Oxide removal and selective etching of in from InSb(100) with TiCl 4

Fee Li Lie, Willy Rachmady, Anthony J Muscat

Research output: Contribution to journalArticle

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Abstract

The reaction of TiCl4 with a native oxide-covered InSb(100) film grown epitaxially on GaAs(100) was investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. At room temperature and low pressure (∼3 × 10-7 Torr), TiCl 4 reacted with In and Sb oxides, producing a stable indium chloride overlayer and removing a small amount of Sb, likely as SbCl3, after a subsequent vacuum annealing step at 500 K. About 25% of the O was removed, likely as TiOCl2, and a submonolayer of TiO2 was deposited, which competed with oxide etching. When TiCl4 was dosed with the substrate temperature maintained at 470-560 K, the etching reaction prevailed, resulting in complete removal of the native oxide without depositing TiO2. Heating alone could not account for the results because the oxide desorption onset was 550 K and some oxide was present even after annealing in vacuum to 650 K. TiCl4 exposure at elevated temperatures not only removed the native oxide but also preferentially etched substrate In atoms by forming volatile indium chlorides. Residual indium chlorides remained on the surface in the 470-530 K range but were completely removed at 500-560 K. The depletion of In from the surface promoted the out-diffusion of In from the substrate, allowing bulk etching and accumulation of at least a 72 Å thick Sb layer. Accumulation of Sb on the surface is consistent with a higher kinetic barrier for chlorination of Sb compared to In. The atomic ratio of Ti to Sb in elemental states was 0.43-0.46, suggesting TiSb2 alloy formation. Surface height modulations on the order of 100 nm and the presence of pits and grain boundaries were observed.

Original languageEnglish (US)
Pages (from-to)19733-19740
Number of pages8
JournalJournal of Physical Chemistry C
Volume115
Issue number40
DOIs
StatePublished - Oct 13 2011

Fingerprint

Oxides
Etching
etching
oxides
Indium
indium
chlorides
Substrates
Vacuum
Annealing
chlorination
vacuum
annealing
Chlorination
Temperature
Atomic force microscopy
Desorption
Grain boundaries
depletion
X ray photoelectron spectroscopy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Oxide removal and selective etching of in from InSb(100) with TiCl 4. / Lie, Fee Li; Rachmady, Willy; Muscat, Anthony J.

In: Journal of Physical Chemistry C, Vol. 115, No. 40, 13.10.2011, p. 19733-19740.

Research output: Contribution to journalArticle

Lie, Fee Li ; Rachmady, Willy ; Muscat, Anthony J. / Oxide removal and selective etching of in from InSb(100) with TiCl 4. In: Journal of Physical Chemistry C. 2011 ; Vol. 115, No. 40. pp. 19733-19740.
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abstract = "The reaction of TiCl4 with a native oxide-covered InSb(100) film grown epitaxially on GaAs(100) was investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. At room temperature and low pressure (∼3 × 10-7 Torr), TiCl 4 reacted with In and Sb oxides, producing a stable indium chloride overlayer and removing a small amount of Sb, likely as SbCl3, after a subsequent vacuum annealing step at 500 K. About 25{\%} of the O was removed, likely as TiOCl2, and a submonolayer of TiO2 was deposited, which competed with oxide etching. When TiCl4 was dosed with the substrate temperature maintained at 470-560 K, the etching reaction prevailed, resulting in complete removal of the native oxide without depositing TiO2. Heating alone could not account for the results because the oxide desorption onset was 550 K and some oxide was present even after annealing in vacuum to 650 K. TiCl4 exposure at elevated temperatures not only removed the native oxide but also preferentially etched substrate In atoms by forming volatile indium chlorides. Residual indium chlorides remained on the surface in the 470-530 K range but were completely removed at 500-560 K. The depletion of In from the surface promoted the out-diffusion of In from the substrate, allowing bulk etching and accumulation of at least a 72 {\AA} thick Sb layer. Accumulation of Sb on the surface is consistent with a higher kinetic barrier for chlorination of Sb compared to In. The atomic ratio of Ti to Sb in elemental states was 0.43-0.46, suggesting TiSb2 alloy formation. Surface height modulations on the order of 100 nm and the presence of pits and grain boundaries were observed.",
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