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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. [ABSTRACT FROM AUTHOR]

Recently, ferroelectric polarization coupling has been exploited for non-volatile p- and n-type doping of two-dimensional (2D) materials, which enables the design of 2D functional devices via a local polarization pattern. Here, we took advantage of this tool and study the effect of base width to the gain and photodetection performance of bipolar transistors made of few layer MoS2. We found that the space charge region in the base have typical width ∼150–250 nm, and depends on the applied external bias. Such a characteristic causes the compromise between transistor gain and shunt resistance when changing the base width. For photodetection, this hinders the optimization of responsivity without increasing the dark current. As a result, an optimal device was made at the base width ∼1040 nm, from which a responsivity of 160 A W−1, specific detectivity of ∼1.3 × 1012 and the response time ∼9 μs to 680 nm incident light was obtained. The results from the present study shed light on the further design of 2D functional devices that use lateral pn junctions as the basic building blocks. [ABSTRACT FROM AUTHOR]

We report the fabrication of high performance MoTe2/Si heterojunction photodiodes by direct growth of MoTe2 patterns on a commercial Si substrate by a feasible chemical vapor deposition method. The devices exhibit an ultrafast response speed with a rise/fall time of 5/8 μs, a broadband (400–1550 nm) photoresponse, a high on/off ratio of ∼104, and self-powered photo-detection with a zero bias responsivity of 0.26 A W−1 and a detectivity of 2 × 1013 Jones at 700 nm wavelength. The devices further show high stability in air for one month. This investigation offers the feasibility to fabricate high performance MoTe2/Si photodiodes for future vital optoelectronic applications. [ABSTRACT FROM AUTHOR]

The crystalline structure of Zn2 (OH)PO4 (ZPOH) belongs to orthorhombic unit cell structure, space group of P21212, which has no center of symmetry. Based on the plane-wave pseudopotential ab initio method, the electronic structure, linear refractive indices and second harmonic generation (SHG) coefficients of Zn2 (OH) PO4 were calculated and the Sellmeier equations were also fitted. To verify the calculated values, ZPOH was synthesized using hydrothermal method, and the measured SHG effect is in accordance with the theoretical calculation. The ultraviolet (UV) cut-off edge and thermal stability of ZPOH were also reported for the first time. [ABSTRACT FROM AUTHOR]