Quasi-intrinsic semiconducting state of titanyl-phthalocyanine films obtained under ultrahigh vacuum conditions

Abstract

We investigated electrical properties of titanyl-phthalocyanine (TiOPc) films under ultrahigh vacuum (UHV) conditions to avoid the influence of gas adsorption. The field-effect measurement revealed that TiOPc films exhibited an n-type semiconducting behavior in UHV. The electron mobility at room temperature was 9×10−6 cm2 V−1 s−1 with activation energy of 0.20 eV. The conductivity and carrier density were 9×10−8 S cm−1 and 6×1016 cm−3, respectively. A clear conversion from n-type to p-type behavior was observed when the film was exposed to oxygen. Strict control of atmosphere made it possible to obtain a quasi-intrinsic state where both p- and n-type conductions appeared simultaneously.