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Multielement, multiphase disordered metal hydride alloys have enabled the widespread commercialization of NiMH batteries by allowing high capacity and good kinetics while overcoming the crucial barrier of unstable oxidation/corrosion behavior to obtain long cycle life. Atomic engineering is used to promote a high concentration of active hydrogen storage sites vital for raising NiMH specific energy to 100 Wh kg−1 by utilizing metal hydride materials having in excess of 440 mAh g−1 specific capacity. New commercial applications demand fundamentally higher specific power and discharge rate kinetics. Disorder at the metal/electrolyte interface has enabled a surface oxide with metallic nickel alloy inclusions having a diameter less than 70 A embedded within the oxide, which provide exceptional catalytic activity to the metal hydride electrode surface and allowed NiMH specific power exceeding 1000 W kg−1.

With their impressive energy performance and their outstanding power capability, Ni-MH batteries are equally suitable for use in pure and hybrid electric vehicles. This is due to the basic nickel-metal hydride technology. For one thing, hydrogen can be stored in metal-hydride alloys at very high volumetric densities, comparable to the density in liquid hydrogen, leading to the superior energy density of metal-hydride batteries. The operating principles of the Ni-MH battery are described as is their construction and manufacture. The on-road performance of Ni-MH batteries and hybrid electric vehicle batteries are discussed.

Nickel/metal hydride batteries today represent the fastest growing market segment for rechargeable batteries due to the high energy density and more environmentally acceptable chemistry offered by this technology. The high energy density of nickel/metal hydride batteries coupled with high power density and long cycle life make this battery chemistry a key enabling technology for practical electric vehicles, including cars, vans, trucks, and other forms of transportation such as scooters, bicycles, and three-wheelers. This paper provides a review of Ovonic technology and up-dates recent developments in materials and cell development for both consumer electronic and EV applications, and highlights areas for future development.

The crystallization of amorphous carbon films, under inert atmospheres, occurs at annealing temperatures above 800 °C. In this work we have found that when the annealing of carbon films is performed under atmospheric conditions, crystallization occurs at temperatures as low as 200 °C. The catalytic effect of oxygen in the crystallization process is understood in terms of the generation of a porous structure in the carbon film due to the vaporization of carbon oxides.

Neutral and ionic gas temperatures (Tn and Ti) are crucial parameters in the plasma processing of materials (etching and film deposition). Here we evaluate a method used for obtaining the temperatures, i.e., the Doppler broadening, of emission lines. We focus on Ar lines from microwave electron cyclotron resonance plasmas. We use the same technique for both ions and neutrals. Three factors are important in achieving accuracy: (1) knowing the correct instrument width at the central wavelength of each ion and neutral line, (2) understanding the noise‐dependent variation in the measured widths, and (3) knowing how the magnetic field affects the spectra. We find that T can be determined to within ∼100 °C. Ti and Tn are typically found to be ∼0.5 and

We report the effect that thermal annealing in inert and oxidizing atmospheres, and with and without encapsulating layers, has on the structure of tungsten/carbon [W/C] multilayer thin films. This study focuses on the tungsten component and deals mainly with multilayers where the ratio of thickness of tungsten layers is equal to or greater than for the carbon layers (that is, γ ≤ 0.5). This is in contrast to prior studies where the tungsten layer thickness was generally held constant and the carbon layer was varied. Thermal annealing in inert atmospheres produces reactions and other structural changes in the tungsten and carbide layers which depend on the as-deposited multilayer structure which depends, in turn, on the thickness of the tungsten layer. In samples where both the tungsten and carbide fractions of the multilayer are completely amorphous as deposited, which is the case for thin tungsten layers (thickness of tungsten (tw)4 nm/period), the reactions in the tungsten layer forming crystalline tungsten and tungsten carbide occur at annealing temperatures above 900°C. The layer pair spacing, or period, (d), in this group shows an expansion of up to 10-15% of the original value as has been reported in the past. Changes in both the tungsten and carbide layers, and their interfaces, contribute to changes in d spacing and relative thickness of the high and low Z components. When the tungsten layer thickness exceeds 4 nm per period the tungsten is partially crystallized in as-prepared samples. In such multilayers interfacial reactions, producing an oriented partially crystalline W2C/C superlattice, occur at temperatures of 600°C and below. The fact that W2C crystallites in one period can form a structure which is correlated to W2C crystallites in neighboring layers is somewhat surprising, since layers are presumably still separated by amorphous carbon which is still visible via Raman. The expansion of the layer pair spacing is relatively small (5%) in this group and, more importantly, mostly involves increases in the thickness of the high Z components. Samples annealed in air at temperatures below 300°C are progressively destroyed by the oxidation of both tungsten and carbide layers. Encapsulation of similar multilayers with a thin (30 nm) dielectric layer of any of several types can retard oxidation to 600°C. The silicon-containing encapsulants generally perform better. Failure at this temperature is seen to occur from pinhole formation.

