纳米管低维复合结构的制备及其光电特性研究

发布时间：2018-06-21 05:21

本文选题：阳极氧化法 + TiO_2纳米管阵列　；参考：《清华大学》2015年博士论文

【摘要】：纳米管具有中空结构、比表面积大、吸附能力强等优点,与其它一维纳米材料相比,对外界环境和外场更加敏感。本论文以阳极氧化法制备的TiO_2纳米管阵列和化学气相沉积(CVD)法制备的双壁碳纳米管为基础,设计、制备了几种低维复合结构,深入研究了这些复合结构在光场和电场作用下的输运特性。利用扫描电子显微镜对纳米结构的微观形貌进行了观察和表征。首先,采用“两步”阳极氧化法制备出高度有序的TiO_2纳米管阵列,其长度可以通过氧化电压和生长时间进行控制。对无定型TiO_2纳米管阵列进行退火处理,得到了锐钛矿TiO_2纳米颗粒膜。以碳纳米管膜为顶电极,制备了碳纳米管/TiO_2纳米管阵列异质结光电探测器,利用TiO_2的阻变效应,提出一个提高探测器性能的新方法,即通过预先电处理,使其从高阻态转变为低阻态,光电测试结果表明:零偏压下,探测器在532 nm和1064 nm激光照射下的光响应度都显著提高。其次,分别在空气中和真空中详细研究了碳纳米管膜的光电导性质,样品表现出强烈的光波长依赖特性。空气中,碳纳米管膜的光电导为负,这是由O_2的光解吸附效应造成的,光波长越短,解吸附效应越显著。真空中,在405 nm和532 nm激光照射下,光电导转变为正;而在1064 nm激光照射下,光电导仍然为负,表面等离激元和电子的相互作用是造成负光电导的主要原因。通过改变光波长,即可调节光电导的大小和正负,这对设计基于碳纳米管的光电器件具有重要的指导意义。利用碳纳米管的超宽带光谱响应能力,制备了碳纳米管/金属异质结室温太赫兹探测器,实现了对太赫兹辐射(2.52 T)的自驱动(零偏压)光探测,电压光响应度和电流光响应度分别达到22 mV/W和166.7mA/W。最后,制备了由碳纳米管膜和RbAg4I5快离子导体膜构成的离子-电子混合导体复合结构,其中碳纳米管提供电子传输通道,RbAg4I5提供银离子传输通道。在界面附近,由于库仑相互作用,形成“离子-电子束缚态”,导致复合结构的电导显著减小;而在外电场或光场作用下,部分“离子-电子束缚态”被解离,引起电导增大,实现了银离子对碳纳米管中电子输运的调控。在此基础上,制备了基于离子-电子相互作用的新型电子器件,类似于传统的场效应管,通过改变栅压可以线性调控漏源电流的大小。
[Abstract]:Nanotubes have the advantages of hollow structure, large specific surface area, strong adsorption ability and so on. Compared with other one-dimensional nano-materials, nanotubes are more sensitive to the external environment and external field. Based on TiO-2 nanotube arrays prepared by anodic oxidation method and double-walled carbon nanotubes prepared by chemical vapor deposition (CVD) method, several low-dimensional composite structures were designed and fabricated in this paper. The transport characteristics of these composite structures under the action of light field and electric field are studied. Scanning electron microscopy (SEM) was used to observe and characterize the microstructure. Firstly, a highly ordered TIO _ 2 nanotube array was prepared by "two-step" anodic oxidation method, the length of which can be controlled by oxidation voltage and growth time. Anatase TiO2 nanocrystalline films were obtained by annealing the amorphous TiO-2 nanotube arrays. Using carbon nanotube film as the top electrode, the carbon nanotube / TIO _ 2 nanotube array heterojunction photodetectors were prepared. A new method to improve the performance of the detector was proposed by using the resistive effect of TIO _ 2. The photoelectronic measurement results show that the photo-responsivity of the detector under the irradiation of 532nm and 1064 nm laser is significantly improved at zero bias voltage. Secondly, the photoconductive properties of carbon nanotube films were studied in air and vacuum respectively. In the air, the photoconductivity of the carbon nanotube film is negative, which is caused by the photodesorption effect of O _ s _ 2. The shorter the optical wave length, the more significant the desorption effect is. Under the irradiation of 405nm and 532nm laser, the photoconductivity is positive, but the photoconductivity is still negative under the irradiation of 1064 nm laser. The interaction of surface isotherms and electrons is the main cause of the negative photoconductivity. By changing the wavelength of light, the size and the positive and negative photoconductivity can be adjusted, which is of great significance for the design of photovoltaic devices based on carbon nanotubes. Based on the ultra-wideband spectral response of carbon nanotubes (CNTs), a room temperature terahertz detector with carbon nanotubes / metal heterostructures has been fabricated. The self-driving (zero-bias) optical detection of THz radiation (2.52 T) has been achieved. The voltage-light responsivity and current-light responsivity are 22 MV / W and 166.7 Ma / W, respectively. Finally, a composite structure consisting of carbon nanotube film and RbAg4I5 fast ion conductor membrane was prepared, in which carbon nanotubes provide electron transport channel and RbAg4I5 provide silver ion transport channel. Near the interface, due to the Coulomb interaction, a "ion-electron bound state" is formed, which results in a significant decrease in the conductance of the composite structure, while under the action of an external electric field or a light field, part of the "ion-electron bound state" is dissociated, resulting in the increase of the conductivity. The electron transport in carbon nanotubes was regulated by silver ions. On this basis, a novel electronic device based on ion-electron interaction is fabricated, which is similar to the conventional FET, and the leakage current can be adjusted linearly by changing the gate voltage.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

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