Growth and Stability of H2-Phthalocyanine Thin Films on MoS2 Surfaces Studied by Means of Low-Energy Electron Transmission Spectroscopy

Abstract

The growth of H2-phthalocyanine ( H2Pc) thin films on MoS2 single-crystal surfaces was studied by low-energy electron transmission (LEET) spectroscopy. We observed LEET features typical of ultrathin films prepared by direct molecular-beam deposition of H2Pc molecules as well as by thinning thicker films by heat treatment. The dependence of the work function of the film on the film thickness showed the minimum value at the film thickness at which LEET features characteristic of ultrathin film were observed. The results indicate that the ultrathin film consists of a monolayer of H2Pc molecules, and the growth of the H2Pc monolayer is realizable on the MoS2 surface. Furthermore, it was found that films about 100 Å thick show poor molecular order due to aging at room temperature, while multilayer films of thickness below ∼50 Å are stable. The latter results indicate the difficulty in preparing well-ordered H2Pc multilayers of sufficient thickness on the MoS2 surface at room temperature.