Study on intrinsic properties of organic semiconductors appeared under ultrahigh vacuum

有机半导体的载流子输运机制和金属电极的载流子注入机制是构建高性能有机薄膜器件的重要课题。电性能很容易被吸附的气体分子改变，这使得很难获得可靠的实验结果。我们已经研究了在高真空条件下剥离氧气面纱的本征性质。为了避免气体吸附对薄膜电学性能的影响，研究了超高真空条件下制备的酞菁氧钛（TiOPc）薄膜的电学性能。场效应测量结果表明，TiOPc薄膜在超高真空下表现出n型半导体特性。室温下的电子迁移率为9 × 10^<-6>cm ^2 V ^<-1>S^，<-1>激活能为0.20 eV。电导率和载流子密度分别为9 × 10 - <-8>5cm-3<-1>和6 × 10 - <16>5cm-3<-3>。当薄膜暴露于氧气中时，观察到从n型到p型的明显转变。严格控制的tmosphere使人们有可能获得一个准本征态，其中p型和n型导电同时出现。

The mechanism of carrier transport in organic semiconductors and carrier injection from metal electrodes becomes the most important subject to be elucidated for the construction of high performance organic thin film devices. The electrical properties are modified easily by adsorbed gas molecules, which makes it difficult to obtain reliable experimental results. We have studied intrinsic properties under ultrahigh vacuum conditions to strip away the veil of oxygen. We investigated electrical properties of titanyl-phthalocy anine (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> cm^2V^<-1>S^<-1> with activation energy of 0.20 eV. The conductivity and carrier density were 9 x 10^<-8> Scm^<-1> and 6 x 10^<16> cm^<-3>, respectively. A clear conversion from n-type to p-type behavior was observed when the films was exposed to oxygen. Strict control of a tmosphere made it possible to obtain a quasi-intrinsic state where both p- and n-type conductions appeared simultaneously.