Electronic Properties of Two-Dimensional Nicrocluster Arrays

通过准分子激光烧蚀或在真空和He气体中对组成元素进行普通热汽化，在高取向热解石墨的C平面上沉积了Au、C、Sb、Bi和Te的微团簇。在空气中使用扫描隧道显微镜（纳米显微镜II）检查沉积表面。微团簇被吸附成各种大小和形状。对于少于100个原子组成的小团簇，可以观察到团簇的原子图像。在激光烧蚀沉积碳的过程中，一些小簇以单层形式吸附在基体上。在大约50托的He气体下，它们主要以三维形式堆积在衬底上，即使对于那些只有几个原子的衬底也是如此。虽然大多数团簇在衬底表面随机分布，但它们往往吸附在晶体缺陷周围，如沿台阶或台阶。这些星团具有相似的大小和形状，并以几乎相等的间隔排列，从而形成大小选择星团的规则排列。通过激光烧蚀可以观察到碳团簇，通过热蒸发可以观察到Au、C、Sb和Te团簇。

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.