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类型 基础研究 预答辩日期 2017-11-23
开始(开题)日期 2016-04-11 论文结束日期 2017-09-14
地点 田家炳南楼205 论文选题来源 国家自然科学基金项目     论文字数 4.7 (万字)
题目 石墨烯光电性能调控及功能化器件的研究
主题词 石墨烯,探测器,光响应,位置灵敏性,静电场
摘要 石墨烯是由单层碳原子组成的二维蜂窝状晶体,由于其独特的零带隙结构,超高的载流子迁移率,超宽的光谱吸收,在电子和光电子学领域引起了广泛的关注。基于石墨烯的探测器、传感器等各种高性能器件也被不断地研究并报导。然而,石墨烯较低的光吸收率使其在光电探测器中的应用受到了一定程度的限制。基于此,研究者开发了多种提高光吸收或载流子分离效率的方法用来改善石墨烯光电探测器的性能,如采用非对称电极、PN结、光学微腔、硅波导、等离激元等。此外,通过复合量子点、制备异质结构等方法在探测器中引入增益机制,也可以极大地提高了探测器的性能。尽管如此,石墨烯光电探测器在成本、制备技术、性能稳定性等方面仍需要进一步改善。为了加快石墨烯的应用进程,还可以开发新型功能器件并拓展新的应用领域。当前基于石墨烯的功能化器件还有气体传感器,压力传感器,生物探测器,PH传感器,重金属探测器等。新型探测器的出现,不仅为石墨烯的发展和应用提供了广阔的空间,也让相应的探测传感领域出现了新的发展机遇。本论文研究了石墨烯光电性能的调控方法,并制备了基于石墨烯的多种功能性探测器,具体内容如下: 1.利用激光辐照改性的方法在石墨烯器件上制备结区,拉曼光谱证明了激光辐照区引入了P型掺杂,并且可以通过控制激光辐照时间调控掺杂程度。在P-P+结区产生的光电流与掺杂程度相关,P型掺杂越重,光电流越大。随后对结区产生光电流的机制进行了仔细的分析,表明光热电效应主导了结区光电流的产生。 2.设计并制备了一种基于石墨烯-SiO2/Si结构的位置灵敏探测器。该探测器摒弃了常规位置灵敏探测器整体为PN结或肖特基结的结构,巧妙的利用SiO2/Si界面态导致的能带弯曲和界面处载流子的横向传输实现了横向光电效应,并利用gating效应在石墨烯器件引起光响应。到达石墨烯下方的载流子数量取决于光照点到石墨烯沟道的距离,从而可以实现入射光的位置探测。由于石墨烯超高的载流子迁移率使该器件存在高达104的增益。增益的引入使该探测器可以探测nW级弱光的精确位置,而且响应速度很快。这种界面增益效应和Si工艺相兼容,也可以适用于其他探测系统。 3.制备了石墨烯-Si结构的无源位置灵敏探测器,石墨烯不仅可以作为光吸收层,还可以作为载流子的分离和传输层。石墨烯超高的迁移率使载流子可以超远传输,保证了该探测器较大的工作面积。传输距离越远,到达电极的载流子数量越少,通过测量对应电极上的电压输出可以实现对光照点位置的探测。位置灵敏特性研究表明该探测器可以实现nW级弱光的远距离(> 8 mm)位置探测。此外,该器件具有很快的响应速度,且非线性度只有3%。红外测量结果显示该探测器可在1319 nm 和1550 nm下工作,有效延伸了位置灵敏探测器的工作波长。 4.制备了一种基于石墨烯的静电探测器,实现了快速,高灵敏静电探测。该探测器利用SiO2/Si界面gating效应,使静电引起的Si中载流子的移动分布在石墨烯沟道中进行了放大。该探测器可以感应~5 V的静电势,响应时间小于2 μs,相比与常规探测器性能有大幅提升。该探测器也可以通过电学调控的方式实现静电响应的调制。这种非接触式的静电探测器制备简单、性能优良且成本较低,在可携带、柔性传感等领域具有较好的应用前景。
英文题目 The study of optoelectronic properties and functional devices of graphene
英文主题词 Graphene, Detector, Photoresponse, Position sensitivity, Electrostatic field
英文摘要 Graphene, a single layer of carbon atoms arranged in hexagonal honeycomb, has aroused significant interests in electronic and optoelectronic applications due to its unique zero-band structure, ultra-high carrier mobility and broadband absorption. Recently, graphene-based detectors, sensors and other high-performance devices are constantly studied and reported. However, the low light absorptivity of graphene limits the application of graphene in photodetectors to a certain extent. Based on this, many methods are employed to increase the light absorption or photo-excited carrier separation rate for improving the performance of photodetectors, such as adopting asymmetric electrode, PN junctions, optical microcavity, waveguide integration, as well as plasmonic structure. In addition, quantum dots, heterostructures are adopted to introduce a high gain mechanism in photodetector, which have greatly improved the performance of the detector. Nonetheless, graphene photodetectors still need to be further improved in the cost, preparation technology, performance stability. In order to promote the application of graphene, another method is to develop new functional devices, expanding new applications. Currently graphene-based functional devices mainly include gas sensors, pressure sensors, biological detectors, PH sensors, heavy metal detectors and so on. The emergence of those new detectors, not only accelerate the development and application of graphene, but also provide an opportunity for the development of the corresponding detector. Here, the modulation method of optoelectronic properties of graphene have been studied, and different functional detectors have been fabricated and studied. The specific contents are as follows: 1. A junction in graphene device was prepared by using laser irradiation. The Raman spectrum demonstrates that P-type doping is introduced in the radiation region, and the doping degree can be modulated by controlling the irradiation time. The doping degree dependence of photocurrent generated at the P-P + junction shows that the photocurrent increases with P-doping degree. Then, the mechanism of photocurrent generation at the junction is analyzed carefully and the photothermal effect is proved to dominate the generation of photocurrent at the junction. 