Development of Photoelectron Emitting Materials in Ambient Atmosphere

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Photoelectron emission from Au thin films was measured in ambient atmosphere with the presence of various kinds of organic vapors under irradiation of ultraviolet light (254 nm). The photoelectron emission was greatly influenced by the introduction of vapors. The observed effects were classified into three types; (i) Alkenes such as cyclohexene gave a large increase of photoelectron current with 02 in the atmosphere. (ii) Ethanol and water showed moderate and quick increases of the current irrespective to the presence of oxygen. (iii) Acetone reduced the photoelectron current irreversibly to near zero. The work function of Au thin films changed considerably upon the introduction of vapors ; a decrease with cyclohexene and an increase with acetone. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that molecular oxygen reacted with cyclohexene to form oxygenated species on Au thin films under the irradiation of UV light, which appeared to induce the decrease of work function of the films.