H.F. Yu

Ultrahigh piezoelectric response perpendicular to special cleavage plane in BaTiO3 single crystals

We report on the ultrahigh piezoelectric response perpendicular to some special cleavage plane in BaTiO3 single crystals. An extremely high value of piezoelectric coefficient d33 value over 2000pC∕N was obtained after being poled perpendicular to special plane (270) in BaTiO3 crystal, which is more than 20 times higher than those poled along spontaneous polarization direction ⟨001⟩ (d33⟨001⟩=87pC∕N). A large strain of 0.6% was obtained at a very low electric field.

Distribution and formation mechanism of the domain structure in PMN?33% PT single crystals

Domain structures investigation in (110)-oriented Pb(Mg1/3Nb2/3)O3–33% PbTiO3 (PMN–33% PT) single crystals has been performed by piezoresponse force microscopy. Submicron-sized fingerprint pattern and tweed pattern domains (TPDs) have been observed in large parallel domains with typical sizes of 20–30 µm. Based on the existence of gradual transition regions between fingerprint pattern domains and TPDs in the same large ferroelectric domain, the relationship between the two pattern domains is discussed and a possible formation mechanism of the domain structure in PMN–33% PT single crystal is proposed.

Near-field acoustic and piezoresponse microscopy of domain structures in ferroelectric material

Three kinds of near-field microscopy imaging mode including SEAM (Scanning electron acoustic microscopy), PFM (Piezoresponse force microscopy) and SPAM (Scanning probe acoustic microscopy) have been developed to investigate domain structures of ferroelectric ceramics, crystals and thin films in our studies. The domain imaging mechanisms are presented individually in three imaging modes. Sub-surface micro-domain configuration of ferroelectric BaTiO3 ceramics and single crystal and their dynamic behavior under external fields were clearly visualized by SEAM. Ferroelectric domain structures of ferroelectric PZT thin film and PMN-PT single crystal were characterized by PFM. Nanoscale switching behavior and local field-induced nanoscale displacement behavior of domain structures in ferroelectric thin film were studied by PFM. Antiparallel domain patterns in ferroelectric transparent PLZT ceramics were also characterized by SPAM. The combination of SEAM, PFM and SPAM in application to imaging domain structures undoubtedly enrich our understanding of the nature of piezoelectricity and ferroelectricity at submicro-, even nano-meter scale

NANOSCALE PIEZOELECTRIC AND ELASTIC PHENOMENA OF FERROELECTRIC DOMAIN

ABSTRACT Piezoresponse force microscopy (PFM) and scanning probe acoustic microscopy (SPAM) were combined to characterize locally piezoelectric and elastic phenomena of domain structures in lead-free Bi4Ti3O12 piezoelectric ceramics and ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals. The acoustic images of ferroelectric domain were firstly visualized by SPAM at low frequency below 10 kHz. The domain imaging mechanisms are ascribed to the elastic response of ferroelectric domain to local contact stiffness difference of the individual domains in response to local elastic stress fields. An interesting proportional relationship was revealed between the local piezoelectricity and elasticity for ferroelectric domains.

Local Piezoresponse and Electrical Behavior of Multiferroic BiFe0.95Mn0.05O3 Epitaxial Thin Films Deposited Under Different Oxygen Pressure

Multiferroic BiFe0.95Mn0.05O3 (BFMO) epitaxial thin films were grown on SrRuO3, SrTiO3 and TiN-buffered (001)-oriented Si substrates under different oxygen pressure by pulsed laser deposition. The influence of oxygen pressure on the microstructures, domain configurations and their local piezoresponse and electrical behaviors were investigated by the piezoresponse force microcopy and conductive atomic force microscopy. BFMO thin film at low oxygen pressure was found to demonstrate pure phase state, inhomogeneous piezoresponse and low leakage behavior with diode-like behavior, while high oxygen pressure leads to impurity Bi2O3 phase-enclosed BFMO films with higher leakage current above 2 nA, revealing the importance of the oxygen pressure in governing the physical properties of BFMO films.

Influence of Oxygen Pressure on the Domain Dynamics and Local Electrical Properties of BiFe0.95Mn0.05O3 Thin Films Studied by Piezoresponse Force Microscopy and Conductive Atomic Force Microscopy

In this work, we have studied the microstructures, nanodomains, polarization preservation behaviors, and electrical properties of BiFe0.95Mn0.05O3 (BFMO) multiferroic thin films, which have been epitaxially created on the substrates of SrRuO3, SrTiO3, and TiN-buffered (001)-oriented Si at different oxygen pressures via piezoresponse force microscopy and conductive atomic force microscopy. We found that the pure phase state, inhomogeneous piezoresponse force microscopy (PFM) response, low leakage current with unidirectional diode-like properties, and orientation-dependent polarization reversal properties were found in BFMO thin films deposited at low oxygen pressure. Meanwhile, these films under high oxygen pressures resulted in impurities in the secondary phase in BFMO films, which caused a greater leakage that hindered the polarization preservation capability. Thus, this shows the important impact of the oxygen pressure on modulating the physical effects of BFMO films.