Structural and electrical properties of Bi₂O₃-Nb ₂O₅ thin films grown at low temperatures by pulsed laser deposition

The dielectric constant (_r) of the films grown at 100 °C increased as the beam energy density increased and a saturated value of 80 was obtained for the film grown under 6.0 J cm^-2. The larger _r value was attributed to the increased amount of nano-sized Bi ₃NbO₇ crystals. The _r values also increased with the beam energy density for films grown at 300 °C and a very high _r value of 135.6 with a low loss of 3.0% at 100 kHz was obtained for the film grown at 300 °C under a beam density of 3.0 J cm^-2. The crystalline BiNbO₄ phase developed, but the amount of Bi ₃NbO₇ crystals decreased as the beam energy density increased, indicating that the increased _r values of the films grown at 300 °C could be due to the formation of the crystalline BiNbO₄ phase. The electrical properties of the films grown at 300 °C under a beam density of 3.0 J cm^-2 were considerably influenced by the oxygen partial pressure (OPP) during annealing. The film annealed at 300 °C under a 50.0 torr OPP exhibited a low leakage current density of 5.4 × 10 ^-9 A cm^-2 at 0.3 MV cm^-1 with a relatively high breakdown field of 0.4 MV cm^-1.