Unusual modification of CuCl or CuBr films by He plasma exposure resulting in nanowire formation.

In this paper, we present a method for growing copper-based nanowires. The method is based on the unusual modification of a halogenated copper surface by exposure to a helium plasma. The nanowires have diameters ranging between 50 and 150 nm and lengths up to 50 microm. They are polycrystalline, and large parts of the wires have a pronounced core-shell structure with a dense shell and less material inside. The wires are grown in a plasma environment at room temperature, and large amounts can be grown in a matter of minutes. The critical process parameters for the growth process are the gas flow and pressure settings, and the impact thereof will be discussed in detail. In order to gain insight in a possible growth mechanism, our observations are compared with literature on the growth of silver whiskers from halogenated silver crystallites. Finally, photoluminescence spectra of the wires are discussed in view of the analytical data about the stoichiometry and structure of the nanowires.