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Yu-Ze Chen, Yen-Ting You, Pin-Jung Chen, Dapan Li, Teng-Yu Su, Ling Lee, Yu-Chuan Shih, Chia-Wei Chen, Ching-Chen Chang, Yi-Chung Wang, Cheng-You Hong, Tzu-Chien Wei, Johnny C Ho, Kung-Hwa Wei, Chang-Hong Shen, Yu-Lun Chueh
Selenium (Se) is one of the potential candidates as photodetector because of its outstanding properties such as high photoconductivity (~8x104 S. cm-1), piezoelectricity, thermoelectricity and nonlinear optical responses. Solution phase synthesis becomes an efficient way to produce Se while a contamination issue should be taken into account, deteriorating the electric characteristic of Se. In this work, a facile, controllable approach of synthesizing Se NWs/films via a plasma-assisted growth process was demonstrated at the low substrate temperature of 100 oC...
August 14, 2018: ACS Applied Materials & Interfaces
Shaili Sett, Subhamita Sengupta, N Ganesh, K S Narayan, Arup Kumar Raychaudhuri
Self-powered photodetectors have been fabricated from a single Germanium nanowire (NW) in the metal-semiconductor-metal (MSM) device configuration. The self-powered devices show high photoresponse (Responsivity~ 10<sup>3</sup>-10<sup>5</sup>A/W) in the wavelength range 300-1100 nm. It has been established from I-V characteristics that there exists asymmetry in Schottky Barrier Height (SBH) at the two MS contacts. We have used simulation to establish that the asymmetric SBH at the metal contacts in a MSM device is a major cause for the "built-in" axial field that leads to separation of light generated electron-hole pair in the absence of an applied bias...
August 14, 2018: Nanotechnology
Siyong Gu, Chien-Te Hsieh, Tzu-Wei Lin, Chun-Yao Yuan, Yasser Ashraf Gandomi, Jeng-Kuei Chang, Jianlin Li
Graphene sheets that can exhibit electrical conducting and semiconducting properties are highly desirable and have potential applications in fiber communications, photodetectors, solar cells, semiconductors, and broadband modulators. However, there is currently no efficient method that is able to tune the band gap of graphene sheets. This work adopts an efficient atomic layer oxidation (ALO) technique to cyclically increase the oxidation level of graphene sheets, thus, tuning their electrical conductance, band-gap structure, and photoluminescence (PL) response...
August 13, 2018: Nanoscale
Mingjin Dai, Hongyu Chen, Rui Feng, Wei Feng, Yunxia Hu, Huihui Yang, Guangbo Liu, Xiaoshuang Chen, Jia Zhang, Cheng-Yan Xu, PingAn Hu
A dual-band self-powered photodetector (SPPD) with high sensitivity is realized by a facile combination of InSe Schottky diode and Au plasmonic nanoparticle (NP) arrays. Comparing with pristine InSe devices, InSe/Au photodetectors possess an additional capability of photodetection in visible to near-infrared (NIR) region. This intriguing phenomenon is attributed to the wavelength selective enhancement of pristine responsivities by hybridized quadrupole plasmons resonance of Au NPs. It is worth pointing out that the maximum of enhancement ratio in responsivity reaches up to ~1200% at wavelength of 685 nm...
August 10, 2018: ACS Nano
Joohoon Kang, Spencer A Wells, Vinod K Sangwan, David Lam, Xiaolong Liu, Jan Luxa, Zdeněk Sofer, Mark C Hersam
Layered indium selenide (InSe) presents unique properties for high-performance electronic and optoelectronic device applications. However, efforts to process InSe using traditional liquid phase exfoliation methods based on surfactant-assisted aqueous dispersions or organic solvents with high boiling points compromise electronic properties due to residual surface contamination and chemical degradation. Here, these limitations are overcome by utilizing a surfactant-free, low boiling point, deoxygenated cosolvent system...
August 10, 2018: Advanced Materials
Hirokazu Tahara, Masanori Sakamoto, Toshiharu Teranishi, Yoshihiko Kanemitsu
Multiple excitons in semiconductor nanocrystals have been extensively studied with respect to unique carrier dynamics including quantized Auger recombination and implementation in optoelectronic devices such as solar cells and photodetectors. However, the generation mechanism of multiple excitons still remains unclear. Here, we study instantaneous and delayed multiple exciton generation processes in PbS/CdS core/shell nanocrystals. The absorption cross-sections of biexcitons and triexcitons are identical to that of single excitons under instantaneous excitation with a single pulse...
