Increased Cycling Efficiency and Rate Capability of Copper-coated Silicon Anodes in Lithium-ion Batteries

Cycling efficiency and rate capability of porous copper-coated, amorphous silicon thin-film negative electrodes are compared to equivalent silicon thin-film electrodes in lithium-ion batteries. The presence of a copper layer coated on the active material plays a beneficial role in increasing the cycling efficiency and the rate capability of silicon thin-film electrodes. Between 3C and C/8 discharge rates, the available cell energy decreased by 8% and 18% for 40 nm copper-coated silicon and equivalent silicon thin-film electrodes, respectively. Copper-coated silicon thin-film electrodes also show higher cycling efficiency, resulting in lower capacity fade, than equivalent silicon thin-film electrodes. We believe that copper appears to act as a glue that binds the electrode together and prevents the electronic isolation of silicon particles, thereby decreasing capacity loss. Rate capability decreases significantly at higher copper-coating thicknesses as the silicon active-material is not accessed, suggesting that the thickness and porosity of the copper coating need to be optimized for enhanced capacity retention and rate capability in this system.Comment: 15 pages, 6 figure

Thin film gauge

A thin film gauge for use in measuring distributed convective heat transfer rates occurring along given surfaces, is described. The gauge is particularly suited to measuring test surfaces in the air stream of a wind tunnel. The gauge is characterized by a plurality of painted platinum leads extend across the surface of a substrate; a pair of leads on the surface is adapted to deliver an electric current at a constant amperage through a selected thermally active area. Leads are also coupled at opposite sides of the thermally active area for detecting induced voltage drops occurring in the area so that the active length of the gauge is defined between voltage output leads. Changes in heat transfer to the thermally active area are isolated and determined by detecting induces changes in voltage drop

Electrical phase change of CVD-grown Ge-Sb-Te thin film device

A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film has been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The CVD-grown Ge-Sb-Te thin film shows promise for the phase change memory applications

Synthesis of large-area and aligned copper oxide nanowires from copper thin film on silicon substrate

Large-area and aligned copper oxide nanowires have been synthesized by thermal annealing of copper thin films deposited onto silicon substrate. The effects of the film deposition method, annealing temperature, film thickness, annealing gas, and patterning by photolithography are systematically investigated. Long and aligned nanowires can only be formed within a narrow temperature range from 400 to 500°C. Electroplated copper film is favourable for the nanowire growth, compared to that deposited by thermal evaporation. Annealing copper thin film in static air produces large-area, uniform, but not well vertically aligned nanowires along the thin film surface. Annealing copper thin film under a N2/O2 gas flow generates vertically aligned, but not very uniform nanowires on large areas. Patterning copper thin film by photolithography helps to synthesize large-area, uniform, and vertically aligned nanowires along the film surface. The copper thin film is converted into bicrystal CuO nanowires, Cu2O film, and also perhaps some CuO film after the thermal treatment in static air. Only CuO in the form of bicrystal nanowires and thin film is observed after the copper thin film is annealed under a N2/O2 gas flow

Accuracy of defect distributions measured by bias dependent admittance spectroscopy on thin film solar cells

Thin film solar cells have achieved efficiencies up to 20%. Despite these excellent results, the understanding of the underlying mechanisms and the influence of defects on their performance is still incomplete. In thin film solar cells often defect level distributions are present rather than discrete defects. These distributions can be calculated from admittance measurements, however several assumptions are needed which hinder an exact defect density determination. By performing the measurements under different bias voltage conditions the accuracy of the method can be improved and assessed. This is illustrated with measurements on a flexible thin film Cu(In,Ga)Se2- based (CIGS) solar cell

Thin Film Superconducting Devices

Techniques have been developed with which it is possible to fabricate superconducting thin film structures (“bridges”) which show Josephson-like phenomena, with a wide variety of electrical and superconducting parameters. These bridges—based on the proximity effect—are made in layered thin film substrates which have been fabricated from many different, both hard and soft, superconducting materials. The fabrication techniques and the electrical and superconducting characteristics for these proximity effect bridges including a simple low frequency (≤10 GHz) equivalent circuit will be discussed. These bridges have been incorporated into simple thin film circuits for use as galvanometers, magnetometers, gradiometers, detector arrays, etc. Extension of these techniques to more complex superconducting thin film bridge circuits including resistors, capacitors, and inductors will be indicated

Nanostructured titanium dioxide thin film for dye-sensitized Solar cell applications

