Thin gold films offer a broad range of benefits for electronics due to their high electrical conductivity and transparency. Current manufacturing methods are unable to achieve gold films thinner than 10 nm, and are also limited in the area and continuity of films they can produce, due to the formation of “metal islands” — clusters of atoms on the substrate that can hinder conductivity, mechanical stability and substrate coverage. A new high-vacuum deposition process that takes inspiration from the chemical vapor deposition of graphene, developed in a collaboration between Xpanceo (Dubai, U.A.E.; www.xpanceo.com) and professor Konstantin S. Novoselov from the University of Manchester (U.K.; www.manchester.ac.uk), overcomes these challenges, producing films as thin as 3.5 nm with continuous, unrestricted area — moving a step closer to atomically thin gold films.
“We developed a graphene-based method for synthesizing transferable, wafer-scale ultrathin gold films with exceptional conductivity and transparency. These new films are ideal for applications like flexible electrodes, biosensing and thermal management. Unlike traditional methods, our approach avoids percolation issues and enables new study techniques to be used on atomically thin metals, such as plasmonics. This work marks a milestone whereby two-dimensional (2-D) fabrication techniques start making their way into the domain of conventional 3-D materials,” says Valentyn Volkov, Xpanceo co-founder and chief technology officer.
Using traditional production techniques, gold atoms are evaporated within a vacuum chamber until they form clusters on the substrate that then merge into a continuous film around 10–20-nm thick. If they are any thinner, they lack continuous morphology. With Xpanceo’s new method, gold films are deposited onto a copper substrate (which itself is deposited onto a silicon/graphene substrate) and coated with polymethyl methacrylate (PMMA). The PMMA/Au/Cu structure then undergoes electrochemical delamination from the silicon/graphene layer in potassium chloride solution, followed by dissolution of the Cu layer and cleaning, resulting in a free-standing PMMA/Au film (diagram; source: Nano Lett. 2024, 24, 51, 16,270–16,275). “These films feature continuous structures and can be transferred to any substrate via electrochemical techniques. The films maintain their conductivity under extreme bending and offer balance between transmittance and conductivity,” explains Volkov.
According to Volkov, the method allows for the scalable production of 2-D metallic films greater than 1 m2 in area using established roll-to-roll techniques — a significant improvement over current 2-D gold films, which are typically no more than 0.000001 mm2.