Synthesis of Few-Layer GaSe Nanosheets for High Performance Photodetectors

Two-dimensional (2D) semiconductor nanomaterials hold great promises for future electronics and optics. In this paper, a 2D nanosheets of ultrathin GaSe has been prepared by using mechanical cleavage and solvent exfoliation method. Single- and few-layer GaSe nanosheets are exfoliated on an SiO₂/Si substrate and characterized by atomic force microscopy and Raman spectroscopy. Ultrathin GaSe-based photodetector shows a fast response of 0.02 s, high responsivity of 2.8 AW^–1 and high external quantum efficiency of 1367% at 254 nm, indicating that the two-dimensional nanostructure of GaSe is a new promising material for high performance photodetectors

Controllable Synthesis of Two-Dimensional Ruddlesden–Popper-Type Perovskite Heterostructures

Two-dimensional Ruddlesden–Popper type perovskites (2D perovskites) have recently attracted increasing attention. It is expected that 2D perovskite-based heterostructures can significantly improve the efficiency of the optoelectronic devices and extend the material functionalities; however, rational synthesis of such heterostructures has not been realized to date. We report on a general low-temperature synthetic strategy for the synthesis of 2D perovskite-based lateral and vertical (<i>n</i>-CH₃(CH₂)₃NH₃)₂PbI₄/(<i>n</i>-CH₃(CH₂)₃NH₃)₂(CH₃NH₃)­Pb₂I₇ heterostructures for the first time. A combination of solution synthesis and gas–solid phase intercalation approach allows us to efficiently synthesize both lateral and vertical heterostructures with great flexibility. X-ray diffraction, photoluminescence, and photoluminescence excitation mapping and electrical transport measurement studies reveal the successful synthesis of lateral and vertical heterostructures with precisely spatial-modulation control and distinguishable interfaces. Our studies not only provide an efficient synthetic strategy with great flexibility, enabling us to create 2D perovskite-based heterostructures, but also offer a platform to investigate the physical processes in those heterostructures

Near Full-Composition-Range High-Quality GaAs_1–<i>x</i>Sb_<i>x</i> Nanowires Grown by Molecular-Beam Epitaxy

Here we report on the Ga self-catalyzed growth of near full-composition-range energy-gap-tunable GaAs_1–<i>x</i>Sb_<i>x</i> nanowires by molecular-beam epitaxy. GaAs_1–<i>x</i>Sb_<i>x</i> nanowires with different Sb content are systematically grown by tuning the Sb and As fluxes, and the As background. We find that GaAs_1–<i>x</i>Sb_<i>x</i> nanowires with low Sb content can be grown directly on Si(111) substrates (0 ≤ <i>x</i> ≤ 0.60) and GaAs nanowire stems (0 ≤ <i>x</i> ≤ 0.50) by tuning the Sb and As fluxes. To obtain GaAs_1–<i>x</i>Sb_<i>x</i> nanowires with <i>x</i> ranging from 0.60 to 0.93, we grow the GaAs_1–<i>x</i>Sb_<i>x</i> nanowires on GaAs nanowire stems by tuning the As background. Photoluminescence measurements confirm that the emission wavelength of the GaAs_1–<i>x</i>Sb_<i>x</i> nanowires is tunable from 844 nm (GaAs) to 1760 nm (GaAs_0.07Sb_0.93). High-resolution transmission electron microscopy images show that the grown GaAs_1–<i>x</i>Sb_<i>x</i> nanowires have pure zinc-blende crystal structure. Room-temperature Raman spectra reveal a redshift of the optical phonons in the GaAs_1–<i>x</i>Sb_<i>x</i> nanowires with <i>x</i> increasing from 0 to 0.93. Field-effect transistors based on individual GaAs_1–<i>x</i>Sb_<i>x</i> nanowires are fabricated, and rectifying behavior is observed in devices with low Sb content, which disappears in devices with high Sb content. The successful growth of high-quality GaAs_1–<i>x</i>Sb_<i>x</i> nanowires with near full-range bandgap tuning may speed up the development of high-performance nanowire devices based on such ternaries