Silver overlayers on (110) indium phosphide: film growth and Schottky barrier formation

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Abstract
The early formation and subsequent growth of evaporated silver films on atomically clean cleaved InP (110) surfaces have been probed using low-energy electron diffraction, Auger spectroscopy and angle-resolved photoelectron spectroscopy. Experimental data obtained would suggest that the silver film at room temperature grows initially as islands or rafts with possible nucleating sites at surface steps. Facet formation of the silver film is found to occur where mainly silver (111) facets are obtained. The formation of the Schottky barrier has been probed using photoemission and it is found that in this system the barrier is largely formed for a silver coverage which is equivalent to only about 10-20% of the surface. The abruptness and adhesion at the interface has also been considered. Strong adhesion is obtained for silver deposited at room temperature on the atomically clean cleaved InP (110) surface. This strong adhesion has been attributed to interdiffusion at the interface and for the etched InP surface the oxide layer presents leads to a considerable reduction of the interfacial mixing at room temperature. The mechanisms influencing the Schottky barrier formation have been considered and the defect model possibly involving indium vacancies initiating at step edges is thought the most likely reason for the pinning of the Fermi level at around 0.5 eV below the conduction band edge for silver contacts on the atomically clean cleaved InP (110) surface.