镉、锡和锗的硒化物低维结构生长与光、电辐射下的电子输运性能

发布时间：2018-05-01 21:21

本文选题：II-VI族半导体 + 二硒化锡　；参考：《中国科学院研究生院(上海技术物理研究所)》2015年博士论文

【摘要】：近年来,基于电子显微镜原位研究低维结构物理性能是纳米科学与技术领域的重要研究方向。这些研究有两个共同点:1)多为真空环境;2)研究对象无法避免电子束辐照。那么,电子束辐照对于材料性能的影响问题显得尤为重要,但目前为止,鲜有报道。本文在合成几种典型的半导体低维材料以及系统研究了这些材料电子传输和光电性能的基础上,进一步研究了SEM电子束辐照对这些材料电子传输和光电性能的影响。主要体现在以下几方面。(1)II-VI族二元(Cd Se)和三元(Cd SxSe1-x)化合物直接带隙半导体低维纳米结构在电子、光电子器件领域有广泛应用。本征Cd Se纳米结构电导率极低,不利于其在某些方面的应用。与Cd Se类似,Cd SxSe1-x低维纳米结构通常也处于高阻态。就Cd SxSe1-x而言,现有的研究工作主要集中在能带结构的控制方面,关于该化合物纳米结构尤其是杂原子掺杂的纳米结构电子传输和光电性能方面的研究甚少。本文用化学气相沉积法(CVD)制备了Sb掺杂的Cd Se(Cd Se:Sb)纳米带和In、Cl掺杂的Cd SxSe1-x纳米结构,并把所制备的材料应用于场效应晶体管、肖特基二极管和光电探测器,系统研究了材料的电子传输和光电性能。研究结果表明,Cd Se:Sb纳米带展现出n型半导体特性以及比本征纳米带更高的电导率(~105倍)。此外,Cd Se:Sb纳米带光电探测器表现出优异性能:高光谱响应率(650 nm,6.1×104 A/W)、高外量子效率(1.2×105)以及高电流开关比(~253)。Cd Se:Sb纳米带/Au肖特基二极管表现出高的矫正特性(~2×106),同时具有良好的光电性能。In、Cl掺杂的Cd SxSe1-x纳米结构也为n型半导体,单根纳米线背栅场效应晶体管具有较大的电流开关比(~200)和较高的迁移率(62.2 cm2V-1s-1),推算出纳米线中电子浓度为1.9×1017/cm3。统计了掺杂的Cd SxSe1-x纳米线的电导率和黄色光(1.53 m W/cm2)照射时的光电导率,分别为1-10和0.1-20 S/cm。结合电学表征和XPS分析结果,证明了In和Cl已经成功掺入Cd SxSe1-x纳米结构,且In和Cl作为施主杂质分别取代了Cd和S(或Se)的晶格位置,使纳米结构电子浓度增加。研究了单根Cd SxSe1-x纳米线的I-V曲线随温度的变化关系,结果表明纳米线的电阻随温度的降低而升高。以上结果表明,掺杂的Cd Se和Cd SxSe1-x纳米结构均具有优异的电子传输和光电特性,在电子和光电子器件领域有潜在的应用前景。(2)Sn Se、Sn Se2和Ge Se2是IV-VI族重要的具有层状晶体结构的半导体。本文采用CVD法一步合成了Sn Se和Sn Se2低维结构并研究了其生长机理。结果表明Sn Se和Sn Se2由于熔点不同分别沉积在高温和低温区,此外,Sn Se2六角片的生长过程和参与反应的气相分子或基团的浓度相关。电学测试结果表明,Sn Se2纳米片[001]晶向的电阻率是垂直该方向的电阻率的~15倍;Sn Se晶体[100]方向的电阻率是垂直于该方向的电阻率的~105倍。本文还用热蒸发法制备了Ge Se2纳米带。由于生长过程中同时存在气-液-固和气-固过程,因而生长成锯齿形分段结构的Ge Se2纳米带。(3)研究了低能电子束辐照(≤30 ke V)对Cd Se、Cd S、Cd SxSe1-x、Ge Se2和Zn Se低维结构电子传输和光电性能的影响。结果表明电子束辐照会永久性提高Cd Se、Cd S和Cd SxSe1-x纳米材料的电导率。电子束辐照后的本征Cd Se纳米带场效应晶体管的性能参数得到提高:电流开关比从~12到5×107、迁移率从0.15到155.3 cm2V-1s-1、载流子浓度从~1.1×1014到~1.3×1016 cm-3。辐照后的本征Cd S纳米带的电导率是辐照前的~106倍;辐照后的纳米带电导率随着电子束能量提升呈现出先提高后下降的趋势。与辐照前相比,辐照后的Cd SxSe1-x纳米线场效应晶体管的电流开关比从~4.2降至~1.3,载流子浓度从7.62×1017增加至2.13×1018 cm-3。直径越小的Cd SxSe1-x纳米线,电子束辐照后电导率增幅(辐照后与辐照前电导率之差)越大;此外,辐照前电导率越大的纳米线,电子束辐照后电导率增幅也越大。对Cd S光电性能测试结果表明,电子束辐照后的Cd S纳米带器件的光电流和外量子效率均比辐照前提高近一个数量级,但响应时间变长。把电子束辐照后的Cd Se纳米带放置空气中合适时间,纳米带电子传输性能会恢复到接近于电子束辐照前状态。电子束辐照改变半导体低维结构电子传输和光电性能的机理如下:材料被电子束辐照时产生大量二次电子和电子-空穴对,关闭电子束后,电子-空穴对复合,但是大量的二次电子残留在材料中或表层成为自由电子;从能带角度来说,这些残留的二次电子进入材料导带,从而提高其电子浓度和电导率,进而改变光电响应性能。但是,电子束辐照并不会显著提高Zn Se和Ge Se2的电导率。因此,电子束辐照后的二次电子能否进入半导体材料导带改变其电子传输性能是和材料固有性质有关。
[Abstract]:In recent years, it is an important research direction in the field of nanoscale science and technology to study the physical properties of low dimensional structures based on the electron microscope in situ. These studies have two common points: 1) mostly vacuum environment; 2) the research objects can not avoid electron beam irradiation. On the basis of the synthesis of several typical semiconductor low dimensional materials and the systematic study of the electronic transmission and photoelectric properties of these materials, the effects of SEM electron beam irradiation on the electronic transmission and photoelectric properties of these materials are further studied. (1) II-VI family two (Cd Se) and three yuan (Cd Sx). Se1-x) compound direct band gap semiconductor low dimensional nanostructures are widely used in the field of electronic and optoelectronic devices. The intrinsic conductivity of the intrinsic Cd Se nanostructures is extremely low and is not