摘要:

We attained a wide modulation of the Si(111)–Au interface reaction by deposition of controlled amounts of Cr on the semiconductor surface beforeinsitujunction formation. Synchrotron radiation photoemission studies show that Cr deposition gives rise to a Si/Cr reacted interlayer that dramatically affects the subsequent Si–Au interdiffusion. Negligible interdiffusion of Cr and Au atoms was found in all cases so that the Si–Au intermixing depends upon an exchange reaction at the Si/Cr–Au interface in which Si is the only moving species. Large reduction of the interdiffusion occurs sharply above a critical value of Cr deposition (10 monolayers) that corresponds to a fully reacted Si(111)–Cr interface.

ISSN:0734-211X    

DOI:10.1116/1.582590

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We present the first evidence of formation of mixed valent compounds at the Si(111)/Yb interface upon annealing. Two stable and uniform compositions were found, these being related to the known bulk silicides YbSi and YbSi2. The mixed valence behavior is seen in the presence of the strong 4f13(Yb3+) signal and in the shift of the 4f14(Yb2+) signal to the Fermi level.

ISSN:0734-211X    

DOI:10.1116/1.582593

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

In this paper we describe typical and simple results concerning the deposition of metal on GaAs surfaces and the first steps of Si oxidation. In the case of GaAs/metal, typical results illustrating the barrier formation, the electron affinity modification, the contribution of initial surface defects, and metal induced defects are presented and discussed, using the unified model of Spicer, Lindauetal. In the case of Si/SiO2, we focus on illustrating the method of the growth of the oxide and the resulting work function modifications.

ISSN:0734-211X    

DOI:10.1116/1.582595

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The initial stages of the Cu growth on top of a 7×7 Si(111) surface were monitored with LEED, AES, UPS, and XPS techniques. Results suggest that at room temperature the Cu growth proceeds by a laminar fashion. An intermixing between Si and Cu takes place giving rise to a diffuse interface extending to several first monolayers. This fact is testified by the splitting of the SiLVVtransition in AES spectra, by the deviation of the AES and XPS Cu and Si signal plot versus coverage from a perfect layer by layer growth plot, and by a strong diffuse background intensity in LEED diagram. Moreover, at this coverage range, a slight narrowing and a shift (0.7 eV±0.2 eV) of the 3dCu peak towards higher binding energy as compared with the bulk metal are observed in valence band photoemission spectra. With increasing coverage, a metal rich phase is found displaying an ordered 1×1 Cu(111) planelike structure. No Si enrichment at the topmost metallic layer is observed by XPS. Core level spectroscopy gives similar results showing a noticeable energy shift (0.6 eV±0.2 eV) for the Cu 2pline. A depth profile confirms the interface structure which is rather metastable at room temperature. At high temperature (T>400 °C), an ordered Cu induced pattern is found at θ∼1 monolayer. The diagram resembles a 5×5 superstructure. With increasing coverage, 3D crystallites are growing on top of the first ordered layer. The interface is stable at high temperature.

ISSN:0734-211X    

DOI:10.1116/1.582596

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The deposition of thin films of Ag on clean Ge(001) substrates has been investigated using low energy electron diffraction, Auger electron spectroscopy, and scanning electron microscopy. Ag was deposited from an effusion source onto Ge at both 325 and 600 K substrate temperatures. Deposition on high temperature substrates resulted in the formation of Ag islands with no apparent crystalline order, whereas films deposited at temperatures near 325 K onto clean Ge(001) 2×1 surfaces were oriented. The deposition of the equivalent of one Ag(001) monolayer on the Ge surfaces resulted in a Ge(001) 1×1‐like LEED pattern. As deposition was continued (up to 500 monolayers), a pattern evolved which is consistent with two (011) 1×1 Ag domains oriented at 90° to one another. This behavior is interpreted in terms of a predominantly Stranski–Krastanov growth mechanism for the initial deposition of Ag onto near room temperature Ge(001) substrates. Annealing of a sample with a thin, ordered film revealed the original Ge(001) 2×1 LEED pattern, which demonstrated that the chemical interaction between Ge and Ag is very weak.

