Crystalline thin films of stoichiometric Cu 3N and intercalated Cu 3NM x (M = metals): Growth and physical properties

Abstract

The growth of stoichiometric samples of thermally unstable noble-metal nitrides remains a challenge. Thin films of nearly stoichiometric Cu 3N have been successfully grown on Si (100) wafers by reactive magnetron sputtering of Cu target with mixed nitrogen and argon. The controversies regarding bandgap, lattice constant, decomposition temperature, room-temperature electrical resistivity, etc., can be resolved. Nitrogen re-emission leads to the formation of Cu 3N nanocrystallites, generally 40-60 nm in size, enclosed by Cu-terminated {111} facets. Samples with a slight Cu excess may turn into a metallic conductor with excellent electrical conductivity via a percolation mechanism. Unfavorable growth conditions may give rise to blistering or even mesocaled fivefold symmetrical relief structures in the deposit. These structures result from the rearrangement of nanocrystals via gliding along the {111} facets. Ternary Cu 3NM x (M = Pd, Cu, In, Zn, etc.) compounds, with the excessive metal atoms occupying the cell centers of the Cu 3N lattice, can be obtained by cosputtering under similar conditions. Such ternary compounds can easily be made metallic. In Cu 3NPd 0.238 a constant electrical resistivity was measured in a temperature range ∼200 K. Incorporation of In or O atoms may raise the decomposition temperature but not to more than 400 °C if the decomposition products are required to be as good a conductor as Cu. The present results might be relevant for growing films of thermally unstable materials. The peculiar electrical conduction behavior in the Cu 3NM x structures is expected to inspire the search for nearly zero-band materials similar to Cu 3NPd 0.238 as well as to promote an indepth exploration of potential applications of these materials. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.