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Silicon is the heart of modern semiconductor devices. The dominance of Si in semiconductor technology depends on the superior quality and properties of thermally grown SiO(,2) compared with the oxide that can be placed on any other semiconductor. For this reason, Si-SiO(,2) interface has been an interesting and important research subject for many years.;The well established quasistatic and conductance methods used in the study of the Si-SiO(,2) interface are improved by using (i) an effectively thin composite insulator, (ii) low carrier concentration substrates, and most importantly (iii) low-level illumination at a wavelength that creates electron-hole pairs. Accurate measurements of both the total density of interface states and its major components as a function of energy in the forbidden gap have been made over four decades (10('10) - 10('14) states/eV-cm('2)) due to items (i) and (ii). Item (iii) decreases the response time of the slow states (those in the lower half of the band gap for n-type samples), so the quasistatic condition is well satisfied and the conductance method can be used to study the interface states throughout the band gap on a single sample. Without illumination, the quasistatic condition is not satisfied even for ramp rates on the lower side of those used previously and complementary n- and p-type samples are needed for the conductance method.;The samples investigated have a thermally grown oxide prepared in dry oxygen. They were never exposed to H(,2) or H(,2)O at an elevated temperature. We speculate that this processing provides an abrupt Si-SiO(,2) interface. The composite gate insulator was completed by having an e-gun deposited 250(ANGSTROM) layer on LaF(,3). The resulting interface, subjected to the improved experimental method, yields a wealth of distinctive structure rather than the often-reported featureless U-shaped interface-state density.

We present a thermoelastic derivation of ultrasonic waves propagating in a solid in which an applied homogeneous stress is superimposed on a nonzero initial stress. We also derive the temperature dependence of the elastic coefficients and the linear relationship between the applied stress and a newly defined parameter--the thermal acoustic constant. The stress acoustic constant is defined and its relationship to the acoustic natural velocity is discussed. Experimental considerations pertinent to the ultrasonic measurement techniques used in the investigation are described. The results of the stress-strain and thermal strain experiments verify the predictions of the theory. Finally, we derive an improved formula for correcting the effects of the transducer and the transducer bonding material in ultrasonic standing wave phase velocity measurements. The results are verified by computer models and laboratory experiments.

Amorphous alloys of VAl and VSi have been prepared by a process of r.f. sputtering onto cryogenic substrates. The Nuclear Magnetic Resonance has been examined in an effort to understand how the electronic structure of these amorphous alloys compares to that of the corresponding crystalline alloys, and to extend the study of the electronic properties of these alloy systems into composition ranges where the crystalline alloys do not exist, because of solubility limits.;The Al('27) and V('51) Knight shifts were measured at 77(DEGREES)K and 300(DEGREES)K, for Al concentrations extending from 15 to 85 atomic percent, in amorphous VAl. The results are found not only to agree with those of the crystalline alloys below 40 atomic percent Al (the solubility limit), but to extend the crystalline behavior right into the region of immiscibility. In amorphous VSi only the V('51) Knight shift was measured. The V('51) Knight shift, before annealing, was found to be nearly constant with both temperature and alloy composition. After annealing the amorphous VSi alloys, however, a strong temperature dependence was observed in the V('51) shift, probably due to the formation of the compound V(,3)Si upon crystallization.;These results are explained in terms of a model which treats the amorphous alloys as though they were crystalline but with an extended solubility range. The case of V(,3)Si is considered as an exception due to its peculiar crystal structure and resulting electronic behavior.;The V('51) NMR linewidths were also measured in both amorphous VAl and amorphous VSi. These are discussed in terms of the short range order found in the amorphous alloys.