镍基少层石墨烯电极场发射性能机制与微结构分析  

Field Emission Performance Mechanism and Microdomain Analysis of Nickel-based Few-layer Graphene Electrodes

作　　者：宋小勇[1] 房硕洋 赵明[2,3] 孙陆军 姜志忠[2,3] SONG Xiaoyong;FANG Shuoyang;ZHAO Ming;SUN Lujun;JIANG Zhizhong(College of Energy and Power Engineering,North China University of Water Resources and Electric Power,Zhengzhou 450045,China;Institute of Nuclear Energy Safety Technology,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;Science Island Branch,Graduate School of University of Science and Technology,Hefei 230031,China)

机构地区：[1]华北水利水电大学能源与动力工程学院,郑州450045 [2]中国科学院合肥物质科学研究院核能安全技术研究所,合肥230031 [3]中国科学技术大学研究生院科学岛分院,合肥230031

出　　处：《材料导报》2023年第12期14-19,共6页Materials Reports

基　　金：国家自然科学基金(2180051117);国家磁约束聚变计划(2018YFE0312200)。

摘　　要：石墨烯因具有多种优异性质而被广泛应用于工业技术领域,利用石墨烯的吸附性实现对碱金属原子的吸附,表面功函数将大幅降低,将其应用于热电器件电极材料可显著提高器件的输出性能。研究结果表明,采用“yo-yo”法铯氧交替激活方式对镍基底少层石墨烯样品进行激活实验,铯蒸气以铯原子的形式在少层石墨烯表面均形成稳定的结构,光电流逐渐增加,石墨烯表面功函数随之降低。后续间断通入氧气,氧原子与表面吸附的铯原子相互作用,铯原子在氧原子作用下离子化,光电流迅速增加,进一步降低了石墨烯表面功函数。X射线光电子能谱(XPS)及紫外光电子能(UPS)谱的分析结果表明,二层、三层、五层石墨烯表面功函数在铯氧激活后达到的最小值分别为1.446 eV、1.388 eV、1.253 eV,较激活前分别降低了56.38%、58.55%、62.58%。功函数降低程度与石墨烯层数具有一定的关系,层数增加促进Cs-O-Cs双偶极子结构的产生,Cs2O和CsC8在降低功函数方面具有协同作用。另外,Cs-O-C双偶极子加强C-Cs偶极子对表面纵向电场的影响。在此基础上,通过第一性原理阐述了石墨烯在铯化后功函数降低机制。Graphene has been widely used in the field of industrial technology because of its excellent properties.The adsorption of alkali metal atoms by graphene will greatly reduce the surface work function,and its application in the electrode material of thermoelectric devices can significantly improve the output performance of devices.The results show that the cesium vapor forms a stable structure on the surface of nickel-substrate gra-phene in the form of cesium atoms by using the‘yo-yo’method of alternating activation of cesium and oxygen.The photocurrent increases gradually,and the work function on the surface of graphene decreases.The oxygen atom interacts with the cesium atom adsorbed on the sur-face.Under the action of the oxygen atom,the cesium atom is ionized,and the photocurrent increases rapidly,further reducing the work function on the surface of graphene.XPS and UPS analysis results showed that the minimum values of the surface work function of the bilayer graphene,trilayer graphene and penta layer graphene after cesium oxygen activation were 1.446 eV,1.388 eV and 1.253 eV,respectively,which de-creased by 56.38%,58.55%and 62.58%compared with that before activation.The decreased degree of the work function is related to the num-ber of graphene layers.The increase of the number of graphene layers promotes the generation of the Cs-O-Cs dipole structure,and Cs2 O and CsC8 have a synergistic effect on the decrease of the work function.In addition,the Cs-O-C dipole strengthens the effect of the C-Cs dipole on the longitudinal electric field of the surface,and explains the mechanism of the decrease of the work function of graphene after cesium deposition.

关 键 词：铯氧激活 光电流 偶极子结构 吸附 功函数 

分 类 号：TM915[电气工程—电力电子与电力传动]