화학공학소재연구정보센터
Chemical Physics Letters, Vol.481, No.1-3, 58-61, 2009
Classical and quantum diffusion of hydrogen atoms on Cu(111)
We measured diffusion constants of hydrogen adatoms on Cu(111) using a combination of enabling optical techniques. We observed a steep crossover from a strongly thermal activated hopping (T > 130 K) to a weakly thermal activated 'hopping' (T < 130 K). The diffusion at high temperatures is characterized by a large barrier E-diff((1)) = 450 meV and a large pre-exponential factor Dd(0)((1)) = 162 cm(2)/s, indicating that it is dominated by the kinetics of crossing step edges. The weakly activated diffusion at low temperatures is characterized by a much smaller 'barrier' of Ed(diff)((2)) = 22 meV and a pre-exponential factor Dd(0)((2)) = 0 6: 8 x 10(-14) cm(2)/s, characteristic of a quantum under-barrier tunneling. (C) 2009 Elsevier B.V. All rights reserved.