K Xue et al 2007 Nanotechnology 18 485709 doi:10.1088/0957-4484/18/48/485709
K Xue, J B Xu1 and H P Ho
Show affiliationsA surface chemical reaction—the thermal decomposition of ultrathin silicon oxide (~1 nm) by ultrahigh vacuum (UHV) thermal annealing at 600–800 °C—is in situ investigated on a nanometer scale by high temperature scanning tunneling microscopy (STM). The reaction is initiated by the creation of circular voids which expose the underlying silicon substrate. Growth kinetics of the voids is scrutinized via time-lapse STM movies. It is verified that the void perimeters grow linearly with time before coalescence and the reaction occurs peripherally around the void perimeters. It is also demonstrated that the decomposition rate varies concomitantly with the local environment near the reaction fronts. The observed low–high–low rate evolution is qualitatively explained. Increased reaction activation energy is found in the final decomposition stage and the origin of the increase is proposed to be due to the local morphological evolution.
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
Surfaces, interfaces and thin films
Issue 48 (5 December 2007)
Received 15 August 2007, in final form 26 September 2007
Published 30 October 2007
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