Selective etching of habit faces of ferroelectric Ca2Sr(C2H5CO2)6 crystals

Crystallographically oriented etch traces produced by selective etchant on (111) and (110) habit faces of dicalcium strontium propionate [Ca₂Sr(C₂H₅CO₂)₆] crystals are attributed to the growth traces nucleated during the superficial growth of crystal. This view is supported by the absence of such etch traces on seized habit faces and from the observations of layer structure on the bottom faces. Mother liquid acting as an etchant produces circular terraced depressions on habit faces. These depressions originate at the sites of isolated impurity centres. Identical features such as circular etch structures bounded by cylindrical outer periphery produced on cooled faces are attributed to isolated domains.     

Gallium distribution and electrical activation in Ga+-implanted Si

Gallium distribution profiles in Ga⁺-implanted silicon have been measured by secondary ion mass spectrometry (SIMS) and differential Hall effect methods. The previously reported penetrating tails are not observed for as-implanted samples. The redistribution of Ga during annealing is affected by ion damage and effects due to recrystallization of the amorphous layer. Electrical carrier profiles indicate that carrier concentration higher than the usual Ga solid solubility can be achieved in Ga-implanted Si recrystallized at 600‡C. However, this large acceptor concentration diminishes after higher temperature annealing. For 900‡C anneals, the carrier concentration is limited by the Ga solid solubility and some compensation due to unannealed ion damage. Work Supported by the Joint Service Electronics Program (U.S. Army, U.S. Navy, U.S. Air Force) under Contracts DAAB-07-72-C-0259 and DAAG-16-78-C-0016, and by the National Science Foundation under Grants DMR-77-22228, DMR-76-01058, and CHE-76-03694.     

Sharp line emission spectra from GaAs FET like structures

Magneto-optical analysis of prominent photoluminescence lines from GaAs FET structures has been performed. Fifteen samples were investigated. Each consisted of a sulfur doped active layer on a high resistivity buffer layer (both epitaxially grown films) on a chromium doped GaAs substrate. The active layers were generally 2μm thick or less, except for two thicker layers (4 and 5μm) grown especially for this study. Buffer layer thicknesses ranged from 1.5 to 26μm. A model based on carrier diffusion through the active layer has been used to interpret the spectra as originating from the active-buffer interface region. All spectra contain strong-evidence of two donorbound exciton complexes associated with sulfur (1.51417eV) and silicon (1.51412eV). Other sharp spectral features included up to six lines associated with more complicated complexes. Linear Zeeman and quadratic diamagnetic behavior of the lines in applied magnetic fields are discussed. Supported under AF Contract F33615-77-C-5003 Supported under AF Contract F33615-76-C-1207     

The effective frequency band for free-field measurements under laboratory hydroacoustic tank conditions

The principle of free-field measurements under continuous radiation conditions, based on the use of the properties of the transfer function of a hydroacoustic tank, is analyzed. The radiator can excite signals with a complex spectrum and harmonic signals. The effect of reflections is eliminated by complex averaging of the frequency dependence of the transfer impedance of the converters. The result of these measurements is the value of the free-field transfer impedance, averaged over the effective frequency band of the measuring tank. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 46–51, November, 2006.     

Bekum吹塑机液压故障分析

分析了Bekum吹塑机液压故障的原因。提出相应的解决办法，指出杂质是产生液压故障的主要原因。     

锚杆钢带在顺槽支护中的应用

介绍了锚杆钢带支护效果技术及经济分析。     

纤维素三硝酸酯的能带和电子结构

用推广的Hückel紧束缚（即晶体EH）法计算了纤维素三硝酸酯（或三硝化纤维素）长链大分了在gg构象下的晶体轨道和能带结构。六个k点下的平均Fermi能界为－12．45eV。在第一Brillouin区边缘的带隙为2．31eV,表明纤维素三硝酸酯具有与半导体类拟的导电性。用自洽场CNDO／2法计算了它的局部结构单元（即环和双环体系）在gg、gt和tg构象下的电子结构。讨论了其些性能与结构之间的关系。     

Al_xGa_(1-x)As/GaAsCSP可见光单模激光器

近0.78μm可见光单模激光器在光盘技术,包括视频盘、PCM声频盘和光盘存贮器、激光束高速打印、销售点(POS)终端等信息终端装置中有着广泛的应用前景。特别是打印机和小型光盘应用量大而广。另外,用近可见光单模LDs及其列阵作光源泵浦Nd:YAG激光器和1.06μm单模光纤放大器又是新近国内外十分热门的课题。因此,研制和生产可见光半导体单模激光器,有较大经济效益和发展前景。 本文报道用800℃下液相外延技术研制成稳定基横模、单纵模工作的Al_xGa_(1-x)As/GaAsCSP可见光(λ～779.0nm)单模LDs及其主要性能。     

Horizons for new semiconducting materials*

The properties of existing semiconductors limit performance in a whole range of devices and leave many interesting potential applications (e.g. for lighting, power generation or air-conditioning) possible in principle but technologically impracticable. Better properties, then, could be valuable. They could be obtained in two ways, by discovering new materials (a long-range option apt for academic investigation) or by modifying existing materials either chemically (e.g. by forming solid solutions, perhaps of highly unconventional type) and/or physically (e.g. by low dimensional confinement effects). These options are reviewed and some of their implications explored.     

Correlation between chemical and electrical profiles in Si+, Se+ and S+ implanted bulk and epitaxial GaAs

We compare the chemical profiles of Cr, Mn, Si and Se with the electron concentration profiles in Si, Se and S implanted semi-insulating Cr-O doped bulk GaAs substrates and undoped VPE buffer layers annealed with and without a SiO₂ encapsulant in a H₂-As₄ atmosphere. A higher activation efficiency in the net electron concentration and the gateless saturated channel current is measured for SiO₂ encapsulated wafers annealed under arsine overpressure than for capless annealed ones using Cr-O doped bulk GaAs substrates. On the other hand, the net donor concentration peak is higher for implanted buffer epi layers capless annealed under arsine overpressure than for SiO₂ encapsulated ones. Secondary ion mass spectrometry (SIMS) studies of the Cr decoration of the implant damage indicate that the damage from the 100 keV Si implant anneals out at 840°C while a temperature of 900°C is required to anneal out the 260 keV Se implant damage. An explanation of these differences is provided using an impurity redistribution model and charge neutrality considerations. Excellent Hall electron mobilities at liquid nitrogen temperature of 5400–9200 cm²/V-sec are measured for Si-implanted buffer epi substrates.