Polarization dependence of ZnO Schottky barriers revealed by photoelectron spectroscopy
Polarization dependence of ZnO Schottky barriers revealed by photoelectron spectroscopy
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DOI：
10.1103/physrevmaterials.4.084604
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发表时间：
2020-08
影响因子：
3.4
通讯作者：
Philipp Wendel;S. Periyannan;W. Jaegermann;A. Klein
中科院分区：
文献类型：
--
作者：
Philipp Wendel;S. Periyannan;W. Jaegermann;A. Klein
为了回答极性氧化锌表面肖特基势垒在锌端面和氧端面上是否不同的问题，用原位制样的光电子能谱方法研究了n型氧化锌与不同高功函数金属和金属氧化物(铂和金属氧化物)的界面形成，肖特基势垒高度可达1.5 eV。这些实验旨在排除衬底还原以及由此产生的由高浓度氧空位引起的费米能级钉扎的影响。此外，通过在分析中考虑锌离子的1MM俄歇发射，证明了势垒高度的准确提取需要考虑到光电子核心空穴的屏蔽在接触形成过程中会发生变化。肖特基势垒的偏振相关性在大多数情况下是由缺陷的影响决定的，而肖特基势垒对于压电势垒的应用非常重要。为了减少缺陷的影响，在氧气终止的表面上显示了高达240$MeV的肖特基势垒。这与文献中报道的相反，但与对于铁电材料一样，电极对氧化锌极化的不完全屏蔽所期望的势垒高度的依赖性是一致的。
In order to answer the question of whether Schottky barriers on polar ZnO surfaces are different at Zn- and O-terminated surfaces, the interface formation of $n$-type ZnO and different high work function metals and metal oxides (Pt, ${\mathrm{PtO}}_{x}$, and ${\mathrm{RuO}}_{2}$) with Schottky barrier heights of up to 1.5 eV has been studied using photoelectron spectroscopy with in situ sample preparation. The experiments are designed to exclude the effects of substrate reduction and consequent Fermi level pinning by high concentrations of oxygen vacancies. Moreover, by including the Zn LMM Auger emission in the analysis, it is demonstrated that an accurate extraction of barrier heights needs to take into account that the screening of the photoelectron core hole can change in the course of contact formation. The polarization dependence of Schottky barriers, which is important for piezotronic applications, is in most cases dominated by the influence of defects. Reducing the influence of defects, up to $\ensuremath{\sim}240$ meV higher Schottky barriers are revealed on oxygen-terminated surfaces. This is opposite to what has been reported in the literature but agrees with the dependence of barrier heights expected for an incomplete screening of the polarization of ZnO by the electrode as for ferroelectric materials.