conducive to its application in some aspects. Similar to Cd Se, Cd SxSe1-x low dimensional nanostructures are usually in high resistivity states. As far as Cd SxSe1-x is concerned, the existing research work is mainly concentrated. In the control of band structure, there are few studies on the electronic transmission and photoelectric properties of nanostructures, especially heteroatom doped nanostructures. In this paper, Sb doped Cd Se (Cd Se:Sb) nanoribbons and In, Cl doped Cd SxSe1-x nanostructures were prepared by chemical vapor deposition (CVD), and the materials prepared were applied. In the field effect transistors, Schottky diodes and photodetectors, the electronic transmission and photoelectric properties of the materials are systematically studied. The results show that the Cd Se:Sb nanoribbons exhibit the N type semiconductor properties and the higher conductivity (~105 times) than the intrinsic nanbands. Furthermore, the Cd Se:Sb nanoscale photodetectors exhibit excellent performance: hyperspectral The response rate (650 nm, 6.1 x 104 A/W), high external quantum efficiency (1.2 x 105) and high current switching ratio (~253).Cd Se:Sb nanband /Au Schottky diode show high correction characteristics (~2 x 106), with good photoelectric performance.In, Cl doped Cd SxSe1-x nanostructures are also N type semiconductors, single nanowire back gate field effect transistors With a larger current switching ratio (~200) and a higher mobility (62.2 cm2V-1s-1), the electron concentration in the teller's rice line is calculated to be 1.9 x 1017/cm3., and the conductivity of the doped Cd SxSe1-x nanowire and the photoconductivity of the yellow light (1.53 m W/cm2) irradiation are calculated, which are 1-10 and 0.1-20 S/cm. binding electrical characterization and XPS analysis results, respectively. And Cl has been successfully incorporated into the Cd SxSe1-x nanostructures, and In and Cl have replaced the lattice positions of Cd and S (or Se) as donor impurities, respectively, to increase the electronic concentration of the nanostructures. The relationship between the I-V curves of the single Cd SxSe1-x nanowires with the temperature is studied. The results show that the resistance of the nanowires increases with the decrease of temperature. The above results show that the resistance of the nanowires increases with the temperature. The doped Cd Se and Cd SxSe1-x nanostructures have excellent electronic transmission and photoelectric properties, and have potential applications in the field of electronic and optoelectronic devices. (2) Sn Se, Sn Se2 and Ge Se2 are important semiconductors with layered crystal structures. The growth mechanism. The results show that Sn Se and Sn Se2 are deposited at high temperature and low temperature zone respectively because of different melting points. In addition, the growth process of Sn Se2 six angle slices is related to the concentration of gas phase molecules or groups involved in the reaction. The electrical test results show that the resistivity of [001] crystal direction of Sn Se2 nanometers is the ~15 times of the resistivity in the vertical direction; Sn Se crystal. The resistivity of the 00] direction is ~105 times that of the resistivity perpendicular to that direction. In