摘要:

The mixing rates of the Ni‐Pt and Rene´ N4‐Pt systems under high‐energy ion bombardment were measured using Rutherford backscattering spectroscopy. The mixing was induced by various fluences of 1‐MeV Pt+ions. The extent of mixing in Rene´ N4‐Pt was the same as in Ni‐Pt, suggesting the absence of any effects of high voume fraction of ordered second phase (gamma prime) on the mixing phenomenon in the former system. The amounts of mixing predicted by the model based on thermochemical effects were very close to those measured, while cascade collision theory could account for only 2%–3% of the mixing.

ISSN:0021-8979    

DOI:10.1063/1.341064

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The crystallization of undoped amorphous silicon films deposited by low‐pressure chemical vapor deposition in the temperature range 580–530 °C and annealed from 550 to 950 °C has been studied by transmission electron microscopy. The average grain size of the crystallized films depends on the annealing temperature and the deposition conditions. The nucleation rate of new grains during annealing decreases as the deposition temperature decreases from 580 to 545 °C and/or when the deposition rate increases. The final grain size is also influenced by the annealing temperature with the largest grain size obtained at low annealing temperatures. A simple model is described which explains the dependence of grain size on the annealing temperature. An average grain size of 500 nm has been obtained in a 200‐nm film deposited at 545 °C and annealed at 550 °C.

ISSN:0021-8979    

DOI:10.1063/1.341065

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Thick‐film resistive inks have been prepared starting from powders obtained by precipitation of RuCl3on two different lead‐containing glasses. The structural and electrical properties of the films have been investigated after heat treatment at various temperatures. The evolution of the microstructure involves phase transformations from Pb‐rich (Ru‐deficient) pyrochlores to Ru pyrochlores and finally to RuO2. Together with these crystallographic features, the atomic absorption spectroscopy shows a gradual decrease of the Ru dissolved in the glass when the firing temperature increases. The conductivity of the samples decreases according to the transition from pyrochlore to dioxide. These results emphasize the role played by exchange reactions in the control of transport mechanisms in thick‐film cermet resistors.

ISSN:0021-8979    

DOI:10.1063/1.341119

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The kinetics of molecular‐beam epitaxy are examined by means of Monte Carlo simulations in combination with a new approach for monitoring surface growth, i.e., by calculating the evolution of the surface step density. The evolution of the step density is shown to have a remarkable correspondence to that of the measured reflection high‐energy electron diffraction (RHEED) specular spot intensities for III‐V semiconductor compounds. We study growth in a variety of systems, including flat and stepped surfaces, as a function of substrate temperature and draw several conclusions concerning the relation between RHEED measurements, kinetics, and growth quality. The range of validity of the kinematic approach to RHEED is discussed and the importance of multiple scattering in the high step density regime is highlighted.

ISSN:0021-8979    

DOI:10.1063/1.341041

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The growth behavior during nonplanar metalorganic vapor phase epitaxy on patterned GaAs substrates was investigated by using a periodic structure of GaAs/AlGaAs layers. At the channel edges, nongrowing and slow growing low‐index planes were observed, indicating local kinetic limitation of growth. A number of different channel orientations were studied and a theoretical model was used to explain the resulting growth planes. The kinetic limitation is further demonstrated by the temperature dependence of the growth behavior and by the use of different profiles. The influence of misoriented substrates is discussed. A reduction of the growth velocity was observed in the channels as compared with the surrounding area.

ISSN:0021-8979    

DOI:10.1063/1.341042

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report depth profiles of the hydrogen concentrations in metal‐oxide‐semiconductor structures measured using the nuclear reaction profiling technique with a 6.4‐MeV15N beam. In both conventionally grown and ultra‐dry thermal oxide samples with aluminum or gold gate metal, a peak of hydrogen concentration is observed at the metal/SiO2interface. The amount of hydrogen at this interface varied from sample to sample in the range 2–6×1015H/cm2, which was at least 20 times as much as in the SiO2layers. By continued irradiation with the measuring beam, most of this hydrogen was detrapped from the metal/SiO2interface and diffused into the SiO2. The detrapping occurred much more rapidly in samples made with Al metallization than in Au gate or unmetallized samples. The data can be fitted by a model in which hydrogen is detrapped from the metal/SiO2interface by the beam, then diffuses into the SiO2. Redistribution of hydrogen was found to continue until it was uniformly distributed throughout the SiO2, with a residual peak of strongly trapped hydrogen remaining at the metal/SiO2boundary. At the same time the concentration of hydrogen in the SiO2increased from an initial low level to about 4×1020cm−3, depending on the amount of hydrogen initially at the Al/SiO2interface.

ISSN:0021-8979    

DOI:10.1063/1.341043

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report the results of an investigation of the structural properties and relaxation of misfit stress with transmission electron microscopy and x‐ray diffraction techniques. Epitaxial films of ZnSe were grown on GaAs by molecular‐beam epitaxy of thicknesses ranging from 0.05 to 4.9 &mgr;m. The films contain stacking fault defects up to thicknesses of about 150 nm. Above 150 nm perfect misfit dislocations are generated from surface sources and the stacking fault defects to accommodate the lattice mismatch. The majority of dislocations observed are of the 60° type with Lomer edge type dislocations observed in a much lower concentration. The density of misfit dislocations increases with increasing epilayer thickness. Above about 1 &mgr;m the films exhibit biaxial tension which we believe is due to thermal expansion differences of ZnSe and GaAs. Good agreement is observed between microscopic and diffraction measurements of the relaxation phenomena.

ISSN:0021-8979    

DOI:10.1063/1.341044

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Tungsten‐related deep levels in a silicon crystal are investigated using microwave and conventional deep level transient spectroscopy. It is found that tungsten atoms have two diffusion constants. Most tungsten atoms stay near the surface of Si crystal, but the remainder go deeper than 1 &mgr;m from the surface. It is also found that tungsten atoms make both a hole trap of 0.41 eV and an electron trap of 0.22 eV. Device characteristics are found to be seriously degraded due to deep levels made of deeply diffused tungsten atoms.

ISSN:0021-8979    

DOI:10.1063/1.341045

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Different aspects of the metastable character of Si‐related localized states in modulation‐doped heterostructures of GaAs/GaAlAs have been studied. Hydrostatic pressure was used to change the two‐dimensional electron‐gas concentration at the active interface of the system. The performed studies give evidence that below a critical temperature ofTc=135 K for a given sample, at the same temperature and pressure conditions, an arbitrary carrier concentration in the quantum well can be obtained depending on the pressure at which the sample was cooled.

ISSN:0021-8979    

DOI:10.1063/1.341134

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Current‐voltage characteristics of polycrystalline silicon films highly doped with phosphorus and boron were studied over a wide range of temperatures (40–300 K) and applied electric fields (up to 5 kV cm−1). After the usual ohmic regime, we observed a large increase in dc current versus applied voltage. Moreover, at higher electric fields, a new ohmic conduction regime appeared which has not yet been reported in polycrystalline silicon. Thermoemission‐based models cannot fully interpret our results. We present a new interpretation of current‐voltage characteristics based on a model previously used to interpret the electrical properties of these films at low electric fields. This model takes into account the existence of fluctuations both in intergranular potential and in the grain boundary barrier heights. They result from all of the macroscopic inhomogeneities due to the growth conditions of the material. The high electric field detraps carriers from grain boundaries and extracts the carriers located in the valleys of potential created by the fluctuations, thus inducing transition in conductivity.

ISSN:0021-8979    

DOI:10.1063/1.341046

出版商:AIP    

年代:1988

数据来源: AIP