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Title: The evolution of Ga and As core levels in the formation of Fe/GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study

Abstract

A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 A results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two additional As environments of metallic character: one bound to the interfacial region and another which, as confirmed by in situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three additional environments--also metallic in nature. Two of the three are interface resident whereas themore » third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical makeup of the Fe/GaAs (001) system.« less

Authors:
; ;  [1]; ;  [2];  [3];  [4];  [5];  [6]
  1. Joule Physics Laboratory, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom)
  2. Lawrence Livermore National Laboratory, California 94550 (United States)
  3. Physics Department, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)
  4. Department of Physics, University of York, York YO1 5DD (United Kingdom)
  5. Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)
  6. EPSRC National Centre for III-V Technologies, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)
Publication Date:
OSTI Identifier:
21137409
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 104; Journal Issue: 2; Other Information: DOI: 10.1063/1.2942395; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL GROWTH; ENERGY SPECTRA; FERROMAGNETIC MATERIALS; GALLIUM ARSENIDES; IRON; LAYERS; OXIDATION; SEGREGATION; SEMICONDUCTOR MATERIALS; SOFT X RADIATION; SUBSTRATES; THICKNESS; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Thompson, Jamie D. W., Neal, James R., Shen, Tiehan H., Morton, Simon A., Tobin, James G., Dan Waddill, G., Matthew, Jim A. D., Greig, Denis, and Hopkinson, Mark. The evolution of Ga and As core levels in the formation of Fe/GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study. United States: N. p., 2008. Web. doi:10.1063/1.2942395.
Thompson, Jamie D. W., Neal, James R., Shen, Tiehan H., Morton, Simon A., Tobin, James G., Dan Waddill, G., Matthew, Jim A. D., Greig, Denis, & Hopkinson, Mark. The evolution of Ga and As core levels in the formation of Fe/GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study. United States. doi:10.1063/1.2942395.
Thompson, Jamie D. W., Neal, James R., Shen, Tiehan H., Morton, Simon A., Tobin, James G., Dan Waddill, G., Matthew, Jim A. D., Greig, Denis, and Hopkinson, Mark. Tue . "The evolution of Ga and As core levels in the formation of Fe/GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study". United States. doi:10.1063/1.2942395.
@article{osti_21137409,
title = {The evolution of Ga and As core levels in the formation of Fe/GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study},
author = {Thompson, Jamie D. W. and Neal, James R. and Shen, Tiehan H. and Morton, Simon A. and Tobin, James G. and Dan Waddill, G. and Matthew, Jim A. D. and Greig, Denis and Hopkinson, Mark},
abstractNote = {A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 A results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two additional As environments of metallic character: one bound to the interfacial region and another which, as confirmed by in situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three additional environments--also metallic in nature. Two of the three are interface resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical makeup of the Fe/GaAs (001) system.},
doi = {10.1063/1.2942395},
journal = {Journal of Applied Physics},
number = 2,
volume = 104,
place = {United States},
year = {Tue Jul 15 00:00:00 EDT 2008},
month = {Tue Jul 15 00:00:00 EDT 2008}
}
  • A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence onmore » the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 {angstrom} results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two new As environments of metallic character; one bound to the interfacial region and another which, as confirmed by in-situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three new environments--also metallic in nature. Two of the three are interface-resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical make-up of the Fe/GaAs (001) system.« less
  • A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence onmore » the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 Angstrom results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two additional As environments of metallic character: one bound to the interfacial region and another which, as confirmed by in situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three additional environments--also metallic in nature. Two of the three are interface resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical makeup of the Fe/GaAs (001) system.« less
  • Schottky barrier formation and thermal stability of the LaB/sub 6//GaAs(001) c (4 x 4) interface were investigated by x-ray photoelectron spectroscopy. Results show an excellent thermal stability without any appreciable interface reactions such as interdiffusion. Band bending induced by LaB/sub 6/ deposition is found to depend on the evaporation condition. However, the Fermi level pinning position does not change due to heat treatments between 300 and 700 /sup 0/C. This indicates that LaB/sub 6/ is a promising gate material for GaAs integrated circuits.
  • High-resolution soft X-ray photoelectron spectroscopy was used to investigate the oxidation of alkylated silicon(111) surfaces under ambient conditions. Silicon(111) surfaces were functionalized through a two-step route involving radical chlorination of the H-terminated surface followed by alkylation with alkylmagnesium halide reagents. After 24 h in air, surface species representing Si{sup +}, Si{sup 2+}, Si{sup 3+}, and Si{sup 4+} were detected on the Cl-terminated surface, with the highest oxidation state (Si{sup 4+}) oxide signal appearing at +3.79 eV higher in energy than the bulk Si 2p{sub 3/2} peak. The growth of silicon oxide was accompanied by a reduction in the surface-bound Clmore » signal. After 48 h of exposure to air, the Cl-terminated Si(111) surface exhibited 3.63 equivalent monolyers (ML) of silicon oxides. In contrast, after exposure to air for 48 h, CH{sub 3}-, C{sub 2}H{sub 5}-, or C{sub 6}H{sub 5}CH{sub 2}-terminated Si surfaces displayed <0.4 ML of surface oxide, and in most cases only displayed 0.20 ML of oxide. This oxide was principally composed of Si{sup +} and Si{sup 3+} species with peaks centered at +0.8 and +3.2 eV above the bulk Si 2p{sub 3/2} peak, respectively. The silicon 2p SXPS peaks that have previously been assigned to surface Si-C bonds did not change significantly, either in binding energy or in relative intensity, during such air exposure. Use of a high miscut-angle surface (7{sup o} vs 0.5{sup o} off of the (111) surface orientation) yielded no increase in the rate of oxidation nor change in binding energy of the resultant oxide that formed on the alkylated Si surfaces. Scanning Auger microscopy indicated that the alkylated surfaces formed oxide in isolated, inhomogeneous patches on the surface.« less
  • High-resolution soft X-ray photoelectron spectroscopy was used to investigate the oxidation of alkylated silicon(111) surfaces under ambient conditions. Silicon(111) surfaces were functionalized through a two-step route involving radical chlorination of the H-terminated surface followed by alkylation with alkylmagnesium halide reagents. After 24 h in air, surface species representing Si+, Si2+, Si3+, and Si4+ were detected on the Cl-terminated surface, with the highest oxidation state (Si4+) oxide signal appearing at +3.79 eV higher in energy than the bulk Si 2p3/2 peak. The growth of silicon oxide was accompanied by a reduction in the surface-bound Cl signal. After 48 h of exposuremore » to air, the Cl-terminated Si(111) surface exhibited 3.63 equivalent monolyers (ML) of silicon oxides. In contrast, after exposure to air for 48 h, CH3-, C2H5-, or C6H5CH2-terminated Si surfaces displayed <0.4 ML of surface oxide, and in most cases only displayed 0.20 ML of oxide. This oxide was principally composed of Si+ and Si3+ species with peaks centered at +0.8 and +3.2 eV above the bulk Si 2p3/2 peak, respectively. The silicon 2p SXPS peaks that have previously been assigned to surface Si-C bonds did not change significantly, either in binding energy or in relative intensity, during such air exposure. Use of a high miscut-angle surface (7 vs e0.5 off of the (111) surface orientation) yielded no increase in the rate of oxidation nor change in binding energy of the resultant oxide that formed on the alkylated Si surfaces. Scanning Auger microscopy indicated that the alkylated surfaces formed oxide in isolated, inhomogeneous patches on the surface.« less