August 9, 2018: Nature Communications
Weixin Ouyang, Longxing Su, Xiaosheng Fang
A facile chemical bath method is adopted to grow bismuth oxychloride (BiOCl) nanosheet arrays on a piece of Cu foil (denoted as BiOCl-Cu) and isolated BiOCl nanosheets are collected by ultrasonication. A self-supporting BiOCl film is obtained by the removal of Cu foil. Photodetectors (PDs) based on these BiOCl materials are assembled and the effects of morphologies and electrode configurations on the photoelectric performance of these PDs are examined. The BiOCl nanosheet PD achieves high responsivities in the spectral range from 250 to 350 nm, while it presents quite a small photocurrent and slow response speed...
August 9, 2018: Small
Kibret A Messalea, Benjamin J Carey, Azmira Jannat, Nitu Syed, Md Mohiuddin, Bao Yue Zhang, Ali Zavabeti, Taimur Ahmed, Nasir Mahmood, Enrico Della Gaspera, Khashayar Khoshmanesh, Kourosh Kalantar-Zadeh, Torben Daeneke
Atomically thin, semiconducting transition and post transition metal oxides are emerging as a promising category of materials for high-performance oxide optoelectronic applications. However, the wafer-scale synthesis of crystalline atomically thin samples has been a challenge, particularly for oxides that do not present layered crystal structures. Herein we use a facile, scalable method to synthesise ultrathin bismuth oxide nanosheets using a liquid metal facilitated synthesis approach. Monolayers of α-Bi2O3 featuring sub-nanometre thickness, high crystallinity and large lateral dimensions could be isolated from the liquid bismuth surface...
August 9, 2018: Nanoscale
Yujie Ke, Shancheng Wang, Guowei Liu, Ming Li, Timothy J White, Yi Long
The reversible, ultrafast, and multistimuli responsive phase transition of vanadium dioxide (VO2 ) makes it an intriguing "smart" material. Its crystallographic transition from the monoclinic to tetragonal phases can be triggered by diverse stimuli including optical, thermal, electrical, electrochemical, mechanical, or magnetic perturbations. Consequently, the development of high-performance smart devices based on VO2 grows rapidly. This review systematically summarizes VO2 -based emerging technologies by classifying different stimuli (inputs) with their corresponding responses (outputs) including consideration of the mechanisms at play...
August 7, 2018: Small
Leilei Gu, Daquan Zhang, Matthew Kam, Qianpeng Zhang, Swapnadeep Poddar, Yu Fu, Xiaoliang Mo, Zhiyong Fan
The formamidinium lead iodide (FAPbI3) perovskite has attracted immense research interest as it has much improved stability than methylammonium lead iodide (MAPbI3) while still maintaining excellent optoelectronic properties. Compared to MAPbI3, FAPbI3 has shown an elevated decomposition temperature and a slower decomposition process and therefore it is considered as a more promising candidate for future high-efficiency and reliable optoelectronic devices. However, these excellent optoelectronic properties only exist in the alpha phase and this phase will spontaneously transform into an undesired delta phase with much poorer optoelectronic properties regardless of the environment...
August 7, 2018: Nanoscale
Liam Collins, Mahshid Ahmadi, Jiajun Qin, Yongtao Liu, Olga Ovchinnikova, Bin Hu, Stephen Jesse, Sergei V Kalinin
Optoelectronic behavior in materials such as organic/inorganic hybrid perovskites depend on a complex interplay between fast (electronic) and slower (ionic) processes. These processes are thought to be influenced by structural inhomogeneities (e.g. interfaces and grain boundaries) bringing forward the necessity for development of techniques capable of correlating nanostructure and photo-transport behavior. While Kelvin probe force microscopy (KPFM) is ideally suited to map surface potentials on relevant length scales, it lacks sufficient temporal resolution to extract the meaningful system dynamics...
August 7, 2018: Nanotechnology
Yunzhou Xue, Jian Yuan, Jingying Liu, Shaojuan Li
Perovskites have recently attracted intense interests for optoelectronic devices application due to their excellent photovoltaic and photoelectric properties. The performance of perovskite-based devices highly depends on the perovskite material properties. However, the widely used spin-coating method can only prepare polycrystalline perovskite and physical vapor deposition (PVD) method requires a higher melting point (>350 °C) substrate due to the high growth temperature, which is not suitable for low melting point substrates, especially for flexible substrates...
August 3, 2018: Nanomaterials
Wei Feng, Feng Gao, Yunxia Hu, Mingjin Dai, He Liu, Lifeng Wang, PingAn Hu
Here, we report electronic and optoelectronic performance of multilayer In2Se3 are effectively regulated by phase-engineering. The electron mobility is increased to 22.8 cm2V-1s-1 for β-In2Se3 FETs, which is 18 times higher than 1.26 cm2V-1s-1 of α-In2Se3 FETs. The enhanced electronic performance is attributed to larger carrier sheet density and lower contact resistance. Multilayer β-In2Se3 photodetector exhibits an ultrahigh responsivity of 8.8×104 A/W under 800 nm illumination, which is 574 times larger than 154...
