标题： KTaO3(001)真空制备方法：对表面化学计量比、晶体学及带隙态的影响 显示英文标题

标题： KTaO3(001) Preparation Methods in Vacuum: Effects on Surface Stoichiometry, Crystallography, and in-gap States

摘要： 使用不同取向的KTaO3单晶作为外延生长薄膜的基底和/或作为二维电子气体的宿主。 由于KTaO3(001)表面具有极性，因此可以预期其制备过程中会出现困难和挑战。 在不添加不良的间隙电子态的情况下保持良好的绝缘特性，获得良好的晶体有序性直至顶层表面，足够平坦的表面以及完全清洁的表面（无水、碳或羟基污染物），通常这些条件难以同时实现。 真空解理可能是获得清洁表面的最佳选择。 然而，由于KTaO3是立方结构且缺乏明确的解理面，这种方法不适合样品生长或可重复的器件制造。 在这里，我们系统地评估了应用于KTaO3(001)单晶表面的典型制备方法的效果。 特别是，我们在不同的温度下进行了真空退火，在低能量（500 eV）下使用Ar+离子轻度溅射后退火，重Ar+离子轰击和退火，以及在连续方位角旋转下进行掠射Ar+离子轰击，并结合在真空和O2气氛中的退火。 通过包括前向角度低能离子散射、俄歇电子能谱、低能电子能量损失、X射线光电子能谱、低能电子衍射和飞行时间二次离子质谱在内的多种技术组合，评估每种处理后的可能副作用。 详细讨论了每种制备方法的优点和缺点。 显示英文摘要

摘要： KTaO3 single crystals with different orientations are used as substrates for the epitaxial growth of thin films and/or as hosts for two-dimensional electron gases. Due to the polar nature of the KTaO3(001) surface, one can expect difficulties and challenges to arise in its preparation. Maintaining good insulating characteristics without adding undesirable in-gap electronic states, obtaining good crystalline order up to the top surface layer, a sufficiently flat surface, and complete cleanliness of the surface (without water, C or OH contaminants), are in general difficult conditions to accomplish simultaneously. Cleaving in vacuum is likely the best option for obtaining a clean surface. However, since KTaO3 is cubic and lacks a well-defined cleavage plane, this method is notsuitable for sample growth or reproducible device fabrication. Here, we systematically evaluate the effect of typical preparation methods applied on the surfaces of KTaO3(001) single crystals. In particular, we used annealing in vacuum at different temperatures, light sputtering with Ar+ ions at low energy (500 eV) followed by annealing, heavy Ar+ ion bombardment and annealing, and grazing Ar+ ion bombardment under continuous azimuthal rotation combined with both annealing in vacuum and in O2 atmosphere. Possible side effects after each treatment are evaluated by a combination of techniques, including low-energy ion scattering at forward angles, Auger electron spectroscopy, low-energy electron energy loss, X-ray photoelectron spectroscopy, low-energy electron diffraction, and time of flightsecondary ion mass spectrometry. Advantages and shortcomings of each preparation method are discussed in detail.