The environmental advantages of ovonic NiH/sub 2/ batteries, due to the nontoxicity of ovonic alloys, are briefly discussed, and their general performance is described. Commercial progress in their development is summarized. Their use in electric vehicles is examined. >

Among the various alternative fuels, hydrogen is the only fuel, which is clean and sustainable. More importantly, if hydrogen is produced from renewable resources, virtually no CO 2 emissions are produced. Texaco Ovonic Hydrogen Systems (TOHS) has converted a gasoline internal combustion engine (ICE) hybrid vehicle to a hydrogen vehicle using its advanced metal hydride storage. Compared to its gasoline counterpart, the converted vehiole demonstrated a reduction in CO 2 tailpipe emission of 220 grams per mile. Ovonic metal hydride hydrogen storage systems consist of three critical elements: (1) an advanced metal hydride alloy, (2) an efficient heat exchanger and (3) a lightweight fiber wrapped pressure container. A 50 liter Ovonic metal hydride storage vessel installed in the vehicle provides a storage capacity of 3 kg hydrogen and a driving range of 130-150 miles.

The authors have investigated variations in the a-Si deposition process to achieve a high V/sub oc/ a-Si solar cell to be used as the top cell of a triple-junction stacked solar cell. In this investigation, a-Si n-i-p solar cells were deposited on stainless steel substrates in a multichamber RF PECVD deposition system. Different deposition conditions were explored for the intrinsic a-Si layer with the goal of obtaining high V/sub oc/. After process optimization, the authors have achieved a V/sub oc/ of 1.04 V for a-Si n-i-p solar cells with the intrinsic layer deposited at 150/spl deg/C at high hydrogen dilution. This V/sub oc/ is higher than any V/sub oc/ achieved for a single-junction solar cell using a-SiC as the intrinsic layer. This high V/sub oc/ a-Si material is a better choice for the top cell i layer of a triple-junction a-Si alloy solar cell than high bandgap a-SiC alloys.

Microcrystalline Si p-layers have been widely used in a-Si solar cell technology to achieve high efficiency. To improve the solar cell performance further, the authors have studied the deposition of high quality /spl mu/c-Si p-layer material using a modified VHF plasma enhanced CVD process and consequently have improved the solar cell current. This improvement was primarily in the blue response which leads to a 6-10% improvement in the overall solar cell efficiency. In addition, they have explored the deposition of a-Si at high rates using VHF plasma and compared these VHF i-layers with RF plasma deposited i-layers. With improved deposition conditions, VHF intrinsic layers deposited at a rate up to 15 /spl Aring//s show similar device performance and light stability to VHF and RF i-layers deposited at low rates and show higher stability than RF i-layers deposited at high rates in the same deposition system. A 10.9% efficient single-junction solar cell was fabricated using a VHF deposited i-layer.

The successful introduction of hydrogen for transportation, consumer and military applications will require the simultaneous introduction of small scale hydrogen production-storage and distribution systems for central depot and residential use. These systems will have to be flexible, safe and economical. An integrated photovoltaic-electrolyzer-metal hydride system will meet these requirements. The system makes use of high efficiency, low cost amorphous silicon photovoltaic panels coupled to alkaline electrolysis cell stacks. The produced hydrogen is in turn stored as a metal hydride. The system can be scaled from a few watts to several kilowatts and installed in virtually any location. Metal hydride hydrogen storage is an inherently safe, low-pressure storage method. The system can be designed to be coupled directly to the application device or used to refill other storage containers. It will therefore be applicable to virtually all hydrogen applications such as fuel cells, combustion and chemical processes. The development of economical, small-scale hydrogen production-storage systems, especially utilizing renewable energy sources, will enable the successful introduction of hydrogen applications in the marketplace. This paper addresses the conceptual design, integration and sizing of the system components.

