DC surface conductance as a tool for the study of electrochemical interfaces

ALDABE BILMES, S; D. POSADAS

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1998 vol. 134 p. 47 - 57

0927-7757

DC surface conductance is a simple and powerful method for the study of electrochemical interfaces. Its applicability to semiconductor film/electrolyte junctions is analyzed from a theoretical and experimental approach. The experimental design and the fundamentals of the measuring method for semiconductor film electrodes are presented, taking into account the potential and current distribution arising from the polarization current and its influence on the measuring current. The dependence of surface conductance on the electrode potential is modeled by describing the space charge layer as that of an ideal Schottky junction. Corrections due to the decrease of carrier mobility in strong accumulation layers are also included in the model. Surface conductance-potential curves for CdS films in electrolytes are interpreted with this simple model, and parameters such as flat band potential, donor density and mobility are obtained for these interfaces. These results correlate with those obtained from capacitance and modulated transmittance experiments. Conductance measurements for CdS surface modified by S2− or by Au deposits reveal that there is a change in the density of filled carrier traps with energy levels in the band gap.