摘要:

Studies of subgrain structures in Tl3AsSe3have been performed by x‐ray topography. Birefringent interference patterns show that a direct correlation exists between the subgrain structures and the optical homogeneity of the crystals. A quantitative measurement of lattice misorientation was performed from the interference patterns and compared with x‐ray rocking measurements. The origin of the subgrains is also discussed in detail.

ISSN:0021-8979    

DOI:10.1063/1.341932

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The collective sputtering effect of fast primary cluster ions on the yield of secondary molecular ions has been demonstrated for the first time. Results show that the sputtering yield of valine negative molecular ions per incident carbon atom, in a C+nincident cluster ion, increases with increasingn. The yield results are interpreted as a direct effect of the enhancement in the electronic stopping power per atom in cluster ions compared to atomic ions.

ISSN:0021-8979    

DOI:10.1063/1.341933

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Single‐crystal LiNbO3is etched in an atmosphere of 500‐Torr Cl2by focusing a 257‐nm, frequency‐doubled CW argon‐ion laser beam onto the surface. The observed laser intensity threshold for etching is consistent with a process involving surface melting of the crystal. A single laser scan forms a shallow depression with marked ripples transverse to the direction of laser polarization, while repeated scans give a groove with a nearly triangular cross section. During laser etching, reacted material is redeposited on the crystal surface. This material is subsequently analyzed for chemical composition. The LiNbO3surface is partially depleted of Li and O both at the etched grooves and at significant distances away from the grooves. Studies at low light intensities suggest that photochemical generation of gas‐phase Cl radicals is responsible for the O depletion and part of the Li depletion. In addition, a dark reaction between Cl2and LiNbO3depletes only Li.

ISSN:0021-8979    

DOI:10.1063/1.341934

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Silicon nitride films were deposited in an rf glow discharge from various mixtures of NH3, H2, and N2with 1,1,3,3,5,5‐hexamethylcyclotrisilazane (HMCTSZN). Fourier transform infrared spectroscopy, Rutherford backscattering spectroscopy, and proton magnetic resonance spectroscopy, indicate that the films deposited with NH3are essentially silicon nitride (<4 at. % C) and contain 25 at. % H , when deposited from dilute HMCTSZN mixtures at elevated rf power. Gas phase neutral mass spectroscopy indicates a relative abundance of NHxradicals produced under these conditions, which actively remove carbon and enhance Si‐NH‐Si bonding. Films deposited in NH3/H2mixtures result in still greater Si–N bonding, since NH3/H2plasmas are more NHxradical rich than NH3discharges. Films deposited from H2/HMCTSZN plasmas contain significant carbon concentrations (30–40 at. %), but those formed from dilute HMCTSZN mixtures at elevated rf power are low in H content (21 at. %) and are highly cross‐linked due to H abstraction from radicals produced in the discharge.

ISSN:0021-8979    

DOI:10.1063/1.341935

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Effects of high carbon concentration upon oxygen precipitation and related phenomena in Czochralski (Cz) silicon have been investigated by combining various furnace and rapid thermal anneals. Our data show that oxide precipitate (OP) density, estimated from changes in interstitial oxygen concentration (&Dgr;Oi), increases with increasing substitutional carbon concentration, Cs, while thermal donor (TD) formation is inhibited at high Cs. Even though &Dgr;Oiincreases monotonically with Cs, synchrotron radiation section topographs of processed high carbon content wafers (Cs∼4 ppma) exhibit Pendello¨sung fringes, indicating a strain‐free bulk state. Our transmission electron microscope and optical microscopic data also show very few resolvable structural defects associated with precipitates inside the bulk Si. Using a thermodynamic and kinetic model, we attempt to explain: (1) reduced thermal donor formation, (2) lack of bulk stress notwithstanding high &Dgr;Oi, and (3) predominantly polyhedral precipitate morphologies in high carbon content CzSi.

ISSN:0021-8979    

DOI:10.1063/1.341936

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Based on an approximate method by the authors for calculating void deformation in crystalline solids, the global response of a small continuum material element which contains microcavities is studied. A rate‐dependent power‐law plastic flow by double‐slip is assumed to govern the local inelastic deformation. The local field variables are analytically calculated in an incremental manner. The average stress and strain are then computed by the integration of the local stress and strain over the continuum element. These average variables are used to describe the overall response of the material element under high loading rates. Several illustrative examples are given. It is shown that the global response of the material is significantly affected by the loading rate: the material response becomes tougher as the loading rate increases, but once the entire matrix becomes plastic, a strong ductility develops. It is observed that the large overall plastic deformation of crystalline solids stems not only from a uniform plastic flow in the entire matrix but also from the slip caused by the stress concentration near cavities; even under all‐around uniform compression or tension, significant plastic deformations can take place in the vicinity of preexisting cavities, and affect the overall response of the material. The global material response, in general, is anisotropic, being induced by local flow on geometric slip systems. In addition, it is shown that the overall material response under compression is not, in general, the reverse of that under tension. The overall failure of crystalline solids, caused by void collapse or void growth, is investigated under compressive and tensile loads applied at various rates.

