摘要:

Ion beam induced damaging and amorphization of crystalline InP is investigated. 100 keVB+,300 keVSi+,200 keVAr+and 600 keVSe+ions are implanted into⟨100⟩InP at temperatures ranging from 80 K to 420 K. The implanted layers are analyzed using Rutherford backscattering spectrometry in channeling configuration, cross section transmission electron microscopy and optical spectroscopy in the sub-gap frequency region. The temperature dependence of damage production can be represented assuming a thermally stimulated defect diffusion within the primary collision cascades, resulting in a shrinkage of the remaining defect clusters. At a critical temperatureT∞these clusters dissolve completely and only point defect complexes nucleate. Then, amorphization occurs only at very large ion fluences(≈1016cm−2)and the process seems to be influenced by the high amount of implanted ions. A defect band forms around the projected range of the implanted ions, which may act as a diffusion barrier for point defects. The range ofT∞from≈350K forB+and≈420K forSe+ions corresponds to the annealing stage II of defects in InP, which can be related to the mobility of phosphorous interstitials. This indicates that phosphorous interstitials play an important role during ion irradiation of InP. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366499

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The vibrational densities of states for theSiO2Bethe lattices of different Si–O–Si angles and various local bonding structures ina-SiO2:Hare calculated. It is found that the Si–O–Si bond-stretching mode shifts to a higher frequency and the bond-bending mode shifts to a lower frequency when the Si–O–Si bond angle increases. The SiH bond-bending mode lies at876 cm−1and there is an additional mode, which comes from the coupled motions of SiH and Si–O–Si bonds, at a lower frequency. This mode is not revealed by experiments. The Si-dangling bond has minor effects to the vibrational spectrum of thea-SiO2.The Si–O bond-stretching mode, of the O atom with dangling bond, shifts to a much lower950 cm−1compared to the1200 cm−1of the Si–O–Si bond-stretching mode of bulkSiO2.The Si–OH bond-stretching mode has a peak at932 cm−1which is slightly less than that of the Si–O bond of the dangling O atom. Under thermal annealing, some H atoms will evolve and the O atom will become a dangling atom or form a Si–O–Si bond with the other Si atom. The Si–Si bond gives an additional Si–Si vibrational mode at464 cm−1in the spectrum. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366488

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We introduce the collective pinning of dislocations in disordered quenched solid solutions and calculate the macroscopic mechanical response to a small dc or ac applied stress. This work is a generalization of the Granato–Lu¨cke string model, able to describe self-consistently short and long range dislocation motion. Under dc applied stress the long distance dislocation creep has at the microscopic level avalanche features, which result in a macroscopic nonlinear “glassy” velocity-stress characteristic. Under ac conditions the model predicts, in addition to the anelastic internal friction relaxation in the high frequency regime, a linear internal friction background which remains amplitude-independent down to a crossover frequency to a strongly nonlinear internal friction regime. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366463

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The origins of two types of electromigration failure models are explored starting with the basic transport differential equations including the effects of electromigration-induced mechanical stress. We compare the results of a nucleation model, in which failure is determined by the time required to build up a critical stress or a critical vacancy concentration at a site of atomic flux divergence, with a void-growth model, in which failure is linked to the growth of a void to a critical size. Two particular applications of the model are investigated, and the results are shown to be in good agreement with available experimental data. In one example, the effect of the presence of a field-free reservoir region extending beyond the current-carrying region of the line is compared to the case without such a field-free extension. In the other, the effects under pulsed dc current stress are examined in comparison to dc current. Possible applications of this model to design verification are also discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366464

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A diffusional model of interface displacement kinetics is proposed for the growth ofnintermediate compounds at an initially planar interface between two semi-infinite phases. The model is based on the solution of Fick’s equations with the restrictive assumptions of simultaneous growth ofnintermediate phases, unidirectional diffusion flow, and local equilibrium conditions. The velocity of each interface follows the parabolic law and the(n+1)kinetic coefficients are expressed as a function of boundary concentrations and diffusion coefficients of all the phases via(n+1)nonlinear equations. A parametric study of the kinetic coefficients, corresponding to realistic situations of initial solid-solid or solid-liquid interface, is developed for systems with one or two intermediate layers. If two interacting initial phases &agr; and &bgr; are such that the chemical diffusion coefficientD&agr;(in &agr;) is smaller thanD&bgr;(in &bgr;), it is found that the interface velocities are enhanced by: (a) increases inD&bgr;,(b) increases in the solubility limit in &bgr;, and (c) reduced miscibility gaps at the interfaces. Moreover, the widths of the intermediate layers are increased by: (a) decreases inD&bgr;and (b) increases in the diffusion coefficients and solubility limits in these intermediate phases. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366465

