Dielectric, ferroelectric and piezoelectric properties of sputtered PZT thin films on Si substrates: influence of film thickness and orientation

Lead titanate zirconate Pb(Zr,Ti)O₃ (PZT) thin films were deposited on platinized silicon substrates by r.f. magnetron sputtering and crystallized with preferred (110) or (111) orientation by conventional annealing treatment. The film structure evolution was observed as a function of the film thickness. Whatever the film thickness in the range 0.07 - 3 mm, the preferred orientation of the film is maintained. The film microstructure and, in particular, grain sizes varied with the film thickness; more precisely, grain sizes increases, both for (111) and (110) films with the film thickness. The electrical properties such as dielectric, ferroelectric and piezoelectric ones were systematically evaluated functions of the film thickness and their orientation. The relative dielectric constant increases with the film thickness; a saturation value of 920 is attained for film thicknesses higher than 0.6 µm independently of the film orientation. The ferroelectric properties seems to be independent of the film orientation; the coercive field decrease with increasing the film thickness to attain a minimum value of 30 kV/cm for films thicker than 1 mm. The remanent polarization increases with the film thickness and reaches the maximum value of 20 mC/cm². An increase in the piezoelectric constant e₃₁ with increasing the film thickness was observed for two types of films. For films thicker than 0.6 mm, the e₃₁ coefficient remains constant: e₃₁eff.rem. = -4.5 C/m² (which corresponds to d₃₁eff.rem. = -38 pm/V). Identical behavior is observed for the d₃₃eff. coefficient but no saturation effect with the film thickness is observed. The ferroelectric domain walls motion and the interfacial effects could explain partly the observed behavior

Modeling of dielectric hysteresis loops in ferroelectric semiconductors with charged defects

We have proposed the phenomenological description of dielectric hysteresis loops in ferroelectric semiconductors with charged defects and prevailing extrinsic conductivity. Exactly we have modified Landau-Ginsburg approach and shown that the macroscopic state of the aforementioned inhomogeneous system can be described by three coupled equations for three order parameters. Both the experimentally observed coercive field values well below the thermodynamic one and the various hysteresis loop deformations (constricted and double loops) have been obtained in the framework of our model. The obtained results quantitatively explain the ferroelectric switching in such ferroelectric materials as thick PZT films.Comment: 21 pages, 10 figures, sent to Journal of Physics: Condensed Matte

Elaboration and characterization of PNZT thin films deposited on silicon by RF cathodic sputtering

Pb(Zr,Ti)O3 (PZT) and Pb(Zr,Ti,Nb)O3 (PNZT) thin films have been grown on platinized silicon substrates by RF magnetron sputtering followed by a post-annealing treatment. The niobium, Nb, concentration varied from 1 to 7 at.% by increment of 1 at.% The effects of the Nb introduction on the PZT electrical properties, i.e., dielectric and ferroelectric ones have been investigated. We have found that the relative dielectric constant $(\varepsilon_{\rm r})$ is very sensitive to the Nb introduction; $(\varepsilon_{\rm r})$ reaches 1100 for a PNZT film doped at 2 at.% in comparison to 820 for a PZT film. The ferroelectric properties are also dependent of the doping level; in particular the remnant polarization reaches its maximum value ($17 \mu$C/cm2) for a 2 at.% Nb doped PZT film

(Zr/Ti) ratio effect on RF magnetron sputtered lead titanate zirconate films

Sputtered Pb(ZrxTi1−x)O3 thin films with various (Zr/Ti) compositions ranging from 15/85 to 70/30 were grown and characterised in terms of structural and electrical properties. PZT thin films, with 0.7–0.8μm thickness, were deposited on Si/SiO2/Ti/Pt by sputtering followed by conventional annealing. The sputtering conditions were the same for all the compositions. There were no apparent differences in crystallographic orientation as a function of Zr/Ti and the films a-lattice constant evolution is not exactly identical to the one of bulk ceramics. The permittivity increases when the Zr concentration increases and decreases just after the mor-photropic composition i.e. Zr-rich films. The ferroelectric properties are very sensitive to the Zr/Ti ratio. For example, the coercive field increases when the Ti concentration in the film increases

Influence of PbTiO3 buffer layer on structural and electrical properties of Pb(Zr, Ti)O3 films produced by sputter deposition technique

Ferroelectric lead zirconate titanate (PZT) with very thin lead titanate (PT) buffer layer inserted between the PZT films and the Si/SiO2/Ti/Pt substrate have been deposited by r.f. magnetron sputtering. Insertion of a PT buffer layer was found to exert marked effects on the PZT films in terms of structure, microstructure and electrical properties. The orientation of PZT thin films was controlled by changing the orientation of the PT layer. The (111) - oriented and (100) - oriented PZT films were grown on the (111) oriented and the (001) and (100) mixed - oriented PT buffer layers, respectively. The influence of the buffer layer thickness and the orientation of the PZT films on the electrical properties was also investigated

Ferroelectric and piezoelectric properties of Nb doped PZT films

Pb(Zr,Ti)O-3 (PZT) and Pb(Zr,Ti,Nb)O-3 (PNZT) thin films were grown on platinized silicon substrates by r.f. magnetron sputtering followed by a post-annealing treatment. The Niobium, Nb, concentration varied from 1 to 7 at.% by increment of 1 at.%. The effects of the Nb introduction on the PZT electrical properties, i.e, dielectric, ferroelectric and piezoelectric ones were investigated. The relative dielectric constant (epsilon (T)) was very sensitive to the Nb introduction; epsilon (T) reaches 1100 for a PNZT film doped at 2 at.% in comparison to 820 for a PZT film. The ferroelectric properties were also dependent of the doping level; in particular the remnant polarization reaches its maximum value for a 2 at.% Nb doped PZT film. The introduction of Nb enhances the piezoelectric properties of the films. The maximum value of d(33) varied from 55 pm/V for PZT films to 115 pm/V for a 2 at.% Nb doped films. For this doping level, e(31rem). reaches its maximum value: - 4.6 C/m(2). PNZT thin films, with weak Nb concentration (comprised between 1 to 2 at.%) are suitable for microsystems realization