Instability of the Si(1Â 0Â 0) dihydride phases accompanied by molecular emissions under pulsed-H irradiation

We have measured the transient desorption of HD and D2 molecules from D/Si(1 0 0) surfaces during pulsed H dosing for the surface temperatures from 443 to 593 K. Contrary to the direct D abstraction by H to generate HD desorptions, the adsorption-induced-desorption (AID) of D2 takes place preferentially on the 3 × 1 dideuteride domains, with four transient desorption components characterized with ⩽0.005, ≃0.06, ≃0.8 s, and ≃30 s lifetimes. It is considered that the excess dihydrides (dideuterides) generated at the 3 × 1 local domains or at their boundaries may receive a thermal instability towards molecular emissions, either promptly returning to the original 3 × 1 phase or enlarging the dihydride domain area. The long ≃30 s lifetime component could be attributed to the molecular emissions that occur when the 3 × 1 dideuteride domains reduce their size at off-cycle of the H beam.