Electronic Properties of Two-Dimensional Nicrocluster Arrays

微团簇的Au，C，Sb，Bi和Te的沉积在一个单层覆盖的高度取向的热解石墨的c-平面上的准分子激光烧蚀或通过普通的热蒸发的组成元素在真空中，并在He气体。沉积的表面进行检查由扫描隧道显微镜（Nanoscope II）在空气中操作。微团簇以各种尺寸和形状被吸附。原子团簇的原子图像被观察到的小团簇组成的少于一百个原子。在激光烧蚀沉积碳时，一些小团簇以单层形式吸附在基底上。在He气体浓度约为50 μ m时，它们主要以三维方式堆叠在衬底上，即使是那些仅由几个原子组成的。虽然大多数团簇是随机分布在衬底表面上的，但它们往往吸附在晶体缺陷周围，如沿着台阶或平台上，这些团簇具有相似的尺寸和形状，并以几乎相等的间距排列，从而形成规则的尺寸选择团簇排列。通过激光烧蚀碳团簇和通过热蒸发Au、C、Sb和Te团簇观察到这种阵列。

Microclusters of Au, C, Sb, Bi, and Te are deposited under a monolayer coverage on the c-plane of highly oriented pyrolytic graphite by excimer laser ablation or by ordinary thermal vaporization of constituent elements in vacuum and in He gas.Deposited surfaces are examined by a scanning tunneling microscope (Nanoscope II) operated in air. Microclusters are adsorbed in a variety of sizes and shapes. Atomic images of clusters are observed for small clusters consisting of less than a hundred atoms. For depositing carbon by laser ablation, some of small clusters are adsorbed on the substrate in single layers. Under He gas of around 50 torr, they are dominantly stacked in three-dimension on the substrate, even for those consisting of only several atoms. Although most of clusters are distributed randomly over the surface of substrate, they tend to be adsorbed around crystal defects such as along a step or on a terrace.These clusters are of similar sizes as well as shapes and are aligned in nearly an equal separation so that they form a regular arrangement of size selected clusters. Such arrays are observed for carbon clusters by laser ablation, and for Au, C, Sb, and Te clusters by thermal vaporization.