Nickel-metal hydride batteries are in high volume commercial production for mass market portable applications due to an excellent cost to performance ratio, application to a versatile product mix and environmental acceptability. Ovonic Battery Company Inc. (OBC) a subsidiary of Energy Conversion Devices Inc. (ECD) has established the dominant position in Ni-MH batteries by establishing a fundamental patent portfolio, a network of licensees and business affiliates, and continued product improvement based upon its atomic engineering approach. The largest opportunities for Ni-MH market growth are portable power tools, EV, HEV and fuel cell electric vehicles. These applications benefit from improvements in specific energy, cycle life, high temperature performance, activation/formation, and in particular specific power. Advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (1000 W/kg), high temperature operation, charge retention, cycle life and voltage stability. While electrode configuration and packaging are important factors in cell design, at the core of next generation Ni-MH technology are the continuing fundamental improvements to the metal hydride and nickel hydroxide active materials. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible.

Performance data for batteries based on multicomponent hydrogen storage alloys using the principles of atomic engineering are presented. In particular, the successful scale-up of this technology for electric vehicle applications is shown. >

Hydrogen $({\mathrm{H}}_{2})$ dilution of the source gas is known to be a key factor in producing hydrogenated amorphous silicon films that demonstrate a high degree of optoelectronic stability. In this work, we investigate, using Raman spectroscopy and high-resolution transmission electron microscopy (TEM), whether microstructural differences exist between such films and those made with no ${\mathrm{H}}_{2}$ dilution (i.e., that have greater instabilities). The key variable is the ${\mathrm{H}}_{2}$ dilution, which ranges from none to very high levels, producing amorphous and microcrystalline silicon films. The TEM results show that embedded within the amorphous matrix are chainlike objects (CLO's) having \ensuremath{\sim}3 nm widths, \ensuremath{\sim}30 nm lengths, and showing a high degree of order along their length. Such order implies vanishing levels of bond-angle distortion (BAD). These CLO's are present in all samples investigated, but their density increases with the level of ${\mathrm{H}}_{2}$ dilution. The Raman spectra show a TO band centered at $490 {\mathrm{cm}}^{\ensuremath{-}1}$ $(37\ifmmode\pm\else\textpm\fi{}3{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ full width). Quantitative analysis shows this band to exist in all samples investigated, but increases in magnitude with increasing ${\mathrm{H}}_{2}$ dilution. In the highest dilutions when microcrystallites are observed, the band is distinctly evident. Its position and width are also consistent with very low (crystallinelike) levels of BAD \ensuremath{\sim}0\ifmmode^\circ\else\textdegree\fi{}. It is thus likely the $490 {\mathrm{cm}}^{\ensuremath{-}1}$ Raman band is a signature of the intermediate ordered CLO's.

Significant progress has been made recently at ECD (Energy Conversion Devices, Inc.), in developing new manufacturing technologies for a‐Si (amorphous silicon) photovoltaics. In a 2 MW continuous roll‐to‐roll a‐Si PV (photovoltaics) manufacturing plant, designed and constructed by ECD, we have advanced ECD’s PV technology and demonstrated the manufacturing of 4 ft2 PV modules with 9.5% initial and 8% stable efficiencies. In addition, high subcell yield up to 99.7% has been demonstrated in 600 m long (about 15 kWp) production runs with high uniformity and consistency. ECD has recently designed and constructed an additional pilot manufacturing machine to develop new technologies including high throughput serpentine web continuous roll‐to‐roll deposition of a‐Si alloy materials. When it is incorporated into a large‐scale production line, serpentine technology can maximize the throughput for a high volume production plant, reduce the machine cost, improve the gas utilization, reduce power consumption, and improve the material stability. Using a single loop serpentine chamber to deposit the top i layer, we have demonstrated triple‐junction triple‐bandgap solar cells with 95% initial efficiency.