Nanostructured Titanium Dioxide (TiC^) thin film for Dye-Sensitized Solid State Solar Cell (DSSSC) application has been synthesized using sol-gel method and deposited onto silicon and glass substrates using spin coating technique. The optimized annealing temperature and sol-gel concentration were obtained a| 500°C and 0.2M, respectively. Basically, there were four properties studied; surface morphology, structural, electrical and optical properties. Field Emission Scanning Electron Microscopy (FE-SEM) / Scanning Electron microscopy (SEM) were carried out to observe the changes in surface morphology whenever there are changes on the parameters. X-Ray Diffractions (XRD) characterization of the samples was taken to examine the TiC>2 crystalline phases and the intensity of nanocrystalline particles in the thin film. I-V measurement using two-point probe equipment was used to observe the electrical properties which include the measuring of the sheet resistance, the resistivity and the conductivity of the TiC>2 thin film. The optical properties were observed using UV-Vis-NIR spectrophotometer. The thin film transmittance and the band gap energy were also observed using this spectrophotometer. At the end of this research, uniform and homogeneous TiC>2 thin film has successfully prepared. By controlling the sol-gel concentration, a transparent TiC>2 thin film has been developed which has high transmittance property of above 80%. The TiC>2 thin films which were annealed at a temperature of 500°C and prepared at 0.2M of sol-gel precursor concentration gave the optimum results. By adding TiC>2 nanopowder, the surface area and porosity of TiC>2 thin film is improved, thus good candidate to use in DSSSC application

Rapid Fabrication of Smart Tooling with Embedded Sensors by Casting in Molds Made by Three Dimensional Printing

This paper is to investigate the feasibility of constructing “smart tooling” by embedding thin film sensors, specifically, thin film thermocouples (TFTC) in castings made by molds formed by 3 Dimensional Printing (3DP). This study investigates whether thin film sensors can effectively be cast into larger metal structures and if the sensors survive the casting process. The investigation includes making 3DP molds to produce cast lap joint test bars of aluminum A356 and electroplated nickel to characterize by mechanical testing to find the best process conditions to maximize bond strength between the embedded thin film sensors and the cast material. Lastly molds were made and embedded sensors were placed inside the mold for casting. Some of the embedded sensors survived the casting process. In-situ monitoring of casting process with the embedded sensors was accomplished.Mechanical Engineerin

Synthesis of thin-film black phosphorus on a flexible substrate

We report a scalable approach to synthesize a large-area (up to 4 mm) thin black phosphorus (BP) film on a flexible substrate. We first deposited a red phosphorus (RP) thin-film on a flexible polyester substrate, followed by its conversion to BP in a high-pressure multi-anvil cell at room temperature. Raman spectroscopy and transmission electron microscopy measurements confirmed the formation of a nano-crystalline BP thin-film with a thickness of around 40 nm. Optical characterization indicates a bandgap of around 0.28 eV in the converted BP, similar to the bandgap measured in exfoliated thin-films. Thin-film BP transistors exhibit a field-effect mobility of around 0.5 cm2/Vs, which can probably be further enhanced by the optimization of the conversion process at elevated temperatures. Our work opens the avenue for the future demonstration of large-scale, high quality thin-film black phosphorus

Fabrication and optimization of N-Cu2O thin film using electrodeposition method for homojunction solar cell

Cuprous oxide (Cu2O) is a promising semiconductor that has been getting attention as the alternative material for solar cell application. It is abundant, low cost and non-toxic to the environment. A homojunction Cu2O is said to provide high conversion efficiency for solar cell. However, as Cu2O is a natural p-type semiconductor, it is a challenge to make an n-type Cu2O. In this study, n-Cu2O was prepared by using electrochemical deposition. The structural, morphological, optical and electrical properties of the electrodeposited Cu2O were evaluated after optimizing the parameters for Cu2O fabrication. Structural characterization of the deposited thin film was also done via X-Ray Diffractions (XRD) to confirm the existence of Cu2O particles on fluorine-doped tin oxide (FTO) substrate and to determine the crystalline phases of Cu2O in the sample. The surface morphology of Cu2O thin films were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM) in order to examine the changes in the surface morphology of the film as the parameter varied. Ultra violet-visible (UV-Vis) spectrophotometer was used to study the optical absorption of Cu2O and to determine the band gap of the deposited thin film with further calculation including the thickness values of the thin film measured by surface profiler. The resistivity and sheet resistance of Cu2O thin film were determined via four-point probe measurement test. Lastly, the deposited Cu2O thin film was confirmed as n-type by using the photoelectrochemical cell (PEC) test. The parameters for electrodeposition of Cu2O such as the deposition potential, pH solution, solution temperature, and deposition time were optimized at -0.10 V vs. Ag/AgCl, pH 6.5, 60 °C, and 60 minutes, respectively. The band gap obtained from UV-Vis spectrophotometer was 2.45 eV. The successful fabrication of n-Cu2O will open a new door of Cu2O-based homojunction development for thin film solar cell application