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首页> 外文学位 >Ion induced electron emission: The effects of conduction band electrons and surface density of states.
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Ion induced electron emission: The effects of conduction band electrons and surface density of states.

机译：离子感应电子发射：导带电子和状态表面密度的影响。

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摘要

Recent plasma based measurements related to ion induced electron emission (IIEE) have suggested that conduction band electrons in semiconductors may significantly contribute to the overall electron emission. The foundation behind this hypothesis is simple: more electrons near the vacuum level equals more electron emission. Although intuitive, the hypothesis is in direct conflict with fundamental theory that has assumed since the 1960s that only valence band electrons contribute to the primary IIEE mechanism of Auger neutralization. To resolve this apparent contradiction we executed an experimental plan to test conclusively if electrons in the conduction band contribute to the IIEE yield.;The experimental plan consisted of measuring the IIEE yield from Si and Ge for p-type, intrinsic and N-type surfaces. Theoretical calculations of the bulk electron concentration indicate that from p-type to n-type Si the electron density in the conduction band varies by 15 orders of magnitude. For Ge there is 10 order of magnitude variation from p-type to n-type. We found that despite this significant increase in the bulk electron concentration the measured IIEE yield was not found to increase from p-type and n-type for Si or Ge. We verified that the independence of the IIEE yield from the conduction band electron density is not due to surface contamination, by making measurements on chemically cleaned and sputter cleaned surfaces. Both surface types showed a similar trend but sputter cleaned surfaces had larger IIEE yields. We also verified that Fermi level pinning did not cause the independence of IIEE yield from the conduction band electron density by measuring the surface Fermi level using XPS.;Furthermore, since fundamental theory of Auger neutralization assumed that only valence band electrons contributed to the IIEE, we decided to extend the theory to include conduction band electrons. We found that the measured IIEE yield increased by 0.02% when the conduction band electron density was increased by 17 orders of magnitude. We were able to conclude that the insensitivity of the IIEE yield on the conduction band electron densities is due to the larger number of electrons in the valence band compared to the conduction band. Furthermore, chemically cleaned p-type Ge IIEE yields from our modified mass spectrometer suggests that at higher energies above 100 eV the emission process may no longer be dominated by Auger neutralization. This conclusion comes from the observations that the ions have an non-Auger ion kinetic energy dependence and that p-type Ge has large IIEE yields than n-type Ge despite having measurably identical surface density of states.
机译：最近与离子感应电子发射（IIEE）相关的基于等离子体的测量表明，半导体中的导带电子可能会极大地促进总体电子发射。该假设的基础很简单：接近真空能级的更多电子等于更多的电子发射。尽管是直观的，但该假设与自1960年代以来就假定只有价带电子参与俄歇中和作用的主要IIEE机制的基本理论直接冲突。为了解决这个明显的矛盾，我们执行了一个实验计划，最终测试了导带中的电子是否有助于IIEE产率。该实验计划包括测量p型，本征和N型表面的Si和Ge的IIEE产率。 。体电子浓度的理论计算表明，从p型到n型Si，导带中的电子密度变化了15个数量级。对于Ge，从p型到n型有10个数量级的变化。我们发现，尽管体电子浓度显着增加，但对于Si或Ge，未发现所测得的IIEE产率从p型和n型增加。通过在化学清洁和溅射清洁的表面上进行测量，我们验证了IIEE产量与导带电子密度的独立性不是由于表面污染所致。两种表面类型都显示出相似的趋势，但是溅射清洁的表面具有更高的IIEE产量。我们还通过使用XPS测量表面费米能级来验证费米能级钉扎不会导致IIEE产量与导带电子密度无关。此外，由于俄歇中和的基本理论假设只有价带电子对IIEE起作用，我们决定将理论扩展到包括导带电子。我们发现，当导带电子密度增加17个数量级时，测得的IIEE产量增加0.02％。我们能够得出结论，IIEE产率对导带电子密度的不敏感性是由于价带中的电子数量大于导带。此外，我们改良型质谱仪的化学清洗过的p型Ge IIEE产率表明，在高于100 eV的较高能量下，发射过程可能不再被俄歇中和控制。该结论来自于以下观察结果：离子具有非俄歇离子动能依赖性，并且尽管具有可测量的相同的表面状态密度，但p型Ge的n IIEE产率比n型Ge大。

著录项

  • 作者

    Urrabazo, David, Jr.;

  • 作者单位

    The University of Texas at Dallas.;

  • 授予单位 The University of Texas at Dallas.;
  • 学科 Plasma physics.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 135 p.
  • 总页数 135
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 康复医学;
  • 关键词

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