Process Engineering, UBC)
Ultrafine grained dual-phase steel
Ultrafine grained dual phase steel offers an attractive combination of strength and ductility. This property combination makes this kind of steel a good candidate for automotive applications. A suitable processing route to obtain this kind of microstructure containing approximately 80% ultrafine ferrite (bcc phase), and 20% martensite (bct phase) is being studied for a plain C steel (0.06 wt% C-1.8 wt% Mn-balance Fe). For this purpose a separate rolling stand is proposed in the standard 1 stand rolling and 7 stand finishing mill. In this proposed 8th finishing stand undercooled austenite (fcc phase) will be heavily deformed to produced fine grained ferrite by rapid nucleation. This procedure is termed as deformation induced ferrite transformation. A hot torsion simulation of the entire proposed route produced a fine grained dual-phase structure with a mean ferrite grain size of 1.7 um and ferrite fraction of 81%. EBSD characterization of this kind of fine grained dual phase material is being performed on several chemistries (plain C steel, Mo and Nb microalloyed steels). As ferrite and martensite have similar crystal structures it is difficult to distinguish these two phases from the EBSD maps. A scheme is proposed to distinguish ferrite and martensite in the EBSD maps based on the band contrast. Further, the mean ferrite grain sizes obtained from the EBSD study is similar to that obtained from the conventional SEM observations. - O.Pitts, D. Lackner, Y-T. Cherng, S.P. Watkins (Physics, SFU)
Growth of InAsSb and InPSb heterojunctions for mid infrared detectors
Antimonide III-V materials lattice matched to GaSb are promising for detection of mid IR radiation in the 3-4 micron region, and as possible candidates for thermophotovoltaics, in which thermal radiation is directly converted to electrical power. In this poster we review efforts at SFU to grow InAsSb based heterojunction materials on GaSb. The novel aspects are (1) the use of a wide gap InPSb barrier layer to suppress thermal diffusion and thereby improve the higher temperature performance, and (2) the development of strain-balanced InAs/InAsSb superlattice active layers to extend the detection range further into the mid IR. We report materials properties of these highly immiscible alloys, together with preliminary I-V measurements on large area devices. - A. Weck 1, C. W. Sinclair 1, C. Scott 2, R. R. Parson3 (1 Materials Engineering Department, 3 Physics and Astronomy Department, UBC, 2 Arcelor Research, France)
Deposition of Fe-C thin films by magnetron sputtering
Most of the materials used in industry for their structural and functional properties are in a thermodynamically stable state. However, when the fabrication methods involve extremely high cooling rates, these materials do not have time to organise themselves to reach this stable state. In this study, we present various non-equilibrium structures obtained after the deposition of iron-carbon thin film via magnetron sputtering. The as deposited structure is mainly amorphous after a deposition of 50 nm. Thicker films (400 nm) were grown under the same conditions and show a columnar, crystalline structure. When applying a negative bias between target and substrate, the structure becomes crystalline and consists of a super saturated solid solution of carbon in the iron ferrite matrix. Further increasing the bias results in the formation of carbides in the ferrite matrix. These preliminary results demonstrate the ability of tailoring the structure of metallic thin films via changes in the deposition parameters. In future work, the mechanical properties of these various structures will be investigated. The long term goal is to deposit such thin films onto industrial bulk materials to alter their mechanical and functional properties. - Steve Yeoh, Bryan Louis, Yuqin Wan, Frank Ko (Advanced Fibrous Materials Laboratory (AFML), AMPEL, Department of Materials Engineering, UBC)
Structures and Properties of Cellulosic Nanofibres by Electrospinning
Cellulosics, the most abundant natural fibres extractable from wood, will be regenerated by electrospinning, a process for fabricating fibres using electrostatic forces. Commercially available cellulosic fibres have flawed surfaces and become mechanically weak upon moisture absorption, thus limiting their applications in high value-added paper products. In this study, cellulose acetate (CA) nanofibres were electrospun. Physical, structural, and chemical properties of the CA nanofibres were characterized. This study has established the foundation for further development of renewable nanomaterials. - H. Azizi-Alizamini, M. Militzer, W.J. Poole (The Centre for Metallurgical Process Engineering, UBC)