Proprietary, multicomponent hydrogen storage materials have been developed making use of the principles of disorder by atomic engineering of the short-range and intermediate -range order. These materials form the basis for Ovonic Nickel-Metal Hydride batteries which have emerged as the leading battery technology for electric vehicle applications. Ovonic Batteries have the highest volumetric energy density available extending the practical range of electric vehicles from under 100 miles to over 200 miles.

Tungsten/carbon (W/C) multilayer thin films prepared by sputtering on unheated Si(100) substrates were encapsulated with various types of layer having low x-ray absorption. Isochronal annealings for 1 hr in the temperature range from 300 to 600 degree(s)C and isothermal annealings at 300 and 400 degree(s)C were carried out under ambient conditions (in air) on coated and uncoated multilayers. The encapsulated layers are: SiN x and SiO 2 prepared by plasma enhanced chemical vapor deposition (PECVD) and SiC, Al 2 O 3 , C and B 4 C prepared by sputtering techniques. Previous studies have shown that unprotected W/C multilayers annealed in air exhibit oxidation at relatively low temperatures (approximately 300 degree(s)C). In the present study, we have used Raman scattering (RS), Auger depth profiling and scanning electron microscopy (SEM) to investigate the effects of thermal treatments on the encapsulated W/C multilayers. The results indicate that oxidation of both W and C layers takes place during annealing at temperatures which depend on the type of protective layer. For example, in the isochronal annealing experiments, multilayers coated with C, Al 2 O 3 and B 4 C suffer oxidation during annealing at 400 degree(s)C, whereas multilayers coated with the other three types of protective films prevent multilayers from oxidation at annealing temperatures as high as 600 degree(s)C. SEM micrographs show that the formation of pinholes through the protective layer occurred during annealing at the temperatures for which oxidation was first detected. Auger profiling shows the loss of compositional modulation in the region reached by oxygen. A WO 3 phase is identified by RS in the oxidized region, and the loss of the C layers is most likely due to the formation of carbon oxide vapors.

Tungsten/carbon (W/C) multilayer thin films with a nominal d spacing varying from 2.5 to 14 nm were prepared by magnetron sputtering technique. The thicknesses of the W and C layers were varied from 0.5 to 12 nm. The multilayers were subjected to isochronal anneals in a quartz tube furnace in the range of 300 to 1000 C under high purity Ar flow conditions. X-ray diffraction, Raman scattering and Auger depth profiling were used to characterize the structure of the as-prepared and annealed films. It is found that an overcoat layer of silicon nitride (30-50 nm) prevents the multilayers from oxidation during the 1 hr heat treatment at temperatures as high as 1000 C in Ar flow. In all studied W/C multilayers, the carbon layers are amorphous (up to 12 nm). The tungsten layers are also amorphous when their thicknesses are less than 5 nm. Tungsten layers thicker than 5 nm show crystalline W peaks in addition to the amorphous W feature. Annealing of samples with a silicon nitride protective layer results in several structural changes which depend on annealing temperature, d spacing, the as-deposited W layer structure and the layer thickness ratio of W to C. For W layer thicker than C layer and W layer thickness > 4 nm and/or C layer thickness < 1 nm, the multilayers show the initial crystal formation of microcrystalline W2C occurring at C-W interfaces (that interface in which C was deposited on W) after 600 C anneal, followed by a second crystallization of a-W or a-W and WC at W-C interfaces (W was deposited on C) at the annealing temperature of 900 C. They reveal a relatively small (< 5 %) or essentially no layer expansion. For those multilayers having thin W layers (2 nm) and the same or thicker C layer thicknesses, the initial crystallization takes place at both W-C and C-W interfaces at 900 C or higher. The crystal formed is a-W or a-W and WC. The layer pair period of the multilayers in this group increases monotonically with increasing annealing temperature. Expansion is up to 16 % of the original d spacing and occurs in both W and C layers at approximately equal rates. The expansion in all multilayers is interpreted to be associated mainly with the structural ordering processes in the amorphous W and C layers.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bonded hydrogen and improves the material stability under light soaking. Our fluorinated amorphous silicon (a-Si:H:F) is made by if glow discharge at high deposition temperatures up to 430 C from a gas mixture of SiH4 or Si2H6 and F2. These a-Si:H:F films show much lower density of states in the light soaking saturated state than device quality a-Si:H prepared in the same deposition system. It is evident from our results that fluorine incorporated into the network at such high deposition temperature makes for a new configuration which minimizes dangling bonds and other defects.

