摘要:

Vacuum evaporation techniques were applied to the epitaxial growth of CrSi2on Si(111) substrates. There are two CrSi2matching faces which offer good lattice matchings, and which are observed experimentally: the (001) and the (111). These are present together in films grown by reactive deposition at temperatures from 450 to 1000 °C, with the latter matching face becoming more dominant as the growth temperature is raised. During an anneal at 1100 °C, however, the regions of the (111) matching face disappear in films ≥∼84 A˚ thick. Moderately good epitaxial alignment is obtained with the other matching face operative. Films ≤∼30 A˚ thick yield an opposite result: they adopt exclusively the (111) matching face as a result of this anneal. For both heteroepitaxial relationships, a strong islanding tendency is manifested during growth (unless the CrSi2layer is more than a few thousands of angstro¨ms thick), which is accentuated by such a post‐growth anneal. The population of CrSi2islands exhibits a gradual strain relaxation with increasing average island size. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359539

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The detailed structure of erbium (Er) sheet‐doped GaAs grown by molecular‐beam epitaxy is directly determined by analysis of the ion‐channeling spectra in the [100], [110], and [111] directions with 2.0 MeV He+beams followed by a recently developed Monte Carlo simulation. It is shown that Er atoms form NaCl‐type crystalline ErAs clusters in the GaAs epitaxial layer at 500 and 580 °C. The clusters grow in the [100] direction with the common three principal axes of the cubic unit cell; the lattice constant of the clusters coincides exactly with that of the zinc‐blende‐type crystalline GaAs epitaxial layer. The shape and size of the clusters can be roughly deduced in the simulation from the dependence of the visible Er fraction on the cluster size for various cluster shapes. These results are consistent with those obtained by cross‐sectional transmission electron microscopy. Almost all Er atoms are located precisely in tetrahedral interstitial sites with 0.1 A˚ standard deviation; only 2% of the Er atoms occupy random sites. These results mean that the lattice constant of the crystalline ErAs clusters is compressed to that for the crystalline GaAs host during the cluster formation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358660

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The first stages of the growth of highly strained ZnTe on (001) CdTe are investigated by reflection high energy electron diffraction, HRTEM (high resolution transmission electron microscopy), x‐ray photoelectron spectroscopy, and x‐ray double diffraction. A precise study of the factors influencing the critical thickness is presented, with emphasis on the effect of Zn pre‐exposure of the CdTe surface on the subsequent ZnTe growth. Below the critical thickness small lattice distortions attributed to a nontetragonal elastic distortion are detected. An exposure of the (001)CdTe surface to a Zn flux leads to the desorption of the Cd atoms present on the top of the surface and to the formation of ac(2×2) reconstructed surface with half a monolayer of Zn on the top of the surface. Finally, the morphology of an ultrathin strained ZnTe layer embedded in a (001)CdTe matrix will be discussed using results obtained from analysis of the digitized HRTEM image. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358661

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Compositional dependence of the ordering probability in GayIn(1−y)P epitaxial layers grown on GaAs substrates is investigated. Experimental results reveal that band‐gap energy reduction due to the ordering is varied with the Ga composition of GayIn(1−y)P and shows a dependence on growth temperature in a wide range of Ga compositions where no serious lattice mismatch occurs. In addition, the change of the ordering of GayIn(1−y)P is confirmed by transmission electron diffraction patterns. For the calculation of the relative ordering probability of the GayIn(1−y)P alloy, a model representing an ordering state with alternative stacking of two tetrahedral micro‐unit cells (three Ga‐P‐one In)/(one Ga‐P‐three In), is proposed. The results of the calculation on the compositional dependence of ordering probability, which are based on internal strain energy states of the unit cells of the GayIn(1−y)P alloy, show good agreement with experimental results. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358662

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Reflectance anisotropy spectroscopy was used to examine the surfaces of AlxGa1−xAs layers grown on GaAs(001) by molecular beam epitaxy, where the Al mole fraction was varied across the whole composition rangex=(0.0,0.25,0.50,0.75,1.0). All surfaces were also independently characterized using reflection high‐energy electron diffraction, and were found to exhibit ac(4×4) reconstruction. After initial changes in the spectra were observed on depositing very thin layers (≤20 monolayers), in the intermediate thickness range a regime was entered in which strong optical interference effects appeared. These effects are accurately accounted for using a four‐media model. For thicker layers (≥8000 monolayers), interference effects were seen to diminish and spectra representative of the surfaces of bulk AlxGa1−xAs were obtained. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358663

