单质碲纳米薄片的基本物理性质研究

BASIC PHYSICAL PROPERTIES OF TELLURIUM NANOFLAKES

桑忠志

11849401

硕士

物理学

张立源

2020-05-28

2020-07-13

哈尔滨工业大学

深圳

碲是第五周期VI A族（氧族）元素。在所有非金属元素中，金属性最强，具有良好的导电、导热本领。碲是窄带隙半导体材料，间接带隙为0.35 eV。与通常的二维材料不同，单晶碲材料具有独特的一维范德华结构，分子链间通过范德华力相连接，堆垛形成片状材料，无表面悬挂键。该纳米薄片可通过化学方法合成。研究表明，这种材料具有很高的载流子迁移率。并已实现空气稳定性全红外光电探测器件。展现出巨大的研究价值。目前国内文章对于碲的研究主要集中在单质碲纳米线的电输运性质。对碲纳米薄片的报导很少。为了进一步探索单质碲纳米薄片材料的应用和结构特性。本实验将对单质碲纳米薄片材料的基本物理性质进行研究。项目结果如下：实验通过水热法制备单质碲纳米薄片。对材料的基本性质进行表征。得到样品主要呈梯形，尺寸超过10 μm，厚度约为40 nm，处于介观物理的研究范围。材料的拉曼光谱表明结构中存在三种分子振动模式，其中垂直分子链的方向上拉曼振动峰最强。X射线衍射显示材料的晶体结构为六方晶系。实验通过微纳结构加工技术实现单质碲纳米薄片场效应管和霍尔靶器件的制备。在场效应管测量中，可发现材料在常温下展现出p型半导体的性质。门电压可实现载流子的调控。表现为门电压为负，漏极电流增大。门电压为正，漏极电流减小。实验深入研究了碲纳米薄片霍尔靶器件的输运特性。研究表明，碲纳米器件随着温度的降低，表现出金属-半导体转变行为。磁场的增加可导致材料禁带宽度增加，进而引起金属-半导体转变温度向高温区移动。在磁输运测量中，器件霍尔电阻率随着磁场的增加而不断增大，在-4 T到4 T的磁场范围内呈现良好的线性关系。通过单带拟合计算，得到载流子浓度超过1019 cm-3，载流子迁移率处于80-200 cm2 V-1 s-1之间。在纵向电阻率方面，实验观测到磁致电阻现象，在弱磁场下纵向电阻率与磁场呈平方关系，强磁场时呈线性关系。并在温度低于12 K时，发现器件在弱磁场条件下产生局域化负磁阻现象。我们通过Hikami-Larkin-Nagaoka公式对该弱反局域化现象进行分析。发现相位相干长度与温度呈负幂指数关系，指数为-0.5。表明单质碲纳米薄片材料在外加垂直磁场时表现出二维特征。进而表明材料在低温下散射主要是相干散射，高温下主要是自旋轨道耦合和弹性散射的作用。

Tellurium is the fifth group VI A element. It has the strongest electric Among all non-metallic elements, with a good thermal conductivity. Tellurium is a narrow band gap semiconductor material with an indirect band gap of 0.35 eV. Unlike ordinary two-dimensional materials, tellurium have a unique one-dimensional van der Waals structure. The molecular chains are connected by van der Waals forces, stacked to form a sheet material, and there are no hanging bonds on the surface. The nanoflakes can be synthesized by chemical methods. Studies have shown that this material has a very high carrier mobility. At present, full-infrared photoelectric detector of tellurium nanomaterial devices has been achieved. And has achieved air stability full infrared photoelectric detection device. Demonstrates its great research value.Now, domestic researches on tellurium mainly focus on the electrical transport properties of tellurium nanowires. There are few reports on tellurium nanoflakes. In order to further explore the application and Structural properties of elemental tellurium nanoflakes. This experiment will study the basic physical properties of elemental tellurium nanoflakes. The results are as follows:In our experiment, we use hydrothermal method to synthesis tellurium nanoflakes. The samples are mainly trapezoidal, with a size of more than 10 μm and the thickness is about 40 nm. This scale is in the research scope of mesoscopic. Raman spectroscopy measurements show that there are three modes of molecular vibration. Among them, in the direction perpendicular to the molecular chain has the strongest Raman peak. X-ray diffraction shows that the crystal structure is hexagonal.We use micro-nano structure processing technology to achieve field effect tube and Hall electrode. In the field effect tube measurement, the material exhibits p-type hole properties. And gate voltage can control the carrier. It shows that the drain current increases when the gate voltage is negative. And decreases when the gate voltage is positive.We studied the transport characteristics of tellurium nanoflakes. Which shown that tellurium nanodevices behave as metal-semiconductor transitions with decreasing temperature. And magnetic field can increase the materials band gap, result in the metal-semiconductor transition move to a high temperature region. In the magnetic transport measurement, it was found that the Hall resistivity increased continuously with the increase of the magnetic field. The carrier type is hole. In the magnetic field range of -4 T to 4 T, the Hall resistivity exhibits a good linear relationship. Through single-band fitting, the carrier density exceeds 1019 cm-3 and the carrier mobility is among 80-200 cm2 V-1 s-1. In longitudinal resistivity aspect, the phenomenon of magnetoresistance was observed, which has a square relationship with the magnetic field under a weak magnetic field and a linear relationship with a strong magnetic field. And when the temperature is lower than 12 K, it is observed that the tellurium has a localized negative magnetoresistance phenomenon under the weak magnetic field. We fit this weak anti-localization phenomenon through HLN (Hikami-Larkin-Nagaoka) formula。We found that with the temperature increases, the phase coherence length and temperature have a negative power exponential relationship, and the index is -0.5. It reveals that the tellurium nanosheet shows two-dimensional characteristics when a vertical magnetic field is applied. It is further shown that the scattering of materials at low temperature is mainly coherent scattering, and at high temperatures is mainly the effect of spin-orbit coupling and elastic scattering.

二维材料 输运特性 场效应晶体管 水热法 碲单晶薄膜

2D material transport property field effect transistor hydrothermal method single crystal Tellurium nanoflakes

中文

联合培养

南方科技大学

桑忠志. 单质碲纳米薄片的基本物理性质研究[D]. 深圳. 哈尔滨工业大学,2020.