摘要:

We report results of scanning tunneling microscope measurements andabinitiocalculations for Si(113). This surface is of general interest: Ge islands on Si(001) and Si(111) have (113) facets, Si(113) is thermally stable despite its high index, and it has properties of a good substrate. We bring into focus the peculiar atomic structure of Si(113) which contains a novel structural unit built around a subsurface interstitial atom. Such interstitials may be present also at other surfaces, particularly at steps, and may play an important role in atomic diffusion in the subsurface layer. The interstitials aresixfoldcoordinated; this unexpected result disturbs the simple picture of reconstruction driven by rebonding of dangling bonds. Our calculations indicate that the interstitials are released when the surface dangling orbitals rebond, e.g., as the result of adsorption of atomic hydrogen or during epitaxial growth.

ISSN:0734-211X    

DOI:10.1116/1.587863

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The energy splitting of the conduction‐band minimum of Si1−xGexdue to strain has been directly measured by the application of ballistic‐electron‐emission microscope (BEEM) spectroscopy to Ag/Si1−xGexstructures. Experimental values for this conduction‐band splitting agree well with calculations. For Au/Si1−xGex, however, heterogeneity in the strain of the Si1−xGexlayer is introduced by deposition of the Au. This variation is attributed to species interdiffusion, which produces a rough Si1−xGexsurface. Preliminary modeling indicates that the observed roughness is consistent with the strain variation measured by BEEM.

ISSN:0734-211X    

DOI:10.1116/1.587864

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Atomic force microscopy is used to measure surface morphology of modulation doped Si/SiGe heterostructures. Three components in the surface roughness are observed: μm‐scale roughness arising from misfit dislocations formed to relieve strain, 1000‐Å‐scale roughness believed to be associated with three‐dimensional growth of the electron or hole channel layers, and atomic‐scale roughness with wavelengths of 10–100 Å. Detailed Fourier spectra of the roughness are obtained and used as input to a scattering computation for determining mobility. The results are compared with other mobility‐limiting mechanisms, including scattering from ionized impurities and from dislocations.

ISSN:0734-211X    

DOI:10.1116/1.587865

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

An important issue in semiconductor device operation is the rate at which current or voltage stress creates defects that can eventually degrade device operation. Based on recent results on nitrided gate dielectrics, we have concluded that bonded‐H at the Si–SiO2interface plays a role in the formation of metastable defects that can be activated, and subsequently neutralized, by sequential trapping of injected holes and electrons. In this article, differences in defect behavior for Si–SiO2interfaces that have been exposed to nitrogen (N‐) atoms or N–H groups are discussed. Based on these results, a microscopic model for interfacial defects is proposed.

ISSN:0734-211X    

DOI:10.1116/1.587866

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A model for silicon oxidation that invokes dissociative chemisorption of molecular oxygen at the interface between silicon dioxide and silicon is described. The model accounts for a self‐limiting oxide film thickness of 0.5–0.6 nm (for oxidations performed at temperatures sufficient to dissociate surface dimers and permit oxygen penetration of the substrate beyond a single monolayer of suboxide). Detailed examination of the model suggests a mechanism for an inherent oxide/silicon interface roughness of approximately one atomic diameter. Kinetic rate equations developed from the model successfully account for the observed power law dependence of rate on oxygen partial pressure. These relationships were used in the derivation of an expression for the variation of oxide film growth rate with overlying oxide thickness. The relationship is tested against experimental observations reported in the literature and found to give an excellent fit.

ISSN:0734-211X    

DOI:10.1116/1.587867

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Synchrotron radiation photoemission spectroscopy (PES) has been used to study thermal SiO2/Si(100) interfaces. Oxides were grown at 700, 800, 900, and 1000 °C and etched back to a thickness ∼0.5–1.5 nm for PES measurements. Comparison of Si 2pcore levels withinsituultrahigh vacuum‐grown SiO2on Si(100) indicated that various Si oxidation states, Six+, are present at the interface. The results show that the amount of both Si2+and Si3+increases with increasing oxidation temperature while the amount of Si1+remains constant. For these furnace grown oxides, structural relaxation to relieve strains rather than kinetic growth considerations governs the structure and suboxide distribution at the SiO2/Si(100) interface.

