Ultrasensitive Calorimetry Enabled by Suspended Semiconductor Nanostructures

悬浮半导体纳米结构实现超灵敏量热法

• 批准号: 0102886
• 负责人: Michael Roukes
• 金额: $ 33.5万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-15 至 2004-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0102886&HistoricalAwards=false
• 关键词: Ultrasensitive; Calorimetry; Enabled; Suspended; Semiconductor

In mesoscopic systems at low temperatures, heat transport and thermal equilibration occur in a very different manner from macroscopic systems at room temperature. This is due to the small heat capacities involved, and very long thermal relaxation times to reach equilibrium with a heat reservoir, the environment. At the ultimate limit, thermal transport involves exchange of a single energy channel between a system and the environment. During the preceding phase of this project, investigators observed, for the first time, this predicted quantization of thermal conductance. This places an important, hard upper bound on the thermal conductance available through future molecular electronic devices. The current project continues the investigation of heat capacities of nanomachined mesoscopic systems: Suspended semiconductor nanostructures that are thermally-isolated and have integral transducers that permit the localized introduction of heat and local temperature measurements. Heat capacity measurements on minute samples with unprecedented sensitivity should be possible. This should provide data relevant to the engineering of miniaturized thermal detectors, and will provide crucial information relating to limits of power dissipation in molecular-scale and ultrasmall electronic devices. With this level of sensitivity, calorimetry experiments that elucidate processes involving individual atoms and molecules should also become possible for the first time. The effort will introduce undergraduates, graduate students, and postdoctoral researchers to advanced techniques in nanofabrication and in techniques and principles of ultrasensitive measurements.%%%Future electronics will likely be based upon molecular scale devices. Active electronic devices, at any scale, require power to operate and this must ultimately be dissipated to their surroundings. However at the molecular scale the processes that govern power dissipation become very weak; hence it can be problematic. This domain had remained largely unexplored until 1999, when, in a previous NSF-funded research program, investigators observed the quantization of thermal conductance -- a fundamental limit to the rate at which power can be conducted from a small system to its surroundings. In their current proposal, the authors propose to continue with research in this realm, turning now to the heat capacity of very small systems, i.e. their ability to "store" energy. Their approach involves suspended semiconductor nanostructures, fabricated by new surface nanomachining processes they have developed. These enable the construction of complex exploratory devices at the nanometer-scale, with internal components allowing quantitative and precise measurements on their properties to be carried out. In the proposed research program these will be utilized to obtain a more complete understanding of heat transport and the heat capacity of nanometer-scale structures. They should also prove to be extremely useful for the engineering of miniaturized thermal detectors, and will provide crucial information relating to limits of power dissipation in molecular-scale and ultrasmall electronic devices. With this level of sensitivity, experiments that elucidate processes involving heat flow between individual atoms and molecules should also become possible for the first time. The effort will introduce undergraduates, graduate students, and postdoctoral researchers to advanced techniques in nanofabrication and in techniques and principles of ultrasensitive measurements.

在低温下的介观系统中，热传输和热平衡的发生方式与室温下的宏观系统非常不同。 这是由于所涉及的热容较小，并且与热库（环境）达到平衡的热弛豫时间非常长。 在最终极限下，热传输涉及系统与环境之间的单一能量通道的交换。 在该项目的前一阶段，研究人员首次观察到这种预测的热导量子化。 这为未来分子电子器件的热导率设定了一个重要的、硬性的上限。 当前的项目继续研究纳米机械介观系统的热容量：悬浮的半导体纳米结构是热隔离的，并具有集成传感器，允许局部引入热量和局部温度测量。 以前所未有的灵敏度对微小样品进行热容测量应该是可能的。这应该提供与小型热探测器工程相关的数据，并将提供与分子级和超小型电子设备功耗限制相关的关键信息。 有了这种水平的灵敏度，阐明涉及单个原子和分子的过程的量热实验也应该首次成为可能。 这项工作将向本科生、研究生和博士后研究人员介绍纳米制造以及超灵敏测量技术和原理的先进技术。%%%未来的电子产品可能会基于分子级设备。 任何规模的有源电子设备都需要电力才能运行，而这些电力最终必须耗散到周围环境中。 然而，在分子尺度上，控制功率耗散的过程变得非常弱。因此这可能是有问题的。 直到 1999 年，这一领域在很大程度上仍未得到探索，当时，在之前由 NSF 资助的一项研究计划中，研究人员观察到了热导的量化——这是功率从小系统传导到周围环境的速率的基本限制。 在他们当前的提案中，作者建议继续在这一领域进行研究，现在转向非常小的系统的热容量，即它们“存储”能量的能力。他们的方法涉及悬浮的半导体纳米结构，通过他们开发的新表面纳米加工工艺制造。 这些使得能够构建纳米级的复杂探索装置，其内部组件可以对其特性进行定量和精确的测量。 在拟议的研究计划中，这些将用于更全面地了解纳米级结构的热传输和热容量。 它们还应该被证明对于小型热探测器的工程极其有用，并将提供与分子级和超小型电子设备的功耗限制相关的关键信息。 有了这种水平的灵敏度，阐明涉及单个原子和分子之间热流的过程的实验也应该首次成为可能。 这项工作将向本科生、研究生和博士后研究人员介绍纳米制造以及超灵敏测量技术和原理的先进技术。