DETERMINATION OF THE STICKING COEFFICIENT OF DISILANE ON SI(001) USING THE 1ST REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION OSCILLATION PERIOD

We have investigated the growth of Si from disilane on Si(001) in GSMB E. The growth rates were determined from reflection high energy electr on diffraction (RHEED) intensity oscillations. Close inspection of the oscillation traces revealed a rapid decrease in intensity after begin ning of growth for the first half period. This decrease was always fas ter than half the period of the remaining oscillation trace. The decre ase does not depend on growth temperature but does depend on the incid ent flux. To interpret this effect, we assume that the surface is init ially hydrogen-free. Under these circumstances, a maximum amount of di silane will quickly adsorb and decompose on the Si surface, which acco unts for the sharp decrease in the beginning for high incident fluxes. Further adsorption (and thus regular growth) is only possible after s ubsequent desorption of hydrogen. Thus, in this time, the hydrogen sur face coverage develops towards the equilibrium value, which is constan t during the subsequent growth. It is assumed that during the time to reach the equilibrium (tau(i)), 0.5 ML of Si are deposited, which in t urn corresponds to a minimum in RHEED intensity. Thus, by injecting a certain flux and measuring tau(i), the determination of the reactive s ticking coefficient alpha(r), which is defined as the ratio between th e amount of chemisorbing flux and the incoming flux on a bare surface, is possible. This way, the sticking coefficient of disilane on the Si (001) surface was found to be independent of substrate temperature in the investigated range between 464 and 580-degrees-C.