In the pursuit of ferroic-based (nano)electronics, it is essential to minutely control domain patterns and domain switching. The ability to control domain width, orientation and position is a prerequisite for circuitry based on fine domains. Here, we develop the underlying theory towards growth of ultra-fine domain patterns, substantiate the theory by numerical modelling of practical situations and implement the gained understanding using the most widely applied ferroelectric, Pb(Zr,Ti)O 3 , demonstrating controlled stripes of 10 nm wide domains that extend in one direction along tens of micrometres. The observed electrical conductivity along these thin domains embedded in the otherwise insulating film confirms their potential for electronic applications.

Properties of ferroelectric domain walls are attractive for future nano- and optoelectronics. An important element is the potential to electrically erase/rewrite domain walls inside working devices. Dense domain wall patterns, formed upon cooling through the ferroelectric phase transition, were demonstrated. However, room temperature domain wall writing is done with a cantilever tip, one domain stripe at a time, and reduction of the inter-wall distance is limited by the tip diameter. Here, we show, at room temperature, controlled formation of arrays of domain walls with sub-tip-diameter spacing (i.e., inter-wall distance down to ≈10 nm). Each array contains 100–200 concurrently formed walls. Array rewriting is confirmed. The method is demonstrated in several materials. Dense domain pattern formation through a continuous electrode, practical for potential device applications, is also demonstrated. A quantitative theory of the phenomenon is provided.

While there is extensive literature on the influence of both compressive and tensile strain on the domain patterns of (001) tetragonal ferroelectric thin films, little is known regarding domain engineering in (110) films. The primary reason is the absence of suitable substrates that allow the growth of epitaxial films with this orientation. However, recent works emphasized the importance of this orientation with the possibility for e.g. to achieve ultra-high ferroelectric domain density. This work reports the controlled growth of a/c domain patterns in highly tetragonal monocrystalline (110) oriented Pb(Zr0.05, Ti0.95)O3. It is demonstrated that while a/c patterns can easily be realized in the single layer film relaxed under compressive misfit strain, modulation of tensile misfit strain through the use of buffer layers allows for consistent control of domain periodicity, in which case the average domain period was tuned between 630 and 60 nm. The effects of domain density and defects on both switching behavior and piezoelectric properties in single and multilayered structures are also investigated, revealing an optimum composition of the buffer layer for improved domain compliance and piezoelectric properties.

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We report the thermodynamic potential for single-domain (110) thin films epitaxially grown on dissimilar cubic substrates. Using different sets of paraelectric phase elastic compliance coefficients of PbTiO 3 single crystal, calculated from the experimental room-temperature values, we predict rotational phases similar to those observed in (001) thin films under anisotropic biaxial misfit strain. The new sets of elastic compliance coefficients also predict a triclinic phase that could potentially lead to the enhancement of both dielectric and piezoelectric properties. We also conducted experimental studies on highly tetragonal monocrystalline PbZr 0.05 Ti 0.95 O 3 thin films of different thicknesses, epitaxially grown on (110) SrTiO 3 substrate by pulsed laser deposition technique. Piezoresponse force microscopy measurements showed that the as-grown films were single domain with the a 2 c phase, which corroborates with the prediction of the theory. Moreover, the T c values of both thin and thick films (17-90 nm) also fell within the predicted range (540-600 ±• C). The measured remanet polarization of 57 µC/cm 2 was in good agreement with the theoretical values of 55-58 µC/cm 2 . Small-signal piezoelectric response measurements gave a piezoelectric coefficient of 40 pm/V, which is also in good agreement with the numerically calculated values of 38-42 pm/V.