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Che Hsuan Cheng, Zidong Li, Aaditya Hambarde, Parag B Deotare
Combining organic and inorganic semiconductors enable us to integrate complementary advantages of each material system into a single hybrid material platform. Here we report a study on the energy transport across a hybrid interface consisting of j-aggregates of organic dye and monolayer molybdenum disulphide (MoS2). The excellent overlap between the photoluminescence spectra of j-aggregates and the absorption of MoS2 B-exciton, enables the material system to be used to study Förster resonance energy transfer (FRET) across the hybrid interface...
October 19, 2018: ACS Applied Materials & Interfaces
Sangyeon Pak, Yuljae Cho, John Hong, Juwon Lee, Sanghyo Lee, Bo Hou, Geon-Hyoung An, Young-Woo Lee, Jae Eun Jang, Hyunsik Im, Stephen M Morris, Jung Inn Sohn, SeungNam Cha, Jong Min Kim
Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2 /PbS QDs phototransistor with consecutive type II junctions...
October 19, 2018: ACS Applied Materials & Interfaces
Louisa Reissig, Simon Dalgleish, Kunio Awaga
Organic photodetectors offer distinct advantages over their inorganic analogues, most notably through optical transparency and flexibility, yet their figures-of-merit still lag behind those of inorganic devices, and optimization strategies generally encounter a trade-off between device responsivity and bandwidth. Here we propose a novel photodetector architecture in which an organic photoactive semiconductor layer (S) is sandwiched between two thick insulating layers (I) that separate the semiconductor from the metallic contacts (M)...
October 18, 2018: Scientific Reports
Marian B Tzolov, Nicholas C Barbi, Christopher T Bowser, Owen Healy
Highly luminescent thin films of zinc tungstate (ZT) have been deposited on top of conventional scintillators (Yttrium Aluminum Perovskite, Yttrium Aluminum Garnet) for electron detection in order to replace the need for a top conducting layer, such as indium tin oxide (ITO) or aluminum, which is non-scintillating and electron absorbing. Such conventional conducting layers serve the single purpose of eliminating electrical charge build-up on the scintillator. The ZT film also eliminates charging, which has been verified by measuring the Duane-Hunt limit and electron emission versus accelerating voltage...
October 2018: Microscopy and Microanalysis
Xuechao Yu, Yangyang Li, Xiaonan Hu, Daliang Zhang, Ye Tao, Zhixiong Liu, Yongmin He, Md Azimul Haque, Zheng Liu, Tom Wu, Qi Jie Wang
The pursuit of optoelectronic devices operating in the mid-infrared regime is driven by both fundamental interests and envisioned applications ranging from imaging, sensing to communications. Despite continued achievements in traditional semiconductors, notorious obstacles such as the complicated growth processes and cryogenic operation preclude the usage of infrared detectors. As an alternative path towards high-performance photodetectors, hybrid semiconductor/graphene structures have been intensively explored...
October 16, 2018: Nature Communications
Ao Huang, Jingze Li, Yuehui Wang, Shuanglong Feng
In this work, PbS quantum dots were for the first time directly deposited on graphene nanowalls substrate by electrochemical atomic layer epitaxy (ECALE) deposition method. The morphology, composition and 3D structure of PbS/graphene were characterized by field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD) and Raman spectrum, respectively. The sensitized three-dimensional graphene electrode with PbS quantum dots had great improvement in the performance of photo-electrochemical (PEC), with photocurrent almost four times that of pure graphene film, which presents its great application potential in the fields of photodetector or solar cell...
January 1, 2019: Journal of Nanoscience and Nanotechnology
Jialu Li, Yuan Zhao, Linlong Tang, Changbin Nie, Jing Wang, Wei Yao
We present an insulator-semiconductor-metal plasmonic hot-electron photodetector based on a grating structure that uses monolayer MoS₂ as a semiconductor. Within the MoS₂ bandgap wavelength, the choice of design can be used to increase the photocurrent via the enhanced electric field of surface plasmons. Beyond the bandgap, hot electrons generated by surface plasmons can contribute to the photocurrent, which overcomes the limitation of the semiconductor's bandgap. Using a finite element method simulation, we determined the optimal geometric configuration for the grating and metal parameters...
January 1, 2019: Journal of Nanoscience and Nanotechnology
Lingke Wang, Junchao Huang, Yifei Duan, Liang Liu, Tang Li
Microwave signals generated by photodetection of the pulse train of an optical frequency comb locked to an ultrastable laser have ultrahigh spectral purity and frequency stability. The amplitude-to-phase noise conversion (APC) that occurs in the photodetection, however, degrades the phase noise of the generated microwave signal over the range from tens of hertz to several kilohertz. Here we demonstrate active APC compensation by precisely tuning the bias voltage applied to a photodetector using the APC coefficient measured by comparing with a reference photodetector...
