Blue phosphorene on Au(111) as a decoupling layer for organic epitaxially grown films

Abstract

Blue phosphorene (BlueP) is considered as a promising two-dimensional (2D) material for future-(opto)electronic applications. Monolayer BlueP is often fabricated on Au(111) single-crystal surfaces. It has been suggested that small P domains form a lateral network with Au adatoms. Previous studies attempting to use BlueP/Au(111) as a substrate for the deposition of fullerene indicated that the former is susceptible to structural deterioration, unlike most other 2D materials in this regard. Here, we investigate 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) monolayers and multilayer films deposited on BlueP/Au(111). We monitor the film growth in real time using in situ optical differential reflectance spectroscopy with the substrate kept either at room temperature or at $\ensuremath{\approx}120{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. Furthermore, we examine the epitaxial alignment between PTCDA and BlueP by means of distortion-corrected low-energy electron diffraction and low-temperature scanning tunneling microscopy. Our data clearly reveal that PTCDA exhibits a highly ordered monolayer structure with a herringbone packing motif, whereas the domain orientations differ from all previously reported structures of PTCDA directly on Au(111). Importantly, we find no indications for adsorption-induced reordering or degradation of BlueP/Au(111). At elevated temperatures, PTCDA is observed to form multilayer islands covering only a fraction of the available PTCDA monolayer surface on BlueP/Au(111), and this Stranski-Krastanov growth mode bears similarities to literature results for PTCDA multilayers on pristine coinage metal surfaces.