摘要:

The crystalline quality of Ge films grown on a Si(100)‐2×1 substrate by molecular beam epitaxy has been studied by means ofinsitureflection high‐energy electron diffraction, x‐ray diffraction, and Raman scattering spectroscopy. The Ge layers of thickness up to 4000 A˚ were deposited at 400 °C with and without thin (200 A˚) Ge buffer layers predeposited at 200 °C. It was found that the buffer layers were effective in improving the quality of the thin Ge overlayers, while they had no noticeable effect on the thick layers whose x‐ray and Raman spectra were comparable to that of bulk Ge. It was also found that, even after the Ge films became relaxed with a generation of dislocations, they were not free from strain due to the lattice mismatch. This finding is supported by the quantitative estimate of the Raman frequency shift in terms of the uniaxial strain model.

ISSN:0021-8979    

DOI:10.1063/1.344510

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Several techniques are presented which allow magnetic force microscopy to be performed while simultaneously mapping the surface topographic features of a magnetic sample. The separation of magnetic and topographic features measured simultaneously with a scanning force microscope is made possible by an instrument based on a differential interferometer that can detect cantilever deflections of 0.005 nm at a frequency as low as 1 Hz. Two different applications are presented.

ISSN:0021-8979    

DOI:10.1063/1.344511

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The structures of microcrystalline or amorphous gallium arsenide (GaAs) introduced by 120‐keV Si+‐ or P+‐ion implantation with a dose of 1×1016atoms/cm2and the subsequent regrowth properties annealed by rapid thermal annealing in the range from 300 to 900 °C have been investigated by Raman scattering (RS) and by the van der Pauw measurement (sheet carrier concentration and sheet resistivity) [Phillips Res. Rep.13, (1958)]. Raman spectra of the LO‐phonon mode observed for 514.5‐ and 457.9‐nm excitation of an Ar+laser have been analyzed on the basis of a spatial correlation model [H. Richteretal., Solid State Commun.39, 625 (1981); K. K. Tiongetal., Appl. Phys. Lett.44, 122 (1984)]. The results show that the regrowth stages and the regrowth rates of the disordered GaAs in the annealing process depend on the excitation wavelength and annealing temperature, and the damaged layer regrows epitaxially toward the surface. Sheet carrier concentration was observed to increase steeply, and sheet resistivity decreased rapidly when the annealing temperature was raised from 600 to 700 °C. These results are consistent with the RS result of the 514.5‐nm excitation in the same temperature range. The above results indicate that the implanted silicon atoms replace the GaAs lattice sites and the recrystallization of the microcrystalline GaAs substrate occurs in this temperature range. On the other hand, the sheet resistivities were observed to increase from about 5×104to 5×106(&OHgr;/&laplac;), when the annealing temperature was raised from room temperature to 500 °C, contrary to the 600–700 °C case. From these facts, it is concluded that the regrowth process originates principally from the recrystallization of the ion‐implantation‐induced damaged GaAs substrate.

ISSN:0021-8979    

DOI:10.1063/1.344512

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In the present paper, the characteristics of low‐frequency stable damping are studied in a multiphase eutectoid Al‐Zn alloy. Experimental results show that, within a low‐temperature and low‐strain‐amplitude range, the damping evidently manifests itself by linear viscous characteristics, namely, it obeys a lawQ−1=(B/fn)exp(−nH/kT), whereHis the real process activation energy,Bandn(=0.21) are two experimental parameters, andkis the Boltzmann constant. A value ofH=0.74 eV is obtained, which is closely related to the viscosity during interface motion. Accordingly, a linear viscous interface motion mode is put forward and can explain the experimental results as well.

ISSN:0021-8979    

DOI:10.1063/1.344513

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Ion‐mixed films of Fe53Ti47were produced by ion irradiating a Fe‐Ti multilayer structure on AISI 304 stainless steel. The ion‐mixed films were subsequently implanted with nitrogen, carbon, or both carbon and nitrogen. The microstructure following nitrogen implantation consisted of a bcc solid solution of iron and titanium and finely dispersed TiN precipitates. In the cases of carbon or carbon and nitrogen implantation, a two‐phase structure consisting of an amorphous matrix with TiC or Ti(C,N) precipitates was found. All these films initially possessed improved tribological properties as revealed by lowered friction and increased wear resistance. However, after an extended test of 1000 wear cycles, a reduced friction was only observed for the carbon or carbon and nitrogen implanted samples. The wear track on the dual implanted surface was extremely smooth, while the surface of the nitrogen‐implanted sample was partly worn through, causing the friction to increase to the level of the untreated sample. The improved tribological properties of the implanted films are attributed to an increase in surface hardness. However, the surface hardness is unable to explain differences between different implantations. In the case of the dual carbon and nitrogen implantation, improvements appear to be in part the result from an increased capability to accommodate plastic deformation. These conclusions are supported by transmission electron microscope studies of the wear tracks as well as by nanoindentation measurements.

