Fabrication of thin film solar cell materials by APCVD

Thin film solar cells are currently being implemented commercially as they reduce the amount of semiconductor material required for each cell when compared to silicon wafers, thereby lowering the cost of production. Currently two direct band gap chalcogenide thin-film technologies, CdTe and CuInGa(S,Se)2 (CIGS), yield the highest reported power conversion efficiencies of 16.5% and 20.3%, respectively. In addition, Cu2ZnSnS4 (CZTS) is one of the most promising chalcogenide thin film photovoltaic absorber materials; with an optimal band gap of about 1.5 eV. More importantly, CZTS consists of abundant and non-toxic elements, so research on CZTS thin-film solar cells has been increasing significantly in recent years. Moreover, Sb2S3 based chalcogenide thin films have been proposed for use in photovoltaic applications. The preparation of chalcogenide thin films solar cells commonly use physical vapour deposition methods including thermal/e-beam evaporation, sputtering, and pulsed laser deposition, electrochemical deposition, spray pyrolysis, solution-based synthesis, followed by the sulfurization or selenization annealing process. In this paper, we report a non-vacuum process, using atmospheric pressure chemical vapour deposition (APCVD), to fabricate chalcogenide thin film solar cell materials as well as transparent conductive oxide (TCO) thin films. The optical, electrical, and structural properties of these materials were characterized by UV-VIS-NIR, four-point probes, SEM, EDX, XRD, Micro-Raman

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

Strain engineering in graphene by laser irradiation

We demonstrate that the Raman spectrum of graphene on lithium niobate can be controlled locally by continuous exposure to laser irradiation. We interpret our results in terms of changes to doping and mechanical strain and show that our observations are consistent with light-induced gradual strain relaxation in the graphene layer

Viscoelastic Properties of Foam Under Hydrostatic Pressure and Uniaxial Compression

AbstractFoam is a lightweight material suitable for aerospace applications for load bearing structures or noise reduction media. The microstructure of the foam, which is constructed with cell ribs, allows its unique mechanical properties. In this work, commercial polyurethane foams with a pore size on the order of a few hundred microns were subjected to quasi-static hydrostatic and uniaxial compression at low strain rates, as well as dynamic sinusoidal loading for studying their loss tangent and storage modulus. The identified incremental negative modulus depends on deformation modes, and it is been shown hydrostatic compression may trigger the negative bulk modulus mode, while uniaxial compression may not. The use of negative modulus in composite materials may lead to extreme high damping and high stiffness materials. Furthermore, by finite element calculations on a dodecahedral unit cell with different elastic constant, it is found that high elastic constant of the cell ribs may give rise to larger negative stiffness effects, when the cell in under hydrostatic compression

Singlet-triplet transitions in highly correlated nanowire quantum dots

We consider a quantum dot embedded in a three-dimensional nanowire with tunable aspect ratio a. A configuration interaction theory is developed to calculate the energy spectra of the finite 1D quantum dot systems charged with two electrons in the presence of magnetic fields B along the wire axis. Fruitful singlet-triplet transition behaviors are revealed and explained in terms of the competing exchange interaction, correlation interaction, and spin Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions are shown designable by tuning the parameters a and B. The transitions also manifest the highly correlated nature of long nanowire quantum dots.Comment: 4 pages, 4 figure

Separation of Cholesterol from other Steroids Using Molecularly Imprinted Polymer Prepared by Seeded Suspension Polymerization