August 6, 2018: ACS Applied Materials & Interfaces
Weifeng Zhang, Jianping Yao
An on-chip frequency-tunable bandpass microwave photonic filter (MPF) implemented on a silicon photonic platform is reported. The on-chip MPF consists of a high-speed phase modulator (PM), a thermally tunable high-Q micro-disk resonator (MDR), and a high-speed photodetector (PD). The filtering function of the MPF is realized based on phase modulation and phase modulation to intensity modulation conversion, to translate the spectral response of the MDR in the optical domain to the spectral response of the MPF in the microwave domain...
August 1, 2018: Optics Letters
Chao Xie, Longhui Zeng, Zhixiang Zhang, Yuen-Hong Tsang, Linbao Luo, Jung-Ho Lee
Two-dimensional group-10 transition metal dichalcogenides have recently attracted increasing research interest because of their unique electronic and optoelectronic properties. Herein, we present vertical hybrid heterojunctions of multilayered PtSe2 and Si, which take advantage of large-scale homogeneous PtSe2 films grown directly on Si substrates. These heterojunctions show obvious rectifying behavior and a pronounced photovoltaic effect, enabling them to function as self-driven photodetectors operating at zero bias...
August 1, 2018: Nanoscale
Hai Zhou, Zhaoning Song, Corey R Grice, Cong Chen, Xiaohan Yang, Hao Wang, Yanfa Yan
Owing to their low trap-state density, high carrier mobility and high thermal stability, CsPbBr3 perovskite micro-crystals (MCs) have attracted significant attention for applications as photodetectors (PDs). However, solution synthesis processes lead to MC films with high void density, which seriously limit the performance of the PDs. Here, a pressure-assisted annealing strategy is introduced to significantly reduce the void density and decrease the surface roughness. The resulting self-powered all-inorganic CsPbBr3 perovskite MC thick-film PDs show improved performance characteristics, with responsivities and detectivities of up to 0...
August 1, 2018: Journal of Physical Chemistry Letters
Nengjie Huo, Gerasimos Konstantatos
Conventional semiconductors such as silicon- and indium gallium arsenide (InGaAs)-based photodetectors have encountered a bottleneck in modern electronics and photonics in terms of spectral coverage, low resolution, nontransparency, nonflexibility, and complementary metal-oxide-semiconductor (CMOS) incompatibility. New emerging two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and their hybrid systems thereof, however, can circumvent all these issues benefitting from mechanically flexibility, extraordinary electronic and optical properties, as well as wafer-scale production and integration...
July 31, 2018: Advanced Materials
Chunxiong Bao, Jie Yang, Sai Bai, Weidong Xu, Zhibo Yan, Qingyu Xu, Junming Liu, Wenjing Zhang, Feng Gao
Photodetectors are critical parts of an optical communication system for achieving efficient photoelectronic conversion of signals, and the response speed directly determines the bandwidth of the whole system. Metal halide perovskites, an emerging class of low-cost solution-processed semiconductors, exhibiting strong optical absorption, low trap states, and high carrier mobility, are widely investigated in photodetection applications. Herein, through optimizing the device engineering and film quality, high-performance photodetectors based on all-inorganic cesium lead halide perovskite (CsPbIx Br3- x ), which simultaneously possess high sensitivity and fast response, are demonstrated...
July 31, 2018: Advanced Materials
Jia-Qin Liu, Yang Gao, Guoan Wu, Xiaowei Tong, Chao Xie, Linbao Luo, Lin Liang, Yu-Cheng Wu
In this paper, we developed a highly sensitive near-infrared (NIR) photodetector by directly coating a layer of Cs-doped FAPbI3 perovskite film onto vertical Si nanowires (SiNWs) array. The as-assembled SiNWs array/perovskite core-shell heterojunction exhibits a typical rectifying behavior in the dark and distinct photoresponse characteristics under illumination. Owning to the remarkable photovoltaic effect, the heterojunction can work as a self-driven photodetector without an exterior power supply. Further photoresponse analysis reveals that the device is sensitive in a wide wavelength range with maximum sensitivity at ~850 nm...
July 30, 2018: ACS Applied Materials & Interfaces
Wei Yang, Kai Hu, Feng Teng, Junhui Weng, Yong Zhang, Xiaosheng Fang
A gold-induced NH4 Cl-assisted vapor-based route is proposed and developed to achieve vertically aligned submicron Se crystals on lattice-matched (111)-oriented silicon substrates, based on which a high-performance large-area silicon-compatible photodetector is constructed. Thanks to the energy band structure and the strongly asymmetrical depletion region, the fabricated Se/Si device maintains a similar wavelength cutoff to that of selenium devices before the IR region, along with a high-performance broadband photoresponse in the UV-to-visible region...
August 8, 2018: Nano Letters
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