In situ RHEED observation of MBE growth of organic thin films

Abstract

Studies on molecular beam epitaxial growth for organic molecules (OMBE) have been attracting attentions as a new fabrication method for preparation of ultra-thin films of organic molecules. Molecular beam epitaxy (MBE) has been developed as a deposition technique for the controlled growth of atomically flat multilayer structures. Recently, this method has been applied to organic materials, while the mechanism of the growth has not been thoroughly understood compared to that of semiconductor. In this report, the growth mechanism of Lead Phthalocyanine (PbPc) thin films onto highly oriented pyrolytic graphite (HOPG) substrate by OMBE method was investigated using in situ refraction high energy electron diffraction (RHEED). RHEED has been widely used for in situ monitoring of the thin film MBE growth. The intensity of the RHEED specular beam spot oscillates according to the layer-by-layer growth[1]. In 1981, Joyce et.al. observed an oscillated phenomena of RHEED intensity with growth of semiconductor for the first time[2]. After that, a lot of work in the semiconductor field have been reported and developed. Although application for organic materials is expected, so far RHEED oscillation studies have only been reported for Copper Phthalocyanine (CuPc) on MoS2 substrate[3]. Therefore, we explored the possibilities of using in situ RHEED observations to investigate the OMBE growth mechanism of PbPc on HOPG system.