摘要:

The stresses produced in a solid by cavitation generated in distilled water by 10‐, 20‐, and 30‐kHz vibrations have been determined by a transducer technique. The measured stress pulses are attributed to the concerted collapse of the whole cloud of bubbles created by the pressure changes in the water rather than to the independent effects of individual bubbles. The magnitude and duration of the stress pulses are characteristic of those of a shock wave and can be related directly to the degree and mode of damage which they produce in a solid.

ISSN:0021-8979    

DOI:10.1063/1.322584

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The early growth of Si on (011¯2) ‐oriented sapphire has been examined by transmission electron microscopy. The Si was deposited at 1000 °C by pyrolyzing silane in H2. The nominal growth rate was 0.4 &mgr;m/min. The morphology of the initial Si growth islands was determined after 0.5, 1.0, 2.5, and 3.5 sec of growth. The basic Si orientation is (100) with [01¯1] Si∥[2¯110] Al2O3. Extensive faulting and twinning is observed leading to {221} orientations. These defects apparently form at coalescence sites of adjacent islands. Also present are four {110} orientations occuring as twin‐related pairs. The observation of isolated {110} domains indicates that they nucleate on the sapphire independently of the (100) domains. The {110} and (100) domains grow at about the same rate. Eventually, the {110} domains become trapped by the surrounding (100) domains. The volume percentage of the {110} domains is constant with growth time and equals 7% up to coverages of 90%.

ISSN:0021-8979    

DOI:10.1063/1.322585

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We analyze data obtained on the morphology of (100) silicon on (011¯2) sapphire at early stages of growth. For the sake of simplicity and concreteness, we assume, perhaps incorrectly, that isolated growth islands are hemispherical. In order to account for the observation that the rate of increase of deposited silicon has achieved the bulk value at surface coverages of 50% or less, we postulate a ’’collection zone’’ around each growing island. Material falling in this zone is assumed to all diffuse to the growing island. For our experiments, the width of this zone is some tens of angstroms. We show that the growth rate of {110} islands is not significantly different than that of (100) islands. The eventual disappearance of {110} Si for full growths can be ascribed to the tendency to reduce the high‐energy contact area between (100) and {110} Si. The logarithm of (100) island density appears to be proportional to (growth time)1/2. A simple model of island coalescence yields such a dependence, the proportionality constant being essentially equal to the (initial nucleation site density)1/4multiplied by the (growth rate)1/2. The model for individual island growth in conjunction with the coalescence model yields a satisfactory explanation of the observed time dependence of island density, of surface coverage, and of total deposited volume. We suggest that, under the high effective supersaturations used in the growth of silicon on sapphire, island growth and coalescence are not dominated by surface energies. We speculate that nucleation of silicon on sapphire occurs by a type of homogeneous surface mechanism, rather than being due to either ’’dirt’’ on the substrate or crystallographic defects in the sapphire substrate.

ISSN:0021-8979    

DOI:10.1063/1.322586

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Cds particles, which were prepared in He, Ne, Ar, and Xe gases at pressures of 5–150 Torr, were studied by electron microscopy. Crystals with wurtzite structure grew in single hexagonal plates or prisms or in a more complicated form composed of three or more hexagonal prisms. The mean size of the particles was larger if they were prepared in a heavier gas, and increased almost linearly with gas pressure up to a saturation pressure which was lower for heavier gasses. The particle size distributions in the smokes and the temperature distributions in the chamber are presented for various atmospheres, and on these bases the growth of the particles is discussed.

ISSN:0021-8979    

DOI:10.1063/1.322587

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Polycrystalline silicon films implanted with 1×1012to 7.8×1015/cm2doses of boron and phosphorus were isochronally annealed up to 1100 °C. Annealing below 600 °C removes the radiation damage created by the implantation process. For doses higher than 1×1014/cm2an abrupt decrease in sheet resistance takes place between 650 and 700 °C. Hall measurements show that this decrease is the result of a large increase in both the carrier concentration and mobility. Electron‐reflection diffraction patterns show that recrystallization takes place within this temperature range. Annealing above 700 °C only causes a small further decrease in the sheet resistance.

