Chemical identification of individual surface atoms by atomic force microscopy
Chemical identification of individual surface atoms by atomic force microscopy
复制标题
DOI：
10.1038/nature05530
复制
发表时间：
2007-03-01
期刊：
影响因子：
64.8
通讯作者：
Custance, Oscar
中科院分区：
文献类型：
--
作者：
Sugimoto, Yoshiaki;Pou, Pablo;Custance, Oscar
扫描探针显微镜是一种多功能和强大的方法，使用锐利的尖端成像，测量和操纵物质的表面与原子分辨率（1，2）。在低温下，扫描探针显微镜甚至可以提供电子隧穿光谱，作为吸附分子（3-5）的振动特性和磁性杂质原子（6，7）的电子特性的指纹，从而允许化学鉴定。但在许多情况下，特别是对于绝缘系统，确定表面或纳米结构的确切化学成分仍然是一个相当大的挑战。原则上，动态力显微镜应该可以克服这个问题：它可以成像绝缘体，半导体和金属表面与真正的原子分辨率（8-10），通过检测和精确测量（11-13）的短程力，出现与针尖和表面原子（14，15）之间的化学键合的开始和敏感地依赖于所涉及的原子的化学身份。在这里，我们报告这种短程化学力的精确测量，并表明它们对所使用的力显微镜尖端的依赖性可以通过归一化过程来克服。这使我们能够使用化学力测量作为原子识别的基础，即使在室温下。我们通过对一个特别具有挑战性的合金系统的表面进行成像，并成功地识别出三种组成原子物种硅，锡和铅，来说明这种方法的性能，即使这些具有非常相似的化学性质和相同的表面位置偏好，使得任何基于地形测量的歧视尝试都是不可能的。
Scanning probe microscopy is a versatile and powerful method that uses sharp tips to image, measure and manipulate matter at surfaces with atomic resolution(1,2). At cryogenic temperatures, scanning probe microscopy can even provide electron tunnelling spectra that serve as fingerprints of the vibrational properties of adsorbed molecules(3-5) and of the electronic properties of magnetic impurity atoms(6,7), thereby allowing chemical identification. But in many instances, and particularly for insulating systems, determining the exact chemical composition of surfaces or nanostructures remains a considerable challenge. In principle, dynamic force microscopy should make it possible to overcome this problem: it can image insulator, semiconductor and metal surfaces with true atomic resolution(8-10), by detecting and precisely measuring(11-13) the short-range forces that arise with the onset of chemical bonding between the tip and surface atoms(14,15) and that depend sensitively on the chemical identity of the atoms involved. Here we report precise measurements of such short-range chemical forces, and show that their dependence on the force microscope tip used can be overcome through a normalization procedure. This allows us to use the chemical force measurements as the basis for atomic recognition, even at room temperature. We illustrate the performance of this approach by imaging the surface of a particularly challenging alloy system and successfully identifying the three constituent atomic species silicon, tin and lead, even though these exhibit very similar chemical properties and identical surface position preferences that render any discrimination attempt based on topographic measurements impossible.