摘要:

Shock compression measurements of lithium niobate single crystals are carried out up to 121 GPa using the gun method. Hugoniot elastic limits are found to be 2.4 and 6.6 GPa with the shock propagation direction along [0001] and [112¯0], respectively, reflecting a remarkable elastic anisotropy. A phase transition accompanied by a discontinuous volume decrease is induced at the shock pressure of 32.6±0.6 GPa. The zero‐pressure volume of the high‐pressure phase is estimated to be smaller by 20.5% than that of the low‐pressure‐phase lithium niobate. The observed large volume decrease strongly suggests considerable change in the bond character with the phase tranformation.

ISSN:0021-8979    

DOI:10.1063/1.335934

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Infrared absorption measurements of localized vibrational modes (LVM) due to Al in ZnSe performed under high‐resolution conditions reveal additional features as compared to previous data. The cluster of bands near 340 cm−1is resolved into at least six and possibly eight individual absorptions. A Green’s function calculation over various pertinent models best explains most of these LVM as probably arising from a (2 AlZn‐ZnSe) antisite complex (or at least an AlZnpair) with other complexes less likely. The linewidth of individual features can be explained in terms of nearest‐neighbor Se host lattice isotopes. Finally, features perturbed from the isolated AlZncase are considered as well as the remaining LVM of unknown origin.

ISSN:0021-8979    

DOI:10.1063/1.335935

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Gettering of chromium and copper metal impurities to the damaged regions surrounding an implanted buried oxide has been investigated. Cr tends to segregate to the surface Si‐SiO2interface; only a small fraction moves to the damaged regions surrounding the buried oxide. Cu segregates to the damaged regions more readily; in addition, a large fraction of the implanted Cu moves to a location several micrometers beneath the buried oxide layer. The buried oxide does not appear to stop the movement of the Cu.

ISSN:0021-8979    

DOI:10.1063/1.335910

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Measurements have been made of the diffusivity and electromigration of195Au in lead‐tin solders in the composition range 0–12 at. % tin. A marked decrease in the diffusivity is attributed to tin trapping of gold with a binding energy of about 0.21±0.03 eV. The addition of the tin has no perceptible effect on the electromigration of the gold. A curious minimum in theDx/Dvs concentrationxappears in the concentration range, 1–5 at. % tin, for specimens that have been prepared by a slow quench from the melt. This effect disappears when the specimens are heated above 180 °C. The origin of this behavior is still a topic of open speculation.

ISSN:0021-8979    

DOI:10.1063/1.335911

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

(Al,Ga)As layers have rough surface morphologies when deposited under certain growth conditions in molecular beam epitaxy (MBE). This leads to poor interfaces between GaAs and (Al,Ga)As and degraded performance in heterojunction devices. We have observed that by misorienting the substrate slightly from (100), in a manner specific to the growth conditions, smooth (Al,Ga)As layers can be grown at 675 °C for an Al mole fraction of 0.15. Similar conditions for nominal (100) result in a rough, textured morphology. The results suggest that the roughness is due to an energetic instability at the growth surface with respect to the formation of features such as terraces and hillocks. To our knowledge, this is the first reported experimental verification of singular instabilities in (Al,Ga)As grown by MBE. Smooth layers obtained by using an optimal misorientation of 2° 45’from (100) towards (111)A also exhibit superior optical properties as determined from low‐temperature photoluminescence measurements. These findings may have major implications for the performance of heterojunction device structures grown by MBE.

ISSN:0021-8979    

DOI:10.1063/1.335884

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A computer simulation is employed to demonstrate, in a two‐dimensional growth model, that a vapor‐deposited thin film of low adatom mobility undergoes a sudden change from a porous columnar microstructure to a densely packed film if the substrate temperature is increased to a certain value. The temperature where this structural transition occurs is shown to be related to the lower boundary temperature of the empirical structure‐zone model. The dependence of the transition temperature and range on the vapor deposition rate is discussed.

ISSN:0021-8979    

DOI:10.1063/1.335885

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The initial stage of Ge heteroepitaxy on a Si(100)‐2×1 surface has been investigated by low‐energy electron diffraction (LEED) and Auger‐electron spectroscopy (AES). The growth mode of the Ge films was studied by measuring the decrease in the Si(LVV) AES line at 92 eV with an increase in the Ge overlayer thickness. The Ge films deposited at room temperature exhibit layer‐by‐layer growth up to at least six monolayers. When the substrate is heated up to 350 °C, the growth mode is characterized by the Stranski–Krastanov type; i.e., the first three monolayers of growth is followed by island formation. Although these characteristics of the growth mechanism are similar to the case of Ge on Si(111)‐7×7 surfaces, annealing behavior of the Ge films suggests that the bond strength between Ge and Si is stronger on Si(100) than on Si(111) surfaces. In contrast to the case of Ge on Si(111) surfaces, where the original 7×7 superstructure of the Si surface is replaced by a new 5×5 pattern at about two‐monolayer coverage of Ge, the original 2×1 LEED pattern is not strongly disturbed up to about 1–2 monolayers of Ge. In addition to the detailed study on the initial stage of heteroepitaxial growth, we observed that thick Ge films deposited onto Si(100) surfaces held at 350 and 470 °C display a sharp 2×1 LEED pattern and demonstrate a single‐crystal growth of a Ge(100) face on the Si(100) surface. This is further supported by a measurement of the x‐ray diffraction pattern of the Ge films.

ISSN:0021-8979    

DOI:10.1063/1.335886

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A line‐source electron beam has been used to melt and recrystallize isolated Si layers to form Si‐on‐insulator structures. Heat flow calculations for these layered structures have been developed which correctly predict the observed recrystallization. Using sample sweep speeds of 100–600 cm/s and peak power densities up to 75 kW/cm2in the 1×20‐mm beam, we have obtained single‐crystal areas as large as 50×350 &mgr;m. Seed openings to the substrate are used to control the orientation of the regrowth and the heat flow in the recrystallization film.

ISSN:0021-8979    

DOI:10.1063/1.335887

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thermoelastic attenuation of Rayleigh waves is larger than that of bulk waves because heat is conducted not only in the propagation direction, but also normal to the surface. This attenuation is further enhanced if the thermal expansivity is a function of depth below the surface. Expressions are obtained for the attenuation and some experimental data on Rayleigh wave attenuation is discussed.

ISSN:0021-8979    

DOI:10.1063/1.335888

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The hydrostatic pressure coefficient of Au acceptor levelsETin Si was measured by transient capacitance method. Under the pressure range of 0–8 kbar, the pressure coefficient ∂(Ec−ET)/∂P=−1.9 meV/kbar. The electron capture cross section of Au acceptor centers is independent of pressure within experimental accuracy. For defect levels with defect potential ofTdsymmetry, the uniaxial stress coefficient ∂(E¯c−E¯T)/∂Fis isotropic and equal to one‐third of corresponding hydrostatic pressure coefficient. By comparing the present result of hydrostatic pressure coefficient with the uniaxial stress coefficient reported by X. C. Yau, G. G. Qin, S. R. Zeng, and M. H. Yuan [Acta Phys. Sin.33, 377 (1984)], one concludes that the defect potential is far fromTdsymmetry. Therefore, the Au acceptor levels are unlikely to have been originated by simple gold substitutional or interstitial configuration in Si.

ISSN:0021-8979    

DOI:10.1063/1.335889

出版商:AIP    

年代:1985

数据来源: AIP