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A series of Mg-doped GaN films(∼1–1.3 &mgr;m)grown by reactive molecular beam epitaxy at substrate temperatures of 750 and 800 °C has been studied by high-resolution electron microscopy (HREM) and Raman spectroscopy. Stacking defects parallel to the substrate surface were observed in samples grown on sapphire substrates at 750 °C with AlN buffer layers (60–70 nm) at low Mg concentration. A transition region with mixed zinc-blende cubic(c)and wurtzite hexagonal(h)phases having the relative orientations of(111)c//(00.1)hand(11¯0)c//(10.0)hwas observed for increased Mg concentration. The top surfaces of highly doped samples were rough and assumed a completely zinc-blende phase with some inclined stacking faults. Samples grown with a Mg cell temperature of 350 °C and high doping levels were highly disordered with many small crystals having inclined stacking faults, microtwins, and defective wurtzite and zinc-blende phases. Correlation between HREM and Raman scattering results points towards the presence of compressive lattice distortion along the growth direction which might be attributable to structural defects. The films grown at 800 °C had better quality with less observable defects and less yellow luminescence than samples grown at 750 °C. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366466

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Photoluminescence (PL) and spectroscopic ellipsometry measurements on CdTe/Si strained heterostructures grown by molecular beam epitaxy were carried out to investigate the effect of the strain and the dependence of the strain on the Si tilted substrates. The results of the PL spectra showed that the relative intensity ratio between the peak at 1.452 eV and the bound-exciton peak for the CdTe epilayer grown on the Si (100) 1° tilted substrate had a minimum value and that the strain for the CdTe epilayer grown on the Si (100) 8° tilted substrate had a minimum value. When rapid thermal annealing (RTA) was performed at 55 °C, the PL spectra showed that the relative intensity ratio between the peak at 1.452 eV and that at 1.574 eV for the CdTe epilayer grown on the Si (100) 8° tilted substrate had a minimum value and that the strain for the CdTe epilayer grown on the Si (100) 1° tilted substrate had a minimum value. Spectroscopic ellipsometry measurements showed that the spectrum of the dielectric constant of the CdTe epilayer grown on the Si (100) 8° tilted substrate is similar to that of the CdTe bulk. These results indicate that the strains in the CdTe layers grown on Si substrates are strongly dependent on the Si substrate orientation and that the crystallinity of the CdTe epitaxial layer grown on the Si substrate is remarkably improved by RTA. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366467

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A series of lattice-matched or compressively strained InGaAs layers were grown by gas source molecular beam epitaxy on V grooved InP substrates, with grooves bounded by {211}Aor {111}Bfacets. The stress field associated with the layers was measured by the degree of polarization technique, and compared to the predictions of analytical or finite element models. Good agreement was found for the {211}AV grooves, but both the nominally lattice-matched and compressively strained layers grown on {111}B V grooves displayed similar degree of polarization maps. Analytical electron microscopy demonstrated that the {211}A V-groove samples had the targeted composition, but the {111}B samples showed much higher In/Ga ratios at the bottom of the groove than the expected values. Indium enrichment at the bottom of the groove led to defect formation there, and left the V groove of both the lattice-matched and compressively strained samples under a net compressive force. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366468

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Amorphous carbon films with highsp3content were deposited by magnetron sputtering and intense argon ion plating. Above a compressive stress of 13 GPa a strong increase of the density of the carbon films is observed. We explain the increase of density by a stress-induced phase transition ofsp2configured carbon tosp3configured carbon. Preferential sputtering of thesp2component in the carbon films plays a minor role compared to thesp2⇒sp3transition at high compressive stress formed during the deposition process. Transmission electron microscopy shows evidence of graphitic regions in the magnetron sputtered/Ar plated amorphous carbon thin films. Differences in the microstructure of the tetrahedral amorphous carbon (ta–C) films deposited by filtered arc and mass selected ion beam; and those films deposited using magnetron sputtering combined with intense ion plating can be used to explain the different electronic and optical properties of both kinds of ta–C films. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366469

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The high-index (881) surface has been studied by ultra-high-vacuum scanning tunneling microscopy (STM). Reconstruction of the (881) Si surface was found to occur, as evident from the appearance of a number of different characteristic patterns in the STM image, including various kinds of terraces, step walls, and kinks. A typical terrace had, on average, a (7×2) reconstruction. The step walls consisted of several split lattices. Their multiple reciprocal networks and their relationship to the step walls has been analyzed. The kinks were found to consist of one-dimensional long-period superlattices. The reason for the disorder is discussed in terms of the relationship between the effective dangling-bond density and the periodic bond chain vector approximation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366548

出版商:AIP    

年代:1997

数据来源: AIP