October 15, 2018: Optics Letters
Liang Li, Penglai Gong, Daopeng Sheng, Shuao Wang, Weike Wang, Xiangde Zhu, Xingqiang Shi, Fakun Wang, Wei Han, Sanjun Yang, Kailang Liu, Huiqiao Li, Tianyou Zhai
Due to the intriguing anisotropic optical and electrical properties, low-symmetry 2D materials are attracting a lot of interest both for fundamental studies and fabricating novel electronic and optoelectronic devices. Identifying new promising low-symmetry 2D materials will be rewarding toward the evolution of nanoelectronics and nano-optoelectronics. In this work, germanium diarsenide (GeAs2 ), a group IV-V semiconductor with novel low-symmetry puckered structure, is introduced as a favorable highly anisotropic 2D material into the rapidly growing 2D family...
October 14, 2018: Advanced Materials
Deniz Umut Yildirim, Amir Ghobadi, Ekmel Ozbay
Strong light-graphene interaction is essential for the integration of graphene to nanophotonic and optoelectronic devices. The plasmonic response of graphene in terahertz and mid-infrared regions enhances this interaction, and other resonance mechanisms can be adopted in near-infrared and visible ranges to achieve perfect light absorption. However, obtaining near-absolute polarization insensitivity with ultra-narrow absorption bandwidth in the visible and near-infrared regimes remains a challenge. In this regard, we numerically propose a graphene perfect absorber, utilizing the excitation of guided-modes of a dielectric slab waveguide by a novel sub-wavelength dielectric grating structure...
October 12, 2018: Scientific Reports
Ying Xie, Fei Liang, Dong Wang, Chumeng Chi, Haohai Yu, Zheshuai Lin, Huaijin Zhang, Yanxue Chen, Jiyang Wang, Yicheng Wu
Photodetection using semiconductors is critical for capture, identification, and processing of optical information. Nowadays, broadband photodetection is limited by the underdeveloped mid-IR photodetection at room temperature (RT), primarily as a result of the large dark currents unavoidably generated by the Fermi-Dirac distribution in narrow-bandgap semiconductors, which constrains the development of some modern technologies and systems. Here, an electronic-structure strategy is proposed for designing ultrabroadband covering mid- and even far-IR photodetection materials operating at RT and a layered MoS2 is manifested with an engineered bandgap of 0...
October 11, 2018: Advanced Materials
Yu Wei Zhou, Zhi Feng Li, Jing Zhou, Ning Li, Xiao Hao Zhou, Ping Ping Chen, Yuan Liao Zheng, Xiao Shuang Chen, Wei Lu
Polarization imaging detection has its unique advantage in discriminating the man-made objects from natural objects. Grating integrated super pixel for polarization imaging detection can simultaneously obtain the first three elements of the Stokes vector, which is the trend of infrared polarization imaging detection in recent years. Here, we demonstrate the first super pixel for long wavelength infrared polarization imaging detection with the extinction ratio of its four polarization directions more than 100...
October 10, 2018: Scientific Reports
Ahmad A Darweesh, Stephen J Bauman, Desalegn T Debu, Joseph B Herzog
We propose and report on the design of a 1-D metallo-dielectric nano-grating on a GaAs substrate. We numerically study the impact of grating period, slit and wire widths, and irradiating angle of incidence on the optical response. The optimal wire width, w = 160 nm, was chosen based on previous results from investigations into the influence of wire width and nano-slit dimensions on optical and electrical enhancements in metal-semiconductor-metal photodetectors. In this present project, resonant absorption and reflection modes were observed while varying the wire and nano-slit widths to study the unique optical modes generated by Rayleigh-Wood anomalies and surface plasmon polaritons...
October 9, 2018: Nanomaterials
Gongjin Li, Enming Song, Gaoshan Huang, Ruobing Pan, Qinglei Guo, Fei Ma, Bin Zhou, Zengfeng Di, YongFeng Mei
Flexible transient photodetectors, a form of optoelectronic sensors that can be physically self-destroyed in a controllable manner, could be one of the important components for future transient electronic systems. In this work, a scalable, device-first, and bottom-up thinning process enables the fabrication of a flexible transient phototransistor on a wafer-compatible transferred silicon nanomembrane. A gate modulation significantly restrains the dark current to 10-12 A. With full exposure of the light-sensitive channel, such a device yields an ultrahigh photo-to-dark current ratio of 107 with a responsivity of 1...
