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Growth and characterization of bismuth tri-iodide single crystals by modified vertical Bridgman method.

机译：改进的垂直布里奇曼法生长和表征三碘化铋单晶。

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摘要

Bismuth tri-iodide (Bil3) is a wide band gap semiconductor material with potential for room temperature gamma-ray detection applications. The inability to produce high quality, pure, and large single crystals is one of the major challenges for this material preventing its use in gamma-ray detection. This work presents the growth and characterization of Bil3 single crystals by a modified vertical Bridgman (MVB) method.;The growth parameters to produce Bil3 single crystals were explored by adjusting growth rate and temperature gradient at the solid-liquid interface. Single crystals of Bil3 have been successfully grown in Pyrex glass ampoule at different growth conditions. Through etch pit density (EPD) and X-ray rocking curve measurement, the crystal with the best quality was determined to be obtained at 0.5 mm/h growth rate and 10oC/cm temperature gradient. Single crystal (001) oriented slabs up to 18 x 13 x 5 mm 3 (the largest Bil3 single crystal ever reported) were obtained under this condition. Impurity characterization on the starting Bil 3 powder and the grown crystals indicated a relatively high total impurity concentration up to 1017 cm-3, and the crystal growth using Pyrex glass does not introduce additional impurities to the crystal.;The energy band gap is an important parameter for materials used as a room temperature gamma-ray detector, as it determines the energy to produce an electron-hole pair which is the source of the signal for the detector. Remarkably, very different band gap characteristics and values of Bil 3 have been reported in literature. This study characterized the band gap of Bil3 through Ultraviolet-visible spectroscopy (UV-Vis), which yielded an indirect band gap of 1.68 +/- 0.09 eV at room temperature. Impurity and temperature effects, as commonly observed in many semiconductors, have been investigated as the major extrinsic factors that influence the band gap value of Bil3.;Three different metals, Au, Pd, and Pt were sputtered on the surface of Bil3 single crystal for fabrication of the electrode. The metal-Bil 3 interface was characterized by X-ray photoelectron spectroscopy (XPS). Chemical reactions were observed for the surface sputtered with Pd and Pt electrode, while no reaction was observed on the surface with Au electrode. It was proposed that Au should be used for the contact material for Bil 3. Current-voltage characterization indicated that Bil3 crystal with Au electrode exhibited the highest resistivity with values in the order of magnitude of 109 O·cm, which is sufficiently large for the application of a room temperature gamma-ray detector. Based on the work presented in this dissertation, a series of avenues for future work are presented to be able to take this material into actual devices.
机译：三碘化铋（Bil3）是一种宽带隙半导体材料，具有用于室温伽马射线检测应用的潜力。无法生产高质量，纯净和大尺寸的单晶是该材料无法用于伽马射线检测的主要挑战之一。通过改进的垂直布里奇曼法（MVB）提出了Bil3单晶的生长和表征。通过调节固液界面的生长速率和温度梯度，探索了制备Bil3单晶的生长参数。 Bil3的单晶已在耐热玻璃安瓿瓶中以不同的生长条件成功生长。通过蚀刻坑密度（EPD）和X射线摇摆曲线测量，可以确定在0.5 mm / h的生长速率和10oC / cm的温度梯度下可获得质量最好的晶体。在这种条件下，获得了高达18 x 13 x 5 mm 3的单晶（001）取向平板（有史以来最大的Bil3单晶）。在初始Bil 3粉末和生长的晶体上的杂质表征表明，最高1017 cm-3的总杂质浓度相对较高，并且使用Pyrex玻璃生长的晶体不会向晶体中引入其他杂质。;能带隙是重要的用作室温伽马射线探测器的材料的参数，因为它确定产生电子-空穴对的能量，该电子-空穴对是探测器的信号源。值得注意的是，文献中已经报道了Bil 3的带隙特性和值非常不同。这项研究通过紫外可见光谱（UV-Vis）对Bil3的带隙进行了表征，在室温下产生的间接带隙为1.68 +/- 0.09 eV。已研究了许多半导体中普遍观察到的杂质和温度效应，这是影响Bil3带隙值的主要外在因素。在Bil3单晶表面上溅射了三种不同的金属Au，Pd和Pt电极的制造。金属-Bil 3界面通过X射线光电子能谱（XPS）表征。在用Pd和Pt电极溅射的表面上观察到化学反应，而在用Au电极的表面上未观察到反应。建议将Au用作Bil 3的接触材料。电流电压表征表明，带有Au电极的Bil3晶体的电阻率最高，约为109 O·cm的量级，这对于Bil 3的接触材料是足够大的。室温伽马射线探测器的应用。基于本论文的工作，提出了一系列未来工作的途径，以便能够将该材料用于实际的设备中。

著录项

  • 作者

    Qui, Wei.;

  • 作者单位

    University of Florida.;

  • 授予单位 University of Florida.;
  • 学科 Engineering General.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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