Ferroelectric and Ferroelastic Domain Related Formation and Influential Mechanisms of Vapor Deposited Piezoelectric Thin Films

Compared to the bulk piezoelectric materials counterpart, piezoelectric thin films (PTFs) possess advantages of smaller size, lower power consumption, better sensitivity, and have broad application in advanced micro-electro-mechanical system (MEMS) devices. However, the performance of MEMS transducers and actuators are largely limited by PTFs piezoelectric properties. In this review, we focus on understanding structure-property relationship of vapor deposited PTFs, with emphasis on the effect of strain energy and electrostatic energy in thin films, especially, energy relaxation induced misfit dislocation and ferroelectric (FS) and ferroelastic (FC) domain formation mechanisms. We then discuss the microstructure of these domains and their influential mechanisms on piezoelectric properties, as well as the domain engineering strategies (i.e., internal and external stimuli). This review will motivate further experimental, theoretical, and simulation studies on FS and FC domain engineering in PTFs.

Large-scale Domain Engineering in Two-Dimensional Ferroelectric CuInP2S6 via Giant Flexoelectric Effect

Room-temperature ferroelectricity in two-dimensional materials offer a potential route for developing atomic-scale functional devices beyond Moore’s law. However, as a key for the technology implementations of ferroelectrics in electronics, the controllable generation of uniform domains remains challenging in two-dimensional ferroelectrics at current stage because domain engineering through an external electric field at 2D limit inevitably leads to large leakage current and material break-down. Here, we demonstrate a voltage-free method, the flexoelectric effect, to artificially generate large-scale stripe domains in two-dimensional ferroelectric CuInP2S6 with single domain lateral size at the scale of several hundred microns. With giant strain gradients (~106 m−1) at nanoscale, we mechanically switch the out-of-plane polarization in ultrathin CuInP2S6. The flexoelectric control of ferroelectric polarization is understood with a distorted Landau-Ginzburg-Devonshire double well model as evidenced by the shifted ferroelectric hysteresis loops and the first-principle calculations. Through substrate mechanical strain engineering, the stripe domain density is controllable. Our results not only highlight the potential of developing van der Waals ferroelectrics-based memories but also offer the opportunity to study ferroelectric domain physics in two-dimensional materials.

Properties of a Feature in Code-Assets: An Exploratory Study

Software product line engineering is a paradigm for developing a family of software products from a repository of reusable assets rather than developing each individual product from scratch. In featureoriented software product line engineering, the common and the variable characteristics of the products are expressed in terms of features. Using software product line engineering approach, software products are produced en masse by means of two engineering phases: (i) Domain Engineering and, (ii) Application Engineering. At the domain engineering phase, reusable assets are developed with variation points where variant features may be bound for each of the diverse products. At the application engineering phase, individual and customized products are developed from the reusable assets. Ideally, the reusable assets should be adaptable with less effort to support additional variations (features) that were not planned beforehand in order to increase the usage context of SPL as a result of expanding markets or when a new usage context of software product line emerges. This paper presents an exploration research to investigate the properties of features, in the code-asset implemented using Object-Oriented Programming Style. In the exploration, we observed that program elements of disparate features formed unions as well as intersections that may affect modifiability of the code-assets. The implication of this research to practice is that an unstable product line and with the tendency of emerging variations should aim for techniques that limit the number of intersections between program elements of different features. Similarly, the implication of the observation to research is that there should be subsequent investigations using multiple case studies in different software domains and programming styles to improve the understanding of the findings.