October 10, 2018: Small
Saiful M Islam, Vinod K Sangwan, Yuan Li, Joohoon Kang, Xiaomi Zhang, Yihui He, Jing Zhao, Akshay A Murthy, Shulan Ma, Vinayak P Dravid, Mark C Hersam, Mercouri G Kanatzidis
Ultrafast synthesis of high quality transition metal dichalcogenide (TMDQ) nanocrystals such as molybdenum disulfide (MoS2) is technologically relevant for large-scale production of electronic and optoelectronic devices. Here, we report a rapid solid-state synthesis route for MoS2 using the chemically homogeneous molecular precursor, (NH4)2Mo3S13·H2O, resulting in nanoparticles with estimated size down to 25 nm only in 10 sec at 1000 oC. Despite the extreme non-equilibrium conditions, the resulting porous MoS2 nanoparticles remain aggregated to preserve the form of the original rod shape bulk morphology of the molecular precursor...
October 9, 2018: ACS Applied Materials & Interfaces
Qiang Li, Zizheng Li, Xiaoyi Wang, Tongtong Wang, Hai Liu, Haigui Yang, Yan Gong, Jinsong Gao
In this paper, we demonstrate a theoretical and experimental study on a nano-hole array that can realize perfect absorption in the visible and near-infrared regions. The absorption spectrum can be easily controlled by adjusting the structural parameters including the radius and period of the nano-hole, and the maximal absorption can reach 99.0% in theory. In order to clarify the physical mechanism of the absorber, we start from the extraordinary optical transmission supported by the nano-hole array in a thin metallic film coated on a glass substrate, and then analyse the perfect absorption in the metal-insulator-metal structure...
October 18, 2018: Nanoscale
Hakan Selvi, Ernie W Hill, Patrick Parkinson, Tim J Echtermeyer
Graphene-silicon (GS) Schottky junctions have been demonstrated as an efficient architecture for photodetection. However, the response speed of such devices for free space light detection has so far been limited to 10s-100s of kHz for wavelength λ >500 nm. Here, we demonstrate GS Schottky junction photodetectors fabricated on a silicon-on-insulator substrate (SOI) with response speeds approaching 1 GHz, attributed to the reduction of the photo-active silicon layer thickness to 10 μm and with it a suppression of speed-limiting diffusion currents...
October 18, 2018: Nanoscale
Verena A Hintermayr, Lakshminarayana Polavarapu, Alexander S Urban, Jochen Feldmann
For high-speed optoelectronic applications relying on fast relaxation or energy transfer mechanisms, understanding of carrier relaxation and recombination dynamics is critical. Here, we compare the differences in photoexcited carrier dynamics in 2D and quasi-3D colloidal methylammonium lead iodide perovskite nanoplatelets via differential transmission spectroscopy. We find that the cooling of excited electron-hole pairs by phonon emission progresses much faster and is intensity-independent in the 2D-case. This is due to the low dielectric surrounding of the thin perovskite layers, for which the Fröhlich interaction is screened less efficiently leading to higher and less density dependent carrier-phonon scattering rates...
October 8, 2018: ACS Nano
Yusong Bai, George Bullard, Jean-Hubert Olivier, Michael J Therien
Gauging free carrier generation (FCG) in optically-excited, charge-neutral single-walled carbon nanotubes (SWNTs) has important implications for SWNT-based optoelectronics that rely upon conversion of photons to electrical current. Earlier investigations have largely provided only qualitative insights into optically-triggered SWNT FCG, due to the heterogeneous nature of commonly interrogated SWNT samples, and the lack of direct, unambiguous spectroscopic signatures that could be used to quantify charges. Here, employing ultrafast pump-probe spectroscopy in conjunction with chirality-enriched, length-sorted, ionic polymer-wrapped SWNTs, we develop a straightforward approach for quantitatively evaluating the extent of optically-driven FCG in SWNTs...
October 5, 2018: Journal of the American Chemical Society
Silah Lee, Jin Sung Kim, Kyeong Rok Ko, Gun Hwan Lee, Dong Jin Lee, Dong Wook Kim, Jin Eui Kim, Ho Kyung Kim, Dong Woon Kim, Seongil Im
Polycrystalline cadmium telluride (CdTe) X-ray photodetector with advanced performance was fabricated in a Schottky diode form by direct thermal deposition (evaporation) on pixelized complementary metal oxide semiconductor (CMOS) readout panel. Our CdTe X-ray detector shows such a variety of benefits as relatively low process temperature, low cost, low operation voltage less than 40 V, and higher sensitivity and spatial resolution than those of commercial a-Se detectors. CdTe has cubic Zinc Blende structure and maintains p-type conduction after growth in general...
October 4, 2018: Scientific Reports
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