THE PHOTOINDUCED REACTION OF DIGERMANE WITH THE SI(100)(2 X 1)-D SURFACE

Photo-induced surface reactions brought about by photolysis of adsorbe d digermane on the Si(100)(2 X 1):D surface have been investigated und er ultrahigh vacuum conditions using Auger electron spectroscopy and t emperature programmed desorption. On the monodeuterated Si(100)(2 X 1) :D surface, no spontaneous thermal reaction of digermane is observed, due to the termination of the dangling bonds with D atoms. Molecular G e2H6, weakly adsorbed on Si(100)(2 X 1):D at 120 K, dissociates upon U V irradiation, leading to the incorporation of Ge atoms and the adsorp tion of H atoms on the surface. The appearance of a new low temperatur e alpha desorption state for hydrogen (deuterium) desorption near 580 K is further evidence for Ge deposition and the photo-induced decompos ition of physi-adsorbed Ge2H6. The observation of alpha-HD and alpha-D 2 desorption indicates that the photoreaction intermediate inserts int o the surface Si-D bond to produce a Ge-D bond. Studies of the thermal reaction of Ge2H6 with partially deuterated (THETA(D) < 1.0) Si(100) surfaces model the chemistry expected for a germyl radical intermediat e, and illustrate that the germyl radical does not give rise to the ob served surface photochemistry. The enhanced production of Ge trihydrid e (deuteride) species with increasing UV exposure, as measured by the GeHxD4-x desorption yield, coupled with the observation of Ge-D bond f ormation, reveals that the photo-induced Ge2H6 surface reaction is dom inated by an insertion reaction into surface hydride (deuteride) bonds by the photo-generated species germylene.