SGER: Surface and Sub-Surface Imaging at Nanometer Scales Using Picosecond Thermoacoustic Microscopy

建议编号：CTS-9910823主要研究人员：A·马琼达在纳米尺度上操纵物质以及观察和控制物理和生物现象的能力为研究人员提供了丰富的基础科学和新技术机会。这项研究的一个最重要的方面是以纳米级的空间分辨率观察物体和现象的能力。扫描隧道显微镜(STM)和原子力显微镜(AFM)，以及一般的扫描探针显微镜(SPM)，使得在固体表面成像单个原子和观察单个生物分子成为可能。然而，目前的扫描电子显微镜未能满足纳米技术中的一些基本需求，即：(I)以纳米垂直和横向分辨率成像表面以下物体的能力，即三维成像的能力；(Ii)为了识别材料的化学含量而进行光谱分析的能力。三维成像极其重要，原因如下：(A)微电子芯片正变得越来越多层；(B)生物分子具有三维结构和功能；(C)纳米材料通常是三维的。弹道电子发射显微镜(BEEM)[1]能够在表面以下100-200A的距离内成像和执行电子能谱。然而，它需要金属和半导体材料才能操作。使用原子力显微镜[2，3]的磁共振成像可以提供三维图像，尽管需要在非常低的温度(1K)下进行实验才能获得亚微米级的分辨率。要对三维物体成像，有两种可能的方法：(I)发射某种形式的辐射并测量其在空间某一点的时间分辨散射(弹性或非弹性)(例如。超声波成像)；或(Ii)通过外场将共振激发限制在某个位置(例如，核磁共振)。这个项目将使用第一种方法。它将结合两种技术--高横向分辨率的扫描探针显微镜和高垂直分辨率的皮秒热声--以获得纳米级分辨率的三维图像。

ABSTRACTProposal Number: CTS-9910823Principal Investigators: A. MajumdarThe ability to manipulate matter and to observe and control physical and biological phenomena at nanometer scales is providing researchers with rich opportunity for basic science as well as new technology. One of the most important aspects of this research is the ability to observe objects and phenomena with nanometer scale spatial resolution. The scanning tunneling (STM) and the atomic force microscopes (AFM) and, in general, the whole class of scanning probe microscopes (SPMs), have made it possible to image single atoms and observe single biological molecules on a solid surface. The current SPMs, however, fail to address some fundamental needs in nanotechnology, namely: (i) the ability to image objects below the surface, i.e. in three dimensions, with nanometer vertical and lateral resolution; (ii) the ability to perform spectroscopy in order to identify the chemical content of the material. Imaging in three dimensions is extremely important because of the following reasons: (a) microelectronics chips are becoming increasingly multilayered; (b) biological molecules have three-dimensional structure and function; (c) nanophase materials are generally three dimensional. The ballistic electron emission microscope (BEEM) [1] is able to image and perform electron spectroscopy below the surface to a distance of about 100-200 A. However, it needs a metal and a semiconducting material to operate. Magnetic resonance imaging using the AFM [2,3] can provide a three-dimensional picture, although one needs to perform experiments at very low temperatures ( 1 K) to obtain sub-micron resolution. To image objects in three dimensions, there are two possible approaches: (i) to either emit some form of radiation and measure its time-resolved scattering (elastic or inelastic) at a certain point in space (eg. ultrasonic imaging); or (ii) to confine resonance excitation to a certain location by an external field (eg. nuclear magnetic resonance). This project will use the first approach. It will combine two techniques - scanning probe microscopy for high lateral resolution and picosecond thermoacoustics for high vertical resolution - to obtain three-dimensional images with nanometer-scale resolution.