Micron-sized particles of cholesterol-imprinted polymers were synthesized by seeded suspension polymerization in a mixture of 2-propanol and water using polystyrene microbeads as the seeds. Methacrylic acid was employed as the functional monomer to form complexes with template (cholesterol), along with ethylene glycol dimethacrylate as the crosslinker. After removal of template molecules, the columns ( H=15 cm, Di= 0.46 cm ) packed with cholesterol-imprinted polymers were effective for the chromatographic separation of cholesterol from other steroids. When the sample of steroids was eluted isocratically at a flow-rate of Q = 0.5 mL min-1, using a mixture of acetonitrile and water (Ψ= 95:5) as the mobile phase, the retention times for estrone, -estradiol and cholesterol were respectively τ = 5.3, 12.3 and 17.2 min. The average retention times were = 5.3, 10.9 and 16.7 min respectively for estrone, progesterone and cholesterol in samples. The separation was based on the specific binding of cholesterol to recognition sites formed on the imprinted polymers. A separation factor of 1.6 for cholesterol and -estradiol was obtained. The chromatographic efficiency was dependent on the mobile phase composition. Reducing the water content in the non-polar mobile phase to zero could significantly enhance the separation. Compared with particles from bulk polymerization, the column packed with cholesterol-imprinted particles from seeded suspension polymerization had a higher chromatographic efficiency and the advantage of microanalysi

Chalcogenide phase change materials for nanoscale switching

Since the demonstration of threshold switching in chalcogenide alloys over forty five years ago, phase change materials have been extensively investigated for switching and data storage applications. Phase change switching is based on the reversible change between crystalline and amorphous states of a material and in many chalcogenides this change of state takes place in nanoseconds

Metamaterial electro-optic switch of nanoscale thickness

We demonstrate an innovative concept for nanoscale electro-optic switching. It exploits the frequency shift of a narrow-band Fano resonance mode in a plasmonic planar metamaterial induced by a change in the dielectric properties of an adjacent chalcogenide glass layer. An electrically stimulated transition between amorphous and crystalline forms of the glass brings about a 150 nm shift in the near-infrared resonance providing transmission modulation with a contrast ratio of 4:1 in a device of subwavelength thickness

The Hedonic Experience of Enjoyment and Its Relationship to Informal Learning: A Study of Museum Websites

Online hedonic experiences are increasingly of interest in both research and practice. In particular, it has been proposed that ‘traditional usability approaches are too limited and must be extended to encompass enjoyment’ (Blythe and Wright 2003, p.xvi). The aim of this study was to investigate the relationships among: (i) website design features; (ii) user’s experience of enjoyment; and (iii) informal learning such as that occurring with a museum website. A cross-over experimental design was employed with web pages from the National Palace Museum, Taiwan. Results indicated that, as expected, a multimedia game-based ‘lesson’ led to both more enjoyment and more learning than a text-based ‘lesson’. With text-based pages more enjoyment also meant more learning. The situation was complicated, however, with the game-based pages, as results were not in the expected direction. The study points to the need for more research in this complex area

How do plant species defend themselves against Oidium lycopersici? : mapping of monogenic and polygenic resistance in Lycopersicon species

The thesis describes: 1)Resistance mechanism of tomato and some other crop plant species against O. lycopersici , a causal agent of the recent outbreaks of tomato powdery mildew; 2) Host range and genetic variation of the pathogen; 3) Inheritance analysis of resistance in wild tomato accessions including L. hirsutum G1.1560 and G1.1290, L. parviflorum G1.1601 and L. peruvianum LA2172; and 4) Mapping of monogenic (in G1.1560 and G1.1290) and polygenic (in G1.1601) resistance.It has been found that: 1) Resistance to O. lycopersici in Lycopersicon species is mainly associated with hypersensitive response. 2) Tobacco may be an alternative host of O. lycopersici . 3) Tomato powdery mildew isolates from different continents are very similar to each other, suggesting a single origin of these (field) isolates. 4) Resistances in G1.1560 and G1.1290 are monogenic and dominant. The two resistance genes Ol-1 and Ol-3 are both mapped between markers SCAF10 and H9A11, and are genetically not distinguishable from each other. 5) Resistance in G1.1601 is polygenic. Three QTLs for the resistance have been identified. 6) Resistance in LA2172 is monogenic and dominant. The corresponding resistance gene is designated Ol-4 .</p