Evidence for the existence of a metal-insulator-semiconductor junction at the electrode interfaces of CaCu3Ti4O12 thin film capacitors

P-type conductivity has been observed in CaCu3Ti4O12 (CCTO) ceramics and also in thin films deposited by pulsed laser deposition. I-V and C-V relationships of the CCTO thin films showed characteristics typical of a tunnel metal-insulator-semiconductor structure, evidencing its capacitance response as the origin of the high apparent dielectric constant observed in CCTO thin films. The very thin insulating layer on top of the film can be reduced in thickness by treatment in HCl acid, as shown by smaller threshold voltages in the I-V curves. The overall behavior is compatible with a conduction activation energy of similar to 80 to 100 meV in the bulk of the film, and a diffusion potential at the interface of 500 to 800 meV. The acceptor concentration is of the order of 10(19) cm(-3). (c) 2007 American Institute of Physics.