ISSN:0021-8979    

DOI:10.1063/1.344514

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Sufficient conditions on the phase geometry for the reduction of even‐order bounds to bounds of second order are derived. It is found that finite‐rank laminates satisfy the sufficient conditions asymptotically as the length scale of the laminar microstructure goes to zero. This result is used to show that the effective elastic tensors of finite‐rank laminates saturate the even‐order bounds in the fine‐scale limit.

ISSN:0021-8979    

DOI:10.1063/1.344515

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Vibrational absorption of semi‐insulating O‐containing GaAs samples has been investigated under high‐resolution spectroscopy at low temperature and many sharp lines due to localized modes have been observed. Some of them, between 714 and 730 cm−1had already been ascribed to some (Ga,O)‐related center having features common with the vacancy‐oxygen defect in silicon, but a new state related to this center, giving a local mode near 713 cm−1is reported here for the first time. Another new low‐frequency mode at 604 cm−1is also reported, involving probably nitrogen or more likely oxygen bonded to two next‐nearest‐neighbor Ga atoms. The attribution of new modes in the 950–1400 cm−1spectral region to complexes involving oxygen, arsenic, and eventually impurities with 100% isotopic abundance is discussed. The effects of near‐infrared illumination on the observation of the (Ga,O)‐related modes between 713 and 730 cm−1and on a new mode at 983 cm−1have been studied. Tentative explanations based either on metastability or on photo‐induced changes of the charge states of the centers are proposed. These results seem to show that in GaAs, oxygen decorates native centers and that this kind of study could provide a clue to their understanding.

ISSN:0021-8979    

DOI:10.1063/1.344516

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the phase formation sequence for the reaction of Nb and Al in multilayer films using cross‐sectional transmission electron microscopy and x‐ray diffraction. NbAl3is the first intermetallic phase to form. Contrary to previous reports, we find evidence from cross‐sectional transmission electron microscopy that the sigma phase, Nb2Al, is not bypassed in the reaction sequence. Instead, its formation is concurrent with the formation of the superconductingA15 phase, Nb3Al. However, depending on the periodicity and the composition of the film, the Nb2Al phase can be consumed by the Nb3Al phase for long annealing times. The significance of this phase formation sequence to powder metallurgically processed magnet wire is discussed.

ISSN:0021-8979    

DOI:10.1063/1.344517

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A light gas gun has been used to measure the Hugoniot of Metglass 2605CO ribbon. Quartz gauges were used to measure stress. Both front‐ and rear‐surface measurements were done. Front‐surface experiments impacted the ribbon onto quartz gauges, while back‐ surface experiments impacted an aluminum plate into the ribbon which was backed by a quartz gauge. Single layers and composite layers of the ribbon were used. Two single‐layer front‐surface experiments provided the most accurate data.

ISSN:0021-8979    

DOI:10.1063/1.344518

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Selected‐area deposition of diamond film has been accomplished on Si substrates prepared by two different methods: reactive‐ion etching (RIE) and amorphous‐Si masking (ASM). In the RIE method, a Si substrate polished by a diamond paste was patterned with a photoresist mask, and the unprotected areas were etched by RIE, followed by a complete removal of the photoresist films. The diamond deposition was done by electron‐assisted chemical‐vapor deposition (CVD), and diamond films grew only in the areas once covered with the photoresist films and not etched by RIE. In the ASM method, a polished Si substrate was also photolithographically masked with photoresist, followed by a uniform deposition of a hydrogenated amorphous silicon (a‐Si:H) film. The photoresist film was then lifted off together with the overlay of depositeda‐Si:H, leaving the polished Si surface patterned with ana‐Si:H mask. In this case, the diamond deposition was done by microwave plasma CVD, and diamond films grew only in the areas not covered witha‐Si:H. In both cases, well‐defined diamond patterns with line/space dimensions of a few micrometers were formed on the substrates.

ISSN:0021-8979    

DOI:10.1063/1.344519

出版商:AIP    

年代:1990

数据来源: AIP