Ronald Dehmlow

On capacity measurements and the energy distribution of surface states at the electrolyte-GaAs interface

Abstract The frequency-dependent values for the capacities obtained for GaAs, GaAsP and GaP were interpreted by means of the usual equivalent circuit with the capacity of the surface states and that of the depletion layer in parallel. Consistent results are obtained only assuming a continuous energetic distribution of surface states in the forbidden gap. Adsorption of a dye and Ru3+ leads to an altered distribution function, the maximum appearing can be accounted for by superimposing a Lorentz function on the cosh type of function. The dye adsorption was determined radiochemically and obeys a Freundlich isotherm. Ellipsometric measurements under the same conditions suggest the formation of non-passivating surface films in the electrolytes used.

Zur elektrochemischen lumineszenz an halbreitern

Abstract The electrochemical luminescence of aromatic compounds in aprotic solvents was investigated using the following semiconductor electrodes: n-GaP, n-ZnO and n-SnO 2 . Electrochemical luminescence by direct heterogeneous electron transfer to the excited singlet or triplet state and subsequent luminescence could in no case be detected. The discussion of the mechanism of the redox processes involved is based on experimental observations and energetic correlations which were partly obtained by measuring the capacity of the semiconductor—solvent systems used. We presume that the directly excited states are deactivated by radiationless transitions due to a heavy atom effect. This conclusion was confirmed to the extent that the naphthalin luminescence was quenched by these semiconductors at 77 K.