Atomic hydrogen-induced abstraction of adsorbed deuterium atoms on the covalent solid surfaces

Hydrogen (H(g)) abstraction of D adatoms (D-ad) and collision-induced desor ption (CID), to form D-2 have been comparatively studied on the single crys taline C, Ge and Si(100) surfaces using a thermal (similar to 0.05 eV) H(g) beam. Strong HD and D-2 desorptions were observed during exposure on D-ad/ Si(100) and D-ad/Ge(100) surfaces. For both surfaces, it was found that the CID reaction follows a fourth-order kinetics in the D-ad coverage theta (D ), while as was expected, the abstraction reaction proceeds at a first-orde r kinetics in D. However, for the fairly smooth D-ad/C(100) surface as rela xed in the plasma CVD process neither abstraction nor CID were admitted, in dicating that the D-covered C(100) surface is quite inactive towards the th ermal H(g) beam particularly at the terrace site. However, it was observed that H(g) abstraction of D-ad takes place as the D-ad/surface was subjected to the D(g) beam in a high vacuum reaction chamber, suggesting that D atom s can stick to the deuterated surface. Sticking efficiency of D atoms was f ound to become high on the less smooth H-ad/C(100) surface, indicating that D sticking becomes efficient as the surface becomes rough. It was argued t hat such additional D sticking to the D or H-terminated C(100) surfaces tak es place at the step edges or the defect sites rather than at the terraces. (C) 2001 Elsevier Science B.V. All rights reserved.