The US Department of Energy is probably the best known body to have claimed that photovoltaic conversion devices cannot compete with fossil tuels or uranium until at the earliest 1986, or more likely 2000. Such statements are based on the known current technological problems of three types of silicon—single crystal, polycrystalline, and amorphous. With amorphous silicon the chief difficulty has been the high density of states (as explained by Taylor on p 672) which restricts the necessary current flow.

The crystallization properties of Te-Ge and Te-Ge-Sb alloys prepared by thermal evaporation were analyzed using various characterization techniques. Similar to previous results, our data for Te-Ge shows that alloys that deviate slightly from Te50Ge50 stoichiometry show drastically slower crystallization kinetics. Raman spectroscopy and x-ray diffraction show that alloys having non-stoichiometric atomic ratios phase separate during crystallization into a Te50Ge50 phase plus pure crystalline tellurium or germanium. It is this relatively slow process of phase segregation which limits the crystallization rate. Phase segregation during crystallization of non-stoichiometric Te-Ge can be eliminated by adding antimony to samples having a tellurium concentration of from 45 to 55 atomic percent over a wide range of Ge:Sb ratios. These alloys can have laser induced crystallization times of less than 50 nsec. The thermal crystallization temperature is reduced only slightly when antimony is substituted for germanium.

Photovoltaic devices based on amorphous alloys of silicon with H and/or F have recently generated substantial interest in the photovoltaic community and the larger solid state physics and electronics communities as well. These developments have been reviewed recently by D. Carlson of RCA Labs(1). It was Carlson’s early collaboration with C. Wronski(2) which served to rekindle scientific and technological interest in a-Si:H produced by the glow discharge induced decomposition of SiH4 gas and the deposition of Si-rich fragments of this gas onto substrates held at 200–300°C(3–5).

The problems of our modern society are directly related to materials. Depletable fossil fuels, shrinking silver supplies, the high cost of gold, platinum and other precious metals all are interfering with industrial growth and creating societal problems. The fossil fuels and uranium supply us with energy without which no society or civilization can endure. However, there is a tendency to focus only on the fuel aspects of materials and ignore the larger materials picture, that is, that materials such as platinum, palladium and iridium, which are the core of the catalytic and electrochemical industries, affect not only the generation but the use of energy in a dramatic fashion.

It is difficult to do justice to the scientific and technological impact of the recent discoveries in high Tc superconducting ceramic oxides. It is now clear that the oxides that were the basis of the lanthanum copper oxide ceramics which moved the superconducting temperature from 23 to 30 to 40K (1) have been around for some time.(2,3)

It is well known in crystalline tetrahedral semiconductors that conventional incorporation of atoms by substitutional doping increases the electrical conductivity by many orders of magnitude. Such doping is the basis of the crystalline semiconducting industry and has recently been extended to amorphous silicon and germanium, with hydrogen appearing to play an important compensating role.(1–3)

The hydrogen economy has already started with the introduction of the Ovonic nickel metal hydride battery, which has enabled the rapid growth of hybrid vehicles. Reversible storage of hydrogen in a solid hydride permits the entire loop of hydrogen generation, storage and use, all of which have been placed some time in the future. It is often stated that the hydrogen infrastructure does not exist and cannot be put in place. I will show that the hydrogen economy based upon hydrogen, the ultimate fuel, is practical, realistic and available near-term to our global society. The crisis regarding global warming, pollution, and wars over oil can be solved, at the same time building much needed basic new industries, providing higher value jobs feeding back into the educational system.

In this paper we extend our previous fluorination work presenting an unusual fluorination effect in growing device quality superconducting film directly on sapphire. The superiority of the film quality is attributed to the fact that fluorine plays a significant role in the control of nucleation and in the enhancement of the growth rate of the superconducting film in the basal plane, therefore, an “epitaxial” film is obtained. Furthermore, the high quality fluorinated film can be grown at a lower temperature. As a result, the grain boundary weak link effect and the interface diffusion between the superconducting film and the substrate are minimized. The superconducting film with a high critical current density and a very smooth surface is achieved. With our technique, we believe that device quality superconducting film could be grown not only on sapphire but on other flexible inexpensive continuous substrates for high field applications which could lead to a major technological advancement.

