Ferroelectric BaTiO$_{3}$ thin film synthesis on Ni substrates by pulsed laser deposition with varying oxygen atmosphere conditions

A KrF excimer laser of 248nm wavelength was used to fabricate ferroelectric Barium Titanate (BaTiO$_{3}$) on nickel substrates. A high vacuum chamber base pressure of $\sim$3.0x10$^{-7}$ Torr was obtained for each sample and a laser repetition rate of 10Hz with an energy of 600mJ was used. The first film was synthesized by depositing BTO for 60min at 850 $^{\circ}$C under HV; prior to annealing the oxygen atmosphere was set to 250mTorr. The second film was deposited at 850$^ {\circ}$C under HV for 1 min followed by an increase in oxygen atmosphere to 250mTorr, resuming deposition for 59min. The third film was deposited under HV at 200$^{\circ}$C for 1min, the oxygen atmosphere and temperature were then set to 250mTorr and 850$^{\circ}$C followed by film deposition for an additional 59min. All three samples were annealed at 840$^{\circ}$C for 15 min and lowered to 20$^{\circ}$C at a rate of 3$^{\circ}$C per min. Hysteresis measurements were obtained for the samples with a Radiant Technologies inc. RT6000HVS system. It was observed that both the first and second films had a hysteresis loop in close resemblance to paraelectric materials while the third film showed an improved square shape hysteresis loop, indicative of ferroelectric properties.