Na掺杂氧化锌一维纳米棒阵列的制备和光电性能研究

发布时间：2018-09-12 05:27

【摘要】：Zn O是一种Ⅱ-Ⅵ族直接带隙宽禁带化合物半导体材料,室温禁带宽度为3.37 e V,激子结合能高达60 me V,在紫外、蓝、绿光发光二极管、激光器和紫外探测器等方面显示了巨大的应用潜力。由于本征Zn O中存在大量的本征施主缺陷,使得p型Zn O较难以合成,成为其实现光电领域应用的瓶颈。近年来,随着材料制备技术和纳米科技的发展,有关p型Zn O掺杂的研究越来越多。而且,理论计算和实验证实V族元素(N、P、As、Sb)和I族元素(Li、Na、K、Cu、Ag、Au)都可作为p型Zn O的受主掺杂元素。本论文主要研究了一维Zn O纳米材料和p型Na掺杂的Zn O纳米棒的制备及光电性能,共分为七章。第一章介绍了一维纳米材料的概念、Zn O纳米材料的基本性能和制备方法以及一维Zn O纳米阵列的p型掺杂和应用的进展,并在此基础上提出了本论文的研究内容。第二章介绍了本文中一维Zn O纳米棒阵列的合成方法和表征。第三章探讨了不同锌原料制备的多种Zn O纳米结构,并在此基础上利用缓冲层技术合成准一维Zn O纳米棒阵列,分析了其生长机理。第四章介绍了增强Zn O纳米棒场发射性能的方法。第五章和第六章介绍了p型Na掺杂Zn O纳米棒的制备及性能研究。第七章为结论。本论文取得的阶段性成果如下:(1)借助缓冲层技术,用化学气相沉积法在Si衬底上制备了一维Zn O纳米棒阵列,研究Zn O缓冲层厚度对纳米棒阵列的生长、光致发光和场发射性能的影响。研究表明,本文中最优缓冲层厚度约为50 nm。这为后文的Na掺杂Zn O纳米棒阵列的生长打下基础。根据Zn O纳米棒截面TEM分析,发现在Zn O纳米棒和缓冲层中间有过渡层形成。该过渡层由沿缓冲层中晶粒的外延晶粒组成,Zn O纳米棒继而沿着过渡层晶粒的生长方向外延生长。缓冲层Zn O沿c轴择优生长,因此Zn O纳米棒近似垂直于衬底生长,呈一维阵列形式排列。(2)探索并研究了一维Zn O纳米棒场发射性能增强的方案:结合等离子体刻蚀减小纳米棒顶端直径和Al N薄膜对Zn O纳米棒进行表面修饰,可以有效降低场发射开启和阈值电场,增强场发射电流密度。(3)采用化学气相沉积法成功制备了p型Na掺杂的Zn O(p-Zn O:Na)纳米棒。XRD、XPS和TEM等表征手段证明Na掺杂Zn O形成NaZn受主。霍尔效应测试表明Na掺杂量介于1.2 at.%至2.1 at.%之间的Zn O纳米棒是p型半导体,空穴浓度约1015 cm-3。低温光致发光光谱和伏安特性测试均进一步证明Na掺杂Zn O纳米棒的p型导电特性。同时,研究了热处理对Zn O:Na纳米棒性能的影响。以50℃/s的速度快速升温,在氮气气氛下热处理Na掺杂的Zn O纳米棒,因为激活间隙Na形成NaZn,使其空穴浓度由3.4×1015 cm-3最大增加到1.2×1016 cm-3。而以10℃/min的速度升温,在氧气气氛下热处理Na掺杂的Zn O纳米棒,则由于Na激活和氧空位减少的共同作用,使其空穴浓度增加,最大达到4.1×1016cm-3。(4)用热扩散的方法制备了p型Na掺杂Zn O纳米棒。在Zn O纳米棒表面旋涂含Na前驱体溶液后再高温热处理。虽然光电子能谱分析测试表明该方法使Na掺入了Zn O,900℃下进行热扩散的Zn O纳米棒中Na含量最高为0.9 at.%;但霍尔测试表明此样品呈弱p型导电特性,空穴浓度为~1014 cm-3。(5)制备并研究了基于p型Na掺杂的Zn O纳米棒的p-Zn O:Na/n-AZO的同质结。Na掺杂Zn O纳米棒的霍尔测试和同质结器件的伏安特性研究证实了Na掺杂的Zn O纳米棒呈p型导电,开启电压约为0.5 V。
[Abstract]:Zn O is a class II-VI semiconductor material with direct band gap and wide band gap. The band gap width is 3.37 e V at room temperature and the exciton binding energy is as high as 60 me V. It shows great potential for applications in ultraviolet, blue, green light emitting diodes, lasers and ultraviolet detectors. In recent years, with the development of material preparation technology and nano-technology, more and more researches on p-type Zn O doping have been carried out. Moreover, theoretical calculation and experimental verification show that both real V-group elements (N, P, As, Sb) and I-group elements (Li, Na, K, Cu, Ag, Au) can be used as acceptor doping elements of p-type Zn O. The preparation and photoelectric properties of one-dimensional Zn O nano-materials and p-type Na-doped Zn O nanorods are mainly studied in this paper, which are divided into seven chapters. In the first chapter, the concept of one-dimensional nano-materials, the basic properties and preparation methods of Zn O nano-materials, and the progress of p-type doping and application of one-dimensional Zn O nano-arrays are introduced. In the second chapter, the synthesis methods and characterization of one-dimensional Zn O nanorod arrays are introduced. In the third chapter, various Zn O nanostructures prepared from different zinc materials are discussed. On this basis, quasi-one-dimensional