Piecewise diffusion of the silicon dimer

Physical Review B - Condensed Matter and Materials Physics

Volumn 59, Issue 3, 1999, Pages 1598-1601

  Borovsky, Brian ^a   Krueger, Michael ^a   Ganz, Eric ^a  

^a University of Minnesota   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000491937     PISSN: 10980121     EISSN: 1550235X     Source Type: Journal    
DOI: 10.1103/PhysRevB.59.1598     Document Type: Article

References (29)

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20. We have measured the hop rate at room temperature and determined that it is dominated by tip-induced hops. We have also determined that this very low rate of tip-induced hops does not affect the rates measured in the temperature range from 360 to 460 K. See Ref. 19.
21. Detailed information on the pathway of Yamasaki, Uda, and Terakura was obtained in communication with the authors. For a brief description, see Ref. 15.
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23. The highest energy reached along the calculated pathway is 1.28 eV (see Fig. 1 of Ref. 22). Therefore, this is the value of the energy barrier for diffusion in the trough. A value of 1.15 eV was misquoted as the energy barrier in the text of Ref. 22.
24. C. M. Goringe and D. R. Bowler note that the possibility of the adatoms diffusing across the rows instead of along them may be discounted since this involves a higher energy barrier, 0.71 eV compared with 0.6 eV (Ref. 17), and will be so unlikely as to affect only the tails of the probability distributions presented.
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26. It was necessary to use a positive sample bias voltage so that the STM image of the trough dimer contrasts sufficiently with the substrate to allow for atom tracking. For hops larger than three lattice spacings, the tracker presumably loses lock and drifts off ending the data set. For information on the identification and bias dependence of the trough dimer, see Ref. 16 and B. Borovsky, M. Krueger, and E. Ganz, Phys. Rev. Lett. 78, 4229 (1997).
27. This value is obtained from a series of data at (Formula presented) Forty hops occurred in 122 sec, giving an average hop rate of 0.33 Hz. According to the model of Goringe and Bowler, only 62% of breakup events result in observable hops, so the rate of breakup events is 0.53 Hz. Assuming a typical prefactor of (Formula presented) we find an energy barrier of (Formula presented) The error bar reflects an uncertainty of 8 K in the temperature and a factor of 4 in the assumed prefactor, as suggested by our measurement of row diffusion.
28. The row diffusion data are taken from atom-tracking runs at (Formula presented) The trough diffusion data are taken from all available atom-tracking runs at temperatures above 430 K. In all cases, the tracker speed (∼50 Hz) is at least two orders of magnitude greater than the average hop rate. In this extremely rare event regime, the probability that two single hops will occur in an interval short enough to appear as one double hop is negligible. This allows us to rule out the possibility that the long hops observed were the result of a rapid succession of single hops.
29. Additional information, including STM movies of diffusion in both channels, is available at our web site: http://www.spa.umn.edu/groups/stmlab/