Heterogeneous microstructures in low carbon steels
Producing ultrafine grained low carbon steels with grain size of 1 um or smaller has been of interest during past decade. The main drawback of these types of structures is extensive lüdering and limited uniform elongation. Heterogeneous microstructures with different grain size regimes, e.g. bimodal grain size, can be an appropriate candidate to improve combination of strength and ductility. In this study two novel techniques are introduced in order to generate heterogeneous microstructures with coarse and fine grain sizes in plain low carbon steels. The first technique is based on cold rolling of a dual phase structure followed by annealing between 500-600 C for different times. Recrystallization of deformed ferrite results in coarser grains in the range of 5-15 um while submicron ferrite grains with an average size of 0.5 um is the product of recrystallization of martensite. Co-deformation of martensite islands and carbide precipitation are the key mechanisms for refining the microstructure. The second approach is based on rapid heating of a conventional cold rolled ferrite-pearlite structure into the intercritical region followed by He quenching to room temperature. A complex multi-phase microstructure results that primarily consists of a bimodal ferrite structure but contains also some pearlite, bainite and MA. The coarse portion of ferrite with a grain size of approximately 6 um is the product of ferrite recrystallization during heating. Upon fast cooling, very fine ferrite grains with an average grain size of about 1.5 um form as a result of austenite decomposition. Further, the presence of small volume fractions (<0.05) of other transformation products (i.e. bainite and MA) is another feature of the fast cooling step. Therefore, the final microstructure is a mixture of coarser ferrite grains with a very fine complex phase structure. - B. Faraji, W. Shi, P. Mensz, D. Pulfrey, L. Chrostowski (Microsystems and Nanotechnology Group (MINA), UBC)
Analytical modeling of Transistor-Vertical Cavity Lasers
Transistor lasers use the advantages of the bipolar transistors and the semiconductor lasers to potentially achieve a large modulation bandwidth (beyond 50 GHz). Bandwidth enhancement is mainly due to the carrier lifetime reduction and suppression of the laser relaxation oscillation (RO). In this study to verify the broad bandwidth operation of a transistor vertical cavity surface-emitting laser (TVCSEL), an analytical model based on the laser rate equations and continuity equation is developed. The model takes into account of the capturing and escaping processes which occur due to carrier transitions from virtual 3D states to 2D states of the quantum well (QW). The model finds the carrier concentration distribution by solving the diffusion equation by using thin base boundary conditions and the laser rate equations. The DC and AC characteristics are obtained by large signal and small signal analysis and an analytical transfer function which relates the output power to base current is derived. The simulations show that bandwidth of 30 GHz can be obtained from the device. - V. Bazargan, B. Stoeber* (Microsystems and Nanotechnology Group (MINA), UBC, Mechanical, *and Electrical and Computer Engineering)
Thermal modulation of microchannels during operation
We demonstrate new methods to modify the geometry and layout of individual flow channels on a microfluidic chip during operation. Using Pluronic, a biocompatible thermally responsive polymer in the fluid stream allows controlled and reversible gel formation in the micro channel at elevated temperatures. This allows arbitrary modulation of the channel width after device fabrication so that flow rate and flow velocity can be set independently. In addition, co-streaming of a Pluronic solution and a saline solution in a T-shape microfluidic device, can lead to a gel wall at the fluid-fluid interface for certain concentration and temperature conditions. This mechanism can also be used for automatic formation of a separation wall at constant temperature if the saline concentration is increased. Also, the thickness of the wall at constant temperature can be used as a detection tool to evaluate the concentration of the salt. This effect is an attractive regulation mechanism, where under regular conditions cross-stream diffusion is desired such as in the "T-sensor", while diffusion of ionic solvents such as sodium phosphate into a second stream should be limited. - Azadeh Akhtari Zavareh , Wenjie Li and Karen L. Kavanagh (Physics, SFU), Julia. W. P. Hsu, and A. Alec. Talin, (Sandia National Laboratories, USA)
