A Capacitive Divider Technique for Fast Interface Capacitance Measurement

A fast method of measuring interface capacitance in electrolyte‐semiconductor systems is presented and discussed. The interface capacitance is determined from the voltage response of the interface to a driving voltage applied across the interface and a small series capacitor which form a capacitive voltage divider. In particular, the differential capacitance, related to the derivative of the constant‐current charging curve, is obtained directly if a pulse or square‐wave driving voltage is used. A further advantage is that capacitance can be determined in shorter time intervals than required by previous methods. Experimental results which demonstrate the method are given for the intrinsic Ge‐aqueous electrolyte system, and it is also shown that semiconductor surface fields can be determined in the presence of rapid modulations. Applications to electroreflectance are discussed.