2. A position-sensitive-detector based on graphene-SiO2/Si structure was designed and fabricated. The detector eliminates the PN junction or Schottky junction structure in general position-sensitive-detectors, and smartly utilizes the band bending caused by the SiO2/Si interface state and the lateral diffuse of the carrier at the SiO2/Si interface, achieving the lateral photoeffect. The electrons diffuse to the region under graphene will lead to an effective gating effect, consequently changing the channel current through capacitive coupling. The quantity of the carriers under the graphene channel varies with the incident light position, suggesting that different photocurrent will take place, so that the position of the incident light can be detected. Signal amplification in the order of ~104 has been demonstrated due to the high mobility of graphene, which improve the detection limit of Si-based PSDs from μW to nW level, without sacrificing the spatial resolution and response speed. Such interfacial amplification mechanism is compatible with current Si technology and can be easily extended to other sensing systems. 3. A passive position-sensitive-detector based on graphene-Si structure was presented. The graphene is used as a photon absorbing and carriers separation and diffusion layer. The high mobility allows the carriers to diffuse far away, ensuring large active area of the device. The quantity of carriers which arrived at the electrodes depends on the incident light position, suggesting that the position can be detected by measuring the voltage output of the electrodes. Position sensitive characteristics indicate that the detection of long-range (> 8 mm) weak light at nWs level can be achieved. More importantly, it shows very fast response and low degree of non-linearity of ~3%, and extends the operating wavelength to the near infrared (IR) region (1319 nm and 1550 nm). 4. An electrostatic detector based on graphene was prepared, which realized fast and highly sensitive electrostatic detection. The detector takes advantage of the SiO2/Si interface gating effect and the high mobility of graphene. The movement of carriers in Si induced by electrostatic field is reflected by the current response of graphene with a high gain. The detector can sense ~5 V of the electrostatic potential, and the response time is less than 2 μs. The electrostatic response modulation can be achieved by electrical regulation. Moreover, the non-contact electrostatic detector features simplicity in fabricate process, excellent in performance and low cost, which will have a good application in portable and flexible sensing fields.
学术讨论
主办单位时间地点报告人报告主题
物理系 2016-12-24 田家炳南楼203 王文辉 基于石墨烯-Si结构的 PSD
物理系 2016-02-27 田家炳南楼203 王文辉 基于石墨烯的位置灵敏探测器
物理系 2016-07-04 田家炳南楼203 刘杰 Selective Growth of Semiconducting Single-walled Carbon Nanotubes
物理系 2016-05-25 田家炳南楼203 Boris I. Yakobson Predictive modeling in 2D materials: morphology, dislocations, grain boundaries
物理系 2016-05-24 田家炳南楼203 张华 Synthesis and Applications of Novel Two-Dimensional Nanomaterials
物理系 2015-12-09 田家炳南楼203 Alister J. Page Catalysts, Etchants and Magnetic Fields: How can Carbon Nanostructure Growth be Controlled
物理系 2016-11-26 田家炳南楼203 王文辉 摩擦电学的研究进展
物理系 2016-04-02 田家炳南楼203 王文辉 静电探测器的研究
     
学术会议
会议名称时间地点本人报告本人报告题目
东南大学物理系 2015-11-06 东南大学田家炳楼 石墨烯及其复合结构的光电性能
美国物理协会 2017-03-16 新奥尔良 Distinct photoresponse in graphene induced by laser irradiation and interfacial gating
     
代表作
论文名称
Distinct photoresponse in graphene induced by laser irradiation
High-performance graphene-based electrostatic field sensor
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
缪峰 正高 教授 博导 南京大学
董晓臣 正高 教授 博导 南京工业大学
马延文 正高 教授 博导 南京邮电大学
王肖沐 正高 教授 博导 南京大学
李孝峰 正高 教授 博导 苏州大学
游雨蒙 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
吕俊鹏 正高 教授 东南大学