Co-reporter:Xiaoqing Chen, Xiaolong Liu, Bing Wu, Haiyan Nan, Hui Guo, Zhenhua Ni, Fengqiu Wang, Xiaomu Wang, Yi Shi, and Xinran Wang
Nano Letters October 11, 2017 Volume 17(Issue 10) pp:6391-6391
Publication Date(Web):September 6, 2017
DOI:10.1021/acs.nanolett.7b03263
Interfacing light-sensitive semiconductors with graphene can afford high-gain phototransistors by the multiplication effect of carriers in the semiconductor layer. So far, most devices consist of one semiconductor light-absorbing layer, where the lack of internal built-in field can strongly reduce the quantum efficiency and bandwidth. Here, we demonstrate a much improved graphene phototransistor performances using an epitaxial organic heterostructure composed of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and pentacene as the light-absorbing layer. Compared with single light-absorbing material, the responsivity and response time can be simultaneously improved by 1 and 2 orders of magnitude over a broad band of 400–700 nm, under otherwise the same experimental conditions. As a result, the external quantum efficiency increases by over 800 times. Furthermore, the response time of the heterostructured phototransistor is highly gate-tunable down to sub-30 μs, which is among the fastest in the sensitized graphene phototransistors interfacing with electrically passive light-absorbing semiconductors. We show that the improvement is dominated by the efficient electron–hole pair dissociation due to interfacial built-in field rather than bulk absorption. The structure demonstrated here can be extended to many other organic and inorganic semiconductors, which opens new possibilities for high-performance graphene-based optoelectronics.Keywords: graphene; heterostructure; Organic semiconductors; phototransistors; two-dimensional;
Co-reporter:Lei Song, Yu Wang, Qian Gao, Yu Guo, Qijing Wang, Jun Qian, Sai Jiang, Bing Wu, Xinran Wang, Yi Shi, Youdou Zheng, and Yun Li
ACS Applied Materials & Interfaces May 31, 2017 Volume 9(Issue 21) pp:18127-18127
Publication Date(Web):May 11, 2017
DOI:10.1021/acsami.7b03785
Ferroelectric organic field-effect transistors (Fe-OFETs) have attracted intensive attention because of their promising potential in nonvolatile memory devices. The quick switching between binary states is a significant fundamental feature in evaluating Fe-OFET memories. Here, we employ 2D molecular crystals via a solution-based process as the conducting channels in transistor devices, in which ferroelectric polymer acts as the gate dielectric. A high carrier mobility of up to 5.6 cm2 V–1 s–1 and a high on/off ratio of 106 are obtained. In addition, the efficient charge injection by virtue of the ultrathin 2D molecular crystals is beneficial in achieving rapid operations in the Fe-OFETs; devices exhibit short switching time of ∼2.9 and ∼3.0 ms from the on- to the off-state and from the off- to the on-state, respectively. Consequently, the presented strategy is capable of speeding up Fe-OFET memory devices by using solution-processed 2D molecular crystals.Keywords: 2D molecular crystals; ferroelectric organic field-effect transistor memory; high-speed organic transistor memory; nonvolatile; solution processed;
Co-reporter:Dakuan Zhang, Yun Sheng, Jianyu Wang, Fan Gao, Shancheng Yan, Junzhuan Wang, Lijia Pan, Qing Wan, Yi Shi
Optics Communications 2017 Volume 395(Volume 395) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.optcom.2015.07.007
•We investigate the photoresponse of ZnO nanowires based on Au Schottky contact.•The passivation of the surface states improves the photoresponse performance.•A model is developed to understand the origin of the performance improvement.•The present integrated architecture extracts efficiently phototgenerated carriers.Performance characteristics, such as dark current and response time, of ZnO nanowire (NW) photodetectors are usually degraded by H2O/O2 adsorption on the NW surfaces. In this work, ZnO NW photodetectors based on Au Schottky contact through passivating surface states were investigated. ZnO NW photodetectors were fabricated with a lateral electrode structure, in which Au served as Au/ZnO Schottky contact and semi-transparent top electrode. Specifically, passivation of the surface states of ZnO NWs by using highly intensive UV irradiation effectively improved the photoresponse. A physical model based on surface band theory was developed to understand the origin of the performance improvement of the photodetector. The present device architecture prevents ZnO NWs photodetector from H2O/O2 adsorption in air and efficiently extracts photogenerated carriers across a diametrical direction.Download high-res image (153KB)Download full-size image
