NER: Ultrafast Terahertz Hot Electron Bolometer Heterodyne Detectors Based on Single Wall Carbon Nanotubes

NER：基于单壁碳纳米管的超快太赫兹热电子辐射热计外差探测器

• 批准号: 0508436
• 负责人: Sigfrid Yngvesson
• 金额: --
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0508436&HistoricalAwards=false
• 关键词: NER; Ultrafast; Terahertz; Hot; Electron

This proposal presents a novel idea for a device which takes advantage of the exceptional electronic transport properties of Single-Walled Carbon Nanotubes (SWNTs). SWNTs are basically graphene sheets (graphite consists of a stack of such sheets) that have been folded into tubes of very regular structure, with diameter of typically 1.5 nm. SWNTs of sufficient quality have only been fabricated and characterized in the last three to four years. It has been found that mean free paths (mfp, the distance an electron travels before scattering) for electrons in SWNTs can be as long as 1 um at room temperature, both in metallic and semiconducting versions. The proposed device is a Hot Electron Bolometer (HEB) Heterodyne Detector, for operation up to at least 1 THz. The device would consist of a short (200 nm to 400 nm) SWNT contacted with metallic ohmic contacts in both ends. Under DC bias, such a device is expected to have a temperature-dependent resistance, which will enable it to detect terahertz radiation, while converting the terahertz radiation to a lower frequency (GHz) which can be amplified with a broadband microwave amplifier. HEB heterodyne detectors ("mixers") using superconducting NbN devices are an established technology, which has resulted in increasing the sensitivity of astronomy receivers in the terahertz range by an order-of-magnitude. PI Yngvesson and Co-PI Gerecht are leaders in this international development work. The unique property of the proposed SWNT HEB detector is that it is predicted to have a time-constant two orders-of-magnitude fasterthan the superconducting version (the bandwidth over which it works would be several hundred GHz). This is due to the much faster electron transport in the SWNTs, approaching and reaching "ballistic transport" (when there is no scattering in the nanotube). It is thus critical to understand electronic transport in such devices, and the conditions under which the device responds to terahertz radiation. The power required from the Local Oscillator (LO) is expected to be very low(1 uW or less), and liquid nitrogen temperature operation is expected. The case for the SWNT HEB is supported by a recent result, describing a device that acts as an HEB, while relying on ballistic transport to reach 40 GHz bandwidth. The active medium in that case was twodimensional electron gas (2DEG, a gallium arsenide semiconductor type medium), but no theoretical explanation is available for its operation. A very important component of this proposal is thus to perform simulations of both the 2DEG device and the SWNT devices. Co-PI Fischetti isan internationally recognized expert on ballistic transport in several semiconductor devices. He is joining the UMass/Amherst faculty from the IBM T.J. Watson Research Center, and will performthese studies for the proposed effort.The proposed plan is to perform measurements at about 100 GHz in order to confirm the processwe hypothesize, and measure the time-constant, noise output and LO power of a series of SWNTdevices, selected based on DC tests. The devices will be fabricated and integrated with antenna structures for coupling to the radiation, through collaboration with the National Institute of Standards and Technology, Boulder, CO, (Co-PI Gerecht), and the IBM T.J. Watson Research Center (Collaborator J. Appenzeller). The theoretical analysis will use Monte-Carlo simulations, and a preliminary effort toward a more rigorous approach based on Non-Equilibrium Green's Functions. The potential applications for the proposed device are to Focal Plane Imaging Systems for up to 1 THz, which can be used for security-related detection, as well as medical imaging. The devices could also be applied to terahertz spectroscopy for detection of chemical species.BROADER IMPACT OF THE PROPOSED RESEARCH. The research proposed will be performed at an educational institution, the University of Massachusetts. The Terahertz group has a long record of involving students at all level down to high school in the research activities, including many women students. For instance, many students helped to install a terahertz receiverat the South Pole. The College of Engineering has very active minority and women engineering programs. The PI and one Co-PI teach regular courses in this program. Unique terahertz infrastructure is being built up and the research includes collaboration with NIST as well as IBM. The applications mentioned above can potentially provide substantial benefits to society.

这一提议提出了一种利用单壁碳纳米管(SWNTs)特殊的电子传输特性的器件的新想法。单壁碳纳米管基本上是石墨烯薄片(石墨由一堆这样的薄片组成)，它们被折叠成非常规则的结构，直径通常为1.5纳米。只有在最近三到四年才制造和表征了足够质量的单壁碳纳米管。已经发现，在室温下，无论是金属版本还是半导体版本，单壁碳纳米管中电子的平均自由程(MFP，即电子在散射前的距离)可以长达1微米。该装置是一个热电子测辐射热计(HEB)外差探测器，工作频率至少可达1太赫兹。该器件将由一个短的(200 nm到400 nm)单壁碳纳米管组成，两端与金属欧姆接触。在直流偏置下，这种器件将具有温度相关的电阻，这将使其能够检测太赫兹辐射，同时将太赫兹辐射转换为可以用宽带微波放大器放大的更低频率(GHz)。使用超导NBN器件的Heb外差探测器(“混频器”)是一项成熟的技术，它使太赫兹范围内的天文接收器的灵敏度提高了一个数量级。皮永维森和联合皮格列特是这项国际开发工作的领导者。所提出的SWNT HEB探测器的独特特性是，它被预测具有比超导版本快两个数量级的时间常数(它的工作带宽将是几百GHz)。这是由于单壁碳纳米管中的电子传输速度快得多，接近并达到了“弹道传输”(当纳米管中没有散射时)。因此，了解此类设备中的电子传输以及设备对太赫兹辐射的响应条件至关重要。本地振荡器(LO)所需的功率预计非常低(1微瓦或更低)，预计液氮温度运行。SWNT Heb的情况得到了最近的一项结果的支持，该结果描述了一种在依赖弹道传输达到40 GHz带宽的同时充当Heb的设备。这种情况下的活性介质是二维电子气(2DEG，一种砷化镓半导体型介质)，但它的工作没有理论上的解释。因此，该方案的一个非常重要的组成部分是执行2DEG器件和SWNT器件的模拟。Co-Pi Fischetti是国际公认的几种半导体器件的弹道传输专家。他将从IBM T.J.沃森研究中心加入美国大学质量/阿默斯特学院，并将为拟议的工作进行这些研究。拟议的计划是在约100 GHz进行测量，以确认我们假设的过程，并测量基于直流测试选择的一系列SWNT设备的时间常数、噪声输出和LO功率。这些设备将通过与位于科罗拉多州博尔德的国家标准与技术研究所(Co-Pi Gerecht)和IBM T.J.沃森研究中心(合作者J.Appenzeller)的合作，制造并与天线结构集成，以耦合到辐射。理论分析将使用蒙特卡罗模拟，并初步尝试基于非平衡格林函数的更严格的方法。建议的设备的潜在应用是高达1太赫兹的焦平面成像系统，可用于与安全相关的检测以及医学成像。该装置还可以应用于太赫兹光谱分析，以检测化学物种。这项拟议的研究将在教育机构马萨诸塞大学进行。太赫兹研究小组长期以来一直让所有级别的学生，包括许多女学生，都参与到研究活动中来。例如，许多学生帮助在南极安装了太赫兹接收器。工程学院有非常活跃的少数民族和女性工程课程。在这个项目中，PI和一名Co-PI教授常规课程。独特的太赫兹基础设施正在建设中，这项研究包括与NIST和IBM的合作。以上提到的应用可能会给社会带来实质性的好处。