Reactions of Disilane on Cu(111): Direct Observation of Competitive Dissociation, Disproportionate, and Thin Film Growth Processes

Shrikant P. Lohokare, Benjamin C. Wiegand, Ralph G. Nuzzo

Research output: Contribution to journalArticlepeer-review


We report a detailed study using reflection absorption infrared (RAIR), temperature-programmed reaction (TPR), Auger electron (AES) spectroscopies, and low-energy electron diffraction (LEED) of the interaction and thermolytic reactions of disilane on a Cu(111) surface. Disilane adsorbs dissociatively on Cu(111) at temperatures as low as 90 K. At low coverages Si-Si and Si-H bond scissions yield two adsorbed fragments which are identified as being the SiH fragment and adsorbed H atoms, respectively. Low fluxes of disilane (≤ 5 × 1012 molecules/s) favor the formation of these dissociative adsorption products. Using higher fluxes, the exposures lead to the concomittant formation of SiH2 and SiH3 moieties. The yields of these later species depend very sensitively on both the absolute and relative surface coverages of Si and H. The decomposition processes of adsorbed SiH3 and SiH2 are characterized strongly by coverage dependent kinetics. The SiH3 species is stable over a limited temperature range (T < 150 K); upon heating it undergoes sequential Si-H bond cleavages to form a surface bound monohydnde The dihydride is stable to ∼180 K. The monohydride decomposes at higher temperatures (T > 250 K), leaving behind surface bound Si. The recombinative desorption of dihydrogen occurs at ∼300 K. This bimolecular process competes with another associative reaction which leads to the formation and desorption of silane (T ∼ 230 K) from the surface. The amount of Si deposited on the surface depends sensitively on the surface temperature and the magnitude of the disilane exposure. A high coverage suicide surface phase is readily formed above the dihydrogen desorption temperature. This thin film is characterized by an ordered (√3 × √3)R30° overlaver structure which is thermally stable over a wide range of temperatures. At higher temperatures, where atomic mobilities are higher, the growth of multilayer intermetallic thin films can be effected.

Original languageEnglish (US)
Pages (from-to)3902-3912
Number of pages11
Issue number10
StatePublished - Oct 1 1995

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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