ISSN:0734-211X    

DOI:10.1116/1.582597

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

In a recent paper, we investigated the electronic properties of a set of Ge–Al lattice‐matched interfaces. These interfaces were constructed by placing an ideal (001)Ge substrate next to a 45° rotated (001)Al film. In all cases the Ge–Al interatomic distance was kept fixed at someadhocvalue. Using a self‐consistent pseudopotential approach, we now extend these calculations to consider the case where the interlayer distance is fixed for the on top and interstitial model but the Ge–Al interatomic distance is allowed to vary. One striking result of our calculation is that the differences among diverse interface geometries lead only to small differences in electronic properties if the interlayer distance is kept fixed. Single atomic metal overlayer calculations by Chelikowsky, and Zhang and Schluter in different configurations show more pronounced differences. Our results indicate that inclusion of more than one metal layer tends to smear out these differences. We also calculate an optimal geometrical arrangement by minimizing the total energy of the system. We critically discuss the weakly interacting cluster model and the chemisorption model of metal–semiconductor interfaces and place our work in context. We also present a semiclassical calculation which relates the interface density of occupied states to surface quantized level spacing. It suggests a possible surface absorption experiment for determining this state density. Future ramifications of our idealized model and the role it can play in simulating interfacial chemical reactions are briefly stated.

ISSN:0734-211X    

DOI:10.1116/1.582598

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Adsorption processes were investigated for the first time on a IV–VI substrate, PbTe, by photoemission spectroscopy with synchrotron radiation Ge, Al, and In overlayers on cleaved PbTe(100) all create an inversion layer at the PbTe side of the interface. Substantial Pb and Te outdiffusion is observed even at room temperature, resulting in nonabrupt interfaces. The band discontinuities of the PbTe–Ge interface are much different from those theoretically predicted by the electron affinity rule.

ISSN:0734-211X    

DOI:10.1116/1.582600

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

A systematic study of the Al Schottky barrier height on clean GaAs(100) and AlAs(100) as a function of initial arsenic surface coverage has been performed. Two new surface phases on AlAs(100) have been observed. Al Schottky barrier height showed a steady decrease with increasing arsenic coverage on GaAs, and showed steady increase with increasing arsenic coverage on AlAs. The results are compared with current models of Schottky barrier formation.

ISSN:0734-211X    

DOI:10.1116/1.582601

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Photoemission studies of Ag deposits on cleavedn‐ andp‐type GaAs for coverages from ∼0.003 to 20 monolayers indicate clustered Ag growth and undetectable chemical interactions with the substrate. The position of the surface Fermi level changed throughout the deposit range. The data is inconsistent with most of the existing Schottky barrier models. The results are interpreted in terms of donor‐ and acceptorlike interface states which are characteristic of the clusters but modified by the screening at the interface. Values for the Schottky barrier of 0.89 eV onn‐type and 0.35 eV onp‐type material were obtained for the thickest coverage.

ISSN:0734-211X    

DOI:10.1116/1.582602

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Photoemission measurements are used to study the Schottky barrier formation and the intermixing (with GaAs) of the three metals, Cu, Ag, and Au, deposited at room temperature on GaAs(110) cleaved surfaces. It is tentatively concluded that Fermi level pinning cannot be followed satisfactorily for metal coverages above a monolayer. The work of Palau on Schottky barrier height (I–VandC–V) for Au and Ag deposited on cleaved GaAs(110) in UHV indicate pinning positions surprisingly close to those found for other overlayers in the ‘‘unified defect’’ model. It was found that ‘‘intermixing’’ between noble metals and GaAs decreases in the order of Cu, Au, and Ag. Although island formation probably occurs, it is tentatively concluded that the principle reason for difficulty in using our photoemission measurements to determineEfsfor the noble metals is the inclusion of Ga (as well as As) in or on the noble metal overlayer.

ISSN:0734-211X    

DOI:10.1116/1.582604

出版商:American Vacuum Society    

年代:1983

数据来源: AIP