摘要:

X‐ray Bragg reflection widths and reflectivities are calculated by the dynamical scattering theory. Results on the binary II‐VI semiconductors CdTe, HgTe, and the ternary alloys CdHgTe and CdZnTe are reported. For comparison, results on several III‐V compounds are also reported. The dependence of the reflection widths and reflectivities on alloy composition, wavelength, layer thickness, and material properties are discussed. Especially in alloys, interesting effects, such as drastic changes of the reflectivity depending on the alloy composition, appear. The behavior of the widths and reflectivities can be understood by the examination of the competing processes of absorption and extinction. The results from calculated intrinsic reflex profiles are compared with approximation formulas.  

ISSN:0021-8979    

DOI:10.1063/1.352040

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A method is presented to calculate two‐dimensional defect distributions induced by ion implantation through openings in a masking layer. It is shown that a realistic description of this model requires depth‐dependent lateral standard deviations to describe the dopant and the damage point response functions. Further refinements of the theory include arbitrary shapes for the mask edges and different materials in the masking layer and in the substrate. Cross‐sectional electron microscopy observations have been carried out to visualize the two‐dimensional extension of amorphous layers created by As implantation in silicon for different mask edge angles. It is shown that the theory fits well the cross‐sectional transmission electron microscopy observations. More generally, this study shows that for abrupt mask edges, the lateral extension of the two‐dimensional defect profile beneath the mask edge is directly governed by scattering of the ions and of the subsequent recoil atoms and, as a direct consequence, by the lateral standard deviation of the damage point response function. For tapered mask edges, however, the contribution of ions that pass through the mask edge region before damaging the substrate may be very high with respect to scattering effects.

ISSN:0021-8979    

DOI:10.1063/1.352041

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Polycrystalline Fe78B13Si9alloys with nanoscale grain sizes prepared by the crystallization method have been studied by positron lifetime and Doppler‐broadened line‐shape measurements. The results obtained are different from those on amorphous or coarse‐grained crystalline alloys with the same composition. When the grain sizes are clearly smaller than the mean positron diffusion length (L+&bartil;100 nm), saturation trapping and annihilation of the positrons in the samples should occur at traps within the interfaces. There are two kinds of defects in the interfaces of the nanocrystalline FeBSi alloys, i.e., the free volumes (the size of which is slightly smaller than that of the amorphous counterpart) and the microvoids. The dependence of grain sizes on the type of interface defects and structure‐sensitive properties has also been studied by positron spectroscopy. The measurements and comparison of the mean positron lifetime &tgr;¯ and the Doppler parameterSon the nanocrystalline, amorphous, and coarse‐grained crystalline alloys have given a satisfactory explanation for the relationship between the structure‐sensitive properties, grain sizes, and crystalline states.

ISSN:0021-8979    

DOI:10.1063/1.352042

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The precipitation of oxygen has been investigated for 2 MeV electron irradiated silicon samples, with irradiation doses 1015–1018cm−2, at an annealing temperature of 900 °C for up to 444 h. The samples initially contained either different concentrations of the vacancy‐oxygen (VO) center created at the irradiation, or the vacancy‐dioxygen (VO2) center created by annealing at 350 °C after the irradiation. It was found that the incubation time and oxygen decay rate for the precipitation process was irradiation dose dependent. Among the VO samples this could be caused by a supersaturation of vacancies, which would both decrease the critical precipitate radius and enhance oxygen diffusion. It was also found that an enhanced precipitation among VO samples appeared as a transient process, which has not been observed at this high temperature before. A different mechanism could account for the enhanced precipitation rate for samples with VO2. For these samples results from transmission electron microscopy studies, Wright etching, and growth of precipitate related infrared (IR)‐absorption bands all indicate increased precipitate number densities. High temperature rapid thermal annealing shows that VO2develops into VO2+Oi. It is therefore suggested that the VO2center is a nucleus for oxygen precipitation. Different incubation times were observed for the growth of the precipitate IR bands, which is explained by the appearance of differently shaped precipitate particles.

ISSN:0021-8979    

DOI:10.1063/1.352043

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In the present work, we have studied the most important parameters which can influence the radiation induced diffusion mechanism of Xe ions implanted into a photoresist film. With this aim, we have Ar post‐bombarded the Xe implanted samples at a fixed Ar ion energy, covering a wide range of fluences. In addition, the implantation fluences, as well as the ion species used in the bombardment, were changed. The results show that the radiation induced diffusion process undergoes a trapping‐detrapping mechanism. The trapping probability is proportional to the implanted fluence, and the detrapping one depends on the kind of ion used in the bombarding experiment. Finally, it is shown that the nuclear energy transfer plays an important role in the radiation induced diffusion mechanism.

