Fig. 5.
Evidence for hydrogen atom migration from small palladium islands on Ag(111) is obtained from scanning tunneling microscopy experiments. (A) Images obtained after exposure of palladium islands (θPd = 0.05 ML) on silver to 20 L of dihydrogen on Ag(111) at 150 K in which the palladium islands ∼10 nm across (white region) and hydrogen atoms present on the Ag(111) surface appear as depressions (purple) on the Ag(111) surface. (B) An apparent height profile along the black line scan in A illustrates that the features attributed to hydrogen atoms appear as depressions of ∼30 pm; 0.05 ML of palladium was deposited on Ag(111) at 300 K. The number of hydrogen atoms imaged on silver is small because of the low exposure of dihydrogen (20 L) and low palladium coverage (θPd = 0.05 ML). Imaging conditions are 0.030 V, 0.020 nA, 5 K.