ISSN:0021-8979    

DOI:10.1063/1.322588

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Silicon carbide is difficult to sinter without the aid of additives and/or pressure. Additions of boron carbide, boron or alumina were made to obtain dense materials. This is explained in terms of surface free energy modifications taking place in the grain boundaries. An expression of the chemical potential over the grain boundaries is developed to show that there is no theoretical limitation for the sintering of covalent ceramics if the grain size of the starting powder is small enough.

ISSN:0021-8979    

DOI:10.1063/1.322589

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The interdiffusion and intermetallic formation in thin‐film sandwiches of platinum on preannealed aluminum has been investigated at temperatures in the range 200–500 °C. X‐ray diffractometer studies, sheet‐resistivity measurements, and microscopic studies were employed to follow the metallurgical reaction. It has been found that Al‐Pt interact very rapidly, leading to the formation of several intermetallics. In heat‐treated samples with thick aluminum (?6000 A˚), Pt2Al3, PtAl2, PtAl3, and PtAl4were present. In others with 4000 A˚ or less Al, platinum‐rich phases Pt5Al3and Pt3Al2were detected. After prolonged or high‐temperature anneals, phases comparatively richer in Al were found to grow at the expense of other phases formed earlier. The Al‐Pt interaction rate was found to be dependent on the annealing ambient, being significantly higher in forming gas, argon, or helium than in vacuum or air. Also, the intermetallic formation resulted in large stress changes in the composite Al‐Pt films due to a volume increase accompanying the formation of Al‐rich phases, which led to the loss of adhesion.

ISSN:0021-8979    

DOI:10.1063/1.322590

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We have measured the kinetic rate of formation of CrSi2using 2.0‐MeV4He+backscattering spectrometry. CrSi2was formed on single‐crystal ⟨100⟩‐ and ⟨111⟩‐oriented Si and on Pd2Si grown on ⟨100⟩ Si. For both Si‐Cr and Si‐Pd2Si‐Cr samples the rate of growth of CrSi2is linear in time with an activation energy of 1.7±0.1 eV and a value of 0.7 A˚/sec at 450 °C. For all annealing temperatures, the growth becomes nonlinear at long annealing times. The nonlinearity is attributed to a contaminant, probably oxygen. On Pd2Si, CrSi2starts to form at about 400 °C, while on Si, CrSi2formation is observed at 450 °C and above. The difference in formation temperatures is due to contamination at the Si‐Cr interface, quite probably a thin oxide layer. The growth rate of CrSi2in the Si‐Pd2Si‐Cr samples is independent of the thickness of Pd2Si.

ISSN:0021-8979    

DOI:10.1063/1.322591

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We propose a new nonlinear theory including the gate‐voltage dependence and the effect of surface states based on a simple model (low‐frequency limit) of surface‐acoustic‐wave (SAW) convolver in monolithic MIS structure, and we confirm our theory by experiment on then‐Si/SiO2/ZnO/Al system. Our results show that the convolution signal corresponds to the derivatives ofC‐Vcurves in the ideal MIS structure and the effect of surface states appears in the peak shift.

ISSN:0021-8979    

DOI:10.1063/1.322580

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The time variations of the shape and position of the crystal‐melt interface in a crystal pulling system, caused by sudden changes of different parameters, are investigated. Zero pull rate and vacuum surroundings are assumed throughout. In particular, the effects of the variation of the after‐heater height and the Peltier current are determined in detail for germanium. It is found that the Peltier current affects the interface more strongly than the after heater.

ISSN:0021-8979    

DOI:10.1063/1.322581

出版商:AIP    

年代:1976

数据来源: AIP