摘要 :
In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indic...
展开
In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indicate ordering of the solutions at compositions corresponding to about 12, 50, and 67 atom% of alkali atoms. The electrical conductivity and thermopower data confirm that these liquids are true semiconductors. The neutron diffraction patterns coupled with the above information indicate that in the case of liquid K(sub 0.12)Te(sub 0.88) the measured structure is dominated by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium, while the equiatomic alloy K(sub 0.50)Te(sub 0.50) is shown to contain mostly Te pairs which are identified with Zintl ions, Te(sub 2)(sup 2(minus)).
收起
摘要 :
A model has been developed for the ohmic low-resistivity Ni contact to p-CdTe etched by K2Cr2O7:H2SO4:H2O,which involves the formation of a thin layer of Te at the surface,followed by diffusion of the Te into the CdTe upon heat tr...
展开
A model has been developed for the ohmic low-resistivity Ni contact to p-CdTe etched by K2Cr2O7:H2SO4:H2O,which involves the formation of a thin layer of Te at the surface,followed by diffusion of the Te into the CdTe upon heat treatment to form a p(+) layer. Auger analysis supports this model,showing an abrupt junction between Ni and p-CdTe when ohmic,and formation of tellurides when non-ohmic because of over-heating. Fabrication of transparent conducting films has been initiated with application to the CdS film as the intended goal. The high vacuum evaporator is ready to be used for evaporation of CdS and CdTe films. Three cells of p-ZnTe/n-CdSe have been prepared by CSVT deposition of CdSe,indicating a quantum efficiency possible of at least 0.5.
收起
摘要 :
Spectrophotometric methods for the analysis of gallium arsenide and bismuth telluride for their major elements, with a precision suitable for stoichiometry studies are developed. Utilizing the EDTA complex, bismuth is determined b...
展开
Spectrophotometric methods for the analysis of gallium arsenide and bismuth telluride for their major elements, with a precision suitable for stoichiometry studies are developed. Utilizing the EDTA complex, bismuth is determined by direct differential spectrophotometry with a precision (standard deviation) of better than one part per thousand of the amount present. Arsenic, tellurium, and gallium are determined by the technique of indirect spectrophotometry, with a precision in the low parts per ten thousand range. Potassium dichromate is used as the reagent for arsenic and tellurium; gallium is determined by EDTA in the presence of copper. Analyses are presented on synthetic and actual samples of the compounds, including total analyses of gallium arsenide prepared under various arsenic pressures. Some gallium arsenide samples are very close to theoretical in composition, while one sample made under excess arsenic pressure shows an excess of this element in the main body of the ingot. Segregation of the elements in the tail sections of the ingots is evident. Republic suggests that methods for the analysis of gallium arsenide be utilized to see if a correlation can be established between major composition and electronic properties such as laser action. The technique of indirect precision spectrophotometry should also be applied to other electronic material systems. (Author)
收起
摘要 :
Reflection spectra were recorded on selected thin film materials from 2.5micrometers to 17.0micrometers using light polarized parallel to the plane of incidence. The materials were CdS,CdSe,CdTe,Ge,ZnS,ZnSe,and ZnTe vacuum evapora...
展开
Reflection spectra were recorded on selected thin film materials from 2.5micrometers to 17.0micrometers using light polarized parallel to the plane of incidence. The materials were CdS,CdSe,CdTe,Ge,ZnS,ZnSe,and ZnTe vacuum evaporated onto KCl substrates. The spectra were analyzed using two different techniques: (1) The Fresnel reflection coefficients were applied to a three media model,where the second medium had an extinction coefficient,and (2) an index of refraction was computed from the interference fringes of the spectra. The interference-fringe analysis indicates that the index of refraction of the thin film coatings is approximately the same as that of the bulk material in the 10.0micrometer region,except for CdS. (Author)
收起
摘要 :
In order to better prepare coatings for infrared laser windows, a program has been initiated to thoroughly study the science and technology of the deposition of inorganic elements and compounds as thin films. Deposition techniques...