Co-reporter:Fan Yang;Junzhuan Wang;Jiawen Lu;Zhongwei Yu;Linwei Yu;Jun Xu;Kunji Chen;Pere Roca i Cabarrocas
Advanced Optical Materials 2017 Volume 5(Issue 19) pp:
Publication Date(Web):2017/10/01
DOI:10.1002/adom.201700390
Imitating natural rod or cone cells in human eyes can inspire a biomimetic design of filter-free color sensing photodetector with the aid of three-dimensional (3D) nanophotonic engineering. Here, a novel radial tandem junction (RTJ) super-rod structure is proposed and demonstrated, which consists of coaxially stacking hydrogenated amorphous silicon PIN junctions upon silicon nanowires, resembling to the live retinal cells in terms of both geometry and dimension. As a consequence, these RTJ units enjoy a unique wavelength-selective and cavity-mode-assisted light absorption/responses in the inner and the outer radial PIN junctions, which are readily tunable to achieve natural RGB color discrimination in the RTJ rod-cells without the need of any filter system. This unique RTJ design can indicate a new 3D implementation of color sensing photodetectors enabled by advanced nanophotonic structuring and engineering.
Co-reporter:Zhihao Yu;Zhun-Yong Ong;Songlin Li;Jian-Bin Xu;Gang Zhang;Yong-Wei Zhang;Xinran Wang
Advanced Functional Materials 2017 Volume 27(Issue 19) pp:
Publication Date(Web):2017/05/01
DOI:10.1002/adfm.201604093
Transition-metal dichalcogenides (TMDCs) are an important class of two-dimensional (2D) layered materials for electronic and optoelectronic applications, due to their ultimate body thickness, sizable and tunable bandgap, and decent theoretical room-temperature mobility. So far, however, all TMDCs show much lower mobility experimentally because of the collective effects by foreign impurities, which has become one of the most important limitations for their device applications. Here, taking MoS2 as an example, the key factors that bring down the mobility in TMDC transistors, including phonons, charged impurities, defects, and charge traps, are reviewed. A theoretical model that quantitatively captures the scaling of mobility with temperature, carrier density, and thickness is introduced. By fitting the available mobility data from literature over the past few years, one obtains the density of impurities and traps for a wide range of transistor structures. It shows that interface engineering can effectively reduce the impurities, leading to improved device performances. For few-layer TMDCs, the lopsided carrier distribution is analytically modeled to elucidate the experimental increase of mobility with the number of layers. From our analysis, it is clear that the charge transport in TMDC samples is a very complex problem that must be handled carefully.
Co-reporter:Haizeng Song, Bin Zhao, Xin Xu, Shancheng Yan, Yi Shi
Materials Science and Engineering: B 2017 Volume 225(Volume 225) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.mseb.2017.08.021
•We develop in situ synthesis of GeO2/RGO nanocomposites.•The clathrate retains original 2D features of graphene and high-loading GeO2.•The nanocomposites show the high capacity of 1024.4 mA h g−1 at 0.1 A g−1.•They also exhibit good performance 464 mA h g−1 at 1 A g−1 after 100 cycles.Germanium dioxide/reduced graphene oxide (GeO2/RGO) nanocomposites are promising anode materials for applications in lithium ion batteries because they have ultrahigh lithium ion storage capacity and high structural stability. However, the design of GeO2 based anodes with satisfactory cycling ability and high capacity still presents a big challenge because of strict requirements in the need for a special type of solvent, a complicated preparation process, high energy and material costs, and/or difficulty in process upscaling. In the present work, GeO2/RGO nanocomposite is successfully synthesized as an anode material by a simple and green method, which stacked the GeO2 nanoparticles directly on the reduced graphene oxide sheets in an in situ process. The sample exhibits high specific capacity and enhanced rate capacity as an electrode material for lithium ion batteries. GeO2/RGO nanocomposite shows a higher storage capacity of 1020.4 mA h g−1 (theoretical capacity 1125 mA h g−1) after 30 cycles with a current density of 0.1 A g−1, and a long-term cycle capacity of 464 mA h g−1 even after 100 cycles at 1 A g−1. This good electrochemical performance is due to the superior properties of non-aggregated graphene sheets and homogeneously dispersed GeO2 nanoparticles in GeO2/RGO nanocomposite.
