The natural symmetry breaking of heterojunction interfaces has led to a rich variety of physical effects and functions, such as Rashba type spin orbit coupling, rectification effect, photovoltaic effect, etc. The non centrosymmetry of the interface can also induce piezoelectric effects in heterojunctions, achieving the mutual conversion of mechanical and electrical energy, known as interface piezoelectric effects [M.M. Yang, et al., Nature 584, 377 (2020)].
Compared to traditional piezoelectric effects based on symmetry breaking, interface piezoelectric effects are not limited to insulating dielectric materials with non centrosymmetry, but exist in all heterojunction systems with internal resistance, even heterostructures composed of centrosymmetric semiconductors. Therefore, the interface piezoelectric effect greatly expands the research field and application scope of piezoelectric effect, and also provides new opportunities for the physical property control and device design of piezoelectric materials.
Recently, Ming Min Yang from the University of Science and Technology of China, Marin Alexe from the University of Warwick in the UK, and Shi Liu from Westlake University published a paper in Nature Materials, which for the first time achieved a phenomenon called "auxetic piezoelectric effect" by precisely regulating the polarity symmetry of heterojunction interfaces.
This effect allows piezoelectric materials to contract or expand simultaneously in both horizontal and vertical directions under external electric field stimulation, similar to the negative Poisson's ratio effect in electricity. This discovery breaks through the limitation of traditional piezoelectric materials exhibiting opposite signs of longitudinal (d33) and transverse piezoelectric coefficients (d31, d32), enriches the behavioral patterns of piezoelectric effects, and provides new potential for the development of all semiconductor drivers, sensors, and filters.
Figure 1: The phenomenological theory and characteristics of the dilatancy piezoelectric effect.
Figure 2: Experimental evidence of the stretching piezoelectric effect in Au/Nb: SrTiO3 Schottky junction.
Figure 3: Demonstration of the dilatancy piezoelectric effect in a (110) - oriented Au/Nb: SrTiO3 Schottky junction.
Figure 4: Demonstration of the inverse tensile dilation piezoelectric effect.
Figure 5: In heterostructures, the coefficients of tension, dilation, and piezoelectricity.
Editor: Sichuan Jinzhongde Science and Technology Research Institute
Source: Today's New Materials
