Evolution kinetics of elementary point defects in ZnO implanted with low fluences of helium at cryogenic temperature
Evolution kinetics of elementary point defects in ZnO implanted with low fluences of helium at cryogenic temperature
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DOI：
10.1103/physrevb.94.205204
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发表时间：
2016-11
影响因子：
3.7
通讯作者：
C. Bhoodoo;A. Hupfer;L. Vines;E. Monakhov;B. Svensson
中科院分区：
文献类型：
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作者：
C. Bhoodoo;A. Hupfer;L. Vines;E. Monakhov;B. Svensson
采用电容电压（CV）和结谱测量方法，对水热法生长的n型ZnO样品进行了原位研究，样品温度为40 K，注量为5 × 109和5 × 1010 cm−2。结果补充了二次离子质谱和傅里叶变换红外吸收测量和第一性原理计算的数据。退火后观察到退火诱导的浅施主中心的去除/钝化或深受主缺陷的生长，通过电荷载流子浓度（Nd）与从CV数据提取的深度分布进行监测。在290-325 K的温度范围内进行等温退火以研究Nd的演化，揭示了一级动力学，活化能Ea为0.7 eV，频率因子c 0为106 s−1。两个模型进行了讨论，以解释这些退火结果。一种依赖于氧电子（Oi）从分裂构型（中性态）到八面体构型（深双受体态）的转变作为关键特征。另一种是基于Zn原子（双施主）的迁移和中性Zn-空位-氢络合物作为核心成分的捕获。特别是，后者的模型表现出良好的定量与实验数据的一致性，并给出了一个激活能为10.75 eV的迁移的Zn晶体。
Hydrothermally grown n-type ZnO samples, implanted with helium (He+) at a sample temperature of ∼40 K and fluences of 5 × 109 and 5 × 1010 cm−2, have been studied in situ by capacitance voltage (CV) and junction spectroscopy measurements. The results are complemented by data from secondary ion mass spectrometry and Fourier transform infrared absorption measurements and first-principles calculations. Removal/passivation of an implantation-induced shallow donor center or alternatively growth of a deep acceptor defect are observed after annealing, monitored via charge carrier concentration (Nd ) versus depth profiles extracted from CV data. Isothermal anneals in the temperature range of 290–325 K were performed to study the evolution in Nd , revealing a first-order kinetics with an activation energy, Ea ≈ 0.7 eV and frequency factor, c0 ∼ 106 s−1. Two models are discussed in order to explain these annealing results. One relies on transition of oxygen interstitials (Oi) from a split configuration (neutral state) to an octahedral configuration (deep double acceptor state) as a key feature. The other one is based on the migration of Zn interstitials (double donor) and trapping by neutral Zn-vacancy-hydrogen complexes as the core ingredient. In particular, the latter model exhibits good quantitative agreement with the experimental data and gives an activation energy of ∼0.75 eV for the migration of Zn interstitials.