Pd Dithiol Molecular Contacts to GaAs
Investigation of electron transport across individual, or small numbers of organic molecules has attracted a great deal of attention and controversy in the past five years. Ballistic electron emission microscopy (BEEM) offers a way to study local transport through a buried layer, such as a thin molecular layer, without biasing the molecule and with nanometer lateral resolution. We are interested in the effect of Pd as an interlayer between Au and the molecular layer on GaAs. We used epitaxially grown or bulk n-GaAs (001) (2x1017/cm3 doping) as a substrate with molecules deposited from ethanol solutions distinguished by the number of carbons and the presence and location of a thiol bond (Monothiol : C16MT ; Dithiol: C8DT). We have a thin (8 nm to e-beam evaporated (Au-Pd) metal layer on top of the molecules. BEEM spectra are obtained by varying the tip voltage while maintaining a constant tunnelling current. BEEM images are obtained by scanning across the sample while a feedback loop maintains constant tip voltage and tunneling current. With C8DT the BEEM signal is very weak, almost submerged in the background noise, therefore the dithiol case behaves like a continuous insulating layer. For C16MT, we obtain a strong signal (with a threshold of 0.87 eV) likely due to Au or Pd - molecule interdiffusion. - Jeremy Finden (Chemistry, SFU) Tamara Kunz (Chemistry, UBC) Neil R. Branda (Chemistry, SFU) and Michael Wolf (Chemistry, UBC)
Reversible Amplified Fluorescence Quenching of a Dithienylethene Functionalized Polythiophene
Conjugated polymers are an important class of materials with multi-functional properties. Polythiophenes are one of the most studied classes of conjugated polymers due to their semiconducting and luminescent properties, as well as their relatively high stability and ease of synthesis. The extensive pi-conjugation in the polythiophene backbone allows stimulation at a single point along the backbone to be translated along the chain, potentially with an amplified effect to the electronic structure. A dithienylethene (DTE) functionalized polythiophene has been prepared, and the effect of photochromic switching of the DTE on the polymer backbone studied. Reversible quenching of the backbone emission and amplification of the effect of the ring-closing reaction will be demonstrated. - Christine Lavigueur, Vance E. Williams (Chemistry, SFU)
A Capillary Furnace for Variable Temperature X-Ray Diffraction of Liquid Crystals
Liquid crystals have generated much interest, both as prime examples of self-assembly and as candidates for numerous applications such as displays, light emitting devices and organic field effect transistors. The determination of the structure of liquid crystalline phases commonly requires the use of variable temperature XRD. An inexpensive capillary furnace has been developed for variable temperature X-ray diffraction in transmission geometry of air stable liquid crystals and other materials. It offers temperature control with fluctuations of less than ± 1 oC in the range of interest for these samples, from room temperature to near 300 oC. Phases can be accessed through heating or cooling with no significant overshooting of the target temperature. The furnace is designed to fit on a classical goniometer, and can be controlled by any standard temperature controller. The simple design of this furnace means that it is both inexpensive to build and easy to operate. - Haijun Qiao and Jeff Young (Physics, UBC), Mingqian Tan and Frank van Veggel (U. Victoria)
The temperature dependence of photoluminescence from the assembled colloidal lead selenide quantum dots
The temperature dependent photoluminescence (PL) emission from the assembled PbSe quantum dots (Qdots) capped by oleic acid ligands is reported. The peak energy of the PL emission shifts to the high energy direction and the linewidth is found to be broadened by a factor of 2 as the temperature goes up from 5 K to the room temperature, due to the dephasing of the quantum electronic states. The homogenous line broadening of the PbSe Qdots can be derived by deconvolving the PL lineshape with the low temperature PL lineshape, which has a Gaussian lineshape. The dephasing mechanism is attributed to the interaction between the carriers and the phonons in the Qdots. The results show that the carrier-acoustic phonon interaction is playing a main role in PbSe Qdots. - Mrigank Sharma, Akila Kannan and Edmond Cretu (Microsystems and Nanotechnology Group MiNa, UBC)
