PHOTOELECTROCHEMICAL AND SOLID-STATE PROPERTIES OF LuRhO//3.

Results are reported for an electrochemically stable p-type oxide, LuRhO//3, which both resists corrosion and possesses a sufficiently large photopotential, and which may be used in conjunction with an n-type anode, such as TiO//2, to photoelectrolyze water spontaneously without an externally applied potential. As synthesized, LuRhO//3 is p type as determined by thermoelectric power measurements, but may be doped n type by the introduction of Th** plus **4 during synthesis. Electrical resistivity data indicate that this oxide passes through compensation as the doping level increases, the activation energy at compensation being one-half the optical band gap. The concentration of donor and acceptor impurities was determined by magnetic susceptibility to be in the vicinity of 1% for all samples. From these data, an estimate of 2. 5 cm**2/V sec can be made for the mobility of holes and 1 cm**2/V sec for the mobility of electrons. Unlike most n-type oxides reported, LuRhO//3 possesses deep lying impurity levels and surface capacitance is far from Mott-Schottky behavior. A theory of surface capacitance for deep levels has been developed, and the data agree well with theory.