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

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 9x10(-6) cm(2) V-1 s(-1) with activation energy of 0.20 eV. The conductivity and carrier density were 9x10(-8) S cm(-1) and 6x10(16) 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. (C) 2000 American Institute of Physics. [S0003-6951(00)01507-2].