It is natural to assume that group V impurities diffuse in silicon by a vacancy mechanism, because they occupy substitutional sites. Based on the pair diffusion model that the impurities diffuse in silicon only via the diffusion of impurity-vacancy pair (E center), anomalous diffusions of phosphorus and arsenic can be explained. On the other hand the relation between the enhancement of diffusion and the growth of extrinsic stacking fault during oxidation can be explained only on an interstitialcy mechanism. Therefore it is the purpose of present note to introduce the recent studies of a vacancy and an interstitia silicon and to discuss the diffusion mechanisms of impurities. Even if the interstitialcy mechanism is correct, the impurities should diffuse likewise only via the diffusion of the pair of an interstitial silicon and an impurity. Therefore the atomistic model of this pair should be studied for the interstitialcy mechanism.
DH AlGaAs lasers with relatively low DC bias under the oscillation threshold superposed by high RF modulation were demonstrated to be quite feasible for the generation of a train of about 30 ps optical pulses at a modulated frequency of sub GHz range. The pulse width was measured by an SHG correlation method as well as an ultrafast streak camera, and both the results agreed fairly well. To explain the generation mechanism of these ultrashort optical pulses in a highly modulated semiconductor laser, the rate equation analysis was performed and the results were generally in good agreement with the experimental ones. Furthermore by analyzing the SHG correlation traces by a computer simulation, it was inferred that the individual ultrashort optical pulses obtained have internal substructures of periodic noises, whose spike widths were of an order of subpicoseconds, due to the randomness of phases among lasing modes.
A high power He-Ne laser with a folded cavity was constructed to obtain a beat frequency with the third harmonic of the 10.2μm R (30) radiation of a CO2 laser. The He-Ne laser was offset locked to a methane-stabilized 3.39μm He-Ne laser. The beat frequency and the third harmonic of the CO2 laser are generated in a tungsten-nickel point contact diode. The measured frequency difference is 48 731.796±0.281MHz. This result agrees well with both the value obtained at the National Bureau of Standards and the value obtained at the National Physical Laboratory.
Several dye vapors, which give emissions in the ultra-violet region, such as fluorene, dibenzofran and p-terphenyl, are excited by an electron beam. In these vapors mixed with high pressure argon as a buffer gas, the fluorescence spectra give bathochromic shift upon increasing the temperature and the buffer-gas pressure. The fluorescence intensities increase with the dye vapor densities and with argon pressures up to 3 atm. The results indicate that the dye vapor is dominantly pumped by an energy transfer from the excited states of argon to the dye, which effect is quenched at high argon pressure. The absorption characteristics of these dye vapors are also measured. The present research gives basic data towards the realization of an electrically pumped ultra-violet dye laser.
Power characteristics of a cw electric-discharge convective-cooled CO2 laser, operated at high pressure (70_??_200 Torr) sealed-off condition were obtained. The dependence of smallsignal gain and saturation intensity on pressure and gas species were investigated on the basis of the experimental results. It is found that N2 and He are both essential for the CO2 laser of this type and a partial exchange of He for Ar can be made without any reduction of efficiency. It enables us to reduce consumption of expensive He gas. Glow discharge tends to be unstable when N2 and/or Ar addition ratio increase. However, it is shown that N2 and Ar increase saturation intensity and small signal gain respectively.
There has recently risen much expectation for the improvement in multiplexability of Twisted Nematic Liquid Crystal Displays (TN-LCDs). It is, therefore, important to understand the effects of material constants and cell design parameters on the characteristics of TN-LCDs. In this paper, the influence of optical anisotropy and cell thickness d on the characteristics of TN-LCDs are investigated from the viewpoint of visual perception, and it is clarified that the minimum value of d is given as dmin=1.0/Δn (550) μm, where Δn (550) is the optical anisotropy at wavelength of 550 nm.
Researches on the very early stages of metal film growth on single crystal surface using AES, LEED, and some other such methods are reviewed. According to the cap shape model, the relation among the three magnitudes, i. e., the two intrinsic surface energies of substrate and deposit and the interfacial tension between them, are discussed. The interfacial tension is only qualitatively estimated from the difference between their lattice constants and the chemical or electrical relation between them. However, depending upon the experimental results referred to, it is believed that the growth mode of the film, i. e., the island mode, the layer-by-layer mode, or the Stranski-Krastanov mode, is governed principally by the relation among the three magnitudes. Finally, some interesting film growths, in which the two-dimensional lattice structures change before the completion of the first monolayer, are referred to and discussed.
Applications of laser-Raman spectroscopy to characterization of semiconductors are reviewed. Principles in the Raman scattering from semiconductors and methods of measurements are summarized at first. Fundamental phenomena included in the Raman scattering from semiconductors, that is, the so-called selection rule and effects of stress and carriers are described then. Some practical examples of characterization of semiconductors such as ion-implanted and/or annealed crystals, thermally treated GaAs and amorphous Si are shown. Identification of materials included at the interface between a dielectric layer and a semiconductor substrate is also described.
The atom-probe field-ion microscope identifies a single atom or analyzes a small surface area seen in an field-ion microscope. The present time of flight type achieves a resolution ΔM/M of 1/1000 and is thus adequate for most routine metallurgical application. Previous atom-prove investigation of metallurgical interest are listed and the usefulness of the instrument for metallurgical studies is discussed. Through the use of the field ion microscope, it is possible to image directory individual atoms and its cluster on metal surfaces and to examine the details of the random walk. New surface effects, discovered by field ion microscope, are reviewed. Possibility of atomic layer depth profiling of a compound semiconductor surface and interfaces are also discussed.