ISSN:0021-8979    

DOI:10.1063/1.341937

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report determination of the mechanism of photochemical oxide growth (after initial film formation) when transport through the film dominates. Photochemical oxides grown in different ambients, i.e., O2or N2O, are found to have different stoichiometry, especially at the ambient/oxide interface. Oxides grown in O2with ultraviolet light exhibit Hg‐rich surface layers, however growth in N2O often results in Hg‐depleted surfaces. By sequentially oxidizing Hg1−xCdxTe epilayers in these ambients and analyzing the in‐depth atomic profiles with Rutherford backscattering spectrometry and secondary ion mass spectrometry, the dominant diffusion mechanism is determined. Investigation of the migration of oxygen during the oxidation is carried out by oxidation in an18O enriched ambient. We conclude that growth of these photochemical oxides involves both the diffusion of the substrate elements and oxygen, with the oxidation occurring primarily at the oxygen‐oxide interface.

ISSN:0021-8979    

DOI:10.1063/1.341938

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Various procedures for heavy metal gettering in siliconp‐njunctions have been compared in order to test the effectiveness of dopants and extended defects as getter sites; the role of silicon interstitials in the gettering process has also been studied. It has been found that only phosphorus and boron atoms are effective getter sites, while arsenic and antimony are not; such gettering effectiveness is independent of the presence of extended defects in the heavily doped regions. During a moderate temperature annealing (segregation annealing) dissolved metal impurities diffuse from the space‐charge region of the devices and segregate at getter sites. Extended defects generated by oxygen precipitation and stacking fault backside damage have some ability to capture metal impurities, but electrical tests show that they do not provide a satisfactory gettering technique. The role of self‐interstitials consists of increasing the dissolution rate of metal precipitates with subcritical radii, so that the segregation of metal impurities into getter sites is made easier; however, a complete gettering process requires three steps, that is: (1) the creation of effective getter sites; (2) the dissolution of metal precipitates; (3) the segregation of dissolved metal impurities at getter sites. Some of these steps may be activated simultaneously.

ISSN:0021-8979    

DOI:10.1063/1.341939

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Recently we have reported the measurement of reflection high‐energy electron diffraction intensity oscillations during chemical‐beam epitaxy of GaAs using triethylgallium (TEG) and As2derived from an arsine cracker [Appl. Phys. Lett.50, 19 (1987)]. In this study we observed a significant variation of the GaAs growth rate with substrate temperature at constant TEG flux. In addition, the variation of growth rate with incident flux at constant temperature was found to be nonlinear below approximately 500 °C and linear above 500 °C for incident fluxes yielding maximum growth rates between 0.2 and 1.8 monolayers/s. We have developed a model of the surface pyrolysis of triethylgallium which explains the qualitative behavior of the above data. The model assumes the existence of adsorbed triethyl, diethyl, and monoethyl gallium species as well as adsorbed ethyl radicals. As a starting point, the rate limiting step to epitaxial incorporation of atomic gallium is assumed to be cleavage of the second ethyl–gallium bond. Elimination of atomic hydrogen from adsorbed ethyl groups to form ethylene is also included in the model, as is recombination of one ethyl group and a diethylgallium to form adsorbed triethylgallium. Assuming Arrhenius behavior for the rate constants of the elementary steps of the reaction mechanism and steady‐state behavior an expression for the temperature dependence of the growth rate is derived. Using realistic values for the preexponential factors and activation energies of the elementary steps a reasonable fit to the experimental data was obtained. The model reproduces the nonlinear dependence of growth rate on incident flux below 500 °C and the fall‐off growth rate at higher temperature. The nonlinearity is due to the second‐order recombination of an adsorbed diethyl gallium radical with an adsorbed ethyl radical followed by desorption of triethylgallium. The fall‐off in growth rate above 500 °C is due to desorption of diethyl gallium radicals.

ISSN:0021-8979    

DOI:10.1063/1.342508

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Amorphous LaNi5films were prepared using a sputtering method. Mechanical properties and hydrogenation characteristics of the films were investigated and the results were compared with those of the deposited films. The density of the sputtered LaNi5film was about 6 g/cm3, which was larger than that of the evaporation deposited film but smaller than that of crystalline LaNi5. Thermal conductivities of amorphous films were larger than those of bulk samples. Mechanical strength of the sputtered films deposited on various substrates was measured after 100 cycles of hyrogen absorption–desorption process. The result was in the following order for the substrates used: Ni foil>Ni>Al foil>Cu foil>Cu>Al>glass. The hydrogen content in a sputtered film with a thickness of 1.3 &mgr;m was found to be 2.4 H/LaNi5. The hydrogen concentration in the film increased monotonically with increasing the hydrogen pressure in both cases between 333 and 363 K.

ISSN:0021-8979    

DOI:10.1063/1.341943

出版商:AIP    

年代:1988

数据来源: AIP