An electrochemical hydrogen storage material comprising: (Base Alloy)aMb where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca: b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a + b = 100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.

A positive electrode material comprising particles (1) including at least one electrochemically active hydroxide and a substantially continuous, uniform encapsulant layer (4) surrounding the particles of positive electrode material. The encapsulant layer is formed from a material which, upon oxidation during processing or charging of the electrode, is convertible to a highly conductive form and upon subsequent discharging of the electrode does not revert to its previous form. Preferably, the electrochemically active hydroxide includes at least nickel hydroxide. The encapsulant layer is preferably formed from at least cobalt hydroxide or cobalt oxyhydroxide and is formed by precipitation from a cobalt salt solution, which can be a cobalt sulfate solution. Electrodes which include the electrochemically active material as well as a precipitation process for forming the material are disclosed.

We have grown amorphous silicon-germanium alloys by rf glow discharge decomposition of disilane, germane, silicon tetrafluoride and hydrogen. Films with an optical band gap in the range of 1.72 to 1.2e V have been made. The optimized films show the following properties: 1) incorporation of germanium is uniform across the length of the sample; 2) hydrogen is bonded to silicon and germanium uniformly without any preference; 3) the slope of the valence band tail remains constant as the optical gap is lowered down to 1.25eV and 4) use of silicon tetrafluoride in the gas mixture improves the quality of the material. Photothermal deflection spectroscopy and space charge limited conduction were used to obtain information about the deep states. Even for the lowest band gap material, the density of states at the Fermi level is about 10 17 cm −3 eV −1 which demonstrates the high quality of the material.

Tellurium‐based alloys are being applied to phase‐change, reversible optical‐data storage. In order to improve the disk performances, research efforts have been concentrated on increasing the erase speed (crystallization rate) while maintaining good film stability. We report, for the first time, that certain transition‐metal elements added to Te‐alloy films can substantially improve the rate of crystallization without any reduction of the amorphous‐phase stability.

We have made a study of the resistivity, ρ(T), and the structural and superconducting properties of amorphous Mol-xSix Besides the usual interest in studying a metal to nonmetal transition, this system has the additional feature that Si changes from acting metallic for x << 1 to acting nonmetallic for x ~ 1. Murarka et al. (1) measured the resistivity of both amorphous and crystallized cosputtered films of MoSi and a comparison of their data with ours will be made below. We have observed a large increase in dρ(297)/dx with increasing x at x = x0 ≡ 0.63 ± 0.05 which is most likely associated with an electronic transition involving the Si valence electrons. A tentative model for this transition is presented below. Besides observing this increase in d ρ(297)/dx, the specific results pertinent to superconductivity are: 1. The initial linear decrease of the superconducting transition temperature T­c is 0.075 K/at.% Si. This is consistent with the e/a dependence found by Collver and Hammond (2) for near neighbor amorphous 4d metals if one assumes that each Si atom contributes 4 electrons to the conduction band. 2. Supperconductivity persists up to at least 64 at.% i.e., slightly into the concentration region where the resistivity begins to increase. As x→xo ­from below, the superconducting transition width ΔT­c increases rapidly until at x ≃ xo the width ΔTc becomes comparable to Rc. 3. For x > xo, Tc, if it exists, is less than 1.5K.

A NEW TYPE of amorphous semiconductor alloy has recently been reported [1]. This new material has silicon and fluorine as its main structural components. It is multi-elemental and includes hydrogen and can also include other elements such as oxygen without deleterious effects. This Si: F: H alloy, prepared by the glow-discharge decomposition of SiF4 mixed with hydrogen, has been reported to overcome a number of problems of a-Si and a-Si: H. The a-Si: F: H alloy is highly photoconductive, possesses a lower density of states in the upper half of the band gap than the a-Si: H alloy and is devoid of any photostructural changes. In order to gain further information about the electronic and vibrational states of this amorphous semiconductor, we have investigated the electrolyte electroreflectance (EER) and Raman spectra of several samples of this material.

