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Science 19 May 2006:
Vol. 312. no. 5776, pp. 1024 - 1026
DOI: 10.1126/science.1124529
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Reports

Desorption of H from Si(111) by Resonant Excitation of the Si-H Vibrational Stretch Mode

Zhiheng Liu,1,2 L. C. Feldman,2,3 N. H. Tolk,2 Zhenyu Zhang,3,4 P. I. Cohen1*

Past efforts to achieve selective bond scission by vibrational excitation have been thwarted by energy thermalization. Here we report resonant photodesorption of hydrogen from a Si(111) surface using tunable infrared radiation. The wavelength dependence of the desorption yield peaks at 0.26 electron volt: the energy of the Si-H vibrational stretch mode. The desorption yield is quadratic in the infrared intensity. A strong H/D isotope effect rules out thermal desorption mechanisms, and electronic effects are not applicable in this low-energy regime. A molecular mechanism accounting for the desorption event remains elusive.

1 Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
2 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
3 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
4 Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.

* To whom correspondence should be addressed. E-mail: picohen{at}umn.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)