Hydrogen-desorption kinetic measurement on the Si(100)-2x1 : H surface by directly counting desorption sites

The desorption kinetics of hydrogen from the Si(100)-2x1:H monohydride surf ace was investigated by means of variable-temperature scanning-tunneling mi croscopy (STM) in the temperature range between 590 and 668 K. By directly counting the number of desorption sites in the STM images for various annea ling time at several temperatures, an activation barrier of E-d = 2.22+/-0. 20 eV and a pre-exponential factor of nu(d) = 3.4 x 10(13+/-0.3) s(-1) for the H-2 recombinative desorption are deduced. The sequential images acquire d in real times show that hydrogen desorbs in a random manner and the inter action between two neighboring paired dangling bond sites is repulsive.