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Growing high-quality core-shell heterostructure nanowires is still challenging due to the lattice mismatch issue at the radial interface. Herein, a versatile strategy is exploited for the lattice-mismatch-free construction of III-V/chalcogenide core-shell heterostructure nanowires by simply utilizing the surfactant and amorphous natures of chalcogenide semiconductors. Specifically, a variety of III-V/chalcogenide core-shell heterostructure nanowires are successfully constructed with controlled shell thicknesses, compositions, and smooth surfaces. Due to the conformal properties of obtained heterostructure nanowires, the wavelength-dependent bi-directional photoresponse and visible light-assisted infrared photodetection are realized in the type-I GaSb/GeS core-shell heterostructure nanowires. Also, the enhanced infrared photodetection is found in the type-II InGaAs/GeS core-shell heterostructure nanowires compared with the pristine InGaAs nanowires, in which both responsivity and detectivity are improved by more than 2 orders of magnitude. Evidently, this work paves the way for the lattice-mismatch-free construction of core-shell heterostructure nanowires by chemical vapor deposition for next-generation high-performance nanowire optoelectronics. A versatility growth strategy is developed for the lattice-mismatch-free construction of core-shell heterostructure NWs by adopting the promising III-V semiconductors and amorphous chalcogenide semiconductors using simple chemical vapor deposition. [ABSTRACT FROM AUTHOR]

Controllable self‐catalyzed growth of semiconductor nanowires (NWs) is of great importance, particularly to avoid impurities coming from foreign catalysts to deteriorate the NW properties. Although this catalyst‐free NW growth has many obvious advantages, there are very limited works focused on all‐inorganic CsPbBr3 perovskite NWs, which is one of the recent champion materials for electronics and optoelectronics. Here, a direct self‐catalyzed synthesis of freestanding CsPbBr3 NWs via vapor–liquid–solid growth mechanism by chemical vapor deposition is developed. Notably, mainipulation of the substrate surface roughness is the key enabling parameter for the self‐catalyzed NW growth here. It is revealed that the surface energy of substrates, modulated by its surface roughness, is found to effectively mediate the self‐catalytic growth of CsPbBr3 NWs. When configured into photodetectors, the intrinsic p‐type CsPbBr3 NWs exhibit good optoelectronic performance with a photoresponivity of ≈2000 A W−1, a detectivity of ≈2.57 × 1012 Jones, and a fast response down to 362 µs. All these results evidently indicate the technological potential of this self‐catalyzed synthesizing route for other high‐quality all‐inorganic perovskite NWs. [ABSTRACT FROM AUTHOR]

Due to their excellent properties, ternary GaAsxSb1−x nanowires have been extensively investigated to enable various nanodevice structures. However, the surfactant effect of antimony has a notorious impact on the surface morphology and electrical properties of prepared Sb‐rich nanowires, restricting their practical utilization. Herein, through the in situ passivation effect of thiourea, highly‐crystalline, uniform, and thin GaAsxSb1−x nanowires (x ≤ 0.34) are successfully achieved. In contrast to low‐melting‐point sulfur powders typically used in surfactant‐assisted chemical vapor deposition, thiourea has a relatively higher melting point, facilitating the more controllable formation of SbxSy layer on the nanowire surface to minimize the radial growth and to stabilize the sidewalls for high‐quality Sb‐rich nanowires. When configured into field‐effect transistors, the obtained GaSb nanowires exhibit excellent device performance with a hole mobility of over 200 cm2 V−1 s−1. The optimal GaAs0.18Sb0.82 device yields an impressive responsivity of 5.4 × 104 A W−1 and an external quantum efficiency of 4.4 × 106% under near‐infrared light illumination. Importantly, the rise and decay times are as efficient as 80 and 104 µs, respectively, which are better than any values reported for GaAsSb nanowire photoconductors to date. All these results demonstrate the promising potential of GaAsxSb1−x nanowires for high‐mobility electronics and ultrafast near‐infrared optoelectronics. [ABSTRACT FROM AUTHOR]

The discovery of graphene has triggered the research on 2D layer structured materials. Among many 2D materials, semiconducting transition metal dichalcogenides (TMDs) are widely considered to be the most promising ones due to their excellent electrical and optoelectronic characteristics. Tungsten disulfide (WS2) is a kind of such TMDs with fascinating properties, such as the high carrier mobility, appropriate band gap, strong light–matter interaction with the large light absorption coefficient, very large exciton binding energy, large spin splitting, and polarized light emission. All these interesting properties can make the 2D WS2 being highly favorable for applications in memristors, light‐emitting devices, optical modulators, and many others. Here, the comprehensive review on the properties, vapor phase synthesis, electronic and optoelectronic applications of 2D WS2 is presented. This review does not only serve as a design guideline to elevate the material quality of 2D WS2 films via enhanced synthesis approaches, but also provides valuable insights to various strategies to improve their device performances. With the fast development of wafer‐scale synthesis methods and novel device structures, 2D WS2 can undoubtedly be a rising star for the next‐generation devices in the near future. [ABSTRACT FROM AUTHOR]

