Low-temperature growth of polycrystalline Ge thin film on glass by in situ deposition and ex situ solid-phase crystallization for photovoltaic applications

Poly-crystalline germanium (poly-Ge) thin films have potential for lowering the manufacturing cost of photovoltaic devices especially in tandem solar cells, but high crystalline quality would be required. This work investigates the crystallinity of sputtered Ge thin films on glass prepared by in situ growth and ex situ solid-phase crystallization (SPC). Structural properties of the films were characterized by Raman, X-ray diffraction and ultraviolet-visible reflectance measurements. The results show the transition temperature from amorphous to polycrystalline is between 255 °C and 280 °C for in situ grown poly-Ge films, whereas the transition temperature is between 400 °C and 500 °C for films produced by SPC for a 20 h annealing time. The in situ growth in situ crystallized poly-Ge films at 450 °C exhibit significantly better crystalline quality than those formed by solid-phase crystallization at 600 °C. High crystalline quality at low substrate temperature obtained in this work suggests the poly-Ge films could be promising for use in thin film solar cells on glass.     

Development of a microfabricated optical bend loss sensor for distributive pressure measurement.

A flexible high-resolution sensor capable of measuring the distribution of pressure beneath the foot via a microfabricated optical waveguide system is presented. The uniqueness of the system is in its batch fabrication process, which involves a microfabrication molding technique with polydimethylsiloxane (PDMS) as the optical medium. The sensor manufacturing technique is described in detail, the optical performance of the waveguides is quantified and the effect of using a matching fluid to improve fiber-coupling efficiency is demonstrated. Mechanical loading tests were performed on a 4 x 4 array with a 2-mm spacing between sensing elements. Loading displacement curves were obtained using a 0 to 0.4 mm triangle loading profile. A force of 0.28 N applied to one of the sensing elements produced a displacement of a 0.325 mm and 39% change in the output light intensity. Multiple loadings were conducted to demonstrate the repeatability of the sensor. A force image algorithm with a two-layer neural network system was used to identify four load magnitudes and four different shaped applicators. All four shapes were successfully identified with the neural network.     

Lambertian matched absorption enhancement in PECVD poly‐Si thin film on aluminum induced textured glass superstrates for solar cell applications

This paper examines the effectiveness of a range of aluminum induced textured (AIT) glass topographies at enhancing light absorption in silicon thin film diode structures deposited on the textured glass side, operating in the superstrate configuration. The aluminum layer used to produce the AIT can be deposited either by thermal evaporation or magnetron sputtering. Varying AIT process parameters produces a wide range of feature roughness and uniformity, providing scope to optimize texture effectiveness and process repeatability. We report strong correlation between the degree of absorption enhancement from these textures and both dark field microscope images of the AIT glass and reduction of the interference envelope in spectral reflectance of the deposited silicon films. Our findings corroborate earlier modeling work based on ray tracing, which predicted that the best enhancement occurs when the feature size is close to the film thickness. In this paper we investigate AIT samples in the 1 – 3 µm film thickness range, some of which trap light in silicon as strongly as at the Lambertian limit. Copyright © 2010 John Wiley & Sons, Ltd.     

FlexCore: Utilizing Exposed Datapath Control for Efficient Computing

We introduce FlexCore, the first exemplar of an architecture based on the FlexSoC framework. Comprising the same datapath units found in a conventional five-stage pipeline, the FlexCore has an exposed datapath control and a flexible interconnect to allow the datapath to be dynamically reconfigured as a consequence of code generation. Additionally, the FlexCore allows specialized datapath units to be inserted and utilized within the same architecture and compilation framework. This study shows that, in comparison to a conventional five-stage general-purpose processor, the FlexCore is up to 40% more efficient in terms of cycle count on a set of benchmarks from the embedded application domain. We show that both the fine-grained control and the flexible interconnect contribute to the speedup. Furthermore, according to our VLSI implementation study, the FlexCore architecture offers both time and energy savings. The exposed FlexCore datapath requires a wide control word. The conducted evaluation confirms that this increases the instruction bandwidth and memory footprint. This calls for efficient instruction decoding as proposed in the FlexSoC framework.     

