Preparation of Ultrathin Gold Films with Subatomic Surface Roughness

Abstract

Nanoscale device fabrication requires control over film growth at the atomic scale. Growth conditions must be tuned in consideration of interface parameters like chemical bonding, surface free energy, and lattice matching. In metals, electronic properties may also be utilized for control of physical parameters. Quantum size effects can induce metals to spontaneously form specific shapes and sizes according to their electronic structure. Unfortunately, such electronic growth is generally known only for a few systems and is typically only stable under cryogenic conditions. In this work, we explore a recently discovered class of electronic growth systems in which metal films are grown upon the relatively inert surfaces of van der Waals crystals. In this class of materials, the electronic growth is highly stable at room temperature and actually requires higher temperature annealing to achieve proper equilibrium. We work with the Au/MoS 2 system, which shows excellent stability and can readily form discrete and atomically flat nanostructures. Here, we show how the electronic growth modes facilitate the formation of atomically flat films with nanometer scale thickness. The surface roughness of these films was found to be less than a single atom over several square microns, creating nearly perfect surfaces for studies of self-assembled monolayers or other applications.

Diffusion energy barrier of Au on Bi2Se3: theory and experiment

“…This barrier is six times larger than that calculated for Au on MoS 2 [21,22], also a van der Waals interface. This may be responsible for the difference in growth mode seen on MoS 2 as compared to Bi 2 Se 3 [23][24][25].…”

Scanning Near-Field Optical Microscopy of Ultrathin Gold Films

“…Due to the surface wetting effect and the adhesion of gold to MoS 2 , high nucleation density and unusual kinetics of Au adatoms on MoS 2 surface lead to the growth of continuous and ultrasmooth clusters and highly-percolated structures [13,[20][21][22]. In recent papers, a detailed investigation of metal growth on MoS 2 revealed the formation of atomically flat Au clusters, nanotriangles, and nanoparticles depending on the deposition technique, metal thickness, and temperature [20,21,[23][24][25][26][27]. For example, the presence of MoS 2 could enhance the performance of ultrathin noble metal electrodes and their optical response [22,25,[28][29][30].…”

Optical Nanoimaging of Surface Plasmon Polaritons Supported by Ultrathin Metal Films

“…To resolve these problems, we prepared a high-quality ultrathin film in two steps. First, we deposited 9 nm Au on monolayer MoS 2 , which proved to be a perfect adhesion layer for metal deposition. ,, Then, we annealed this film to increase the size of gold crystallites, thus improving its conductivity and plasmonic response. Next, we performed a comprehensive study of the film using atomic force and scanning electron microscopies, spectroscopic ellipsometry, and sheet resistance measurements.…”