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Very high surface area, self-assembled, highly crystalline mesoporous SrTiO3 (STO) thin films were developed for photoelectrochemical water splitting. Much improved performance of these mesoporous films compared to planar STO thin films and any other form of STO such as single crystal samples and nanostructures was demonstrated. The high performance resulted from very large surface area films and optimization of carrier concentration. [ABSTRACT FROM AUTHOR]

Achieving robust and electrically controlled valley polarization in monolayer transition metal dichalcogenides (ML-TMDs) is a frontier challenge for realistic valleytronic applications. Theoretical investigations show that the integration of 2D materials with ferroelectrics is a promising strategy; however, an experimental demonstration has remained elusive. Here, we fabricate ferroelectric field-effect transistors using a ML-WSe 2 channel and an Al 0.68 Sc 0.32 N (AlScN) ferroelectric dielectric and experimentally demonstrate efficient tuning as well as non-volatile control of valley polarization. We measure a large array of transistors and obtain a maximum valley polarization of ∼27% at 80 K with stable retention up to 5400 s. The enhancement in the valley polarization is ascribed to the efficient exciton-to-trion (X-T) conversion and its coupling with an out-of-plane electric field, viz., the quantum-confined Stark effect. This changes the valley depolarization pathway from strong exchange interactions to slow spin-flip intervalley scattering. Our research demonstrates a promising approach for achieving non-volatile control over valley polarization for practical valleytronic device applications.

Semiconductor heterostructures have attracted intensive research attention during the past few years owing to their great potential for energy and environmental remediation related applications. Effective optical absorption and efficient separation of photogenerated charge carriers are among the key factors for achieving high efficiency in a photocatalytic process. This mini-review summarizes state-of-the-art activities in designing nanosemiconductor heterostructures using multifunctional semiconductors for solar-to-hydrogen conversion and degradation of organic pollutants. Various novel design strategies such as semiconductor/graphene heterojunctions including graphene as a semimetal and photosensitizer, semiconductor/ferromagnetic, and semiconductor/ferroelectric nanoheterostructures for enhancing the performance of photocatalytic processes have been discussed. Finally, key challenges and future prospects for designing more efficient photocatalytic materials are briefly outlined., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Ferroelectric polarization is an intriguing physical phenomenon for tuning charge-transport properties and finds application in a wide range of optoelectronic devices. So far, ferroelectric materials in a planar geometry or chemically grown nanostructures have been used. However, these structural architectures possess serious disadvantages such as small surface areas and structural defects, respectively, leading to reduced performance. Herein, the growth of room-temperature ferroelectric nanoporous/nanocolumnar structure of Ag,Nb-codoped SrTiO 3 (Ag/Nb:STO) using pulsed laser deposition is reported and demonstrated to have enhanced photoelectrochemical (PEC) properties using ferroelectric polarization. By manipulating the external electrical bias, ∼3-fold enhancement in the photocurrent from 40 to 130 μA·cm -2 of film area is obtained. Concurrently, the flat-band potential is decreased from -0.55 to -1.13 V, revealing a giant ferroelectric tuning of the band alignment at the semiconductor surface and enhanced charge transfer. In addition, an electrochemical impedance spectroscopy study confirmed the tuning of the charge transfer with ferroelectric polarization. Our nanoporous ferroelectric-semiconductor approach offers a new platform with great potential for achieving highly efficient PEC devices for renewable energy applications.

Very high surface area, self-assembled, highly crystalline mesoporous SrTiO 3 (STO) thin films were developed for photoelectrochemical water splitting. Much improved performance of these mesoporous films compared to planar STO thin films and any other form of STO such as single crystal samples and nanostructures was demonstrated. The high performance resulted from very large surface area films and optimization of carrier concentration.