We are impressed with the ease and certainty of calibration electronic thermometers with thermistor probes to +/- 0.01 degree C at the gallium melting point, 29.771(4) degrees C. The IFCC reference method for measuring aspartate aminotransferase activity in serum was run at the reaction temperature of 29.771(4) degrees C. By constantly referencing to gallium as an integral part of the assay procedure, we determined the absolute reaction temperature to IPTS-68 (International Practical Temperature Scale of 1968) to +/- 0.02 degrees C. This unique temperature calibration standard near the center of the range of temperatures commonly used in the clinical laboratory is a valuable addition and can be expected to improve the accuracy of measurements, especially in clinical enzymology.

Photovoltaic quality films of a-Si:F:H prepared by the plasma-induced reaction of, for example, SiF4 and H2 appear to contain unusual bonding configurations involving the intimate association of silicon with both fluorine and hydrogen atoms.(1) The creation of radical sub-fluorides of silicon has been suggested as a mechanism for the deposition of such films.(2) Indeed, the presence of various excited-state neutral and ionic silicon radical species has been demonstrated in the optical emission of plasmas containing SiH4, SiF4 and H2,(3,4) and the silylene radical, SiH2, has been proposed to play a dominant role in the deposition of a-Si:H from the H0M0CVD of SiH4.(5)

We describe here a rapid and reversible transition between a highly resistive and a conductive state effected by an electric field which we have observed in various types of disordered materials, particularly amorphous semiconductors1,2 covering a wide range of compositions. These include oxide- and boron-based glasses and materials which contain the elements tellurium and/or arsenic combined with other elements such as those of groups III, IV, and VI.

The accomplishment of high-temperature superconductivity is of immense scientific and technological importance. Several critical transition-temperature barriers have recently been breached since the long-standing record temperature of 23.2 K for Nb3Ge was exceeded. The most important milestones were the announcement of T c ≈ 30 K in lanthanum barium copper oxide by Bed-norz and Muller,1 whose work was based upon materials developed by Michel and Raveau,2 and the work of Chu, Wu, and others,3 based upon the replacement of lanthanum by yttrium, which resulted in superconductivity at temperatures of approximately 95 K.

The need for continuous monitoring of species like H/sub 2/S and CH/sub 3/SH in the atmosphere is obvious because of their toxic nature and is particularly important in synfuel production and geothermal energy utilization. Chemiluminescence under the right conditions is an extremely sensitive method, with the possibility of obtaining one photon for each molecule of interest. It is apparent that a selective detector should be based on emission from a species related chemically to the analyte rather than the reagent. ClO/sub 2/ is an interesting reagent in that it reacts, vide infra, with H/sub 2/S and CH/sub 3/SH to produce sulfur atoms, which recombine to form electronically excited S/sub 2/ and in turn result in fluorescence. To minimize the effects of quenching, one must keep the reaction zone at reduced pressures. To maximize sensitivity despite the high-order reaction, one must keep the volume of the reaction zone small, and the reagent gas (ClO/sub 2/) must be in excess to produce complete reaction in a pseudo-first-order regime. A successful on-line chemiluminescence detector is therefore dependent on meeting these various design parameters and is reported here.

We have developed an amorphous silicon alloy based solar cell with a novel structure in which the optical gap of the intrinsic layer changes in a substantial portion of the bulk. Computer simulation studies show that for a given short circuit current, it is possible with this structure to obtain higher open circuit voltage and fill factor than in a conventional cell design. Experimental cell structures have been made and confirm the theoretical prediction. The new cell design shows a considerable improvement in efficiency. Incorporation of this structure in the bottom cell of a triple device has resulted in the achievement of 13.7% efficiency under global AM1.5 illumination.

A process is described which provides a simple, automatic means for quickly reducing the deleterious effects of shunts in completed thin‐film solar cells. The method has been used to passivate current shunting defects in large area, mass produced solar cells made from amorphous silicon alloys. In the passivation process, photovoltaic devices are exposed to an electrochemical bath which selectively converts the top surface conducting oxide to a lesser conducting state at the vicinity of shunts. The process and its utility in repairing defects will be described.

