Visible-NIR Photodetectors Based on Low-Dimensional GeSe Micro-Crystals: Designed Morphology and Improved Photoresponsivity

GeSe micro-sheets and micro-belts have been synthesized by a facile one-pot wet chemical method in 1-octadecene solvent and oleic acid solvent, respectively. The adsorption of more oleic acid molecules on the (002) plane promoted growth along [010] direction of the GeSe micro-belts and limited carrier transport in this direction, resulting in higher carrier concentration and mobility of the GeSe micro-belts. The performance of the photodetectors based on the single GeSe micro-sheet and the single GeSe micro-belt was investigated under illumination at 532 nm, 980 nm and 1319 nm. Both, photodetectors based on a single GeSe micro-sheet and a single GeSe micro-belt, exhibit a high photoresponse, short response/recovery times, and long-term durability. Moreover, the photodetector based on a single GeSe micro-belt displays a broadband response with a high responsivity (5562 A/W at 532 nm, 1546 A/W at 980 nm) and detectivity (3.01×10¹² Jones at 532 nm, 8.38×10¹¹ Jones at 980 nm). These excellent characteristics render single GeSe micro-belts very interesting for use as highly efficient photodetectors, especially in the NIR region.     

Pulsed Laser Deposition of Photoresponsive Two‐Dimensional GaSe Nanosheet Networks

Synthesis of functional metal chalcogenide (GaSe) nanosheet networks by stoichiometric transfer of laser‐vaporized material from bulk GaSe targets is presented. Uniform coverage of interconnected, crystalline, and photoresponsive GaSe nanosheets in both in‐plane and out‐of‐plane orientations are achieved under different ablation conditions. The propagation of the laser‐vaporized material is characterized by in situ ICCD‐imaging. High (1 Torr) Ar background gas pressure is found to be crucial for the stoichiometric growth of GaSe nanosheet networks. Individual 1–3 layer GaSe triangular nanosheets of ≈200 nm domain size are formed within 30 laser pulses, coalescing to form nanosheet networks in as few as 100 laser pulses. The thickness of the deposited networks increases linearly with pulse number, adding layers in a two‐dimensional (2D) growth mode. GaSe nanosheet networks show p‐type semiconducting characteristics with mobilities reaching as high as 0.1 cm²V^?1s^?1. Spectrally‐resolved photoresponsivities and external quantum efficiencies range from 0.4 AW^?1 and 100% at 700 nm, to 1.4 AW^?1 and 600% at 240 nm, respectively. Pulsed laser deposition under these conditions appears to provide a versatile and rapid approach to stoichiometrically transfer and deposit functional networks of 2D nanosheets with digital thickness control and uniformity for a variety of applications.     

Strong Interlayer Transition in Few-Layer InSe/PdSe2 van der Waals Heterostructure for Near-Infrared Photodetection

Near infrared (NIR) photodetectors based on 2D materials are widely studied for their potential application in next generation sensing, thermal imaging, and optical communication. Construction of van der Waals (vdWs) heterostructure provides a tremendous degree of freedom to combine and extend the features of 2D materials, opening up new functionalities on photonic and optoelectronic devices. Herein, a type-II InSe/PdSe₂ vdWs heterostructure with strong interlayer transition for NIR photodetection is demonstrated. Strong interlayer transition between InSe and PdSe₂ is predicted via density functional theory calculation and confirmed by photoluminance spectroscopy and Kelvin probe force microscopy. The heterostructure exhibits highly sensitive photodetection in NIR region up to 1650 nm. The photoresponsivity, detectivity, and external quantum efficiency at this wavelength respectively reaches up to 58.8 A W⁻¹, 1 × 10¹⁰ Jones, and 4660%. The results suggest that the construction of vdWs heterostructure with strong interlayer transition is a promising strategy for infrared photodetection, and this work paves the way to developing high-performance optoelectronic devices based on 2D vdWs heterostructures.     

MoS2/HfO2/Silicon‐On‐Insulator Dual‐Photogating Transistor with Ambipolar Photoresponsivity for High‐Resolution Light Wavelength Detection

Photogating detectors based on 2D materials attract significant research interests. However, most of these photodetectors are only sensitive to the incident intensities and lack the ability to distinguish different wavelengths. Color imaging based on these detectors usually requires additional optical filter arrays to collect red, green, and blue (RGB) colors in different photodetectors to restore the true color of one pixel. In this study, an MoS₂/HfO₂/silicon‐on‐insulator field effect phototransistor with wavelength distinguishing ability is presented, where the photogating effect can be simultaneously formed in the top MoS₂ gate and bottom Si substrate gate. These two individual photogating effects can reduce and increase the read current in the middle 12 nm Si channel, respectively. Thus, by tuning the applied voltages on these two gates, the device can be used to obtain tunable ambipolar photoresponsivity from +7000 A W^?1 (Si bottom gate dominated) to 0 A W^?1 (balanced), and finally to ?8000 A W^?1 (MoS₂ gate dominated). In addition, the experimental results show that the corresponding top gate voltage to the zero responsivity (0 A W^?1) point can be positively shifted by the increasing of incident wavelength with high resolution up to 2 nm and is insensitive to the incident intensity.     

