Formation of vacancy clusters and cavities in He-implanted silicon studied by slow-positron annihilation spectroscopy
Formation of vacancy clusters and cavities in He-implanted silicon studied by slow-positron annihilation spectroscopy
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DOI：
10.1103/physrevb.61.10154
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发表时间：
2000-04
影响因子：
3.7
通讯作者：
R. Brusa;G. Karwasz;N. Tiengo;A. Zecca;F. Corni;R. Tonini;G. Ottaviani
中科院分区：
文献类型：
--
作者：
R. Brusa;G. Karwasz;N. Tiengo;A. Zecca;F. Corni;R. Tonini;G. Ottaviani
通过慢正电子束和多普勒展宽技术，在 20 keV 能量下注入 He 的 Si 中测量了开放体积缺陷的深度剖面。在 5× 10 15 和 2× 10 16 He cm− 2 注量下注入的两个系列样品中，缺陷分布的演变作为等时退火的函数进行了研究。拟合程序已应用于实验数据，以提取表征每个开放体积缺陷的正电子参数。通过将该参数与最近的理论计算进行比较来识别缺陷。在注入样品中，注入产生的空位和双空位的主要部分因 He 的存在而被钝化。正电子湮灭技术所看到的缺陷平均深度大约比氦投射范围小五倍。在连续的等时退火过程中，正电子陷阱的数量先减少，然后增加，最后在最高退火温度下，仅在以最低注量注入的样品中消失。两个系列的退火温度为 250°C 时，开孔体积缺陷均达到最低限度。温度高于 250°C 时，开孔体积缺陷的增加是由于空位簇尺寸增大造成的，平均深度分布向 He 预测范围移动。空位团簇的出现与He的向外扩散密切相关。在5× 10 15 cm− 2 注入的样品中，空位簇主要是由He 相关缺陷稳定的四个空位团聚体。它们从 700 C 的退火温度开始消失。在以 2× 10 16 cm− 2 注入并在 850–900 C 退火的样品中，空位簇消失，仅保留以 He 投影范围为中心的空穴分布。讨论了空位在 He 簇形成中的作用，He 簇在气泡中演化，然后在空腔中演化。
The depth profile of open volume defects has been measured in Si implanted with He at an energy of 20 keV, by means of a slow-positron beam and the Doppler broadening technique. The evolution of defect distributions has been studied as a function of isochronal annealing in two series of samples implanted at the fluence of 5× 10 15 and 2× 10 16 He cm− 2. A fitting procedure has been applied to the experimental data to extract a positron parameter characterizing each open volume defect. The defects have been identified by comparing this parameter with recent theoretical calculations. In as-implanted samples the major part of vacancies and divacancies produced by implantation is passivated by the presence of He. The mean depth of defects as seen by the positron annihilation technique is about five times less than the helium projected range. During the successive isochronal annealing the number of positron traps decreases, then increases and finally, at the highest annealing temperatures, disappears only in the samples implanted at the lowest fluence. A minimum of open volume defects is reached at the annealing temperature of 250 C in both series. The increase of open volume defects at temperatures higher than 250 C is due to the appearance of vacancy clusters of increasing size, with a mean depth distribution that moves towards the He projected range. The appearance of vacancy clusters is strictly related to the out diffusion of He. In the samples implanted at 5× 10 15 cm− 2 the vacancy clusters are mainly four vacancy agglomerates stabilized by He related defects. They disappear starting from an annealing temperature of 700 C. In the samples implanted at 2× 10 16 cm− 2 and annealed at 850–900 C the vacancy clusters disappear and only a distribution of cavities centered around the He projected range remains. The role of vacancies in the formation of He clusters, which evolve in bubble and then in cavities, is discussed.