展开
In order to better prepare coatings for infrared laser windows, a program has been initiated to thoroughly study the science and technology of the deposition of inorganic elements and compounds as thin films. Deposition techniques include sputtering,PVD,and CVD;characterization techniques include ellipsometry,SEM, x-ray emission analysis,IR and Raman spectroscopy,ISS,AES,SIMS,and strain measurements. Extensive theoretical calculations by Loomis have shown that effective coatings with the requisite optical properties can be prepared using two-layer films of the appropriate materials and thicknesses. Germanium can be used as the first layer on KCl,ZnSe and CdTe window materials,the second layer can be chosen (theoretically) from a number of other materials. Since this laboratory has extensive experience in the controlled deposition of germanium films,efforts are being concentrated on using this material as the first layer film. (Modified author abstract)
收起
摘要 :
The results reported here represent significant advances in the state of the art of high-power laser windows and coatings. An order-of-magnitude improvement was achieved in the material parameters of single crystal KCl over the va...
展开
The results reported here represent significant advances in the state of the art of high-power laser windows and coatings. An order-of-magnitude improvement was achieved in the material parameters of single crystal KCl over the values which characterized the best available materials at the beginning of the study. The RAP technique,involving processing under an atmosphere of He + CCl4,was used for window materials purification,crystal growth,and for surface layer exchange in KCl crystals. It led to the development of a one-step processing for KCl crystal growth,from powder to crystal,which minimizes the incorporation of OH(-) in the KCl crystals. Optical,mechanical,and surface stability evaluations of various fluoride and chloride crystals are also reported. The coating program goal,which was to achieve 0.1% or less absorption per coated window surface at 10.6micrometers,has been demonstrated for some of the optical coatings prepared during the program. Theoretical designs and experimental results for coatings for alkali halides,zinc selenide,and cadmium telluride are presented with emphasis placed on coatings for KCl. (Modified author abstract)
收起
摘要 :
Contents: Epitaxial growth of semi-insulating GaAs from Ga solutions; Optimization of alkali halide window materials; Fabrication of polycrystalline IR window materials; Mechanical behavior and dielectric constant measurements; St...
展开
Contents: Epitaxial growth of semi-insulating GaAs from Ga solutions; Optimization of alkali halide window materials; Fabrication of polycrystalline IR window materials; Mechanical behavior and dielectric constant measurements; Study of defects in CdTe; Theoretical studies of absorption mechanism in IR window materials; Wavelength and temperature dependent calorimetry measurements on GaAs; Alkali halide (KCl) surface studies with acoustic probe techniques; Absorption studies of CdTe and ZnSe; Characterization of optical performance of IR window systems; Initial investigation of the role of inclusion damage in the failure of 10.6 micrometer optics.
收起
摘要 :
The temperature dependence of the 10micrometer absorption of GaAs in air shows contributions by free carriers above 250C,and surface effects due to oxidation. The dielectric constant of GaAs is found to be 12.4plus or minus 0.12. ...
展开
The temperature dependence of the 10micrometer absorption of GaAs in air shows contributions by free carriers above 250C,and surface effects due to oxidation. The dielectric constant of GaAs is found to be 12.4plus or minus 0.12. An accurate method to determine the oxygen content of GaAs has been developed. Results obtained so far given 10to the 17power - 10to the 18th power/cc or 6 x 10to the 14th power O atoms per sqcm surface. Conditions favorable to the growth of thick layer GaAs have been established. Pure KCl has K approximately = 10to the minus 4th power/cm. KBr has been purified and crystals have been grown. Analysis of the defect structure of CdTe was completed. Experimental conditions leading to high resistivity,stoichiometric material were established. Hot pressing of CdTe was started. The fundamental processes underlying multiphonon absoroption were investigated. A caustic surface analysis for thermal lensing was made,and the stress and the stress fields in non-uniformly stresses windows were determined. (Modified author abstract)
收起
摘要 :
Advances were made in the theory of multiple phonon absorption mechanisms,the theory of thermal skewing of asymmetric beams,and in the experimental characterization of IR window materials. Preliminary calorimetric measurements of ...
展开
Advances were made in the theory of multiple phonon absorption mechanisms,the theory of thermal skewing of asymmetric beams,and in the experimental characterization of IR window materials. Preliminary calorimetric measurements of the absorption coefficient in melt grown chromium-free GaAs versus wavelength yield values lower than any previously measured in chromium doped samples. The results of measurements of the mechanical properties of GaAs,and data related to the defect chemistry of CdTe and CdS are also reported. Systems for the production of ultra pure alkali halide and III-V compounds are nearing completion. (Author)
收起
摘要 :
This report describes progress on a program to characterize laser induced damage in CdTe,ZnSe and KCl and to identify the role of microstructural defects in altering infrared transmission of laser windows and optical coatings.
