Stress and Film Thickness Effects on the Optical Properties of Ferroelectric Pb(Zr_xTi_{1 −x})O₃Films

Abstract

Spectrophotometry measurements at wavelengths from 180 nm to 3000 nm, x-ray diffraction, and Raman spectroscopy were used in the characterization of polycrystalline Pb(Zr x Ti 1−x )O 3 films with various thicknesses deposited by pulsed laser deposition on MgO substrates. It was found that films were under a strong compressive stress increasing up to 1.3 GPa with decreasing film thickness down to 80 nm. A clear blue shift of the optical absorption edge was found in transmission spectra leading to an increase of band gap energy from 3.9 eV to 4.5 eV. Both refractive index and extinction coefficient increased at the wavelengths below 500 nm with decreasing film thickness.

Raman and x-ray photoelectron spectroscopy study of ferroelectric switching in Pb(Nb,Zr,Ti)O3 thin films

“…Peaks at 277 cm À1 and 506 cm À1 represent the paraelectric behavior of the structure. According to the normal modes description 21,22 of PZT, the Raman spectrum at room temperature corresponds to the point group symmetry C 4V associated with a tetragonal structure, and the Raman active vibrations correspond to A 1 , B 1 , and E modes. Although Nb doping might modify the phonon dispersion, 23 we focus on the study of bands associated with the ferroelectric phase, as determined by comparing spectra below and above T C (Fig.…”

Thickness Dependence of Ferroelectric and Optical Properties in Pb(Zr0.53Ti0.47)O3 Thin Films

“…Studying Pb(Zr 0.2 Ti 0.8 ) 0.70 Ni 0.30 O 3− δ (PZTNi30) thin films in the thickness range of 5–400 nm, Shalini and co-workers found the bandgap can change regularly with thickness, and considered the PZTNi30 as a ferroelectric photovoltaic material [20]. Lappalainen et al also found the bandgap increased as the thickness of Pb 0.97 Nd 0.02 (Zr 0.55 Ti 0.45 )O 3 film decreased from 465 to 80 nm, with regular changes in refractive index and absorption coefficient [21].…”

Optical scattering of nanocrystalline Pb(ZrxTi1−x)O3 films

“…Same kind of correlation between the phase structure and microstrain of the films has been also observed in PNZT thin films deposited with different laser beam fluence. 8 From AFM measurements it was found that films with amorphous structure had smooth surfaces, while in films having pyrochlore phase the surface roughness was high (R q > 30 nm). For films with high tetragonal or trigonal crystal structure surface roughness were lower (R q ≈ 10 nm), bearing area curves steeper and surface curvatures lower compared to films with tetragonaltrigonal phase co-existence (R q ≈ 25 nm).…”