Carborane Nanomembranes

We report on the fabrication of a boron-based two-dimensional (2D) material via electron irradiation-induced cross-linking of carborane self-assembled monolayers (SAMs) on crystalline silver substrates. The SAMs of 1,2-dicarba-closo-dodecarborane-9,12-dithiol (O9,12) were prepared on flat crystalline silver substrates and irradiated with low-energy electrons, resulting in a 2D nanomembrane. The mechanical stability and compact character of the carborane nanomembrane were improved by using 12-(1',12'-dicarba-closo-dodecarboran-1'-yl)-1,12-dicarba-closo-dodecarborane-1-thiol (1-HS-bis-), a longer, rod-like SAM precursor with two para-carborane units linked linearly together. The self-assembly, cross-linking process, and transfer of the resulting membranes onto holey substrates were characterized with different complementary surface-sensitive techniques including X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and low-energy electron diffraction (LEED) as well as scanning tunneling and electron microscopies (STM, SEM) to provide insight on the structural changes within the cross-linked SAMs. The presented methodology has potential for the development of boron-based 2D materials for applications in electronic and optical devices.