A new technique to determine the flat-band potential of semiconductors as well as to distinguish the direct photoresponse from the indirect processes has been developed. Chopped light was used for illuminating the SC and the oscillating photocurrent was measured in a storage oscilloscope at varying potentials. Cathodic photo-response was observed with TiO//2 prepared by thermal oxidation of Ti without further thermal hydrogenation or doping. V//f//b of this was different from that of the former one. Their energy level diagrams and nature of surface states have been discussed.