Electronic structure of quasi free 2 dimensional HfS_2 clusters

Abstract

Cluster research so far only dealt with either 3D free clusters or clusters on substrates with strong electronic coupling at the interface. Preparation of free and orientated 2D clusters is usually not possible because one of these conditions generally excludes the other. We demonstrate a new way to grow 2D clusters of transition metal dichalcogenides which are only weakly bound to the substrate, i.e. quasi free, but all show the same orientation thus allowing angle resolved photoemission experiments. In combination with scanning tunneling microscopy this provides for the first time the possibility to investigate the correlation between the size of quasi free 2D clusters and its associated electronic structure. For 2D HfS_2 clusters grown by van der Waals epitaxy we demonstrate that k_parallel-dispersion of electronic states already occurs for cluster diameters above ~100 nm.