Optical and electrical properties of (Ba1-xCax)(ZryTi1-y)O3 polycrystalline thin films growth by pulsed laser deposition

Piezoelectric and ferroelectric materials are keys to modern technologies due to his high dielectric constant and strong piezoelectric response. The well known Piezoelectric material are the lead zirconium titanate (PZT) but the main drawback of PZT is the high toxicity of lead and for that reason new materials are being developed. Recent studies [1-3] demonstrated the possibility to obtain lead-free (Ba1?xCax)(ZryTi1?y)O3 (BCZT) ferroelectric materials with very high dielectric permittivity and piezoelectric coefficients, opening the way to competitive devices free of toxic elements. In this work, BCTZ thin films, with different compositions,.were deposited using pulsed laser deposition method (PLD) with a ArF excimer laser, on platinum coated silicon substrate in a reactive environment (oxygen). The targets have been prepared by conventional ceramic processing and sintering at temperatures of about 1500 oC. The properties of the BCTZ thin films such as optical and electrical properties, thickness, roughness and dielectric constant were investigated by X -ray diffraction, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Spectroscopic Ellipsometry (SE) techniques. The films deposited on Pt/Si substrates are policrystalline and show (110) and (111) orientation. Atomic force microscopy evidenced a uniform surface microstructure with small roughness. Using spectro-ellipsometry (SE) technique, the optical behavior and band gap characteristics were determined. A high refractive index and low extinction coefficient for a large spectrum of wavelength(n>2 and k<10-4 for near UV-VIS-near IR) was found. The thickness of samples and their rough layer obtained from SE was compared with SEM and AFM results and were found in good agreement. Dielectric spectroscopy measurements carried out at room temperature and different frequency values. Excellent dielectric properties (relative permittivity of about 2000 and tangent loss ~ 3% at frequency of 10 KHz) have been measured.