Scanning tunneling microscope study of nanosized metal-semiconductor contacts between ErSi2 nanoislands and Si(0 0 1) substrate

The current-voltage (I-V) characteristics of the nanosized metal-semiconductor contacts formed between the epitaxially grown ErSi2 islands and p-Si(0 0 1) substrate are measured in situ by the scanning tunneling microscope. Experimental results show that the current densities passing through the nanocontacts are five orders of magnitude larger than that of the macroscopic ones and have an obvious dependence on the contact area. Especially, it is found that I-V characteristics of the contacts are sensitive to the sample surface adsorption. Our investigations indicate that surface conduction plays an important role in the electrical transport process from ErSi2 islands to the Si(0 0 1) substrate. Furthermore, for the nanocontacts with surface currents suppressed effectively, the ideality factor and the effective Schottky barrier height are estimated by using the standard thermionic emission model. Our analysis suggests that the current through the interface between ErSi2 nanoislands and the p-Si(0 0 1) substrate is enhanced due to the effects of tunneling and image force lowering.