Improved electrical conductivity in Pr2Ni(Cu,Ga)O4 film with nano thickness

Pr1.91Ni0.71Cu0.24Ga0.05O4 (PNCG) thin film with few 100 nm thickness was prepared on polycrystalline MgO substrate with pulsed laser deposition (PLD) method. The prepared film was dense and uniform, and formation of Pr2NiO4 phase was observed after a post annealing treatment. Electrical conductivity was significantly changed in the film and increase in conductivity was observed when the film thickness was 320 nm. However, the conductivity decreased with decreasing the film thickness less than 300 nm and Hall coefficient measurements suggested that the electronic hole concentration increased, however its mobility decreased in PNCG film because of the expanded lattice. Increased conductivity in the PNCG film with 320 nm could be explained by the increased amount of electronic hole and its high mobility. XPS measurement also showed that Pr and Ni were an oxidized state comparing with that in bulk and so excess oxygen may be introduced in the PNCG thin film by charge compensation.