Co-reporter:Gang Wang, Yu Wang, Junzhuan Wang, Lijia Pan, Linwei Yu, Youdou Zheng, Yi Shi
Applied Surface Science 2017 Volume 414(Volume 414) pp:
Publication Date(Web):31 August 2017
DOI:10.1016/j.apsusc.2017.04.002
•The KMC method is adopted to investigate the relationships between surface evolution and hydrogen thermal treatment conditions.•The reduction in surface roughness is divided into two stages at relatively low temperatures, both exhibiting exponential dependence on the time.•The optimized surface structure can be obtained by precisely adjusting thermal treatment temperatures and hydrogen pressures.The evolution of a two-dimensional silicon surface under hydrogen thermal treatment is studied by kinetic Monte Carlo simulations, focusing on the dependence of the migration behaviors of surface atoms on both the temperature and hydrogen pressure. We adopt different activation energies to analyze the influence of hydrogen pressure on the evolution of surface morphology at high temperatures. The reduction in surface roughness is divided into two stages, both exhibiting exponential dependence on the equilibrium time. Our results indicate that a high hydrogen pressure is conducive to obtaining optimized surfaces, as a strategy in the applications of three-dimensional devices.
Co-reporter:Yujia Zhang;Yu Guo;Lei Song;Jun Qian;Sai Jiang;Qijing Wang;Xinran Wang;Xiaomu Wang;Yun Li
Journal of Materials Chemistry C 2017 vol. 5(Issue 43) pp:11246-11251
Publication Date(Web):2017/11/09
DOI:10.1039/C7TC02348K
Solution-processed 2D organic crystals are of significant interest because of their unique characteristics that ensure promising applications in electronics. In this study, a simple and efficient approach to directly write 2D organic crystals using a rollerball pen has been presented. The obtained crystals exhibit highly crystalline features with atomic smoothness and large size. Field-effect transistors composed of the obtained crystals yield an average and a maximum carrier mobility values of 3.1 and 5.9 cm2 V−1 s−1, respectively. This study presents significant potential of the writing technique via a rollerball pen for the solution-processed fabrication of 2D organic crystals for high-performance, large-area printed electronics.
Co-reporter:Zhihao Yu;Zhun-Yong Ong;Yiming Pan;Yang Cui;Run Xin;Baigeng Wang;Yun Wu;Tangsheng Chen;Yong-Wei Zhang;Gang Zhang;Xinran Wang
Advanced Materials 2016 Volume 28( Issue 3) pp:547-552
Publication Date(Web):
DOI:10.1002/adma.201503033
Co-reporter:Xiaolong Liu;Xiaoguang Luo;Haiyan Nan;Hui Guo;Peng Wang;Linglong Zhang;Minmin Zhou;Ziyi Yang;Weida Hu;Zhenhua Ni;Teng Qiu;Zongfu Yu;Jian-Bin Xu;Xinran Wang
Advanced Materials 2016 Volume 28( Issue 26) pp:5200-5205
Publication Date(Web):
DOI:10.1002/adma.201600400
Co-reporter:Chang Jin Wan;Yang Hui Liu;Ping Feng;Wei Wang;Li Qiang Zhu;Zhao Ping Liu;Qing Wan
Advanced Materials 2016 Volume 28( Issue 28) pp:5878-5885
Publication Date(Web):
DOI:10.1002/adma.201600820
Co-reporter:Chang Jin Wan;Li Qiang Zhu;Yang Hui Liu;Ping Feng;Zhao Ping Liu;Hai Liang Cao;Peng Xiao;Qing Wan
Advanced Materials 2016 Volume 28( Issue 18) pp:3557-3563
Publication Date(Web):
DOI:10.1002/adma.201505898
Co-reporter:Bing Wu, Yinghe Zhao, Haiyan Nan, Ziyi Yang, Yuhan Zhang, Huijuan Zhao, Daowei He, Zonglin Jiang, Xiaolong Liu, Yun Li, Yi Shi, Zhenhua Ni, Jinlan Wang, Jian-Bin Xu, and Xinran Wang
Nano Letters 2016 Volume 16(Issue 6) pp:3754-3759
Publication Date(Web):May 16, 2016
DOI:10.1021/acs.nanolett.6b01108
Precise assembly of semiconductor heterojunctions is the key to realize many optoelectronic devices. By exploiting the strong and tunable van der Waals (vdW) forces between graphene and organic small molecules, we demonstrate layer-by-layer epitaxy of ultrathin organic semiconductors and heterostructures with unprecedented precision with well-defined number of layers and self-limited characteristics. We further demonstrate organic p–n heterojunctions with molecularly flat interface, which exhibit excellent rectifying behavior and photovoltaic responses. The self-limited organic molecular beam epitaxy (SLOMBE) is generically applicable for many layered small-molecule semiconductors and may lead to advanced organic optoelectronic devices beyond bulk heterojunctions.
