Previous work has demonstrated that B-H pairs in silicon thermally dissociate obeying simple first order kinetics if theyare located in a region depleted of majority carriers. B.H debonding in equilibrium, however, is a slower, more complex process. We have investigated the dissociation of B.H pairs under a variety of equilibrium and non-equilibrium conditionsand have demonstrated that the dissociation process is strongly influenced by the local concentration of majority and minority carriers. In particular, we show that injection of minority carriers can markedly accelerate the dissociation process. A model is proposed which suggests that hydrogen released from an acceptor, while initially positive, must always beneutralized before escape is possible. This picture correctly describes the time dependence of debonding in equilibrium, and it predicts the enhanced debonding in forward biassed diodes provided the characteristic time for H charge conversionislong.

Mercuric iodide (HgI2) single crystals deposited with semitransparent Pd, Al and Ag contacts were studied by thermally stimulated current spectroscopy (TSC). Distinct differences were found among spectra obtained friom samples withdifferentmetal contacts, indicating that interactions between the metal contacts and mercuric iodide substrates have strong effects on the deep defect levels in mercuric iodide. The activation energies of some of these defect levels were estimated bytaking TSC spectra with different heating rates. In addition, a pyroelectric effect was observed in Ag-contactedsamplesbythermally stimulated depolarization current technique (TSDC). The implications of these results in device applicationsof mercuric iodide are discussed.

Every semiconductor device contains as grown and process induced defects even though the techniques to minimize the density of defects are known. Conventional DLTS methods are used to identify the trapping defects in the device. However, the activity of the traps could be suppressed or enhanced by the operating conditions of the device such as temperature, current through the device or light directed onto the device. We studied the DLTS spectra of silicon polycrystaline solar cells, as well as silicon and GaAs photodetectors in the dynamic regime, namely under light and at elevated temperature. Significant change in the resulting spectra were observed when compared to the spectra obtained by conventional DLTS methods.

Amorphous hydrogenated and unhydrogenated germanium-nitrogen alloys were prepared by rf glow discharge using a GeH4+NH3atmosphere and by rf sputtering using a Ge target with different gases (Ar, N2, NH3 , and mixtures). A difficulty in obtaining nonstoichiometric films was encountered for both methods. Films prepared by rf glow discharge tend to be either Gerich or close to stoichiometric composition, and films prepared by sputtering tend to have low nitrogen concentration. Thesamples prepared by glow discharge at 220°C do not contain the NH2 absorption band, which is usually present in filmsprepared by sputtering. The Urbach energy (determined by PDS), Tauc's gap, refractive index, dark conductivity and activation energy are also reported.

Point defects occur in every solid material. No crystalline lattice is perfect, and no amorphous network has only unbroken sequences of bonds. Every material contains a greater or smaller number of vacancies, interstitials, substitutional atoms, and broken bonds. Many of these have only minor effects on the behavior of the material, but in a surprisingly large number of cases, point defects can have significant and even decisive effects on material performance. This can be true even when the defects are present in very small concentrations.

This paper discusses the temperature dependence of recombination lifetime in a variety of silicon materials using energy level as a parameter. A theoretical approach based on the Shockley-Read-Hall theory for energy level calculations has been used. Various types of defects created by introducing impurities, dislocations and grain boundaries into silicon waferswere studied. Results are presented for Czochralski grown Si wafers intentionally contaminated with gold and chromium, EFG ribbon with varying concentration of oxygen, web ribbons with extended defects and contaminants, large grain polycrystalline material, and Si/Si-Ge/Si heterostructures with varying misfit and threading dislocation density.

Deuterium diffusion profiles in medium phosphorus doped silicon (1016 and 1017 cm−3) at two different deuteration temperatures (120 and 150°C) are simulated with an improved version of a previously reported model. The new approach which excludes the H2 molecule formation, as applied recently to ptype silicon, allows the determination of kinetic and thermodynamic parameters such as diffusion coefficients, activation and dissociation energies. These parameters 6re compared with those found for p-type silicon and discussed in the light ofavailable data for n-type material.

The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U3Si and U3Si2 amorphous at temperatures below about 250 C [1], and that U3Si becomes mechanically unstable suffering rapid growth by plastic flow [2,3]. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier filtering analysis of the non-crystalline scattering component [4].

Modifications in the structural parameters of n type a-Si:H due to bombardment of different doses of 10 keV and 1 MeV electrons and the consequent changes in the gap state distribution are studied. A systematic dependance of the changes on the energy and dosage of electrons is observed. The Deep Level Transient Spectroscopy results reveal that apart from increasing the gap state density over a broad energy range, the electron bombardment also modifies the charge state of the defect, which is conclusively brought out by the result of C-V measurements. An understanding of the reason behind such modifications is sought by studying the structural parameters of the bombarded films directly with the help of Laser Raman Spectroscopy.

The x-ray diffuse scattering pattern from a commercial bulk n-type Hg0.80Cd0.20Te single crystal was measured in absolute units. Anomalous dispersion techniques near the Hg LIII edge were used to determine theintensity due to Hg interactions. Diffuse x-ray superlattice reflections are reported that are forbidden by the zinc-blende structure. The systematic absences in these peaks eliminate the possibility that they are the result of a Cu3Au ordering scheme.

The motion under an applied stress of dislocations in silicon crystals is slowed and stopped by the presence of oxygen inthe material. A model is presented that quantitatively describes the inhibition of dislocation motion by accounting for the oxygen gettering to dislocations caused by diffusion and stress-enhanced migration. Drag on the dislocation motion ismodelled using the elastic interactions between the interstitial oxygen and the dislocation and the energy needed to breakbonds formed between silicon and aggregated oxygen atoms within the dislocation core. The predictions of the model agree quantitatively with the experimental data of Imai and Sumino.