ISSN:0021-8979    

DOI:10.1063/1.352044

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The structure of pure amorphous Si, prepared by ion implantation, has been investigated by variable‐energy positron annihilation spectroscopy (PAS) and lifetime measurements of optically generated free carriers. In general, PAS measurements are thought to be sensitive to vacancy‐type defects while the carrier lifetime depends on the density of band‐gap states (e.g., dangling bonds). The PAS measurements indicate that the density of positron‐trapping defects can be reduced by thermal annealing at 500 °C. Concurrent with the removal of structural defects the density of band gap states is reduced as indicated by an increased photocarrier lifetime by a factor of 10. Some material has been implanted with H+and annealed at a low temperature (150 °C). The hydrogen is expected to passivate electrical defects associated with strained and dangling bonds and indeed the photocarrier lifetime is increased in this material. Moreover, the PAS measurements cannot distinguish this material from 500 °C annealed amorphous Si, indicating that (some of) the electrical defects are associated with positron‐trapping, and therefore possibly vacancy‐type, structural defects. Finally, both methods have been used to detect small amounts of ion irradiation damage in annealed amorphous Si.

ISSN:0021-8979    

DOI:10.1063/1.351993

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The incubation time for the crystallization of amorphous Ge (a‐Ge) films was studied as a function of temperature between 150 and 500 °C by means of bothinsitutransmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of the incubation time for free‐sustaineda‐Ge films follows an Arrhenius curve with an overall (nucleation+growth) crystallization process activation energy of 2.0 eV. In the case where thea‐Ge films were on Si3N4substrates, an earlier stage of the crystallization was observed (nucleation), having an activation energy of 1.3 eV. In addition, it was found that a thin metallic layer of Al or Au, deposited on thea‐Ge films, induces a very fast crystallization in the mode of dendritic growth, as reflected by a low activation energy (0.9 eV) for the incubation time temperature dependence.

ISSN:0021-8979    

DOI:10.1063/1.351994

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

High‐resolution triple crystal x‐ray diffraction has been used to monitor the magnitude of diffuse scattering from chemical‐mechanical (CM) polished GaAs. The diffuse scattering, which is attributed to kinematic scattering arising from polish‐induced crystallographic defects, was found to be only slightly affected when each of four CM polish parameters (bromine concentration in Br2/methanol, total polish time, polish pad rotation speed, and force on sample) was varied individually. The combined effect of increases in both the pad rotation speed and the force on the sample increased the magnitude of the diffuse scattering, suggesting the generation of mechanical damage. When all four variables were increased to their maximum values, the diffuse scattering increased dramatically and became anisotropic. We have expressed the magnitude of the diffuse scattering in terms of an ‘‘excess intensity’’ in reciprocal space to provide a semi‐quantitative relation between CM polish parameters and the generation of polish‐induced damage.

ISSN:0021-8979    

DOI:10.1063/1.351995

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Mo/Si soft x‐ray multilayer films have been imaged in cross section by high resolution electron microscopy and the dependence of important multilayer parameters on imaging conditions has been investigated. Multiple measurements of the widths of the Mo crystalline layers were made from images recorded as part of a through‐focal series. The layer thicknesses were found to be insensitive to the focus setting near the Scherzer defocus value (+160 A˚ to −800 A˚). At larger defocus conditions, however, additional Mo fringes were visible so that the Mo crystalline region seemed to become thicker at the expense of the pure Si and interlayer regions. Micrographs recorded with the ML slightly tilted (∼1–2°) from the edge‐on orientation suggested thicker Mo and thinner Si and interlayer regions but the apparent bilayer periodicity did not change measurably. The possibility of changes in multilayer structure induced during cross‐sectional specimen preparation was also shown. Finally, the results of the image analysis are compared with those obtained from small and large angle x‐ray scattering experiments from the same sample.

ISSN:0021-8979    

DOI:10.1063/1.351996

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A photothermal model of ablation is used to investigate the time scales for polymer degradation by UV laser light. In the absence of a significant incubation effect, strong absorbers (e.g., polyimide) are expected to decompose roughly three orders of magnitude faster than weak absorbers (e.g., polymethylmethacrylate), owing to the higher surface temperature attained during the absorption. This difference in the time scales reflects processes taking place at significantly different temperatures and should extrapolate to the overall ablation process. The very short calculated time scales (femtoseconds for polyimide and picoseconds for polymethylmethacrylate) indicate that polymer decomposition occurs rapidly compared to the actual ejection of material. For multipulsed ablation experiments, significant incubation modification tends to increase the absorbance of weak absorbers, making the effect less marked than in the ideal case. Incubation effects are attributed to nonablative decomposition that occurs at cooler temperatures (<1000 K).

ISSN:0021-8979    

DOI:10.1063/1.351997

出版商:AIP    

年代:1992

数据来源: AIP