Co-reporter:Qijing Wang;Jun Qian;Yun Li;Yuhan Zhang;Daowei He;Sai Jiang;Yu Wang;Xinran Wang;Lijia Pan;Junzhuan Wang;Xizhang Wang;Zheng Hu;Haiyan Nan;Zhenhua Ni;Youdou Zheng
Advanced Functional Materials 2016 Volume 26( Issue 19) pp:3191-3198
Publication Date(Web):
DOI:10.1002/adfm.201600304
2D organic materials with in-plane van der Waals forces among molecules have unique characteristics that ensure a brilliant future for multifunctional applications. Soluble organic semiconductors can be used to achieve low-cost and high-throughput manufacturing of electronic devices. However, achieving solution-processed 2D single-crystalline semiconductors with uniform morphology remains a substantial challenge. Here, the fabrication of 2D molecular single-crystal semiconductors with precise layer definition by using a floating-coffee-ring-driven assembly is presented. In particular, bilayer molecular films exhibit single-crystalline features with atomic smoothness and high film uniformity over a large area; field-effect transistors yield average and maximum carrier mobilities of 4.8 and 13.0 cm2 V−1 s−1, respectively. This work demonstrates the strong potential of 2D molecular crystals for low-cost, large-area, and high-performance electronics.
Co-reporter:Jianyu Wang, Huabin Sun, Yun Sheng, Lijun Yang, Fan Gao, Yao Yin, Zheng Hu, Qin Wan, Rong Zhang, Youdou Zheng, Yi Shi
Applied Surface Science 2016 Volume 361() pp:221-225
Publication Date(Web):15 January 2016
DOI:10.1016/j.apsusc.2015.11.177
Highlights
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Surface-diffusion enhanced Ga incorporation in ZnO nanowires grown on GaN substrate.
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Uniform distributions of Ga incorporation along ZnO nanowires.
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Diffusion barrier for Ga atoms decreased with the assistance of an oxygen vacancy.
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Two orders of magnitude increase in the surface diffusion coefficient caused by oxygen vacancies on ZnO nanowire sidewalls.
Co-reporter:Shancheng Yan, Keyu Li, Zixia Lin, Haizeng Song, Tian Jiang, Jiansheng Wu and Yi Shi
RSC Advances 2016 vol. 6(Issue 38) pp:32414-32421
Publication Date(Web):24 Mar 2016
DOI:10.1039/C6RA03124B
SnS2/graphene (SnS2/G) composites have been explored extensively as a promising candidate for Lithium Ion Battery (LIB) anodes in recent years. Previously, the SnS2 conversion/reduction step of the reaction mechanism is generally believed to be irreversible or only partially reversible, which severely underestimates the theoretical capacity of SnS2. In this work, SnS2 nanoparticles have been successfully stacked on reduced graphene oxide (RGO) via a facile and effective solvothermal method using ethylene glycol as a chelant. The SnS2/graphene nanocomposite retained many of the original 2D characteristics of the graphene nanosheets. As a result, Li+ storage properties were significantly improved. The SnS2/RGO nanocomposites show a higher storage capacity of 939.0 mA h g−1 after 30 cycles at a current density of 0.1 A g−1, and a long-term cycle capacity of 615.5 mA h g−1 even after 200 cycles at 1 A g−1. The superior cycling stability of the SnS2/RGO electrode is attributed to greater reversibility in the initial conversion reaction, ascribed to the presence of the Sn nanoparticles.
