The authors investigated the Cu-Al surface alloy formation by depositing thin films of Al by radio frequency magnetron sputtering on commercially available pure copper substrates kept at different temperatures. The crystal structure and composition of the alloys were studied by x-ray diffraction and x-ray photoelectron spectroscopy. Despite the polycrystalline nature of the copper substrate, CuAl alloy films are highly oriented along the Cu(111) direction. The deposition of Al onto Cu substrates in the temperature range from 450 to 500 degrees C leads to a mixture of intermetallic Cu9Al4 and alpha Cu phases. However, 525 degrees C deposition temperature is enough to get alpha Cu solid solution. These findings can be replicated on Cu single crystals to get a CuAl alloy free from intermetallic phases, which can be used as a substrate to fabricate an electron emitter with a metal-insulator-metal structure.