Noise Analysis and Noise-based Optimization for Resonant MEMS Structures
A design for high sensitivity of MEMS structures needs to take into account the noise shaping induced by damping phenomena at micro scale. The existing scientific literature analyzes the mechano-thermal noise in microstructures based on the assumption of a constant damping coefficient . This might be a correct assumption for low-frequencies, but fails to consider the more complex behavior of gas damping as the operating frequency increases, which is the case for resonators and resonating sensors. There are nevertheless detailed models of the combined elasto-damping action of the gas upon the movable plate in the case of squeeze-film damping, but without considering its impact on noise analysis. This work bridges these two aspects, and presents a noise analysis and optimization process based on simulated behavior of a MEMS resonating sensor. This methodology also optimizes the signal to noise ratio by exploiting the spectral noise shaping of the equivalent input noise source and tuning the mechanical suspensions to an optimal value. - Syed Farid Ullah Khan, Mu Chiao (Mechanical Engineering, Microsystems and Nanotechnology Group MiNa, UBC)
Fabrication of Vibration-based Micro Electromagnetic Energy Scavenger for MEMS Applications
This work reports on the research project on vibrational micro electromagnetic energy scavenger that would convert the ambient vibration into electrical energy according to Faraday’s Law of electromagnetism. The micro power generator will consist of stationary permanent magnet and movable Nickel coil, due to the ambient vibration as the coil will move relative to the magnet and as it cut the magnetic flux, voltage will be induced in the two ends of the coil. The proposed research will focus on the following objectives:
To design and fabricate an Electromagnetic vibrational Micro Power Generator, that could scavenge the power from the ambient vibration and rotational energy, compatible with standard MEMS fabrication processing, batch producible and cost effective.
To develop the fabrication setup for SU8 molding and MEMS electroplating, which could be used to fabricate Electromagnetic Energy Scavenger.
To Design and fabricate an array of different sizes and designs of Electromagnetic Micro Power Generators, which could operate over a wide band of frequencies and produce steady power all the times.
To evaluate the performance of the developed Micro Power Generators with respect to power requirement of the existing wireless sensor node, using analysis, computer simulation and experimentation. - X. Lu, D. Beaton, M. Whitwick, T. Tiedje (AMPEL, UBC)
Molecular beam epitaxy growth of GaAs1-xBix epilayers with high Bi content
Bismuth diluted III-V alloy, GaAs1-xBix, has attracted much interest in their growth and basic physical properties recently because the incorporation of a small amount of bismuth, acting as an isoelectronic impurity, leads to a strong modification of the host band structure, which results in a very large reduction of the band-gap energy. This finding of the large band-gap reduction (7x bigger than comparable In concentration) has important consequences for the application of GaAs1-xBix in long-wavelength semiconductor light sources grown on GaAs substrates. Although much effort has been put into the growth of GaAs1-xBix epilayers, how to grow high quality GaAs1-xBix epilayer with high Bi content and without Bi droplets is still a problem. Under growth conditions reported so far in the literature, only a small amount of Bi can be incorporated and it is also easy to form Bi droplets. Further effort is needed. In a recent study, we have successfully modified the growth conditions used in the molecular beam epitaxy growth of GaAs1-xBix epilayers, to achieve extremely high Bi content (up to 10%) without Bi droplets. Strong room temperature photoluminescence was observed. - M. Chen, J. Flueckiger, K. Cheung (Microsystems and Nanotechnology Group (MINA), Biomedical Engineering, UBC, Electrical and Computer Engineering)
Reversible cell trapping in microfluidic channels using hydrogels
