内嵌CuO薄膜对并五苯薄膜晶体管性能的改善

制备了基于内嵌氧化物铜(CuO)薄膜的并五苯薄膜晶体管器件. 将3 nm CuO薄膜内嵌入到并五苯(pentacene)中, 作为空穴注入层, 降低电极与并五苯之间的空穴注入势垒. 相对于纯并五苯薄膜晶体管器件, 研制的晶体管的迁移率、阈值电压(V_TH)、电流开关比(I_on/I_off) 等参数都有明显改善. X射线光电子能谱数据表明, 这种空穴注入势垒的降低源自并五苯向CuO的电子转移.

Analysis of improved characteristics of pentacene thin-film transistor with an embedded copper oxide layer

Organic thin-film transistor (OTFT) based on pentacene semiconductor with an embedded copper oxide (CuO) thin layer is investigated. With the 3 nm-thick CuO layer embedded in the pentacene semiconductor, the drain current of the OTFT increases more than 3 times compared with that of pentacene organic field-effect transistor without CuO layer, and the absolute threshold voltage reduces from -21 V to -7.9 V. The hole mobility and current on/off ratio are much improved. It is interpreted by the mechanism based on the analysis of the interface charge transfer between pentacene layer and CuO layer. Results of X-ray photoelectron reveal electron transfer from pentacene to high work function CuO and the formation of charge transfer (CT) complexes based on electron transfer near the contact of CuO and pentacene. The CT complexes between pentacene layer and CuO layer could reduce the exponential density of state near the band edge of pentacene and the pentacene bulk hole trap density, and enhance the pentacene bulk hole carriers injection, which leads to the improvement of the field-effect mobility of OTFT with CuO layer. Electrons are transfered from the highest occupied molecular orbital of pentacene to the thin CuO layer which can generate holes in pentacene. The generated hole has the same effect as that with applying negative gate voltage which influences the threshold voltage. The drain current of the device increases and the threshold voltage shifts from -21 V to -7.9 V. Therefore, the thin CuO layer that is directly embedded in the organic semiconductor layer, serves as the hole-injection layer, which is responsible for reducing the contact barrier of OTFT with CuO layer.