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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

XPS Study of Thermally Evaporated Ge-Sb-Te Amorphous Thin Films

Amorphous thin films were prepared from the bulk composition of Ge{sub 22}Sb{sub 22}Te{sub 56}(GST) alloy by thermal evaporation in good vacuum condition. The amorphous nature of as-deposited films was checked with x-ray diffraction (XRD) studies. X-ray photoelectron spectroscopy (XPS) has been used to determine the binding energies of the core electrons in amorphous thin GST films. In XPS, we performed the survey scan from the binding energy (BE) range from 0-1100 eV and core level spectra of Ge 3d, Sb 3d and Te 3d.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Controlling Dopant Profiles in Hyperdoped Silicon by Modifying Dopant Evaporation Rates During Pulsed Laser Melting

We describe a method to control the sub-surface dopant profile in 'hyperdoped' silicon fabricated by ion implantation and pulsed laser melting. Dipping silicon ion implanted with sulfur into hydrofluoric acid prior to nanosecond pulsed laser melting leads to a tenfold increase in the rate of sulfur evaporation from the surface of the melt. This results in an 80% reduction of the near-surface dopant concentration, effectively embedding the hyperdoped region in a layer up to 180 nm beneath the surface. This method should facilitate the development of blocked impurity band devices.

14 SOLAR ENERGY↗
DOE OSTI2012

Characterization of GaN nanowires grown on PSi, PZnO and PGaN on Si (111) substrates by thermal evaporation

In this research, we used an easy and inexpensive method to synthesize highly crystalline GaN nanowires (NWs); on different substrates such as porous silicon (PSi), porous zinc oxide (PZnO) and porous gallium nitride (PGaN) on Si (111) wafer by thermal evaporation using commercial GaN powder without any catalyst. Micro structural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of different substrates in the morphology, nucleation and alignment of the GaN nanowires. The degree of alignment of the synthesized nanowires does not depend on the lattice mismatch between wires and their substrates. Further structural and optical characterizations were performed using high resolution X-ray diffraction and energy-dispersive X-ray spectroscopy. Results indicate that the nanowires are of single-crystal hexagonal GaN. The quality and density of grown GaN nanowires for different substrates are highly dependent on the lattice mismatch between the nanowires and their substrates and also on the size of the porosity of the substrates. Nanowires grown on PGaN have the best quality and highest density as compared to nanowires on other substrates. By using three kinds of porous substrates, we are able to study the increase in the alignment and density of the nanowires.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Growth study of ion assisted evaporated molybdenum thin films

We reported optimization of ion-to-atom ratios and ion energy for growth of molybdenum thin film on oxidized silicon substrate using ion assisted electron beam evaporation system. The ion-to-atom ratio is varied by independently adjusting the ion current density and deposition rate. The structural characterization of the films is carried out by hard X-ray reflectivity. We observed improvement in film density from 85.5% to 98.2% and film roughness from {approx}2 nm to 0.84nm on {approx}26 nm thick Mo film by optimizing ion parameters. The observed results are discussed considering the effect of kinetic of adatoms during growth of film.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Synthesis, structural and electrochemical properties of electron beam evaporated V{sub 2}O{sub 5} thin films

Vanadium pentoxide is one of the most promising cathode materials because it offers high energy density, low cost, low toxicity over the other cathode materials. Its layered and open structure makes this material in thin film form well suited for electro-chemical insertion reactions with the Li ions. In the present investigation, V{sub 2}O{sub 5} thin films have been prepared by electron beam evaporation technique on gold coated silicon substrates maintained at a substrate temperature of 250 Degree-Sign C in an oxygen partial pressure of 2 Multiplication-Sign 10{sup -4} mbar. The XRD patterns exhibited three predominant diffraction peaks corresponding to (200) (001) and (400) planes of orthorhombic phase of V{sub 2}O{sub 5} with P{sub mnm} space group. The electrochemical characteristics of V{sub 2}O{sub 5} thin films with thickness of 600 nm were examined in non-aqueous region. The film exhibited step wise discharge with two plateaus. The as-deposited film delivered a discharge capacity of 70 {mu}Ah/(cm{sup 2}-{mu}m) at a current density of 30 {mu}A/cm{sup 2}. Annealing of these films at 450 Degree-Sign C exhibited a better discharge capacity of 90 {mu}Ah/(cm{sup 2}-{mu}m).

