We investigated the zirconium-oxide-coated-tungsten (100) surface, which is widely used as the electron-emitting surface in Schottky electron sources. To extract electrons, the emitter is heated to approximately 1800 K. When the surface reaches a temperature greater than 1400 K, the work function of the (100) surface is selectively lowered by the coating of zirconium and oxygen, and surface diffusion of the atoms is rapid on the tungsten surface. The mechanism behind this process, however, is not clear because it is difficult to analyze the surface at high temperatures. In this study, we resolved this issue by improving our sample heating system and investigated the zirconium and oxygen-coated tungsten (100) surface using X-ray photoemission spectroscopy at 1500 K. The stable heating system helped us acquire highly reliable spectra, enabling us to elucidate the detailed bonding state of the atoms on the surface. We also found that a large amount of oxygen is present on the surface even at high operating temperatures. Moreover, zirconium and tungsten are partially oxidized, and the stoichiometry of these oxides is distinctly different from that of the stable oxide within the bulk.

我们研究了氧化锆涂层钨（100）表面，该表面被广泛用作肖特基电子源中的电子发射表面。为了提取电子，将发射极加热到大约1800K。当表面温度超过1400 K时，（100）表面的功函数会因锆和氧的涂层以及原子的表面扩散而有选择地降低在钨表面上很快。但是，该过程背后的机理尚不清楚，因为很难在高温下分析表面。在这项研究中，我们通过改进样品加热系统解决了这个问题，并使用1500 K的X射线光电子能谱研究了锆和氧包覆的钨（100）表面。稳定的加热系统帮助我们获得了高度可靠的光谱，使我们能够阐明表面上原子的详细键合状态。我们还发现，即使在较高的工作温度下，表面上也会存在大量的氧气。此外，锆和钨被部分氧化，这些氧化物的化学计量与本体中稳定氧化物的化学计量有明显不同。