Temperature-Dependent Structure of Two-Dimensional Hybrid NaCl-PTCDI Nanoarchitectures on Au(111)

Abstract

PTCDI molecules and NaCl self-assemble on the Au(111) surface to form two-dimensional porous hybrid nanoarchitectures. Scanning tunneling microscopy (STM) reveals that temperature can drastically influence the structure of these nanoarchitectures. A PTCDI-NaCl flower structure is created after codeposition onto a surface at 20 °C. The molecules and the ionic compound form a mesh nanoarchitecture after annealing at 100 °C, a ladder nanoarchitecture after annealing at 140 °C, and a chain nanoarchitecture after annealing at 150 °C. Close-packed PTCDI islands surrounded by single PTCDI-NaCl chains are observed after annealing at 160 °C. STM shows that NaCl interacts selectively and locally with molecular N-H groups. This organic–ionic interaction is highly directional. A temperature increase appears to first favor the ordering of PTCDI and NaCl compound and then to favor the formation of higher density structures. At high temperature, the ionic compound desorbs from the surface. This combination of organic and ionic compounds is a promising system to engineer novel 2D materials with a tunable internal structure.