Abstract
The role of oxygen pressure on the structural and physical properties of various copper oxide phases, grown by Pulsed Laser Deposition (PLD) on MgO (100), has been investigated over the pressure range of 1.10(-5) Pa(-1) Pa. Positron annihilation spectroscopy revealed positrons trapped at vacancies and large vacancy clusters with lifetimes ranging from 400 ps to 500 ps.
Single copper vacancies V(Cu), interesting for p-type applications, were found in the CuO phase, whereas in the Cu(2)O phase copper vacancy complexes coupled with oxygen vacancies {V(Cu) + V(O) and V(Cu) + 2V(O)} were seen. Suitable O(2) atmosphere conditions, which induced a mixture of copper oxide phases with CuO crystals growing on top of Cu(2)O films were found.
The deposition process was monitored with in situ diagnostic techniques based on Optical Emission Spectroscopy and Langmuir Probe, and enabled identification of kinetic energy ranges for Cu ions, which promote the formation of CuO or Cu(2)O phases. Kinetics of the plasma during the deposition process correlate well with the properties of the deposited films.