Zn O nanorod arrays are synthesized by buffer layer technology, and their growth mechanism is analyzed. In the fourth chapter, the enhanced Zn O nanorod field is introduced. Chapters 5 and 6 introduce the preparation and properties of p-type Na-doped Zn O nanorods. Chapter 7 is the conclusion. The main achievements of this paper are as follows: (1) One-dimensional Zn O nanorod arrays were fabricated on Si substrates by chemical vapor deposition (CVD) with the aid of buffer layer technology. The results show that the optimum thickness of buffer layer is about 50 nm. This lays the foundation for the growth of Na-doped Zn O nanorod arrays. According to TEM analysis of cross-section of Zn O nanorods, a transition layer is found between Zn O nanorods and buffer layer. Zn O nanorods grow preferentially along the C axis, so the Zn O nanorods grow approximately perpendicular to the substrate and are arranged in one-dimensional arrays. (2) A scheme to enhance the field emission performance of one-dimensional Zn O nanorods is explored and studied: combining with plasma etching reduction. The top diameter of small nanorods and Al N thin films modified Zn O nanorods can effectively reduce the field emission opening and threshold electric field, and enhance the field emission current density. (3) P-type Na-doped Zn O (p-Zn O:Na) nanorods were successfully prepared by chemical vapor deposition. XRD, XPS and TEM characterization showed that Na-doped Zn O formed NaZn O acceptor. Hall effect measurements show that Zn O nanorods doped with Na between 1.2 at.% and 2.1 at.% are p-type semiconductors with a hole concentration of about 1015 cm-3. Low-temperature photoluminescence spectroscopy and voltammetric properties measurements further prove the p-type conductivity of Na-doped Zn O nanorods. Na-doped Zn O nanorods were annealed in nitrogen atmosphere at a rapid heating rate. The Na-doped Zn O nanorods were heated in oxygen atmosphere because of the formation of NaZn in the activation gap Na, which maximized the hole concentration from 3.4 x 1015 cm-3 to 1.2 x 1016 cm-3. P-type Na-doped Zn O nanorods were prepared by thermal diffusion method. The surface of Zn O nanorods was spin-coated with Na-containing precursor solution and then heat-treated at high temperature. Although photoelectron spectroscopy analysis showed that Na was doped into Zn O nanorods for thermal diffusion at 900 C. The highest content was 0.9 at.%. However, Hall test showed that the sample exhibited weak p-type conductivity with a hole concentration of ~1014 cm-3. (5) The p-Zn O:Na/n-AZO homojunction was prepared and studied based on p-type Na-doped Zn O nanorods. The Hall test of Na-doped Zn O nanorods and the voltammetric properties of the homojunction devices confirmed the Na-doped Zn O nanorods. It is p conductive and the opening voltage is about 0.5 V..
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB383.1;TQ132.41

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