ISSN:0734-211X    

DOI:10.1116/1.587868

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The spatial scaling law of the Si/SiO2interface roughness was investigated with atomic force microscopy. Scaling behavior was observed on smaller scales, where the root‐mean‐square (RMS) roughness increased as a power of the scale of observation. When viewed as a fractal geometry, such a structure is characterized as aself‐affinefractal. On larger scales, the roughness was no more dependent on the scale, showing the (macroscopic) RMS roughness in the conventional sense. The observed structure (self‐affine fractal with a finite‐length cut‐off) is consistent with the prediction of the theory of kinetic roughening in a far‐from‐equilibrium growth, where the fluctuation on smaller scales evolves into roughness on larger scales. Statistical description of the Si/SiO2interface roughness was also given in terms of autocorrelation function and power spectral density. It was found that the autocorrelation function of the Si/SiO2interface roughness is well approximated by an exponential form rather than a Gaussian form. Numerical simulation was carried out to explain the kinetic roughening in the oxidation process with relation to the dependence on the oxide thickness.

ISSN:0734-211X    

DOI:10.1116/1.587869

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We present a theoretical investigation of the band lineups between crystalline and amorphous silicon, based on the first‐principles pseudopotential method and the model‐solid theory. We find that the offsets are very sensitive to the hydrogen content of the material; the valence‐band offset for a junction with unhydrogenateda‐Si is −0.25 eV, while for hydrogenateda‐Si with a hydrogen content of 11% the offset becomes 0.20 eV. Consequences for the interpretation of experimental data are discussed.

ISSN:0734-211X    

DOI:10.1116/1.587870

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Homoepitaxy and controlled oxidation of silicon at low temperatures have been achieved using a dual source, mass‐selected, low‐energy, ion beam deposition system. For Si homoepitaxy,28Si+ions in the energy range 8–40 eV were used to grow films on Si{100} in the temperature range of 50–750 °C. The films were analyzedinsituby reflection high‐energy electron diffraction and Auger electron spectroscopy (AES) andexsituby high‐resolution transmission electron microscopy, Rutherford backscattering spectrometry, and atomic force microscopy. For silicon oxidation, films of SiO2on Si{100} at room temperature were grown by using 25 eV beams of28Si+and16O+. Fast switching of the magnetic sectors allows deposition of these ions in alternating pulses. The pulse increments used were 1×1014cm −2for Si+and 4×1014cm−2for O+. Analysis of the oxide films byinsituAES andexsitux‐ray photoelectron spectroscopy show that the films are SiO2, that the suboxides are localized at the interface, and that there is no limitation to the thickness of the oxide films that can be grown. The effects of ion energy and substrate temperature, contamination, and surface damage on the growth mechanism are discussed.

ISSN:0734-211X    

DOI:10.1116/1.587871

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The stability of CaF2/Si(111) and Al/CaF2/Si(111) interfaces under irradiation by light or electrons and upon thermal annealing was investigated by photoelectron spectroscopy and scanning‐tunneling microscopy. Deposition of CaF2on Si(111)7×7 at 700 °C leads to a shift of the Fermi‐level position (EF) towards the Si valence‐band maximum (VBM), while subsequent light irradiation results in a back‐shift ofEFtowards its initial value. Upon flashing the irradiated surface at 700 °C, it shifts again towards the VBM. The variation ofEFis assigned to a competition of interface states with surface states related to irradiation‐induced fluorine vacancies. These surface defects are observed as localized surface charges in the scanning tunneling microscopy images. A thin epitaxial Al layer on top of the CaF2surface strongly reduces the irradiation‐induced effects and leads to a stabilization ofEFat 0.30 eV above the VBM.

ISSN:0734-211X    

DOI:10.1116/1.587872

出版商:American Vacuum Society    

年代:1995

数据来源: AIP