Extendable piezo/ferroelectricity in nonstoichiometric 2D transition metal dichalcogenides.

Engineering piezo/ferroelectricity in two-dimensional materials holds significant implications for advancing the manufacture of state-of-the-art multifunctional materials. The inborn nonstoichiometric propensity of two-dimensional transition metal dichalcogenides provides a spiffy ready-available solution for breaking inversion centrosymmetry, thereby conducing to circumvent size effect challenges in conventional perovskite oxide ferroelectrics. Here, we show the extendable and ubiquitous piezo/ferroelectricity within nonstoichiometric two-dimensional transition metal dichalcogenides that are predominantly centrosymmetric during standard stoichiometric cases.

Ferroelectricity in untwisted heterobilayers of transition metal dichalcogenides.

Two-dimensional materials with out-of-plane (OOP) ferroelectric and piezoelectric properties are highly desirable for the realization of ultrathin ferro- and piezoelectronic devices. We demonstrate unexpected OOP ferroelectricity and piezoelectricity in untwisted, commensurate, and epitaxial MoS/WS heterobilayers synthesized by scalable one-step chemical vapor deposition. We show piezoelectric constants of 1.

Unlocking surface octahedral tilt in two-dimensional Ruddlesden-Popper perovskites.

Molecularly soft organic-inorganic hybrid perovskites are susceptible to dynamic instabilities of the lattice called octahedral tilt, which directly impacts their carrier transport and exciton-phonon coupling. Although the structural phase transitions associated with octahedral tilt has been extensively studied in 3D hybrid halide perovskites, its impact in hybrid 2D perovskites is not well understood. Here, we used scanning tunneling microscopy (STM) to directly visualize surface octahedral tilt in freshly exfoliated 2D Ruddlesden-Popper perovskites (RPPs) across the homologous series, whereby the steric hindrance imposed by long organic cations is unlocked by exfoliation.

Facile synthesis of AgBiS nanocrystals for high responsivity infrared detectors.

AgBiS nanocrystals are emerging optoelectronic materials due to their solution-processability, earth abundance and non-toxic properties. We report a facile method to prepare AgBiS nanocrystals in ambient conditions. The nanocrystals are of high crystallinity and without byproducts, which make them suitable for solution processable optoelectronic devices.