High‐performance flexible room‐temperature near‐infrared (NIR) photodetectors are one of the important components for image sensing, data communication, environmental monitoring, and bioimaging applications. However, there is still a lack of suitable device channel materials to provide high sensitivity as well as good mechanical flexibility for photodetection, particularly operating at the optical communication wavelength of 1550 nm. In this work, highly crystalline In0.28Ga0.72Sb nanowires (NWs) are successfully grown by the two‐step chemical vapor deposition method and assembled into high‐density regular NW parallel arrays on polyimide substrates. When they are constructed into photodetectors without using any p–n junctions, they exhibit the excellent responsivity up to 1520 A W−1 and ultra‐fast response speed below 20 µs toward 1550 nm irradiation at room temperature, which constitutes a record high performance among all flexible NIR photodetectors reported in recent literature. Notably, these flexible NW parallel‐array photodetectors also display a superior mechanical flexibility and operation durability. They not only provide a stable photoresponse under illumination on–off cycles up to 1000 s, but also maintain the steady photocurrent without any significant degradation after 700 bending cycles. All these results evidently indicate the promising potential of these crystalline In0.28Ga0.72Sb NW parallel arrays for next‐generation flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

Recently, owing to the excellent electrical and optical properties, n-type In2O3 nanowires (NWs) have attracted tremendous attention for application in memory devices, solar cells, and ultra-violet photodetectors. However, the relatively low electron mobility of In2O3 NWs grown by chemical vapor deposition (CVD) has limited their further utilization. In this study, utilizing in-situ Ga alloying, highly crystalline, uniform, and thin In2xGa2−2xO3 NWs with diameters down to 30 nm were successfully prepared via ambient-pressure CVD. Introducing an optimal amount of Ga (10 at.%) into the In2O3 lattice was found to effectively enhance the crystal quality and reduce the number of oxygen vacancies in the NWs. A further increase in the Ga concentration adversely induced the formation of a resistive β-Ga2O3 phase, thereby deteriorating the electrical properties of the NWs. Importantly, when configured into global back-gated NW field-effect transistors, the optimized In1.8Ga0.2O3 NWs exhibit significantly enhanced electron mobility reaching up to 750 cm2·V-1·s-1 as compared with that of the pure In2O3 NW, which can be attributed to the reduction in the number of oxygen vacancies and ionized impurity scattering centers. Highly ordered NW parallel arrayed devices were also fabricated to demonstrate the versatility and potency of these NWs for next-generation, large-scale, and high-performance nanoelectronics, sensors, etc. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) nanomaterials have recently attracted considerable attention due to their promising applications in next-generation electronics and optoelectronics. In particular, the large-scale synthesis of high-quality 2D materials is an essential requirement for their practical applications. Herein, we demonstrate the wafer-scale synthesis of highly crystalline and homogeneous monolayer WS2 by an enhanced chemical vapor deposition (CVD) approach, in which precise control of the precursor vapor pressure can be effectively achieved in a multi-temperature zone horizontal furnace. In contrast to conventional synthesis methods, the obtained monolayer WS2 has excellent uniformity both in terms of crystallinity and morphology across the entire substrate wafer grown (e.g., 2 inches in diameter), as corroborated by the detailed characterization. When incorporated in typical rigid photodetectors, the monolayer WS2 leads to a respectable photodetection performance, with a responsivity of 0.52 mA/W, a detectivity of 4.9 × 109 Jones, and a fast response speed (< 560 μs). Moreover, once fabricated as flexible photodetectors on polyimide, the monolayer WS2 leads to a responsivity of up to 5 mA/W. Importantly, the photocurrent maintains 89% of its initial value even after 3,000 bending cycles. These results highlight the versatility of the present technique, which allows its applications in larger substrates, as well as the excellent mechanical flexibility and robustness of the CVD-grown, homogenous WS2 monolayers, which can promote the development of advanced flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

