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Nanoscale Techniques for Investigating Material Issues in Quantum Dot Based Nanoelectronics.

机译：研究基于量子点的纳米电子学中的材料问题的纳米技术。

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The current scaling of feature size of complementary metal oxide semiconductor transistors has been predicted to reach its limits by around the end of this decade. Therefore, several competing strategies for the post-CMOS era are under investigation.;The focus of this dissertation in on two key materials issues pertaining to semiconductor nanostructures, more specifically Ge-Si quantum dot based nano-electronics. A key issue here is the understanding of local chemistry of these nano-structures because the local chemistry affects the positions of the electronic band edges of these structures relative to that of the surrounding matrix, which in-turn affects the carrier localization properties. While the nano-scale chemistry of the QDs is relatively well understood, the chemistry of QDMs is not as well understood. Therefore, focus of this dissertation is the understanding of detailed nano-scale chemistry of QDMs. Another key issue arises from the use of the focused ion beam (FIB) for controlled delivery of dopant ions into the QDs and the QDMs for creating controlled dopant profiles at the nanoscale, and for templating the growth of these structures. The materials issue associated with this application of the FIB is the damage recovery of ion implanted (FIB) regions.;Although ion implantation damage and recovery of Si implanted using commercial broad area implantation implanters is well understood, the FIB implantation damage and recovery of Si is not as well understood. The focus of this research is thus to understand the effect of high ion implantation current density in the FIB, and the effect of FIB ion species (Si, Ge and Ga) on the damage recovery of Si.;With regards to the first body of research Auger electron spectroscopy (AES) was used for mapping the chemistry of QDMs in the epitaxy of Si 0.7Ge0.3 on Si(100). The AES study shows that the pit bases of QDMs are richest in Ge, which is consistent with one existing paper on composition distribution within these QDMs which employed X-ray diffraction based method. Secondly, our study shows that the Si composition monotonically decreases from the outer edges of the QDMs towards the pit cusps. The segregation of Ge to the pit bases is inconsistent with strain energy minimization, and it is proposed to be due to attachment of Ge to steps within the interiors of the QDMs. The monotonic decrease in Si composition (the total decrease is 12%) across the QDs and towards the pit cusps is inconsistent with literature reports for composition distribution within isolated QD structures. The reason for this observation is unclear at present but it illustrates how the presence of pits adjacent to the QDs can affect the composition of the QDs.;In the second body of research, 30 kV FIB implants of Si2+, Ge2+ and Ga+, and 60 kV broad ion beam Si + implants, in Si(100) were studied using Raman spectroscopy and transmission electron microscopy (TEM). Raman spectroscopy was carried out on the above listed ion implanted Si specimens, both before and after annealing to 730 C, 800 C and 900 C, for different annealing times, using 405 nm and 514 