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We discuss the motion of an amorphous‐crystalline interface in silicon induced by low energy recoils. We employ molecular dynamics simulation with the Stillinger–Weber interatomic potential for silicon. The temperature of the substrate in these simulations was 250 K. Our results show that when 15 or 20 eV recoils are initiated from the amorphous side of the interface, the crystal regrows by solid‐phase epitaxy. On the other hand, no interface motion was detected for 15 eV recoils launched from the crystalline side, and damage accumulation resulted when the recoil energy was set to 20 eV. The efficiency of recrystallization for this process is 0.67, for both 20 and 15 eV recoils. That is, approximately two silicon atoms transform from the amorphous to the crystalline phase per every three incident recoils. The calculated threshold energy required to produce a stable defect in silicon was found to be substantially lower in an amorphous matrix than in a crystalline lattice. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358664

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In the present work nucleation and growth of diamond by chemical vapor deposition (CVD) on highly oriented pyrolitic graphite (HOPG) and glassy carbon (GC) substrates have been investigated. These carbon substrates represent generic forms of well‐characterized ordered and disorderedsp2bonded carbon materials. The nature of the precursor to diamond CVD is assessed by studying nucleation and growth on substrates abraded with hard powders whose debris may act as initial growth centers, e.g., diamond andc‐BN, and hard powders onto which diamond CVD does not grow heteroepitaxially, e.g., alumina. Based on our experimental results it is concluded that the precursor to diamond nucleation may be debris left after the abrasion process and/or damage created preferentially on graphitic prism planes. A higher density of such damaged prism planes on GC than on HOPG resulted in a larger nucleation density on the former. Different morphologies of single particles deposited on HOPG and GC were found: well faceted on the former, and ball‐like on the later as determined by scanning electron microscopy. This difference is explained on the basis of a larger concentration of active carbon species present at the GC surface as compared to the HOPG surface. The additional source of carbon is from etching of the GC and HOPG substrates which, under the diamond CVD conditions used in the present study, is twice higher for GC. The thermal stability of continuous films deposited on HOPG is better than those deposited on GC. The presence of different carbon phases in the deposited material was investigated by micro‐Raman and scanning‐Auger electron spectroscopies. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358665

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The ‘‘electroless’’ deposition method of Au thin films onn‐type ZnCdTe crystal surfaces has been investigated by atomic force microscopy, x‐ray photoelectron spectroscopy, and low temperature photoluminescence. The blocking contact behavior of these films was strongly dependent on post deposition annealing treatments which were also found to induce modifications in the surface morphology and surface chemical composition. Heat treatments (at 300 °C) in vacuum eliminates most of the interfacial tellurium oxide introduced during the deposition. Annealing also reduces the radiative recombination at defects in the region below the interface and increases the barrier height of the contact. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358666

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The lattice mismatch in chemically vapor deposited epitaxial &bgr;‐SiC (3C‐SiC) films on 6H‐ and 15R‐SiC (0001) substrates was investigated using a high‐resolution x‐ray diffractometer. The misfit parallel and perpendicular to the growth plane was determined to be (&Dgr;c/c)∥=−9.3×10−4and (&Dgr;a/a)⊥=1.9×10−4for the 3C/6Hsystem, and (&Dgr;c/c)∥=−10.0×10−4and (&Dgr;a/a)⊥=2.3×10−4for the 3C/15Rsystem. Our analysis of the lattice parameters in these three SiC polytypes revealed that the Si‐C pair spacings along thecdirection increased with substrate hexagonality, while the lattice spacings along theadirection decreased with hexagonality. The extent of relaxation was greater in 3Cfilms grown on 6Hsubstrates, a phenomenon attributed to a higher density of double position boundaries. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358667

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using deep level transient spectroscopy combined with secondary‐ion‐mass spectroscopy and capacitance–voltage profiling, it is demonstrated that lithium diffusion into gold‐dopedn‐type silicon at temperatures between 200 and 300 °C results in the formation of two lithium–gold‐related complexes. One of the Au–Li complexes appears to be electrically passive and is observed indirectly as gold acceptor passivation. Virtually all passivated gold acceptors are reactivated after 30 min annealing at 400 °C of samples with comparable Au and Li concentrations in the 1014atoms/cm3range. The process can be reversed again by additional heat treatment at lower temperatures. The passivation–reactivation cycle can be repeated as long as there is enough Li present in the crystal. This reaction can be described by a mass‐action law between negatively charged gold atoms and positively charged lithium (Au−+Li+) with a free binding energy of approximately 0.87 eV. The other Au–Li complex has a deep level (labeledL1) within the silicon band gap with an activation energy of 0.41 eV. TheL1 signal is strongest after annealing at temperatures between 250 and 300 °C but weaker at lower temperatures where the electrically passive Au–Li complex is favored. From the dissociation kinetics ofL1 during reverse bias annealing it is deduced that the complex consists of one gold atom and one or more lithium atoms. Finally, using DLTS depth profiling it is observed that injection of hydrogen into the sample surface region by wet chemical etching results in deactivation of theL1 trap. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358668

出版商:AIP    

年代:1995

数据来源: AIP