Tip-assisted Directional Growth of Atomically Thin Ag Islands

The growth and decay of metal nanostructures are important in many areas of physical science and catalytic chemistry. Here, we show the directional growth of Ag island stripes at room temperature via tip-assisted coarsening of hexagonal islands on Ag(111) using scanning tunneling microscope (STM). The mechanism of this process is attributed to the alignment of the adatom and vacancy islands along the scanning direction via tip-sample interaction during the process of the intrinsic decay of the metastable Ag islands. We find that this tip-assisted island growth is not directly related to the tunneling current and the bias voltage. Experiments performed using Ag tips and W tips show similar coarsening effects. The chamber pressure and the O-2 exposure also do not have systematic effects on the rate of island growth. The tip-assisted coarsening strongly depends on the tip morphology.