addition, the Ge Se2 nanoribbons were prepared by thermal evaporation. The Ge Se2 nanoribbons were born into a serrated and segmented structure due to the simultaneous existence of gas liquid solid and gas-solid processes in the growth process. (3) the low energy electron beam irradiation (< < 30 Ke V) was studied for Cd Se, Cd S. The effects of Ge Se2 and Zn Se on the electronic transmission and photoelectric properties of low dimensional structures. The results show that the electron beam irradiation will permanently improve the conductivity of Cd Se, Cd S and Cd SxSe1-x nanomaterials. The performance parameters of the intrinsic Cd Se nano field effect transistors after the electron beam irradiation are improved: the electric current switch ratio is 5 * 107 and the mobility is from 0.15 to 155.3. Cm2V-1s-1, the conductivity of the intrinsic Cd S nanoscale with carrier concentration from ~1.1 x 1014 to ~1.3 * 1016 cm-3. is ~106 times before irradiation, and the charge conductivity of nanoscale after irradiation increases first and then decreases with the energy of electron beam. Compared with the radiation before irradiation, the current of the Cd SxSe1-x nanowire field effect transistor is open. The correlation ratio decreased from ~4.2 to ~1.3, the carrier concentration increased from 7.62 x 1017 to 2.13 * 1018 cm-3. diameter Cd SxSe1-x nanowires, the greater the electrical conductivity increased after irradiation (the difference between irradiated and pre irradiated conductivity). In addition, the greater the conductivity of the nanowires before irradiation, the greater the electrical conductivity increased after the electron beam irradiation. The measurement of Cd S photoelectric properties. The test results show that the photocurrent and the external quantum efficiency of the Cd S nano band devices irradiated by the electron beam are almost one order of magnitude higher than that before irradiation, but the response time becomes longer. The Cd Se nanoribbons after the electron beam are placed in the appropriate time in the air, and the electronic transport properties of the nanoribbons will be restored to the state before the electron beam irradiation. The mechanism of changing electronic transmission and photoelectric properties of low dimensional structure of semiconductors is as follows: the material is irradiated by electron beam to produce a large number of two electron and electron hole pairs, after the electron beam is closed, the electron hole pair is compound, but a large number of two electron residues are free electrons in the material or surface; from the angle of energy, the residual two The secondary electrons enter the conduction band of the material, thus increasing the electron concentration and electrical conductivity, and then changing the photoelectric response performance. However, the electron beam irradiation does not significantly increase the electrical conductivity of Zn Se and Ge Se2. Therefore, whether the two electrons after the electron beam can enter the conduction band of the semiconductor material is related to the intrinsic properties of the material.

【学位授予单位】：中国科学院研究生院(上海技术物理研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

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