We have used molecular-beam deposition (MBD) with a base pressure of 10–10 torr to prepare a-Si and a-Ge at relatively low substrate temperatures. The films contain voids which can adsorb gases such as H2, F2, SiF4, GeF4, O2, etc. Due to the high reactivity of the dangling bonds present, these molecules are broken down to their atomic constituents, thereby passivating the dangling bonds. Further annealing is required to form proper chemisorption and drive the passivating agents into smaller or isolated voids. Typically a decrease of dark conductivity by as much as 8 orders of magnitude is observed accompanied by the appearance of few decades of photocurrent above the dark current under (Air Mass 1) AM1. For a-Ge, using a similar procedure, fluorine is more effective as a passivating agent than hydrogen.

Tellurium-based chalcogenide alloys, which are used for electronic switch materials, also have the appropriate optical and thermal properties for reversible optical data recording. One of the major concerns encountered with this type of phase change material is that there can be two contradictory characteristics of the material, i.e., the amorphous phase thermal stability and the crystallization rate are involved. We have demonstrated, in this paper, that this problem can be solved. We report that certain transition metal elements added to Te alloy films can substantially improve the rate of crystallization without any reduction of the amorphous phase stability.

Fluorine substitution for oxygen in the high Tc superconducting ceramic oxides is not only fundamentally but also technologically interesting. We have previously reported the observation of superconducting zero resistance transition at 155–168K, subsequently confirmed by several other groups. We have also observed diamagnetic signals and flux trapping at temperatures as high as 305K. The samples were made from solid-state reaction in a pressed pellet form. Because of the BaF2 formation and the small volume fraction, we have not yet been able to identify the specific high Tc phases.In the course of elucidating and optimizing the fluorination effect, we have carried out other means of low-temperature fluorination experiments. The zero resistance at 154K was repeated.In addition to the observation of these high 1c results, we found that a dopant amount of fluorine promotes the oriented crystal growth. We also found that the replacement of weakly bonded oxygen by fluorine can greatly enhance the material's stability by eliminating the serious problem of oxygen diffusion.

A manufacturing plant for producing thin-film amorphous silicon alloy based solar cells using roll-to-toll deposition is being operated by Sovonics Solar Systems in Troy, Michigan, USA. The authors detail the performance of solar cells produced at this plant. Roll-to-roll deposition on stainless steel has been shown to be a viable method of producing high-quality thin-film solar cell materials. Various thin-film depositions are made on 1000-foot-long rolls of 14-inch-wide, thin stainless steel in the deposition facility. The rolls are then cut into appropriate sizes for module fabrication. Quality analysis, in situ deposition monitoring, and post deposition measurements have enabled a detailed analysis of production run data, including such parameters as layer thickness, adhesion, conversion efficiency, yield, etc. These and other properties of the photovoltaic materials and devices have been monitored and studied in order to optimize the roll-to-roll deposition process. >

The authors have developed an amorphous silicon alloy-based solar cell with a novel structure. Computer simulation studies show that for a given short-circuit current, it is possible to obtain a higher open-circuit voltage and fill factor than in a conventional cell design. For a nominal 1.5 eV a-SiGe alloy, the fill factor under red illumination can be improved from 0.55 to 0.64 for the same short-circuit current. Experimental cell structures confirm the theoretical prediction. The novel cell design shows a considerable improvement in efficiency. Dynamic internal collection efficiency measurements show reduced recombination in these cells, which gives rise to the observed higher fill factors. Incorporation of this structure in the bottom cell of a triple device has resulted in the achievement of 13.7% efficiency under global AM1.5 illumination. >

The solid-state revolution, which began in 1947 with the invention of the transistor, was made possible by the ability to make crystalline materials (at that time germanium) sufficiently free of defects that substitutional dopants could overcome the background noise of other defects and control the electronic transport properties of the semiconductor. Since the early 1930’s Bloch, Wilson, and others had laid a sufficient theoretical groundwork in semiconductors so that transistor action could be predicted, demonstrated, and understood even though the point contact transistor had many mysteries associated with it. Figure 1 shows that historical lever that moved the world, the first transistor.