nm wavelengths. This enabled quantification of structural damage and stress using peak height and shift of the crystalline Si Raman peak at 520 cm-1 (for unstressed Si-Si bonds), as the metrics. Raman measurements from the Si-FIB and the Si-broad beam implants in their as-implanted states show a decrease in Raman peak height, and an increase in peak shift, with dose, implying greater structural damage and stress in the FIB implants. Second, in the Si-FIB implants, higher stresses have been observed to lead to accelerated evolutions of category I {311}s and category II defects, when compared to the corresponding evolution in the corresponding Si-broad beam implants. Third, it is observed that the limited solubility of Ga in Si plays a major role in limiting the recovery of Ga-FIB implanted Si. Fourth, it is observed that the damage in the Si-FIB and Ge-FIB implants can be largely recovered by annealing to 800 C (recovery is at least 94%, a recovery of 100% implies that the substrate is as damage free as a piece of unimplanted Si) and 900 C (recovery is at least 95%), whereas the damage in the Ga-FIB implants cannot be fully recovered for Ga doses beyond the solubility limits at the annealing temperatures used for this study. From the above it can be concluded that the higher ion current density (and therefore ion dose rate) in FIB implanters--relative to that of commercial broad beam implanters--and solubility of FIB ion species in Si can strongly affect the damage recovery of ion implanted Si. (Abstract shortened by UMI.).
机译：预计到本十年末，互补金属氧化物半导体晶体管的特征尺寸的当前缩放比例将达到其极限。因此，正在研究后CMOS时代的几种竞争策略。本文的重点是与半导体纳米结构有关的两个关键材料问题，尤其是基于Ge-Si量子点的纳米电子学。这里的关键问题是对这些纳米结构的局部化学的理解，因为局部化学影响这些结构的电子带边缘相对于周围基质的电子带边缘的位置，进而影响载流子的定位特性。虽然对QD的纳米级化学反应的理解相对较好，但对QDM的化学反应却了解得不够。因此，本文的重点是对QDM的详细纳米级化学的理解。另一个关键问题来自聚焦离子束（FIB）的使用，用于将掺杂剂离子控制传输到QD和QDM中，以在纳米级创建受控的掺杂剂分布，并用于模板化这些结构的生长。与FIB的这种应用相关的材料问题是离子注入（FIB）区域的损伤恢复。尽管人们已经很好地了解了使用商用广域注入注入机注入的离子对Si的损伤和恢复，但是FIB注入对Si的损伤和恢复尚未完全了解。因此，本研究的重点是了解FIB中高离子注入电流密度的影响，以及FIB离子物种（Si，Ge和Ga）对Si的损伤恢复的影响。研究使用俄歇电子能谱（AES）绘制了Si（100）上Si 0.7Ge0.3外延中QDM的化学分布图。 AES研究表明，QDM的凹坑基中的Ge最丰富，这与一篇有关基于X射线衍射的方法在这些QDM中的成分分布的论文相一致。其次，我们的研究表明，硅的组成从QDM的外边缘向凹坑尖端单调减少。 Ge与坑底的偏析与应变能的最小化不一致，并且提出这是由于Ge附着在QDM内部的台阶上。在整个量子点和朝向凹口处，硅成分的单调减少（总减少量为12％）与隔离的量子点结构内的成分分布的文献报道不一致。目前尚不清楚这种观察的原因，但它说明了与量子点相邻的凹坑如何影响量子点的组成。在第二项研究中，使用了30 kV的Si2 +，Ge2 +和Ga +的FIB注入和60使用拉曼光谱和透射电子显微镜（TEM）研究了在Si（100）中的kV宽离子束Si +注入物。在上面列出的离子注入的硅样品上进行拉曼光谱分析，使用405 nm和514 nm波长在730 C，800 C和900 C退火之前和之后进行不同的退火时间。这样就可以使用峰高和520 cm-1处的结晶Si拉曼峰的位移（对于未受应力的Si-Si键）进行量化，以量化结构破坏和应力。 Si-FIB和Si宽束注入物在注入状态下的拉曼测量结果显示，随着剂量的增加，拉曼峰高降低，并且峰位移增加，这意味着FIB注入物中的结构损伤和应力更大。第二，在Si-FIB植入物中，与相应的Si宽束植入物中的相应演化相比，已观察到更高的应力导致I类{311} s和II类缺陷的加速发展。第三，观察到Ga在Si中有限的溶解度在限制Ga-FIB注入的Si的回收中起主要作用。第四，可以观察到，通过退火至800 C，可以大大恢复Si-FIB和Ge-FIB植入物中的损伤（回收率至少为94％，回收率100％意味着该基底的破坏程度与表面处理一样）。一块未注入的Si）和900 C（回收率至少为95％），而当Ga剂量超出本研究使用的退火温度下的溶解度极限时，Ga-FIB注入物中的损伤无法完全恢复。从以上可以得出结论，相对于商用宽束注入机，FIB注入机中较高的离子电流密度（以及因此的离子剂量率）以及FIB离子物质在Si中的溶解度会强烈影响硅的损伤恢复。离子注入硅。 （摘要由UMI缩短。）。

著录项

  • 作者

    Balasubramanian, Ganapathi Prabhu Sai.;

  • 作者单位

    Rensselaer Polytechnic Institute.;

  • 授予单位 Rensselaer Polytechnic Institute.;
  • 学科 Materials science.;Nanoscience.;Nanotechnology.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 168 p.
  • 总页数 168
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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