Electrical conduction mechanism and phase transition studies using dielectric properties and Raman spectroscopy in ferroelectric Pb0.76Ca0.24TiO3 thin films

Abstract

We have studied the phase transition behavior of Pb 0.76 Ca 0.24 TiO 3 thin films using Raman scattering and dielectric measurement techniques. We also have studied the leakage current conduction mechanism as a function of temperature for these thin films on platinized silicon substrates. A Pb 0.76 Ca 0.24 TiO 3 thin film was prepared using a soft chemical process, called the polymeric precursor method. The results showed that the dependence of the dielectric constant upon the frequency does not reveal any relaxor behavior. However, a diffuse character-type phase transition was observed upon transformation from a cubic paraelectric phase to a tetragonal ferroelectric phase. The temperature dependency of Raman scattering spectra was investigated through the ferroelectric phase transition. The soft mode showed a marked dependence on temperature and its disappearance at about 598 K. On the other hand, Raman modes persist above the tetragonal to cubic phase transition temperature, although all optical modes should be Raman inactive above the phase transition temperature. The origin of these modes must be interpreted in terms of a local breakdown of cubic symmetry by some kind of disorder. The lack of a well-defined transition temperature suggested a diffuse-type phase transition. This result corroborate the dielectric constant versus temperature data, which showed a broad ferroelectric phase transition in the thin film. The leakage current density of the PCT24 thin film was studied at elevated temperatures, and the data were well fitted by the Schottky emission model. The Schottky barrier height of the PCT24 thin film was estimated to be 1.49 eV.

Metal-ferroelectric-metal heterostructures with Schottky contacts. I. Influence of the ferroelectric properties

“…[28][29][30][31][32] Therefore, it will be essential to define a sound model of the metal-ferroelectric interface that will be able to properly describe the current-voltage (I-V) and capacitance-voltage (C-V) characteristics within the same formalism.…”

Improvement of the ferroelectric properties of ABO3 (A=Pb, Ca, Ba; B=Ti, Zr) films

“…The κ values observed for PBT8020 and PCT6040 thin films coated on LNO/LAO are significantly higher than those reported in literature. 15,[17][18][19] In fact, at 100 KHz these films presents κ values close to 2250 and 930, respectively, while films grown on platinum electrodes presents κ values of ∼118 and 200 observed for similar PBT and PCT films, respectively. However, the PZT3070 deposited on LNO/LAO presents κ values considerably lower than those reported for similar films also grown on LNO/ALO structures.…”

“…Meanwhile, AFM images obtained for a PCT6040/Pt (1 1 1)/Ti/SiO 2 /Si (1 0 0) thin film reported an R rms value of 4 nm and a t value of 70 nm, such film was heat-treated in a conventional furnace. 17 In this sense, the sample grown on LNO/LAO structures seems to display a higher R rms and big- ger average grain size than those reported for the ABO 3 thin films deposited on Pt-based substrates.…”

The influence of Calcium doping on structural and electrical properties of ferroelectric Lead Titanate ceramic

“…Various types of electronic ceramics are insulators, ferrites, capacitors, PTC materials, ferroelectrics, pyroelectrics, piezoelectrics, electrooptic materials etc. The ferroelectric materials possess the spontaneous polarization even in the absence of an electric field and the direction of spontaneous polarization can be changed by an applied electric field [3][4][5]. Lead Titanate is a ferroelectric material having a structure similar to BaTiO 3 with a high Curie point (490 o C).…”