36 MATERIALS SCIENCE↗
DOE OSTI2013

Catalyst free growth of ZnO nanorods by thermal evaporation method

In this work, we report catalyst free growth of ZnO nanorods on n-Si substrate by a low cost thermal evaporation method. The surface morphology, chemical composition and crystalline structure of ZnO nanorods have been determined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) spectroscopy respectively. It is found that, the as -deposited ZnO seed layer reduces lattice mismatching between ZnO and Si from 40.3 to 0.28%, therefore enhances the subsequent growth and crystalline quality of ZnO nanorods on Si substrate. The present methodology is simple, cost effective and highly applicable for synthesis of ZnO nanorods for optoelectronics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Progress of a room temperature electron cyclotron resonance ion source using evaporative cooling technology at Institute of Modern Physics

A new room temperature ECR ion source, Lanzhou Electron Cyclotron Resonance ion source No. 4 (LECR4, previously named DRAGON), is under intense construction at Institute of Modern Physics. LECR4 is designed to operate with 18 GHz microwave frequency. The maximum axial magnetic fields are 2.3 T at injection and 1.3 T at extraction, and the radial field at the plasma chamber wall of 76 mm inner diameter is 1.0–1.2 T. One of the unique features for LECR4 is that its axial solenoids are winded with solid square copper wires which are immersed in a kind of special evaporative cooling medium for cooling purpose. Till now, a prototype of the cooling system has been successfully constructed and tested, which has demonstrated that the cooling efficiency of the designed system could meet the requirements of LECR4 under the routine operation conditions. All the main components of the ion source have been completed. Assembly and commissioning is ongoing. The latest developments and test results will be presented in this paper.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Imaging the condensation and evaporation of molecularly thin ethanol films with surface forces apparatus

A new method for imaging condensation and evaporation of molecularly thin ethanol films is reported. It is found that the first adsorbed layer of ethanol film on mica surface behaves as solid like structure that cannot flow freely. With the increase of exposure time, more ethanol molecules condense over the mica surface in the saturated ethanol vapor condition. The first layer of adsorbed ethanol film is about 3.8 Å thick measured from the surface forces apparatus, which is believed to be the average diameter of ethanol molecules while they are confined in between two atomically smooth mica surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Study of CeI{sub 3} evaporation in the presence of group 13 metal-iodides

The influences of GaI{sub 3}, InI, and TlI on the evaporation characteristics of CeI{sub 3} have been studied over the temperature range 900 K to 1400 K using x-ray induced fluorescence. The total vapor densities, summed over all atomic and molecular species, of Ce, I, In, and Tl were obtained. Measurements of Ce were limited to temperatures above 1033 K, the melting temperature of CeI{sub 3}. This is the highest temperature range for which measurements of the vapor pressure of CeI{sub 3} have been made. The vapor pressure of the CeI{sub 3} monomer above the pure CeI{sub 3} salt for temperatures exceeding its melting point can be approximated by log{sub 10}p/Pa=11.24(±0.03)−10,690(±40) (T/K){sup −1} where the numbers in parentheses are standard uncertainties. InI and TlI were shown to modestly enhance the presence of Ce in the vapor phase, up to a factor of 5. GaI{sub 3} produced no enhancement in this temperature range. Numerical simulations of the thermochemical equilibrium suggest the importance of both liquid-phase and vapor-phase complexes. Significant improvement to the method of absolute calibration is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Effect of argon gas flow rate on properties of film electrodes prepared by thermal vacuum evaporation from synthesized Cu{sub 2}SnSe{sub 3} source

This work describes a new technique to enhance photoresponse of metal chalcogenide-based semiconductor film electrodes deposited by thermal vacuum evaporation under argon gas flow from synthesized Cu{sub 2}SnSe{sub 3} sources. SnSe formation with Cu-doped was obtained under higher argon gas flow rate (V{sub A} = 25 cm{sup 3}/min). Higher value of photoresponse was observed for films deposited under V{sub A} = 25 cm{sup 3}/min which was 9.1%. This finding indicates that Cu atoms inside the SnSe film were important to increase carrier concentrations that promote higher photoresponse.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structural, compositional and morphological studies of thermally evaporated MoO{sub 3} thin films