Structural features of TiS2 were studied by scanning tunneling microscopy (STM) and single-crystal X-ray diffraction was applied as a complementary technique. STM images in air and at room temperature revealed, beside the trigonal symmetry of the lattice, several new features having this symmetry as well. We conclude that these features not only are to be described by structural defect phenomena which affect octahedral sites in the 1T-CdI2 structure but tetrahedral sites as well. Sample orientation determination by X-ray diffraction provides a unique relation between feature types and sites. A model is proposed in which displaced Ti atoms account for the observed features.

The scanning tunneling microscope has been used to image a reduced TiO2(110) surface in ultrahigh vacuum. Structural units with periodicities ranging from 21Å to 3.4Å have been clearly imaged and the observed surface structures can be explained by a model involving ordered arrangements of two dimensional defects known as crystallographic shear planes. An electronic state 0.5 eV below the conduction band edge, detected in tunneling spectra, has been assigned to reduced Ti cations which reside along the crystallographic shear planes. This state appears to be empty at the surface, possibly due to asmall amount of band bending. The results indicate that the topography of nonstoichiometric oxide surfaces can be rather complex and that the tunneling microscope provides an effective tool for studying the tomic scale surface features of wide band gap semiconductors.

Scanning Tunneling Microscopy (STM) has developed into a useful tool for atomic-scale characterization of material surfaces. It is proving especially useful in the field of fracture, as the vast majority of high-resolution images of fracture processes are made in the transmission electron microscope, where thin film effects and sample preparation may greatly modify crack tip stresses and dislocation structures. This investigation involved imaging of cracks introduced in Si at room temperature and single crystals of galena (PbS) by rapid indentation at 77K. Images were obtained at the arrested cracktip, around the indentation, and along the flanks of the crack in the dynamic growth region. Measurements were made of both crack-tip morphology and upsets observed along the flanks of the cracks in PbS. Interesting results concerning crack tip geometry in Si, the effect of STM tip geometry and scan conditions on the resulting image of the cleavage crack, as well as work in progress on other material systems, will be discussed.

The rate of decay of a macroscopic sinusoidal grating etched into a clean surface can be predicted from its surface and volume diffusion coefficients and the partial pressure of the material. The microscopic theory of crystal growth and evaporation of Hirth and Pound has produced an expression for the step velocity for a surface in equilibrium with its own vapor, which was used to simulate the decay of a sinusoidal surface. The macroscopic decay rate was determined from the measured surface diffusion coefficient and the equilibrium vapor pressure of the Ni (100) surface. The rate of decay of a model sinusoidal grating surface using the microscopic step velocities was inconsistent with the observable mnacroscopic results. Reasons for this are discussed.

Studying crystal surfaces using the forward scattered high energy electrons Is discussed.Performance and applications of the basic REM and several variations of this technique are presented.

General high-angle tilt grain-boundaries may be described by an arrangement of repeating structural units. A particular defect in the normal arrangement of structural units in a Σ=27 <110> tilt grain-boundary in Ge is reported.The defect is characterized by a short segment of (111) facet at the interface, and is associated with a screw dislocation in the boundary plane. This defect accommodates a slight misorientation of the boundary away from the perfect tilt configuration, andmay represent a type of structural unit present in other tilt boundaries containing a small twist component.

The interfacial structure of a large lattice mismatched (˜25%) (111) Ag-Si system was studied by using transmission electron diffraction (SADP - Selected Area Diffraction Pattern). The epitaxial films of Ag (600–1200Å) were grown by MBE on flat Si(111) and misoriented Si(1ll) surfaces. We have examined the interfacial structures of the Ag on 2° misoriented Si(111) using diffraction patterns of cross sectional view. Through a detail analysis of thelocation and shape of the diffraction spots, we can determine the epitaxial relationship between Ag and Si, the small tilt angle of Ag(111) planes withrespect to the misoriented Si(111), the period of the finite terrace size of the misoriented Si substrate, and the size of the ordered region in the Ag film. The O-lattice analysis developed by Bollmann has beenapplied to this interface andthe result is compared with the SADP observation.

Interfaces between aluminum and silicon in samples prepared by solidification of an Al-Si eutectic liquid have been studied by high-resolution electron microscopy. The Al and Si grains have a common [110] axis with a misorientation between grains of 70.5°, thus aligning the (lll)si plane with the (111)ALplane. In general, theinterfaces have a complex structurewith numerous interfacial dislocations and considerable facetting. The core structurescan be characterized in terms of structural unit models. The nature of the facetting has also been investigated, in particular one facet which lies approximately along the (111)AL, and (l15)si planes and another which lies approximately along the (110)AL and (l14)si planes.

Novel application of a combination of TEM and non-destructive synchrotron X-ray topography in both Bragg and grazing Bragg-Laue geometries to the characterization of InxGa1−xAs/GaAs strained layer films is reported. Specialized epilayer lift-off procedures enabled TEM characterization of the defect distributions in macroscopic area films, effectively increasing the field of view of the technique by several orders of magnitude. These lateral distributions correlated well with those observed on both Bragg and grazing Bragg- Laue topographs. Grazing Bragg-Laue images also afforded depth sensitivity. Excellent correlations exist between results obtained with all these techniques for systems with a wide range of In concentrations, corresponding to a broad range of interfacial dislocation densities, although only results for x=;0.085 are presented. This work demonstrates that it is possible to bridge the gap that has traditionally existed between the areas of application of these two generic techniques, in terms of both tolerable defect densities and fields of view. This gap also spans the range of defect densities which is of interest in this and other systems.