The morphologies and microstructures of kinked InP nanowires (NWs) prepared by solid-source chemical vapor deposition method were examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Statistical analysis and structural characterization reveal that four different kinds of kinks are dominant in the grown InP NWs with a bending angle of approximately 70°, 90°, 110°, and 170°, respectively. The formation mechanisms of these kinks are discussed. Specifically, the existence of kinks with bending angles of approximately 70° and 110° are mainly attributed to the occurrence of stacking faults and nanotwins in the NWs, which could easily form by the glide of {111} planes, while approximately 90° kinks result from the local amorphorization of InP NWs. Also, approximately 170° kinks are mainly caused by small-angle boundaries, where the insertion of extra atomic planes could make the NWs slightly bent. In addition, multiple kinks with various angles are also observed. Importantly, all these results are beneficial to understand the formation mechanisms of kinks in compound semiconductor NWs, which could guide the design of nanostructured materials, morphologies, microstructures, and/or enhanced mechanical properties. PACS: 81.07.-b; 81.05.Ea; 81.07.Gf [ABSTRACT FROM AUTHOR]

III-V semiconductor nanowire (NW) materials possess a combination of fascinating properties, including their tunable direct bandgap, high carrier mobility, excellent mechanical flexibility, and extraordinarily large surface-to-volume ratio, making them superior candidates for next generation electronics, photonics, and sensors, even possibly on flexible substrates. Understanding the synthesis, property manipulation, and device integration of these III-V NW materials is therefore crucial for their practical implementations. In this review, we present a comprehensive overview of the recent development in III-V NWs with the focus on their cost-effective synthesis, corresponding property control, and the relevant low-operating-power device applications. We will first introduce the synthesismethods and growthmechanisms of III-VNWs, emphasizing the low-cost solid-source chemical vapor deposition (SSCVD) technique, and then discuss the physical properties of III-V NWs with special attention on their dependences on several typical factors including the choice of catalysts, NW diameters, surface roughness, and surface decorations. After that, we present several different examples in the area of high-performance photovoltaics and low-power electronic circuit prototypes to further demonstrate the potential applications of theseNWmaterials. Towards the end, we alsomake some remarks on the progress made and challenges remaining in the III-V NWresearch field. [ABSTRACT FROM AUTHOR]

In this work, we present a study of the surface roughness dependent electron mobility in InAs nanowires grown by the nickel-catalyzed chemical vapor deposition method. These nanowires have good crystallinity, well-controlled surface morphology without any surface coating or tapering and an excellent peak field-effect mobility up to 15 000 cm² V-1 s-1 when configured into back-gated field-effect nanowire transistors. Detailed electrical characterizations reveal that the electron mobility degrades monotonically with increasing surface roughness and diameter scaling, while low-temperature measurements further decouple the effects of surface/interface traps and phonon scattering, highlighting the dominant impact of surface roughness scattering on the electron mobility for miniaturized and surface disordered nanowires. All these factors suggest that careful consideration of nanowire geometries and surface condition is required for designing devices with optimal performance. [ABSTRACT FROM AUTHOR]

To date, wafer‐scale synthesis of two‐dimensional (2D) materials are well achieved by chemical vapor deposition, but the obtained monolayers typically have multidomains with electrical and optoelectronic properties affected by grain boundaries and domain sizes. When these 2D materials are used as the growth templates, these boundaries would also provide unknown influences to the successive heterostructure formation for extended applications. Here, for the first time, direct visualization of grain boundaries in monolayer WS2 film can be realized by the growth of CdS nanoparticles. Specifically, CdS is found to first preferentially nucleate and form as nanoparticle chains along WS2 grain boundaries in a random manner, independent of the grain boundary characteristics. Due to electron scattering and type II band alignment at the WS2–CdS heterojunction, WS2 reduces in its mobility while becoming enhanced in its electron concentration. Notably, the WS2–CdS heterostructure also yields improved carrier separation and collection for the photodetection performance enhancement. All these results can facilitate the detailed evaluation of crystalline grains‐related information of 2D materials and provide thorough understanding on the effect of these overgrown CdS on underlying WS2 monolayers, being extremely important to further optimize and enable their functionalities for advanced device applications. Grain boundaries in chemical vapor deposited monolayer WS2 induce the growth of CdS nanoparticle chains there, making the grain boundaries visible. This overgrowth of CdS nanoparticles at the WS2 grain boundaries then leads to the formation of a type II heterojunction, which can reduce the carrier mobility while enhancing the photodetection performance of WS2. [ABSTRACT FROM AUTHOR]

Single GaAs nanowire photovoltaic devices were fabricated utilizing rectifying junctions in the Au-Ga catalytic tip/nanowire contact interface. Current-voltage measurements were performed under simulated Air Mass 1.5 global illumination with the best performance delivering an overall energy conversion efficiency of ∼2.8% for a nanowire of 70 nm in diameter. As compared with metal contacts directly deposited on top of the nanowire, this nanoscale contact is found to alleviate the well-known Fermi-level pinning to achieve effective formation of Schottky barrier responsible for the superior photovoltaic response. All these illustrate the potency of these versatile nanoscale contact configurations for future technological device applications. [ABSTRACT FROM AUTHOR]