Domain populations in lead zirconate titanate thin films of different compositions via piezoresponse force microscopy

Abstract

Pb(Zr x Ti 1−x )O 3 (PZT) thin films with (111) texture were deposited onto commercially available Pt/Ti/SiO 2 /Si substrates via the sol-gel technique. Piezoforce microscopy (PFM) was then used to analyse the evolution of domain populations as a function of the Zr content x. Domain structures of virgin films, local piezoelectric properties of individual grains and piezoelectric histograms were studied in films with different compositions (x = 0.2-0.6), which cover both the tetragonal and rhombohedral sides of the phase diagram. In films with low Zr content mainly single-domain grains were observed. As the Zr content increased, a larger fraction of polydomain grains was found. The local piezoelectric response measured inside sufficiently big grains indicated that the strongest piezoelectric effect occurs in PZT30/70 (x = 0.3) films. This was attributed to two different effects: high out-of-plane polarization achieved due to the (111) texture and influence of the dielectric constant. In tetragonal films with their lower dielectric constants the electric field seen by a ferroelectric is higher as compared to other compositions, giving rise to an apparent increase of the effective piezoelectric response measured by PFM. The analysis of the domain images indicated that sol-gel derived PZT films are slightly self-polarized near the free surface. With increasing Zr/Ti ratio, the variation of domain populations resulted in reversing the sign of the average piezoelectric response at x ≈ 0.3. It is demonstrated that PFM histograms are extremely sensitive to PZT composition and can be used as a signature of complex domain structures in ferroelectric thin films.

Piezoresponse force spectroscopy of ferroelectric-semiconductor materials

“…Kalinin et al 37 have extended the one-dimensional ͑1D͒ model by Ganpule et al 52 to describe PFM loop shape in the thermodynamic limit. Wu et al have postulated the existence of nucleation bias from PFM loop observations, 53 in agreement with theoretical studies by Abplanalp, 22 Kalinin et al, 24 Emelyanov, 25 and Morozovska and Eliseev. 26 Finally, Jesse et al 42 have analyzed hysteresis loop shape in kinetic and thermodynamic limits for domain formation.…”

Abnormal domain switching in Pb(Zr,Ti)O3 thin film capacitors

“…2 Currently, piezoresponse force microscopy ͑PFM͒ is widely used for assessment of the local switching properties via visualization of domain structure, after application of an electric potential between the probing tip and the bottom electrode. [3][4][5][6] Generally, domain orientation after poling is consistent with the direction of the applied electric field. However, in some cases this trend is disrupted, i.e., after the external field is turned off the resulting domains exhibit polarization opposite to the direction of the applied field.…”

“…5 The thickness of the films measured in a cross section by scanning electron microscopy was about 370 nm. The PZT capacitors were fabricated by sputtering a gold layer on the surface of the film through a shadow mask.…”

Quantitative determination of tip parameters in piezoresponse force microscopy

“…9 To parallel the spectacular developments in instrumentation, methods, and applications, significant effort has been concentrated on the theoretical description of PFM, including the image formation mechanisms, 10,11 domain wall contrast, 12,13 tip-induced polarization switching, [14][15][16] and hysteresis loop formation. 9,17 However, all theoretical efforts to date assumed ad hoc models for tip geometry, typically using either sphere-plane or point-charge-plane approximations, while the realistic tip geometry is significantly more complex. This lack of knowledge about the tip properties results in large uncertainties in the interpretation of PFM data and precludes reliable quantitative interpretation of switching data, PFM spectroscopy, and domain wall profiles in terms of material parameters.…”