摘要:

Preparation of pseudomorphicSi1−yCy/Si(001)heterostructures using Si molecular beam epitaxy with C obtained from SiC sublimation in a high-temperature cell has been studied. Thick(≈2000 Å)homogenousSi1−yCylayers,y⩽1.5&percent;,andSi1−yCy/Simultiple quantum well (MQW) structures,y⩽8&percent;,have been prepared. There is a growth temperature dependent surface roughness accumulating during the growth sequence that can lead to reduction of C induced strain. Temperature modulation during growth has been used to suppress this effect. Near band gap photoluminescence is reported fromSi1−yCy/SiMQW structures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119819

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We observe unusually strong magnetoresistance commensurability oscillations in two different types of artificial arrays of scattering centers, multiparallel focusing slits and a square antidot lattice, both fabricated on a two-dimensional electron gas by electron-beam lithography and damageless wet etching. The strength of the magnetoresistance peaks is attributed to a high reflection specularity and a small effective antidot cross section. The absence of commensurability effects near Landau level filling factor&ugr;=3/2is attributed to the composite fermion mean free path being smaller than the slit and antidot spacings. The mechanism for the observed commensurability is discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119820

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Recent study indicated that transient enhanced diffusion in implanted silicon is attributed to {113} rodlike defects. We have used plan-view and cross-sectional transmission electron microscopy to study the microstructural evolution of {113} rodlike defects as well as their transition to {111} dislocation loops in heat treatment of Si-amorphized silicon. We found that {113} rodlike defects undergo three stages of change during postimplantation anneals; accumulation of point defects to form homogeneous circular interstitial clusters, growth of these clusters along the ⟨110⟩ direction in a {113} habit plane, and dissolution into the matrix. We observed that the nucleation of {111} dislocation loops at the amorphous/crystalline interface lags behind that of the {113} defects and occurs while the latter grow and/or dissolve. This suggests that there is a period when {113} defects release interstitial point defects before the {111} dislocation loops nucleate from matrix. The {113} defects were found to disappear completely at 900 °C for 120 s, but the {111} dislocation loops disappear at 1100 °C for 60 s. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119821

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this letter, we report the successful growth of an ultrathin organic film onSi(100)-2×1by reactive coupling of polyimide precursors. Using the molecular layer deposition technique, 1,4-phenylene diamine and pyromellitic dianhydride were sequentially dosed on cleanSi(100)-2×1under ultrahigh vacuum conditions. The interfacial imidization was initiated by thermal curing at 200 °C. High resolution electron energy loss spectroscopy was employed to identify surface species. The spectra show clearly, that an oligimide chain has been formed which stands upright on the substrate. The chain bonds to the silicon substrate via a Si–(NH)–C linkage. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119822

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A kinetic model of coherent transport with self-organized carrier transfer via midband gap semiconductor states in metal–insulator–midband gap semiconductor–insulator–semiconductor structure at room temperature is proposed. The coherent transport at room temperature can be a result of continuous oscillations of charge carriers at midband gap semiconductor states. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119823

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We employed deep-level transient spectroscopy to determine the electrical properties of defects introduced in epitaxially grownn-GaAs during dry etching in aSiCl4plasma at different rf powers and plasma pressures. We found thatSiCl4etching introduced two prominent defects, one of which is metastable. Current–voltage measurements demonstrated that high barrier Schottky barrier diodes can be fabricated onSiCl4-etchedn-GaAs surfaces for all power and plasma pressure conditions investigated. The defect concentration decreased and the diode quality improved when etching at lower rf power and higher plasma pressure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119824

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The operation of the intrinsic Stark effect at visible wavelengths is reported, for both cubic and wurtzite type-II CdS–ZnSe strained layer superlattices grown on CdS buffer layers on (111)A GaAs. An observed increase of the effective piezoelectric coefficient from the measured cubic bulk value is attributed to a nonlinear effect, as previously reported for CdTe quantum wells [R. Andre´, J. Cibert, Le Si Dang, J. Zeman, and M. Zigone, Phys. Rev. B53, 6951 (1996)]. Exciton peak shifts of 70 meV per decade change of excitation intensity are similar in magnitude to those found in CdS–CdSe superlattices of similar period. These shifts are attributed to screening of the internal piezoelectric fields by photoexcited carriers. Exciton peak shifts that are smaller by an order of magnitude appear in CdS–ZnSe samples, grown on (100) ZnSe buffers and therefore predicted to exhibit no piezoelectric effects of any order. These small shifts, which we attribute to space charge buildup, are a characteristic feature of type-II superlattices. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119825

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Current–voltage characteristics under illumination of monochromatic light for metal-free tetrabenzporphyrin, metal-free triazatetrabenzporphyrin, and metal-free phthalocyanine in (indium–tin–oxide)/porphyrin/Al sandwich cells seem to show high-energy conversion efficiencies of 14&percent;, 7.7&percent;, and 5.5&percent;, respectively. However, according to the simultaneous measurement of both short-circuit photocurrent and transmittance of the aluminum electrode with time, the transmittance of Al linearly increases as the photocurrent flows into the external circuit. It is concluded that all photocurrents in the above cells arise from photoaccelerated corrosion of aluminum electrode and do not originate from conversion of light energy to electrical energy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119826

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show that surface reconstructions may play an essential role in determining the equilibrium solubilities of N, P, As, and Sb in various III-V compounds. In particular, anion–anion dimerization of the(001)-&bgr;2(2×4)surface can enhance the solubility of N near the surface in GaAs, GaP, and InP by five, three, and two orders of magnitudes, respectively, at 1000 K. With certain assumptions on the growth kinetics, this high concentration of N may be frozen in as the crystal grows. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119827

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present evidence that the energy introduced by a short laser pulse focused to high intensity on a small spot on the surface of neutron-transmutation-doped silicon electrically activates impurities far away from the focal spot. The activation of the impurities is measured by far-infrared spectroscopy of shallow donor levels and by magnetotransport characterization. Electrical activity is comparable to that obtained with conventional thermal annealing. X-ray rocking curve measurements show strain in the area of the focal spot, but none at large distances from the focal spot. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119828

出版商:AIP    

年代:1997

数据来源: AIP