Investigation of Nanoscale Thermal Transport Across a Point Constriction In Contact and Within a Sub-10 nm Gap

虽然最近出现的基于尖端的热应用已经实现了纳米级成像、数据存储和制造的前所未有的质量，但它们也对纳米级热传输的基本理解提出了强烈的要求，这些热传输是通过纳米级间隙或接触的点收缩进行的。这些技术的空间分辨率是由尖端引起的局部温度分布决定的。然而，直接测量纳米尺度的热输运和衬底上的局部温度分布尚未成功，主要原因是：(1)现有温度计的空间分辨率和灵敏度较差；(2)不能精确地将尖端与衬底之间的距离控制在10 nm以下；(3)高度局部源的精确温度控制和精确温度测量的困难。此外，在实际应用的现场环境中，很少有测量和建模同时考虑一种以上的传热机制。这一提议旨在从根本上理解纳米尺度的热能传输通过一个点收缩和基材的非均匀受热区。为此，空间分辨率小到尖端半径的纳米温度计，即10&amp；#8722；将制备并表征50 nm的纳米材料。利用所研制的纳米温度计测量衬底局部温度，同时精确控制悬臂梁的温度和尖端位置，悬停在10 nm以下的间隙内。一个包括亚连续空气传导、接触处固体传导和近场辐射的多尺度模型将被开发，以理解基于尖端的热应用中的物理。智力优势：该项目的成功将提供加热尖端和衬底之间的纳米尺度热传输的定量测量，通过低于10纳米的气隙和接触，以及尖端附近极端局部加热区的温度分布。提出的纳米温度计将提供小于50纳米的传感探针，其制造和表征将在热科学和工程界得到很好的认可。对加热悬臂的10nm以下间隙控制的系统方法将很容易适用于其他基于afm的计量和技术，如SThM和纳米制造。此外，尖端和衬底之间耦合纳米尺度热传递的数值模拟将促进对点收缩的纳米尺度热传递的基本理解。更广泛的影响：测量和模拟的结果将填补知识空白，并为基于尖端的热应用的进一步发展提供及时的支持。这项研究将为一名研究生和本科生提供培训机会，其中许多人将从代表性不足的学生群体中招募。为了在纳米教育方面发挥协同效应，我们将启动跨学院的学期项目。为了鼓励K-12的外展活动，一个用乐高积木建造的AFM将被开发出来，并用于URI的SMILE（科学和数学研究性学习体验）项目。总体而言，本提案所涉及的研究和教育活动将在促进教学、培训和学习的同时增进科学和技术的理解。

Proposal number: 1067441 PI: Keunhan ParkWhile recently emerging tip-based thermal applications have realized unprecedented quality of nanoscale imaging, data storage, and manufacturing, they have also created strong demands on the fundamental understanding of nanoscale thermal transport across a point constriction with a nanometer scale gap or in contact. The spatial resolution of these technologies is determined by the tip- induced localized temperature distribution. However, direct measurement of nanoscale thermal transport and local temperature distribution on the substrate has not been successful mainly due to (1) poor spatial resolution and sensitivity of currently available thermometers; (2) incapability to precisely control the tip-substrate distance below 10 nm; and (3) the difficulty in the precise temperature control of a highly local source and accurate temperature measurement. Moreover, very few measurement and modeling have considered more than one heat transfer mechanisms together in in-situ environments where real applications take place.This proposal aims to fundamentally understand nanoscale thermal energy transport across a point constriction and resultant non-uniform heated zone of the substrate. To this end, nanothermometers that have a spatial resolution as small as the tip radius, i.e., 10−50 nm will be fabricated and characterized. The local substrate temperature will be measured with the developed nanothermometer while the cantilever is precisely controlled in its temperature and tip position hovering with a sub-10 nm gap. A multiscale model that includes sub-continuum air conduction, solid conduction at the contact, and near-field radiation will be developed to understand the physics in tip-based thermal applications.Intellectual Merit: The success of this project will provide the quantitative measurement of nanoscale thermal transport between a heated tip and substrate across a sub-10 nm air gap and in contact, and temperature distribution of extremely localized heated zone near the tip. Proposed nanothermometers will provide a sensing probe size smaller than 50 nm, fabrication and characterization of which will be well recognized in the thermal science and engineering community. Systematic approaches on the sub-10 nm gap control of heated cantilevers will be readily applicable to other AFM-based metrologies and technologies, such as SThM and nanomanufacturing. In addition, numerical modeling of coupled nanoscale thermal transport between the tip and substrate will advance the fundamental understanding of nanoscale heat transfer across a point constriction.Broader Impacts: The results from the measurements and simulations will fill in a knowledge gap and provide timely support for the further advancement of tip-based thermal applications. The research will provide training opportunities for one graduate student and undergraduate students, many of whom will be recruited from underrepresented group of students. To make synergetic effects in nanoscale educations, inter-institute term projects will be initiated. To encourage K-12 outreach activities, an AFM built with LEGO blocks will be developed and used in the SMILE (Science and Mathematics Investigative Learning Experiences) program at URI. Overall, research and education activities involved in this proposal will enhance scientific and technological understanding while promoting teaching, training, and learning.