The depth profile of thermally, anodically and plasma grown oxides on GaAs has been studied by means of X-ray photoelectron spectroscopy (XPS). The ion sputtering effects are taken into account in obtaining quantitative chemical depth profiles. Thermally oxidized film is composed of Ga2O3 (98%) with a large pile up of elemental-arsenic at the interface. In contrast, anodically oxidized film shows As2O3/Ga2O3 ratio of 0.8-0.9 except in the interfacial region, where the concentration ratio of Ga2O3: As2O3: elemental-As is equal to 1:0.7:0.2 for the as-grown oxide and 1:0.55:0.35 for the annealed oxide. The plasma oxidized film consists of Ga2O3 (_??_65%), As2O3 (_??_30%) and elemental-As (_??_5%) with evidence of As5+ at the surface. In the interfacial region, the plasma oxidized film is observed to contain less elemental-As than the anodic oxide/GaAs. The literature on the chemical composition of oxide/GaAs is also discussed.
To improve the image contrast in X-ray transmission micrographs of organisms, a finefocus sealed-off tube with a titanium target has been built, which can produce quasi monochromatic X-rays at the Kα characteristic wavelength of 2.7Å. The intensity ratio of the characteristic ray to continuous ones reaches a maximum when a voltage of 8 kV is applied to the tube. Micrographs of organisms obtained with this tube show up a better image contrast than those taken with a copper-anode tube.
An attempt was made to etch Cu/Cr thin films by CCl2F2 plasma using an L-coupled reactor. Nonvolatile CuCI was found to appear on the surface of the films. The formation of CuCl is the result of a plasma reaction taking place along the grain boundaries. A mass-spectroscopic analysis suggests that the plasma reaction is due to the presence of CF3+ ions. The Cr layer under the Cu one was occasionally found to diffuse onto the surface of the Cu layer during the plasma reaction. The process of the Cr diffusion is probably due to the sinking phenomena observed in Au/Si structure in air, i.e. the out-diffusion of Cr through Cu thin films in CCl2F2 plasma.
A method of measuring velocity using a grating spatial filter in a microscopic area is described. The images corresponding to particles moving in a probing region are formed on the grating placed in front of a photodetector. The particle velocity is determined from the frequency measurement of eletrical output signals obtained from the photodetector. In this paper, the filtering characteristics of the grating used is analyzed by means of the power spectral density function for the two cases of single and differential detection systems. The preliminary experiment of velocity measurements is performed by using a part of the circumference of a rotating random pattern. The theoretical and experimental results show that the differential detection system is useful for measurements of the velocity in a microscopic area where only a small number n of spatial filter lines exists.