摘要:

Temperature profiles induced by a cw laser beam in a semiconductor are calculated. The calculation is done for an elliptical scanning beam and covers a wide range of experimental conditions. The limiting case of a circular beam is also studied. This calculation is developed in the particular cases of silicon and gallium arsenide, where the temperature dependence of the thermal conductivity has been taken into consideration. Using a cylindrical lens to produce an elliptical beam with an aspect ratio of 20, a 1‐mm‐wide area of an ion‐implanted silicon wafer was annealed in a single scan. The experimental data are consistent with the extrapolation of solid‐phase epitaxial regrowth rates to the calculated laser‐induced temperatures.

ISSN:0021-8979    

DOI:10.1063/1.327420

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Identification using the extended x‐ray absorption fine structure technique shows that nickel impurities found in synthetic diamonds exist as fcc Ni and contain an estimated amount of 2.7±1.3 at.% carbon in solution.

ISSN:0021-8979    

DOI:10.1063/1.327366

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Proton‐induced x‐ray emission analysis (PIXEA) and inert gas ion sputtering (IS) have been utilized to generate elemental profiles for three types of ion‐implanted iron alloys. The data were fitted (utilizing a computer program) with symmetrical Gaussian profiles yielding values for the range and range straggle. These parameters were then compared with those obtained from the theory of Lindhard, Scharff, and Schiott (LSS). Changes in the profiles due to annealing were investigated, and values for the diffusion coefficient were obtained assuming Fick’s law. For 25‐keV Ni+and Cr+in iron, the profiles as‐implanted, agree reasonably well with LSS theory and exhibit ’’normal’’ diffusion characteristics at 500 °C. For 25‐keV Al+in iron, the profile as implanted is much broader than predicted and exhibits substantial enhanced diffusion at temperatures up to 500 °C.

ISSN:0021-8979    

DOI:10.1063/1.327367

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

By calculating the value of the unknown oxygen positional parameterxfor a large number ofA3+2B4+2O7pyrochlores, it was determined that increasing the radius of theAcation in a series of constantBincreased the value ofx, and that increasing the radius of the B cation in a series of constantAdecreased the value ofx. The region of pyrochlore formation has a range ofxvalues from 0.404 to 0.432 and containsBO6polyhedra that closely approach Ohsymmetry andAO8polyhedra that are highly deformed. It was shown that the characteristics of theBO6polyhedra were the most important in determining whether or not a pyrochlore would form.

ISSN:0021-8979    

DOI:10.1063/1.327368

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

GaAs single‐crystals wafers are implanted at room temperature with 400‐keV Te+ions to a dose of 1×1015cm−2to form an amorphous surface layer. The recrystallization of this layer is investigated by backscattering spectrometry and transmission electron microscopy after transient annealing byQ‐switched ruby laser irradiation. An energy density threshold of about 1.0 J/cm2exists above which the layer regrows epitaxially. Below the threshold the layer is polycrystalline; the grain size increases as the energy density approaches threshold. The results are analogous to those reported for the elemental semiconductors, Si and Ge. The threshold value observed is in good agreement with that predicted by the simple model successfully applied previously to Si and Ge.

ISSN:0021-8979    

DOI:10.1063/1.327369

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Ion bombardment or backsputtering of SiO2films has been shown to result in severe insulator degradation in device processing. Here we have investigated the effects of low‐energy neutral‐particle bombardment on device quality SiO2films and have compared degradation produced by neutral‐particle bombardment with that produced by ion bombardment. These results show that (1) neutral‐particle bombardment produces substantially less (by two or three orders of magnitude) fixed charge at the SiO2/Si interface than does ion bombardment; (2) the most prominent degradation produced by neutral bombardment is the creation of a large interface state density across the band gap which is not related to a nonuniform charge distribution at the interface; (3) metal‐oxide‐semiconductor degradation produced by neutral bombardment may be removed by annealing at temperatures ?400 °C. Comparison of oxide charge degradation produced in SiO2by ion and neutral‐particle bombardment suggests that the neutralization processes at the vacuum‐SiO2interface, which take place only in ion bombardment, have the dominant role in this degradation. As a result of these processes, in ion bombarded samples, charge carriers migrate to the SiO2/Si interface in the field across the oxide film. This mechanism is absent in the case of neutral bombardment.

ISSN:0021-8979    

DOI:10.1063/1.327370

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Variability of elastic constants in stainless‐steel 304 was determined by measuring longitudinal and transverse ultrasonic velocities in 20 samples acquired randomly. Three kinds of variations—sample to sample, directional within a sample, and repeated measurements on a single sample—are reported for four elastic constants: the bulk modulus, Young’s modulus, shear modulus, and Poisson’s ratio. Because of surprisingly small variations, 1% or less, the principal problem became measurement sensitivity and reproducibility. To overcome this problem, a high‐resolution measurement system was devised using general‐purpose equipment augmented with a very simple impedance‐transforming amplifier and an FET transmission gate. With this system the often‐reported troublesome transit‐time correction disappeared. Effects due to frequency and directionality were negligible.

ISSN:0021-8979    

DOI:10.1063/1.327371

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Ultrasonic measurements of longitudinal and shear sound speeds and absorptions were made on poly(4‐methyl pentene‐1) or PMP. The measurements were made at 1.8 MHz and covered the temperature range from 0 to 70 °C. PMP is of interest because it has a lower density (0.835 g/cm3) than any other commercially available high polymer. PMP was found to have a major structural relaxation (the glass transition) at 25 °C. An analysis of the various Gru¨neisen parameters of the polymer leads to the conclusion that one‐fifth of the normal modes of vibration of PMP are interchain rather than intrachain. PMP was evaluated as an acoustic window material and compared with poly(acrylonitrile butadiene styrene) or ABS, another rigid acoustic window material. For an infinitely thick layer of PMP, the reflected signal is 20 dB less than incident, while for ABS the reflected signal is 16 dB less. For plates of finite thickness, PMP is a better acoustic window than ABS at most, but not all, angles of incidence.

ISSN:0021-8979    

DOI:10.1063/1.327373

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Several semisintered oxides have been developed for transmitting media able to be employed in multianvil high‐pressure vessels. The oxides are MgO, BeO, ZrO2, Al2O3, Fe2O3, and Mg2SiO4, all having porosity of approximately 35–55%. Pressures higher than 220 kbars can be reproducibly generated inside each medium.

ISSN:0021-8979    

DOI:10.1063/1.327374

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Precursor amplitudes have been measured for impact‐produced shock waves traveling in ⟨111⟩ directions in LiF. Impact pressures range from 30 to 98 kbars and precursor amplitudes for the larger pressures are about 60 kbars for crystals containing approximately 100 ppm Mg and about 50 kbars for undoped crystals. The greatest impact pressure at which elastic response is preserved is about 40 kbars. No precursor decay is evident from the measurements, which include sample thicknesses between 0.3 and 5 mm. Mean precursor decay rates inferred for the first 1/2 mm of travel range up to about 100 kbars/mm. Primary slip systems are not active in this geometry and the shear stress on secondary systems ranges up to 38 kbars at the highest impact pressure. This is still well below theoretical shear strength. Mechanisms for the inferred decay are not identified.

ISSN:0021-8979    

DOI:10.1063/1.327375

出版商:AIP    

年代:1980

数据来源: AIP