Browsing by Author "Ku, TS"

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Growth process of Ge on Si(100)-(2x1) in atomic-layer epitaxy from Ge2H6
(1997-08-15)
Huang, KH
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Ku, TS
;
Lin, DS
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物理研究所
;
Institute of Physics
This study investigates the growth process of Ge on Si(100) during atomic-layer epitaxy (ALE) utilizing digermane. The surface ordering, morphology, and stoichiometry of the digermane saturated Si(100) surface at temperatures between 300 and 900 K, as well as the grown films are examined both by scanning tunneling microscopy (STM) and high-resolution core-level photoemission spectroscopy employing synchrotron radiation. An exposure of more than 15 L (1 L=10(-6) T s) of digermane on the Si(100)-(2x1) surface at room-temperature results in a saturated and disordered surface. When the digermane saturated surface is heated to 725 K for 60 s, diluted Ge dimer chains are created and surrounded by SiH species. Further annealing to 810 K completely desorbs hydrogen from the surface, leaving large two-dimensional islands covering similar to 41% of its area. The surface recovers its smooth 2x1 structure, but is interspersed with poorly ordered short dimer vacancy lines at 900 K with no observable contrast on the atomic terraces, indicating displacive adsorption of Ge on the terraces. Significant differences of the surface diffusion phenomena between the gas-phase and solid-phase molecular-beam epitaxy (MBE) are observed. Multilayer Si deposition is performed by ALE, i.e., cyclic digermane adsorption at near room temperature, followed by thermal annealing at 900 K. STM images reveal the formation of 2 x n structures and increasing roughening of the surface as the growth cycle increases, similar to what occurs during MBE. Issues related to the atomic origins of surface core-level shifts and the chemical composition of the surface layer resulting from the formation of mixed Ge-Si or Ge-Ge during the submonolayer adsorption of Ge on Si(100) are also discussed.
Interaction of phosphine with Si(100) from core-level photoemission and real-time scanning tunneling microscopy
(2000-01-15)
Lin, DS
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Ku, TS
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Chen, RP
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物理研究所
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Institute of Physics
In this paper, we investigate the interaction of phosphine (PH3) on the Si(100)-2 x 1 surface at temperatures between 635 and 900 K. The hydrogen desorption, growth mode, surface morphology, and chemical composition and ordering of the surface layer are examined by synchrotron radiation core-level photoemission and real-time high-temperature scanning tunneling microscopy. The P 2p core-level spectra indicate that decomposition of PHn is complete above similar to 550 K and the maximum P coverage is strongly influenced by the growth temperature, which governs the coverage of H-terminated sites. The scanning tunneling microscopy (STM) images taken at real time during PH3 exposure indicate that a surface phosphorus atom readily and randomly displaces one Si atom from the substrate. The ejected Si diffuses, nucleates, and incorporates itself into islands or step edges, leading to similar growth behavior as that found in Si chemical vapor deposition. Line defects both perpendicular and parallel to the dimer rows are observed on the nearly P-saturated surface. Perpendicular line defects act as a strain relief mechanism. Parallel line defects result from growth kinetics. STM images also indicate that incorporating a small amount of phosphorus eliminates the line defects in the Si(100)-2 x n surface.
Thermal reactions of phosphine with Si(100): a combined photoemission and scanning-tunneling-microscopy study
(1999-03-19)
Lin, DS
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Ku, TS
;
Sheu, TJ
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物理研究所
;
Institute of Physics
This study investigates the adsorption and thermal decomposition of phosphine (PH3) on the Si(100)-(2 x 1) surface. The adsorption species, dissociation reactions, atomic ordering, and surface morphology of the phosphine/Si(100) surface at temperatures between 300 and 1060 K are examined by scanning tunneling microscopy (STM) and high-resolution core-level photoemission spectroscopy employing synchrotron radiation. The P 2p core level spectra clearly indicate that phosphine molecularly adsorbs at room temperature and partially dissociates into PH2 and H on a time scale of minutes at low (<0.2ML) coverages. An exposure of >15 Langmuirs (L, 1 Langmuir=10(-6) Torr s(-1)) of phosphine on the Si(100)-(2 x 1) surface at room temperature produces a saturated and disordered surface. The total amount of P on the saturated surface is ca 0.37 ML as calibrated by the P 2p photoemission intensity. Successive annealing of the saturated surface at higher temperatures converts PH, into PH,, converts PH, to P-P dimers, and causes the desorption of PH3. These processes become complete at similar to 700 K, and the resulting surface is a H/Si(LOD)-(2 x 1) surface interspersed with one-dimensional P-P islands. Desorption of hydrogen from that surface occurs at similar to 800 K, and is accompanied by partial displacement of P with Si atoms on the substrate. At 850 K, the Si(100) surface, interspersed with 0.22 ML of two-dimensional islands, is a random alloy of nominal 0.5 ML Si-P heterodimers and 0.5 ML Si-Si dimers. (C) 1999 Published by Elsevier Science B.V. All rights reserved.