ZnO纳米颗粒的紫外光探测器制备及其特性

为了发展高性能、低成本和结构简单的ZnO紫外 光探测器。在本文中,利用溶液法,制备出ZnO 纳米颗粒,采用透射电子显微镜(TEM)、X射线衍射仪(XRD)、紫外-可见分光光度计和荧光 光谱仪,分别 研究了ZnO纳米颗粒的形貌、晶相结构和光学特性。结果显示:样品呈球形状的颗粒,尺寸 分布在6~8.5nm 之间,平均粒径为7.1nm,为六方纤锌矿结构。发现ZnO纳米颗 粒的陡峭吸收边出现在370nm附近,在390nm 处出现一个很强的近带边发射峰和一宽泛的可见光发光带。此外,利用制备的ZnO纳米颗粒 ,旋涂在刻蚀 有叉指电极的FTO(SnO₂:F)上,制备出紫外光探测器,测试了它在暗态和365 nm紫外光照下的电流-电压(I-V) 和电流-时间(I-t)特性。结果表明:紫外光探测器的灵敏度、光响应度、响 应时间、恢复时间分别为62.4(在 －3.5V处),13.6A/W(在+5V处), 15s。另外,它的光响应机理主要由于ZnO纳米 颗粒表面吸附的氧起主导作用。     

ZnO光电导紫外探测器的制备和特性研究

以Si(111)衬底,用脉冲激光沉积(PLD)法制得C轴高度择优取向的ZnO薄膜,并利用剥离技术制备了ZnO光导型紫外探测器.Al叉指状电极是由平面磁控溅射技术沉积得到的.对Al/ZnO/Al的伏安特性和紫外光响应的研究表明,金属铝和ZnO能形成很好的欧姆接触,紫外探测器的电阻值在100KΩ左右.在紫外区域,其5V偏压下的光响应度为0.5A/W.     

二硫化锡薄膜场效应晶体管的可见光探测特性

采用化学气相输运(CVT)法和微机械剥离技术制备了SnS₂薄膜,使用Au电极作为源、漏电极,n型重掺杂Si作为栅极,制备了基于SnS₂薄膜的背栅型场效应晶体管(FET),并研究了其电学特性和可见光探测特性。结果表明,制备的SnS₂薄膜具有良好的结晶度,SnS₂薄膜背栅型FET具备良好的栅压调控特性。器件对波长为405 nm的蓝紫光表现出明显的光响应,光响应度高达456.82 A·W^-1,外量子效率为1.40×10⁵%,比探测率为7.12×10¹²Jones,并且具有较快的光响应速度,上升和下降响应时间分别为1 ms和0.5 ms。器件的光探测性能受栅压调控,当栅压为40 V时,器件的光响应度可达730 A·W^-1。     

基于酞菁铜的有机光敏场效应管

制备了基于酞菁铜(CuPc)的有机光敏场效应晶体管,对器件的光敏特性进行了研究。实验结果表明,基于金源漏电极的器件,在波长655 nm,光强100 mW/cm²的光照下,明/暗电流比约为0.4,光响应度约为2.55 mA/W;而铝为源漏电极的器件,可以获得高达10⁴的明/暗电流比,但光响应度降低为0.39 mA/W。     

Photoconductive UV Detectors Based on ZnO Films Prepared by Sol-Gel Method

Highly c-axis oriented ZnO thin films were deposited on single crystal Si (111) substrates by sol-gel method. The photoconductive UV detectors based on ZnO thin films, being a metal-semiconductor-metal (MSM) structure with interdigital (IDT) configuration, were fabricated by using Au as contact metal. The characteristics of dark and photocurrent of the UV detector, the UV photoresponse of the detector were investigated. The linear current-voltage (I-V) characteristics under both forward and reverse bias exhibit ohmic metal-semiconductor contacts. Under illumination using monochromatic light with a wavelength of 365 nm, photo-generated current arrived at 44.89 μ A at a bias of 6 V. The detector exhibits an evident wide-range spectral responsivity and shows a trend similar to that in photoluminescence (PL) spectrum. PL spectrum of detector exhibits two peaks, one is the near band edge emission, and another is the deep-level emission in the visible region.