摘要:

Hyperfine control of the interface structure and composition between GaAs and AlAs films grown by molecular beam epitaxy has been achieved by deposition on vicinal (100) GaAs substrates. This control is demonstrated by producing (GaAs)m‐(AlAs)nsubmonolayer (mand/orn<1) superlattices over a wide temperature range. Analysis of these submonolayer superlattices by transmission electron microscopy shows that the layer growth regime is dominant and that layer nucleation is initiated preferentially at the step edges on the (100) vicinal surface. Potential applications of submonolayer superlattices including the growth of superlattice layers perpendicular to the substrate surface are described.

ISSN:0003-6951    

DOI:10.1063/1.95332

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

ArF excimer laser radiation has been used to deposit W films on silicon and on SiO2by initiating the gas phase reaction of WF6with H2. Deposition rates >100 nm/min and film resistivities as low as two times the bulk value have been obtained at deposition temperatures of 440 °C. The properties of the laser‐deposited films are compared with those of fims obtained using conventional thermal deposition techniques. Film resistivity correlates with the microstructure which in turn depends on the deposition temperature; above 350 °C the low‐resistivity &agr;‐W phase dominates.

ISSN:0003-6951    

DOI:10.1063/1.95333

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Shock compression experiments were performed on samples of 0.13 g/cm3density silica aerogel. The aerogel is a transparent, homogeneous, open cell, SiO2, glass structure with a pore size of 10 nm. A shock velocity of 11.4 km/s was measured at 14.6 GPa (146 kbar) and over sevenfold compression of the specimen, which is threefold expanded relative to the density of crystalline &agr;‐quartz. A shock temperature of nearly 1 eV was measured at 6.7 GPa. These experiments access a new regime for accurate laboratory measurements on high‐temperature, expanded‐volume states of glass.

ISSN:0003-6951    

DOI:10.1063/1.95334

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Changes in optical reflectivity of hydrogenated amorphous silicon films of up to 90% have been induced by Ar laser processing, and are correlated with hydrogen evolution from the material. Accompanying changes greater than three orders of magnitude in resistivity also provide a mechanism for interrogation of the stored data by an electron beam. Storage densities as high as 109bits/in2for optical recording and 1011bits/in2for recording with electron beams are predicted on the basis of these results.

ISSN:0003-6951    

DOI:10.1063/1.95335

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Solid‐state surface‐energy‐driven grain growth in 30‐nm‐thick Ge films on SiO2, encapsulated with SiO2, produces a predominance of (110) crystallographic texture in secondary grains several micrometers in diameter. If the SiO2substrate is patterned with a 0.2‐&mgr;m period relief grating, ∼10 nm deep, with approximately square‐wave profile, many of the secondary grains that form have (100) texture. These grains show a graphoepitaxial orientation with ⟨100⟩ directions preferentially parallel to the grating axis.

ISSN:0003-6951    

DOI:10.1063/1.95336

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Plasma‐enhanced chemical vapor deposition of a metastable phase of tungsten ( &bgr;‐W) is performed using tungsten hexafluoride and hydrogen as source gases. At 350 °C, the as‐deposited resistivity of these films is ∼50 &mgr;&OHgr; cm. After heat treatments between 650 and 750 °C in forming gas, the resistivity drops below 11 &mgr;&OHgr; cm. Concomitant with this resistivity change is a phase change to &agr;‐W, the equilibrium, body‐centered‐cubic form.

ISSN:0003-6951    

DOI:10.1063/1.95337

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Effects of ion irradiation on lateral diffusion have been studied in device geometry structures prepared by deposition of Cr films on patterned Si substrates with scanning electron microscopy and transmission electron microscopy. Lateral diffusion can be greatly reduced, and even completely suppressed by using arsenic ion implantation, but not by using silicon irradiation. In Cr/Si planar structures the dopant atoms accumulate near the Si‐CrSi2interface or redistribute into the unreacted Cr films. The presence of 1–2 at. % arsenic substantially slows down the CrSi2formation. We attribute the suppression of lateral diffusion in device geometry structures to interactions of impurities with the matrix atoms.

ISSN:0003-6951    

DOI:10.1063/1.95338

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Modulation‐dopedp‐AlGaAs/GaAs heterojunctions have been grown by molecular beam epitaxy. The effects of undoped AlGaAs spacer thickness on sheet carrier density and on Hall mobility have been investigated. A mobility of 97 000 cm2 V−1 s−1has been obtained at 4.2 K for a sheet density of 1.7×1011cm−2. This is the highest mobility reported for holes in III‐V compound semiconductors. A valence‐band offset of 210±30 meV was deduced for Al0.5Ga0.5As /GaAs heterojunctions.

ISSN:0003-6951    

DOI:10.1063/1.95339

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Monte‐Carlo simulation is an efficient means of investigating electron transport in semiconductors. Nevertheless, the prevailing physical phenomena at low electric fields are usually neglected because a Monte‐Carlo algorithm is needed only at rather high fields. It is shown that reaching thermodynamic equilibrium between electrons and crystal lattice in a Monte‐Carlo simulation requires only including inelastic interactions with acoustic phonons at the center of the Brillouin zone. Electron energy and velocity distributions at equilibrium resulting from this umproved model are compared with the theoretical Fermi–Dirac distribution.

ISSN:0003-6951    

DOI:10.1063/1.95340

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Spatially resolved electrical and spectroscopic behavior around isolated grown‐in dislocation inp‐type undoped GaAs crystals grown by liquid‐encapsulated Czochralski technique is investigated. Surface spreading resistance is found to remarkably increase at about 100 &mgr;m in diameter around dislocations. In a corresponding area, photoluminescence intensity of the 1.49‐eV and 1.44‐eV acceptor level peaks decreases. However, that of 0.8‐eV deep level peak does not vary. These results demonstrate that dislocations should give rise to carrier density variation due to the relative concentration change of levels around them.

ISSN:0003-6951    

DOI:10.1063/1.95341

出版商:AIP    

年代:1984

数据来源: AIP