New amorphous semiconductor: 2CdO⋅PbOx

Abstract

A new amorphous semiconductor, 2CdO⋅PbOx (band gap: 1.58 eV), was found. Thin films of this material were prepared by rf sputtering of a Cd2PbO4 target in O2–Ar. The dc conductivity of the resulting amorphous thin films was ∼180 S cm−1 at 300 K and remained almost constant down to ∼4 K. The concentration of carrier electrons and the Hall mobility in the as-deposited state were 1×1020 cm−3 and 9 cm2 V−1 s−1, respectively. When the as-deposited specimens were heated to 250 °C, which is far below the crystallization (to Cd2PbO4) temperature (460 °C), the conductivity and the carrier concentration at 300 K became approximately twice as high. The thermal O2-desorption measurements demonstrated that carrier electrons are generated via the formation of oxygen vacancies at the initial stage (<250 °C) of thermal desorption of O2 from the amorphous structure. The effective mass of carrier electrons was estimated as 0.57m0.