Structural, electrical, and optical properties of hydrogen-doped ZnO films
Structural, electrical, and optical properties of hydrogen-doped ZnO films
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DOI：
10.1103/physrevb.86.115334
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发表时间：
2012-09
影响因子：
3.7
通讯作者：
A. Kronenberger;A. Polity;D. Hofmann;B. Meyer;A. Schleife;F. Bechstedt
中科院分区：
文献类型：
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作者：
A. Kronenberger;A. Polity;D. Hofmann;B. Meyer;A. Schleife;F. Bechstedt
使用 H2 和 O2 作为反应气体，通过射频磁控溅射从陶瓷靶材在 c 面蓝宝石和熔融石英上沉积氢掺杂 ZnO 薄膜。结构分析表明，所有薄膜都是多晶的，c 轴垂直于基底表面。横向晶粒尺寸受到溅射气体的氧含量的强烈影响，并在高于 4.5% 的临界含量时急剧下降。我们能够通过沉积参数将薄膜的载流子密度调整为 1014 到 2 × 1020 cm−3 之间的任何值。使用与温度相关的霍尔效应测量，我们识别了由晶界处的表面陷阱状态和主导载流子传输的隧道效应产生的库仑势垒上的热电子发射。制备并彻底表征薄膜是我们研究光学带隙能量对载流子密度依赖性的先决条件。我们使用实验结果以及第一性原理计算（包括 Burstein-Moss 位移、带隙重正化和激子效应）来了解决定自由电子如何影响光学吸收起始能量位置的机制。
Hydrogen doped ZnO thin films were deposited by radio frequency magnetron sputtering from a ceramic target on c-plane sapphire and fused silica using H2 and O2 as reactive gases. Structural analysis revealed that all films are polycrystalline with the c axis oriented perpendicularly to the substrate surface. The lateral grain size was strongly affected by the oxygen content of the sputtering gas and decreased dramatically above a critical content of 4.5 %. We were able to adjust the carrier density of the films by the deposition parameters to any value between 1014 and 2 × 1020 cm−3. Using temperature-dependent Hall-effect measurements we identified thermionic emission over Coulomb-barriers created by surface trap states at the grain boundaries and tunneling effects to dominate the carrier transport. Preparing and thoroughly characterizing the films is a prerequisite for our investigation of the dependence of the optical band gap energy on the carrier density. We use results from experiment as well as first-principles calculations (including Burstein-Moss shift, band gap renormalization, and excitonic effects) in order to understand the mechanisms that determine how free electrons influence the energy position of the optical absorption onset.