M(F)-dependent lifetimes due to hyperfine induced interference effects

We report on the first theoretical investigation of M(F)-dependent lifetimes due to interference between a magnetic octupole transition and a hyperfine induced electric quadrupole transition. Extensive multiconfiguration Dirac-Fock calculations are used to model the hyperfine quenching of the magnetic octupole decay of 3d(9)4s 3D3 and the state mixing between the 3D3 and 3D2 due to hyperfine interaction in nickel-like Xe26+.     

High‐Performance Ultrathin Flexible Solid‐State Supercapacitors Based on Solution Processable Mo1.33C MXene and PEDOT:PSS

MXenes, a young family of 2D transition metal carbides/nitrides, show great potential in electrochemical energy storage applications. Herein, a high performance ultrathin flexible solid‐state supercapacitor is demonstrated based on a Mo_1.33C MXene with vacancy ordering in an aligned layer structure MXene/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) composite film posttreated with concentrated H₂SO₄. The flexible solid‐state supercapacitor delivers a maximum capacitance of 568 F cm^?3, an ultrahigh energy density of 33.2 mWh cm^?3 and a power density of 19 470 mW cm^?3. The Mo_1.33C MXene/PEDOT:PSS composite film shows a reduction in resistance upon H₂SO₄ treatment, a higher capacitance (1310 F cm^?3) and improved rate capabilities than both pristine Mo_1.33C MXene and the nontreated Mo_1.33C/PEDOT:PSS composite films. The enhanced capacitance and stability are attributed to the synergistic effect of increased interlayer spacing between Mo_1.33C MXene layers due to insertion of conductive PEDOT, and surface redox processes of the PEDOT and the MXene.     

Near-wall turbulence models for 3D boundary layers

Calculations of the three-dimensional boundary layer in an S shaped duct are performed with various – models. Three different near-wall models are used for the – model, of which one is using a new set of near-wall damping functions deduced from direct numerical simulations of turbulent channel flow available in the literature. The results show that it is possible to obtain damping functions giving better agreement, especially for and , with direct simulation data and experiments than with damping functions deduced from trial and error.     

Optimization of peak area precision of a GC–MS drug screening method using a nonparametric sign test

Accreditation and Quality Assurance - The optimization of a number of gas chromatography–mass spectrometry (GC–MS) parameters in order to improve peak area precision through...     

Template-directed oligonucleotide strand ligation, covalent intramolecular DNA circularization and catenation using click chemistry

The copper-catalyzed azide-alkyne cycloaddition reaction has been used for the template-mediated chemical ligation of two oligonucleotide strands, one with a 5'-alkyne and the other with a 3'-azide, to produce a DNA strand with an unnatural backbone at the ligation point. A template-free click-ligation reaction has been used for the intramolecular circularization of a single stranded oligonucleotide which was used as a template for the synthesis of a covalently closed DNA catenane.     

Acyl thiocyanates—III: The synthesis of stable Aroyl thiocyanates

Two methods are devised for the synthesis of aroyl thiocyanates. One method is based on the thermal breakdown of 5-aroylthio-1,2,3,4-thiatriazoles to aroyl thiocyanates, nitrogen and sulfur. The other method is based on the reaction between thioacid salts and cyanogen halides. The latter synthesis also gives rise to diacyldisulfides. A hypothesis for the disulfide formation is advanced. These investigations have revealed that 2,4,6-tribromobenzoyl- and 2,4,6-tridobenzoyl thiocyanate are stable compounds which can be kept at room temperature for prolonged periods without decomposition, while 2,6-dimethyl-4-nitrobenzoyl and 3,4,5-trimethoxybenzoyl thiocyanate are of intermediate stability. The former thiocyanates are the first examples of stable acyl thiocyanates.