In this study, we report that the electrical transport property in monolayer pentacene is highly sensitive to a small amount of exposure to gaseous molecules of oxygen, nitrogen, and argon, by using independently-driven four gallium indium (GaIn) probes. Liquid metal GaIn probes have been used as non-destructive conductivity electrodes for monolayer OFET films in a vacuum chamber. We carried out the fabrication of monolayer pentacene and the four-probe measurement without exposure to atmospheric air. Four GaIn probes were used in situ to measure conductivity in the channel separately from the overall characteristics including contact resistance at the electrode probes. The results demonstrate that oxygen exposure of 1 L (${10}^{-6}$ Torr s) reduces mobility to 8% of the original value in the monolayer film, and the reduction is irreversible, i.e., mobility does not recover its original value after the evacuation of gaseous molecules. Physisorption of gaseous molecules is involved in the gas exposure effects, because chemically inert gases of nitrogen and argon also reduce the mobility. Taking these findings together with the results of photoelectron spectroscopy and atomic force microscopy measurements, we assume that the reduction is attributed to the physisorption at grain boundaries formed by the coalescence of monolayer islands.

在这项研究中，我们报告说，通过使用独立驱动的四镓铟（GaIn）探针，单层并五苯中的电传输性质对少量暴露于气态分子的氧气，氮气和氩气高度敏感。液态金属GaIn探针已用作真空室内单层OFET膜的非破坏性导电电极。我们进行了单层并五苯的制造和四探针测量，而没有暴露于大气中。四个GaIn探头用于原位测量通道中的电导率，与包括电极探头接触电阻在内的总体特性分开。结果表明，氧气暴露量为1 L（${10}^{-6}$Torr（s）将迁移率降低到单层膜原始值的8％，并且降低是不可逆的，即，迁移气体分子后迁移率无法恢复其原始值。气体分子的物理吸附与气体暴露效应有关，因为氮气和氩气的化学惰性气体也会降低迁移率。结合这些发现以及光电子能谱和原子力显微镜测量的结果，我们认为减少的原因是由于单层岛聚结形成的晶界上的物理吸附。