tailieunhanh - Ferroelectrics Physical Effects Part 4

Tham khảo tài liệu 'ferroelectrics physical effects part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 110 Ferroelectrics - Physical Effects It can be concluded that the dominant conduction mechanism at room temperature is not bulk limited but is interface limited Pintilie L. al. 2007 . Current measurements at different temperatures were performed in order to distinguish between Schottky emission over the barrier and Fowler-Nordheim tunneling through the potential barrier at the metal-PZT interface. The results of the temperature measurements are presented in figure 7. 1 01 rT 0 01 3 c 1E-4 D c I 1E-5 Ổ 1E-6 1E-7 -4 -2 0 2 4 Voltage V Fig. 6. The thickness dependence of the I-V characteristics in the case of epitaxial PZT20 80 films. Measurements performed at room temperature. The delay time for current measurements meaning the time between changing the voltage and reading the current was 1 second. Fig. 7. The temperature dependence of the I-V characteristics in the case of epitaxial PZT20 80 films. Measurements performed on a sample with thickness of 230 ran. Charge Transport in Ferroelectric Thin Films 111 The temperature measurements had revealed two temperature domains Below 130 K the FN tunneling is the dominant conduction mechanism the current density being practically independent of temperature. Between 130 K and 350 K the dominant conduction mechanism is the Schottky emission. Over 350 K the film suffer breakdown. It is interesting to note also that the asymmetry is more pronounced at low temperatures. This is due to the fact that the two SRO PZT interfaces were processed slightly different. The bottom one had suffered a temperature annealing during the deposition of the PZT film and is influenced by the strain imposed by the thick STO substrate. The top SRO PZT interface had suffered a shorter temperature annealing and is less exposed to strain. Therefore the density of the interface defects affecting the interface properties can be different. This fact can induce asymmetry at different temperatures if one considers that the occupancy of the interface