Oxidation studies of hydrogenated amorphous silicon

Hydrogenated amorphous silicon surfaces, atomically clean and subsequently oxidized to up to 20 Å oxide thickness, were studied using AES and UPS. The oxidation was made in O₂ in the pressure range 10^?9 Torr to 5 atm and at 23 and 300°C. The oxidation rate at 23°C was found to be the same as that of crystalline silicon while at 300°C it was appreciably faster. Changes in the d $\text{N(E)}\text{dE}$ AES Si LVV line shape near 80 eV upon oxidation could be correlated to changes in the silicon-oxygen bonding level observed in UPS. The detailed line shape of the AES Si LVV transition indicates that at 300°C a more homogeneous oxide is produced than at 23°C.     

An organocatalytic ionic liquid

The carbene concentration in 1-ethyl-3-methylimidazolium-acetate ionic liquid is sufficiently high to act as a catalyst in benzoin condensation, hydroacylation and also in oxidation of an alcohol by using CO(2) and air. This observation reveals the potential of ionic liquid organocatalysts, uniting the beneficial properties of these two families of compounds.     

Contracting on Average Random IFS with Repelling Fixed Point

We consider random iterated function systems which consist of strictly increasing and (not necessarily strictly) convex functions on a compact interval or on a half line. We assume that the system is contracting on average in a sense which is wide enough to permit the existence of a common fixpoint at which some functions of the system are expanding and perhaps none of them are contracting (see Fig. 1). We prove that the Hausdorff dimension of any of the possibly uncountably many invariant measures is smaller than or equal to the accumulated entropy divided by the Liapunov exponent. Mathematics Subject Classification. Primary 42A85 Secondary 11R06; 26A46; 26A30; 26A78; 28A80     

The adsorption of CO on clean and potassium promoted FeO surfaces

The adsorption of CO on a FeO (wustite) surface was investigated using UPS, AES and temperature programmed desorption. These results are compared to those obtained from the same sample following addition of potassium from the decomposition of KOH. CO adsorption was identified following exposure at 300 K to the potassium free surface. The adsorbed species readily desorbs below 500 K. CO adsorption was poisoned by pre-exposure to oxygen at 300 K. This suggests CO is adsorbed at surface oxygen vacancies. CO induced UPS emission features are different from those typically found for CO chemisorbed on transition metal surfaces. The presence of potassium alters the adsorption behavior of CO. The thermal desorption maximum shifts to 625 K. UPS results indicate molecular CO adsorption at 300 K and upon heating to 470 K CO dissociates. The presence of potassium thus promotes CO dissociation on FeO.