Molybdenum oxide (MoO{sub 3}) nanostructures were grown on different substrates such as glass, indium tin oxide coated glass and fluorine doped glass by thermal evaporation of MoO{sub 3} powder at elevated temperature (750°C) using tube furnace without any catalyst and then by subsequent O{sub 2}/Ar flow rate. The morphology, composition and crystal structure were examined by using SEM, EDAX, Laser Raman and XRD. The films are polycrystalline with well-defined diffraction peaks and it consist of MoO{sub 3} with α-orthorhombic structure. The synthesized MoO{sub 3} belongs to different morphologies, generally nanobelt and nanohunk structures. The EDAX spectra confirm the films are composed only of Mo and O atoms. The O/Mo ratio is nearly equal to 3 that shows the stoichiometry of MoO{sub 3}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Structural and optical properties of Sn{sub 1−x}Fe{sub x}O{sub 2} thin films prepared by flash evaporation technique

Sn{sub 1−x}Fe{sub X}O{sub 2} (x = 0, 0.05) thin films were prepared on glass substrate using the flash evaporation technique. The samples were annealed at 773 K for 2 hrs in air atmosphere. A systematic study was carried out on the structural and optical properties of the as deposited and annealed thin films. From the X-ray diffraction analysis it was found that the Sn{sub 1−x}Fe{sub X}O{sub 2} films deposited at 623 K were amorphous in nature and the Sn{sub 1−x}Fe{sub X}O{sub 2} films annealed at 773 K exhibited the tetragonal structure of the SnO{sub 2}. The optical band gap of the SnO{sub 2} thin films was found to be as 3.17 eV whereas the optical band gap of the Sn{sub 1−x}Fe{sub X}O{sub 2} films was found to be as 3.01 eV after air annealing.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Effect of deposition temperature on electron-beam evaporated polycrystalline silicon thin-film and crystallized by diode laser

The effects of the deposition temperature on the microstructure, crystallographic orientation, and electrical properties of a 10-μm thick evaporated Si thin-film deposited on glass and crystallized using a diode laser, are investigated. The crystallization of the Si thin-film is initiated at a deposition temperature between 450 and 550 °C, and the predominant (110) orientation in the normal direction is found. Pole figure maps confirm that all films have a fiber texture and that it becomes stronger with increasing deposition temperature. Diode laser crystallization is performed, resulting in the formation of lateral grains along the laser scan direction. The laser power required to form lateral grains is higher in case of films deposited below 450 °C for all scan speeds. Pole figure maps show 75% occupancies of the (110) orientation in the normal direction when the laser crystallized film is deposited above 550 °C. A higher density of grain boundaries is obtained when the laser crystallized film is deposited below 450 °C, which limits the solar cell performance by n = 2 recombination, and a performance degradation is expected due to severe shunting.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Physical properties of electron beam evaporated CdTe and CdTe:Cu thin films

In this paper, we report on physical properties of pure and Cu doped cadmium telluride (CdTe) films deposited onto corning 7059 microscopic glass substrates by electron beam evaporation technique. X-ray diffraction study showed that all the deposited films belong to amorphous nature. The average transmittance of the films is varied between 77% and 90%. The optical energy band gap of pure CdTe film is 1.57 eV and it decreased to 1.47 eV upon 4 wt. % of Cu addition, which may be due to the extension of localized states in the band structure. The refractive index of the films was calculated using Swanepoel method. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (E{sub d}) parameters, dielectric constants, plasma frequency, and oscillator energy (E{sub o}) of CdTe and CdTe:Cu films were calculated and discussed in detail with the light of possible mechanisms underlying the phenomena. The variation in intensity of photoluminescence band edge emission peak observed at 820 nm with Cu dopant is due to the change in surface state density. The observed trigonal lattice of Te peaks in the micro-Raman spectra confirms the p-type conductive nature of films, which was further corroborated by the Hall effect measurement. The lowest resistivity of 6.61 × 10{sup 4} Ω cm was obtained for the CdTe:Cu (3 wt. %) film.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

