Method of Fabricating Schottky Barrier solar cell

On a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive is deposited a thin layer of heavily doped n-type polycrystalline germanium, with crystalline sizes in the submicron range. A passivation layer may be deposited on the substrate to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes in the germanium layer to not less than 5 micros to serve as a base layer on which a thin layer of gallium arsenide is vapor epitaxially grown to a selected thickness. A thermally-grown oxide layer of a thickness of several tens of angstroms is formed on the gallium arsenide layer. A metal layer, of not more about 100 angstroms thick, is deposited on the oxide layer, and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer. An antireflection coating may be deposited on the exposed top surface of the metal layer

Schottky barrier solar cell

A method of fabricating a Schottky barrier solar cell is described. The cell consists of a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive. A thin layer of heavily doped n-type polycrystalling germanium is deposited on the substrate after a passivation layer is deposited to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes to serve as a base layer on which a thin layer of gallium arsenide is vapor-epitaxilly grown followed by a thermally-grown oxide layer. A metal layer is deposited on the oxide layer and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer

High Dynamic Range RF Front End with Noise Cancellation and Linearization for WiMAX Receivers

This research deals with verification of the high dynamic range for a heterodyne radio frequency (RF) front end. A 2.6 GHz RF front end is designed and implemented in a hybrid microwave integrated circuit (HMIC) for worldwide interoperability for microwave access (WiMAX) receivers. The heterodyne RF front end consists of a low-noise amplifier (LNA) with noise cancellation, an RF bandpass filter (BPF), a downconverter with linearization, and an intermediate frequency (IF) BPF. A noise canceling technique used in the low-noise amplifier eliminates a thermal noise and then reduces the noise figure (NF) of the RF front end by 0.9 dB. Use of a downconverter with diode linearizer also compensates for gain compression, which increases the input-referred third-order intercept point (IIP3) of the RF front end by 4.3 dB. The proposed method substantially increases the spurious-free dynamic range (DRf) of the RF front end by 3.5 dB

Infrared spectra of the cluster ions H7O⁺₃·H2 and H9O⁺₄·H2

Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O + 3 and H9O + 4

Interfacial strain in AlxGa1–xAs layers on GaAs

Detailed analysis of x-ray rocking curves was used to determine the depth profile of strain and composition in a 2500-Å-thick layer of AlxGa1–xAs grown by metalorganic chemical vapor deposition on 100 GaAs. The x value and layer thickness were in good agreement with the values expected from growth parameters. The presence of a transition region, 280 Å thick, was detected by the rocking curve. In this region, the Al concentration varies smoothly from 0 to 0.87. Measurement and control of the sharpness of such interfaces has important implications for heterojunction devices

Cherenkov and Scintillation Light Separation in Organic Liquid Scintillators

The CHErenkov / Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2g/L of PPO as a fluor (LAB/PPO). This is the first such demonstration for the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 +/- 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 +/- 3% and 63 +/- 8% for time- and charge-based separation, respectively, with scintillation contamination of 36 +/- 5% and 38 +/- 4%. LAB/PPO data is consistent with a rise time of 0.75 +/- 0.25 ns

Average and worst-case specifications of precipitating auroral electron environment

The precipitation electrons in the auroral environment are highly variable in their energy and intensity in both space and time. As such they are a source of potential hazard to the operation of the Space Shuttle and other large spacecraft operating in polar orbit. In order to assess these hazards both the average and extreme states of the precipitating electrons must be determined. Work aimed at such a specification is presented. First results of a global study of the average characteristics are presented. In this study the high latitude region was divided into spatial elements in magnetic local time and corrected geomagnetic latitude. The average electron spectrum was then determined in each spatial element for seven different levels of activity as measured by K sub p using an extremely large data set of auroral observations. Second a case study of an extreme auroral electron environment is presented, in which the electrons are accelerated through field aligned potential as high as 30,000 volts and in which the spacecraft is seen to charge negatively to a potential approaching .5 kilovolts

Scanning Tunneling Spectroscopic Studies of the Effects of Dielectrics and Metallic Substrates on the Local Electronic Characteristics of Graphene

Atomically resolved imaging and spectroscopic characteristics of graphene grown by chemical vapor deposition (CVD) on copper foils are investigated and compared with those of mechanical exfoliated graphene on SiO_2. For exfoliated graphene, the local spectral deviations from ideal behavior may be attributed to strain induced by the SiO_2 substrate. For CVD grown graphene, the lattice structure appears strongly distorted by the underlying copper, with regions in direct contact with copper showing nearly square lattices whereas suspended regions from thermal relaxation exhibiting nearly honeycomb or hexagonal lattice structures. The electronic density of states (DOS) correlates closely with the atomic arrangements of carbon, showing excess zero-bias tunneling conductance and nearly energy-independent DOS for strongly distorted graphene, in contrast to the linearly dispersive DOS for suspended graphene. These results suggest that graphene can interact strongly with both metallic and dielectric materials in close proximity, leading to non-negligible modifications to the electronic properties