Adsorption and decomposition of Ge2H6 on Si(100)

Abstract

The adsorption and decomposition of digermane, Ge2H6, on the Si(100)-(2×1) surface has been investigated with the intent of elucidating the surface processes leading to the deposition of epitaxial Ge thin films from gaseous Ge-containing sources. Exposure of Ge2H6 to Si(100) at 110 K results in molecular adsorption. Upon heating to 150 K, Ge–Ge bond scission occurs and a surface covered with germyl groups is observed. Warming the surface to higher temperatures decomposes the germyl surface groups. The final reaction products are H2 and atomic Ge. The hydrogen thermal desorption that results from the decomposition of Ge2H6 contains features from a distribution of surface sites. Some of the desorption sites are strongly influenced by Ge, lowering the desorption temperature of H2 by over 150 K when compared to the clean silicon surface.

Direct dimer-by-dimer identification of clean and monohydride dimers on the Si(001) surface by scanning tunneling microscopy

“…In CVD processes, hydrogen can be deposited through decomposition of precursors such as SiH4 1 -3 , GeH4 4 or Ge2H6 5 , and Si2H6 3 . Since the early observation of the Si(001)-(2xl)H monohydride structure", 1, the adsorption and desorption of hydrogen on Si(001) has been studied by a large number of surface science techniques including low-energy electron diffraction 7 , ultraviolet photoemission spectrosccopy(UPS) 6 , infrared spectroscopys 8 9, highresolution electron energy loss spectroscopy (HREELS)'o, temperature programmed desorption (TPD)It.…”

Coverage-dependent thermal reactions of digermane on Si(100)-(2×1)

“…The intensity is scaled in a manner in which the saturation coverage is set at 0.4 ͑ML͒ ͑1 MLϭ6.8ϫ10 14 cm Ϫ2 ͒, as obtained in a previous study. 13 Based on the slope of the linear region at low Ge 2 H 6 coverages, an initial sticking coefficient of about 0.5 is derived. Restated, every digermane molecule striking the surface has a 50% likelihood of sticking to the surface.…”

“…Again, this temperature range correlates well with the ␣ desorption state in the TPD spectra. 12,13 The lower H 2 desorption temperature and the associated desorption activation energy of GeH, as compared to SiH, can be rationalized by the fact that a Ge-H bond is weaker than a Si-H one.…”

“…Klug, Du, and Greenlief and Ning and Crowell examined the low-temperature adsorption and thermal decomposition of digermane on Si͑100͒-͑2ϫ1͒ using a number of techniques including multiple internal reflection infrared spectroscopy, 11 temperature-programmed desorption ͑TPD͒, 9,12,13 ultraviolet photoemission, 14 and x-ray photoelectron spectroscopy. 13 It is known that digermane adsorbs molecularly at 110 K or below.…”

“…13 It is known that digermane adsorbs molecularly at 110 K or below. When the substrate is heated to ϳ150 K, a physisorbed digermane molecule decomposes into two GeH 3 radicals.…”