The development of a room temperature electron cyclotron resonance ion source (Lanzhou electron cyclotron resonance ion source No. 4) with evaporative cooling technology at Institute of Modern Physics

LECR4 (Lanzhou electron cyclotron resonance ion source No. 4) has been successfully constructed at IMP and has also been connected with the Low Energy Beam Transport (LEBT) and Radio Frequency Quadrupole (RFQ) systems. These source magnet coils are cooled through evaporative cooling technology, which is the first attempt with an ECR ion source in the world. The maximum mirror field is 2.5 T (with iron plug) and the effective plasma chamber volume is 1.2 l. It was designed to be operated at 18 GHz and aimed to produce intense multiple charge state heavy ion beams for the linear injector project SSC-Linac at IMP. In February 2014, the first analyzed beam at 18 GHz was extracted. During about three months’ commissioning, some outstanding results have been achieved, such as 1.97 emA of O{sup 6+}, 1.7 emA of Ar{sup 8+}, 1.07 emA of Ar{sup 9+}, and 118 euA of Bi{sup 28+}. The source has also successfully delivered O{sup 5+} and Ar{sup 8+} ion beams for RFQ commissioning in April 2014. This paper will give a brief overview of the design of LECR4. Then, the latest results of this source at 18 GHz will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Structure and magnetic properties of Fe doped In{sub 2}O{sub 3} thin films prepared by electron beam evaporation

Pure and Fe (7 at.%) doped In{sub 2}O{sub 3} thin films were grown onto the glass substrates by electron beam evaporation technique. The structural and magnetic properties of the pure and Fe doped In{sub 2}O{sub 3} thin films have been studied. The undoped and Fe doped In{sub 2}O{sub 3} thin films shown ferromagnetic property at room temperature. A magnetization of 24 emu/cm{sup 3} was observed for pure In{sub 2}O{sub 3} thin films. The magnetization of 38.23 emu/cm{sup 3} was observed for the Fe (7 at.%) doped In{sub 2}O{sub 3} thin films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

High intensity high charge state ion beam production with an evaporative cooling magnet ECRIS

LECR4 (Lanzhou ECR ion source No. 4) is a room temperature electron cyclotron resonance ion source, designed to produce high current, high charge state ion beams for the SSC-LINAC injector (a new injector for sector separated cyclotron) at the Institute of Modern Physics. LECR4 also serves as a PoP machine for the application of evaporative cooling technology in accelerator field. To achieve those goals, LECR4 ECR ion source has been optimized for the operation at 18 GHz. During 2014, LECR4 ion source was commissioned at 18 GHz microwave of 1.6 kW. To further study the influence of injection stage to the production of medium and high charge state ion beams, in March 2015, the injection stage with pumping system was installed, and some optimum results were produced, such as 560 eμA of O{sup 7+}, 620 eμA of Ar{sup 11+}, 430 eμA of Ar{sup 12+}, 430 eμA of Xe{sup 20+}, and so on. The comparison will be discussed in the paper.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Interface electronic properties of co-evaporated MAPbI{sub 3} on ZnO(0001): In situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy study

In this work, the interface electronic properties of ZnO(0001)/CH{sub 3}NH{sub 3}PbI{sub 3} were investigated by both X-ray and ultraviolet photoelectron spectroscopy. The CH{sub 3}NH{sub 3}PbI{sub 3} thin films were grown on single crystalline ZnO(0001) substrate in situ by co-evaporation of PbI{sub 2} and CH{sub 3}NH{sub 3}I at room temperature with various thickness from 1.5 nm to 190 nm. It was found that the conduction band minimum of ZnO lies 0.3 eV below that of CH{sub 3}NH{sub 3}PbI{sub 3}, while the valence band maximum of ZnO lies 2.1 eV below that of CH{sub 3}NH{sub 3}PbI{sub 3}, implying that the electrons can be effectively transported from CH{sub 3}NH{sub 3}PbI{sub 3} to ZnO, and the holes can be blocked in the same time. A PbI{sub 2} rich layer was initially formed at the interface of ZnO(0001)/CH{sub 3}NH{sub 3}PbI{sub 3} during the growth. As a consequence, an interface barrier was built up which may prevent the electron transport at the interface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