Lattice extension in Cu3NMgx thin films and the induced effect

• Ternary Cu3NMgx thin films with x up to 0.32 were synthesized.
• Mg atoms occupy the previously empty centers of unit cells of the cubic Cu3N lattice.
• Cu3NMgx compounds exhibit a steadily narrowed band gap with increasing Mg content.
• The electrical resistivity at room temperature drops by four orders of magnitude.

Foreign atoms occupying extrinsic positions other than lattice sites of the original matrix can effectively bring out new material properties. Ternary Cu3NMgx thin films with x up to x = 0.32 were synthesized on silicon and quartz substrates by RF reactive magnetron cosputtering of copper and magnesium targets, in which the Mg atoms occupy the previously empty centers of unit cells of the cubic Cu3N lattice. The upper limit was determined by the deteriorated crystallinity of the deposits due to weakened overall bonding strength and lattice expansion. With increasing amount of Mg dopant atoms, the Cu3NMgx compounds exhibit a steadily narrowed band gap that the room temperature electrical resistivity drops by four orders of magnitude, yet all the deposits remain n-type semiconductor. The factors contributing to the reduced electrical resistivity in Cu3NMgx compounds with larger x values are discussed. These results may inspire more efforts towards material design via lattice extension for new and largely adjustable material properties.