AlGaN-based solar-blind ultraviolet photodetectors have attractive potential applications in the fields of missile plume detection, biochemical sensing, solar astronomy, etc. In this work, significant deep ultraviolet detection enhancement is demonstrated on AlGaN-based metal–semiconductor–metal (MSM) solar-blind ultraviolet photodetectors by introducing the coupling of localized surface plasmon from Al nanoparticles with the high-Al-content AlGaN epilayer. The size-controlled Al nanoparticle arrays fabricated by nanosphere lithography can not only reduce the detectors' dark current but also bring about greatly enhanced responsivity. The peak responsivity of AlGaN-based MSM solar-blind ultraviolet photodetectors with Al nanoparticles can reach 2.34 A/W at 269 nm under 20 V bias, enhanced more than 25 times than that without Al nanoparticles. Our approach shows an efficient fabrication technique of high-performance and low-cost plasmonic enhanced AlGaN solar-blind MSM ultraviolet photodetectors.
Phase engineering of two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoTe2 offers tremendous opportunities in various device applications. However, most of the existing methods so far only address the small-area local phase change or the growth of certain kinds of phases of MoTe2 film by laser irradiation, mechanical strain, or procursor type. Obtaining facile, tunable, reversible, and continuous-phase transition and evolution between different phases in direct growth of large-area, few-layer MoTe2 still remains challenging. Here, we develop a facile method to achieve phase control and transition and report a highly tunable, tellurization velocity-dependent metallic–semiconducting–metallic phase evolution in chemical vapor deposition (CVD) growth of large-area, few-layer MoTe2. We found four different phase stages, including two different types of coexistence phases of both 2H and 1 T′ phases, 100% 2H phase, and 100% 1T′ phase, would emerge, relying on the adopted tellurization velocity. Importantly, the tellurization velocity should be extremely controlled to obtain 100% 2H phase MoTe2, while 100% 1T′ phase requires a fast tellurization velocity. We further found that such metallic–semiconducting–metallic phase evolution took place with a homogeneous spatial distribution and differs from previous reports in which obvious phase separations are usually found during the phase transition. The resulting MoTe2 shows high quality with room-temperature mobility comparable with mechanically exfoliated materials. The results might impact large-scale phase engineering of TMDs and other 2D materials for Weyl semimetal topological physics and potential 2D semiconductor device applications.
Abstract To reduce the amount of energy consumed in integrated circuits, high efficiency with the lowest energy is always expected. Self‐drive device is one of the options in the pursuit of low power nanodevices. It is a typical strategy to form an internal electric field by constructing a heterojunction in self‐drive semiconductor system. Here, a two‐step method is proposed to prepare high quality centimeter‐sized 2D tellurium (Te) thin film with hall mobility as high as 37.3 cm 2 V −1 s −1 , and the 2D Te film is further assembled with silicon to form a heterojunction for self‐drive photodetector, which can realize effective detection from visible to near infrared bands. The photodetectivity of the heterojunctions can reach 1.58×10 11 Jones under the illumination of 400 nm@ 1.615 mW/cm 2 and 2.08×10 8 Jones under the illumination of 1550 nm@ 1.511 mW/cm 2 without bias. Our experiments demonstrate the potential of 2D tellurium thin films for wide band and near infrared integrated device applications.
The elastic constants of α-ScH x (x=0, 1/4, 1/8, 1/32) and α-ScHe x (x=0, 1/4, 1/8, 1/32) are studied by the first-principles method. It is found that the addition of hydrogen to the scandium has an effect greatly different from the addition of helium to this rare-earth metal. The elastic constants of the α-ScH x system almost increase with hydrogen concentration increasing, which is in agreement with the experimental observation. Whereas, in the case of α-ScHe x system, the elastic constants almost decrease with the increase of helium concentration.
Possible equilibrium geometries of WnC0,±(n=1,…,6)clusters are optimized with density functional theory at B3LYP/LANL2DZ level.Stability and electronic properties of ground state structures are analyzed.It shows that as n3 cluster undergoes a transition from a two-dimensional structure to a three-dimensional structure,and carbon atom remains on the surface of cluster.Stability of Wn cluster is increased with doped carbon atom.Moreover W3C is the most stable one among WnC0,±(n=1,…,6)clusters,and it is taken as a basic structure.Electronic properties of WnC0,±(n=1,…,6)clusters are characterized by analyzing energy gaps,vertical electron affinities(VEA) and vertical ionization potentials(VIP) of WnC with pure Wnclusters.WnC clusters get electron easily and shows higher nonmetallicity than Wn clusters.
We demonstrated a feasible strategy to fabricate MoTe2/Ge heterojunction by direct growth of Ge flake on a MoTe2 film substrate with a two-step chemical vapor deposition method. A thin transition layer (∼4 nm) mainly composed of polycrystalline germanium at the MoTe2/Ge interface was verified during the Ge flake growth. The MoTe2/Ge heterojunction-based photodetector exhibits both the response speed with a rise/fall time of 7/4 μs and the photoresponsivity and detectivity with 4.87 A W−1 and 5.02 × 1011 Jones under zero bias in the near-infrared regime, respectively. The characteristics of device performance imply its practical applicability as building block for potential near-infrared integrated photonics.
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