Models of Surface Morphology and Electronic Structure of Indium Oxide and Indium Tin Oxide for Several Surface Hydroxylation Levels
Models of Surface Morphology and Electronic Structure of Indium Oxide and Indium Tin Oxide for Several Surface Hydroxylation Levels
复制标题
几种表面羟基化水平下氧化铟和氧化铟锡的表面形貌和电子结构模型
DOI：
10.1021/acs.jpcc.7b10267
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Pavanello, Michele
中科院分区：
文献类型：
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作者：
Harrell, Jaren;Acikgoz, Muhammed;Lieber Sasson, Hela;Visoly-Fisher, Iris;Genova, Alessandro;Pavanello, Michele
氧化铟(IO)和氧化铟锡(ITO)是重要的金属氧化物材料，具有广泛的应用前景。特别是，ITO被用作光伏系统中的透明导电电极。虽然块状金属氧化物通常被很好地表征，但它们的表面，特别是在现实生活中的应用，可能会被羟化并本质上无序到使结构功能预测成为一项艰巨任务的程度。我们通过基于密度泛函理论进行模拟来解决这个问题。我们建议IO和ITO羟化表面来源于体心立方和血栓型IO多形体(考虑100%、66%、33%和0%的羟化覆盖率)。通过关联计算量，如表面偏态密度、功函数和表面偶极子强度，这些模型系统中的结构-函数关系的清晰图景浮出水面。与实验结果一致，我们发现100%羟基表面和体模型的态密度不受锡掺杂的影响，唯一不同的是费米能级的位置。相反，部分羟化的表面表现出丰富的行为，包括在缝隙中出现表面态，以及有趣的形貌的出现，如化学吸附的分子氧。我们还发现，羟化程度对表面偶极子的影响是系统性的，即羟化程度越高，表面偶极子越高(屏蔽/减少功函数)。此外，具有In原子空位的模型显示，由于表面扭曲，具有羟基覆盖的表面偶极子的降幅相对较小。
Indium oxide (IO) and indium tin oxide (ITO) are important metal oxide materials with a wide array of applications. Particularly, ITO is employed as a transparent conductive electrode in photovoltaic systems. While bulk metal oxides are typically well characterized, their surfaces, especially in real-life applications, can be hydroxylated and intrinsically disordered to a level that a structure–function prediction becomes a daunting task. We tackle this problem by carrying out simulations based on Density Functional Theory. We propose IO and ITO hydroxylated surfaces derived from the bcc and rombohedral IO polymorphs (100%, 66%, 33%, and 0% hydroxylation coverages were considered). By correlating computed quantities such as surface partial density of states, work functions, and surface dipole strength, a clear picture of the structure–function relationships in these model systems emerges. In line with conclusions drawn from experiments, we find that the density of states of 100% hydroxylated surfaces and bulk models are unaltered by Sn doping, with the only difference being the position of the Fermi level. The partially hydroxylated surfaces, instead show a rich array of behaviors, including appearance of surface states in the gap and appearance of interesting morphologies, such as chemisorbed molecular oxygen. We also find that the hydroxylation level affects surface dipoles in a systematic way, that is, the higher the hydroxylation level, the higher the surface dipole (screening/reducing the work function). Furthermore, models with In-atom vacancies show a relatively small decrease in surface dipole with hydroxyl coverage due to surface distortions.