Ag-catalyzed GaSb nanowires for flexible near-infrared photodetectors

High-quality narrow bandgap semiconductors nanowires(NWs)challenge the flexible near-infrared(NIR)photodetectors in next-generation imaging,data communication,environmental monitoring,and bioimaging applications.In this work,complementary metal oxide semiconductor-compatible metal of Ag is deposited on glass as the growth catalyst for the surfactantassisted chemical vapor deposition of GaSb NWs.The uniform morphology,balance stoichiometry,high-quality crystallinity,and phase purity of as-prepared NWs are checked by scanning electron microscopy,energy dispersive X-ray spectroscopy,high-resolution transmission electron microscopy,and X-ray diffraction.The electrical properties of as-prepared NWs are studied by constructing back-gated field-effect-transistors,displaying a high I_(on)/I_(off) ratio of 10^(4) and high peak hole mobility of 400 cm^(2)/(V·s).Benefiting from the excellent electrical and mechanical flexibility properties,the as-fabricated NW flexible NIR photodetector exhibits high sensitivity and excellent photoresponse,with responsivity as high as 618 A/W and detectivity as high as 6.7×10^(10) Jones.Furthermore,there is no obvious decline in NIR photodetection behavior,even after parallel and perpendicular folding with 1200 cycles.

Ar Pressure Dependence of the Properties of Molybdenum-doped ZnO Films Grown by RF Magnetron Sputtering

Transparent conducting oxide film of molybdenum-doped zinc oxide （MZO） with high transparency and relatively low resistivity was prepared by RF （radio frequency） magnetron sputtering at room temperature. The structural, electrical, and optical properties of the films deposited under different Ar pressure were investigated.XRD （X-ray diffraction） patterns show that the nature of the films is polycrystalline with a hexagonal structure and a preferred orientation along the c-axis. The resistivity increases as Ar pressure increases. The lowest range exceeds 88% for all the samples. The optical band gap decreases from 3.27 to 3.15 eV with increasing Ar pressure from 0.6 to 3.0 Pa.

Effects of Substrate Temperature on the Properties of Mo-doped ZnO Films Prepared by RF Magnetron Sputtering

Transparent conducting molybdenum-doped zinc oxide （MZO） films were successfully prepared by radio frequency （RF） magnetron sputtering method on glass substrates under different substrate temperatures. The nature of MZO film is polycrystalline with hexagonal structure and a preferred orientation along c-axis. With increasing substrate temperature from room temperature to 400℃, the crystallinity of the films is deteriorated and the resistivity increases sharply due to both the decrease of carrier concentration and Hall mobility. The lowest resistivity achieved is 9.2×10^-4 Ω· cm with a high Hall mobility of 30 cm^2·V^-1·s^-1 for the film deposited at room temperature. The average transmttance in the visible range exceeds 85% for all the samples. The optical band gap decreases from 3.30 to 3.25 eV with substrate temperature from room temperature to 400℃.

Stoichiometric effect on electrical and near-infrared photodetection properties of full-composition-range GaAs1−xSbx nanowires

As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the whole near-infrared (NIR) region, for technological applications in next-generation high-performance electronics and NIR photodetection. However, it is still a challenge to the synthesis of high-quality GaAs1−xSbx NWs across the entire range of composition, resulting in the lack of correlation investigation among stoichiometry, microstructure, electronics, and NIR photodetection. Here, we demonstrate the success growth of high-quality GaAs1−xSbx NWs with full composition range by adopting a simple and low-cost surfactant-assisted solid source chemical vapor deposition method. All of the as-prepared NWs are uniform, smooth, and straight, without any phase segregation in all stoichiometric compositions. The lattice constants of each NW composition have been well correlated with the chemical stoichiometry and confirmed by high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectrum. Moreover, with the increase of Sb concentration, the hole mobility of the as-fabricated field-effect-transistors and the responsivity and detectivity of the as-fabricated NIR photodetectors increase accordingly. All the results suggest a careful stoichiometric design is required for achieving optimal NW device performances.

Annealing Effect on Transport and Magnetic Properties of La_(0.67)Sr_(0.33)MnO_3 Thin Films Grown on Glass Substrates by RF Magnetron Sputtering

The manganite La0.67Sr0.33MnO3 （LSMO） thin films were grown on glass substrates in a mixed argon and oxygen atmosphere by using RF magnetron sputtering. The structural characteristics, transport behaviors and magnetic properties of LSMO films were studied by annealing the films in air at 550 and 620℃. The out-of-plane lattice parameter αLSMO contracted after annealing and was close to that of bulk LSMO abulk, indicating that the internal strain was fully relaxed. Nanocrystalline grains were observed in the annealed films. Enhanced saturation magnetization and metal-to-insulator transition temperature （TMI=268 K） were also obtained. Curie temperatures （Tc） of the as-grown films was 340 K with the same as that of annealed at 550℃, but dropped to 315 K when the annealing temperature increased to 620℃, which can be attributed to the oxygen release during annealing in atmosphere.

Immensely enhanced color-adjustable upconversion fluorescence in electron donor-acceptor exciplex chromophores doped with fluorescent emitters

Two-photon excited fluorescence materials usually suffer from inefficient two-photon absorption(TPA) and nonradiative excited states. Here, upconversion fluorescence in an electron donor-acceptor(DA) exciplex doped with fluorescent emitters are systematically investigated. It has been found that the undoped DA exciplex exhibits enhancements of ~129% and ~365% in upconversion fluorescence compared to donor-and acceptor-only systems, respectively. Interestingly, photoluminescence quantum yields(PLQYs) up to ~98.65% were measured and immensely enhanced upconversion fluorescence was observed after doping various fluorescent emitters into the DA exciplex. Our results reveal the existence of two-photon excited energy harvesting in a thermally activated delayed fluorescence(TADF) DA exciplex doped with fluorescent emitters, via reverse intersystem crossing followed by rapid F?rster resonance energy transfer. Moreover, the additional gain mechanism related to intermolecular CT interaction that occurs at the TPA stage is found in the TADF DA exciplex system.