Until recently cell studies were carried out on cultures which were grown on a planar surface or by keeping the cells suspended in a liquid medium. However the extracellular matrix (ECM) and the 3D environment affect cell-cell interactions, cell growth, adhesion, differentiation, and proliferation. The use of microfluidic technology provides the tools for creating more in-vivo-like environments. In this study we use hydrogels to trap and release cells inside a microfluidic channel, since miniaturization allows us to manipulate small numbers of cells. Hydrogels are used as biomaterials for tissue engineering due to their resemblance to the natural extracellular matrix and their non-cytotoxicity. The porous nature of these gels allows the transport of nutrient and waste. The gel network can also present specific adhesive properties for attachment of cells. By choosing polymers that reversibly undergo gel formation by changes in environmental conditions, such as temperature or ionic factors, cell trapping and release can be triggered externally. We investigate two different approaches to induce gel formation. The first is based on diffusive mixing of alginic acid and calcium ions. Cells trapped in the alginate gel can be released by addition of a calcium chelator. The second approach is based on thermosensitive hydrogels, which gel at the physiological temperature of 37°C, immobilizing cells suspended in the solution. Agarose and N-isopropylacrylamide (NiPAAm) are currently used. - HR TEM Characterization of InAs Nanowires
D. Susac, S.A. Dayeh*, E.T. Yu*, D. Wang* and K. Kavanagh (Physics, SFU, and EECE UC San Diego*)
Semiconductor InAs nanowires have been grown on InAs(111)B substrate using Au catalyzed organometallic vapor-phase epitaxy. Their structure and morphology have been studied as a function of the substrate temperature and input V/III precursor ratios using high resolution transmission electron microscopy (HR TEM). It has been found that these nanowires have hexagonal wurtzite structure with numerous planar defects such as stacking faults. The wire morphology is strongly dependent on the growth temperature while the density of stacking faults increases with both increasing input V/III ratio as well as a substrate temperature. This study advances understanding of the structures formed under specific regimes that may be important for future device applications. - Electrochemically Prepared Fe/GaAs (110)
S. Majumder, S. Shaw, A. S. Arrott, and K. L. Kavanagh (Physics, SFU)
Iron has been deposited electrochemically on oriented, n-type GaAs (110) bulk substrates (2x10^17 Si) at various temperatures in aqueous electrolytes. In this work we report on a study of the film structure and residual strain via ex situ high resolution x-ray diffraction (HRXD) and in situ curvature measurements, and on the film magnetic properties via SQUID magnetometer measurements. The motivation is to eventually compare the spin transport properties of these interfaces to those prepared via ultra-high-vacuum deposition. - Rapid, Layout-based Electrical and Thermal Modelling
Andrew Labun (School of Engineering, UBC Okanagan)
Highly complex interconnect structures described in layout are routinely extracted into network descriptions, often including capacitive coupling between interconnect segments on different nets. Analysis of such networks leads to sparse, diagonally-dominant matrices. In a new symbolic and analytic approach, these matrices are formed and solved symbolically. These solutions are then evaluated to rapidly find both electric current and the analytic temperature trajectories along the interconnect predicted by the 1-D steady-state heat equation. The heat equation solution includes thermal coupling between all the interconnect segments. While the symbolic solution of the network requires O(P^3) operations, where P is the number of nodes in the network, all subsequent evaluations require O(P) operations. - Silicon nanowire synthesis for future electronics
Xiaodan Xu, Edward Sham, Rocky Leung, Kathrine Li, Jason Kuo, Elham Beheshti, Soheil Ebadian, Peyman Servati (Microsystems and Nanotechnology Group, MiNa, UBC)
Silicon nanowires (SiNWs) are one of the most important nanomaterials for future nanotechnology. Potential applications include electronic, optoelectronic/photonic devices. Observation of quantum conduction in SiNWs has suggested their use for channel material of nanoscale and single electron transistors. Here, we explore catalytic synthesis of SiNWs using vapor-liquid-solid (VLS) method. The nucleation sites and diameters of nanowires ranging from 100nm to 1nm can be well controlled by metal catalyst seeds. The catalyst nanoparticles can be generated by separation of a catalyst film patterned by photolithography or by deposition of colloidal nanoparticles. SiNWs synthesized based on VLS mechanism have displayed interesting properties for various technological applications.