Co-reporter:Jianyu Wang, Yuichi Oshima, Yujin Cho, Yi Shi, Takashi Sekiguchi
Superlattices and Microstructures 2016 Volume 99() pp:77-82
Publication Date(Web):November 2016
DOI:10.1016/j.spmi.2016.05.003
•Distinctive etch pits induced by HCl vapor phase etching correspond to different types of threading dislocations in GaN.•H incorporation at threading dislocations in GaN during HCl etching.•Mix dislocations are more favorable for the impurity incorporations than that of edge dislocations.The threading dislocations in GaN provide diffusion routes for impurity incorporation, which substantially influences GaN based optoelectronic devices. Here, we investigated the characteristics of the impurity incorporation at threading dislocations by HCl vapor phase etching and cathodoluminescence (CL) measurements. The distinctive etch pits induced by HCl vapor phase etching correspond definitely to different types of dislocations, and the etching process causes simultaneously H incorporation at a high temperature. CL spectra of the etch pits were analyzed, and the observed difference in the redshift of near band emission peak indicates that mix dislocations are more favorable for impurity incorporations than that of edge dislocations. The understanding on the impurity incorporation behavior at threading dislocations helps to obtain high quality GaN nanostructures.
Co-reporter:Liyan Zhou, Shancheng Yan, Zixia Lin, Yi Shi
Materials Chemistry and Physics 2016 Volume 171() pp:16-21
Publication Date(Web):1 March 2016
DOI:10.1016/j.matchemphys.2015.12.061
•The WS2/rGO composite were synthesized to improve the battery performance.•The WS2/rGO anode shows a capacity of 431.2 mAh/g, much higher than WS2.•The added graphene oxide is reduced to rGO, improving the conductive properties.•The rGO can avoid the restacking, and promote the reduction of WO3.Two-dimensional transition-metal dichalcogenides, such as tungsten disulfide (WS2), have been actively studied as suitable candidates for anode materials used in lithium ion batteries recently, due to their remarkable ion intercalation properties. However, the difficulties in the synthesis of phase-pure WS2, restacking between WS2 nanosheets, low electronic conductivity and brittle nature of WS2 severely limit its Li-ion batteries application. Here, we adopt a one-pot method for synthesizing of WS2/reduced Graphene Oxide (rGO) composite to improve the battery performance dramatically. The WS2/rGO anode shows a stable discharge capacity of 431.2 mAh/g, at a current density of 0.1 A/g after 100 cycles, while the capacity of bare WS2 is only 65.5 mAh/g under the same condition. The added graphene oxide is reduced to rGO in reaction process and constitute stable composite with WS2, not only avoiding the restacking between WS2 nanosheets and improving the conductive properties, but also promoting the reduction of WO3 effectively. Our work may provide a possible route to avoid oxygen impurities in transition metal dichalcogenides.
Co-reporter:Yang Cui;Run Xin;Zhihao Yu;Yiming Pan;Zhun-Yong Ong;Xiaoxu Wei;Junzhuan Wang;Haiyan Nan;Zhenhua Ni;Yun Wu;Tangsheng Chen;Baigeng Wang;Gang Zhang;Yong-Wei Zhang;Xinran Wang
Advanced Materials 2015 Volume 27( Issue 35) pp:5230-5234
Publication Date(Web):
DOI:10.1002/adma.201502222
Co-reporter:Yaqun Wang, Ye Shi, Lijia Pan, Yu Ding, Yu Zhao, Yun Li, Yi Shi, and Guihua Yu
Nano Letters 2015 Volume 15(Issue 11) pp:7736-7741
Publication Date(Web):October 27, 2015
DOI:10.1021/acs.nanolett.5b03891
Conducting polymer hydrogels emerge as a novel class of polymeric materials that show great potential in many energy, environmental, and biomedical devices. We describe here for the first time a general supramolecular approach toward controlled in situ synthesis of one-dimensional nanostructured conductive hydrogels (polypyrrole (PPy) as a model system) using a rational dopant counterion, which is a disc-shaped liquid crystal molecular copper phthalocyanine-3,4′,4″,4‴-tetrasulfonic acid tetrasodium salt (CuPcTs). The dopant molecule CuPcTs cross-linked the PPy chains to form a three-dimensional network that gelated into a hydrogel. The PPy hydrogel could be synthesized in bulk quantities with uniform morphology of self-assembled interconnected nanofibers. The tetra-functional dopant favors a supramolecular self-assembly mechanism to form one-dimensional PPy nanostructures. Furthermore, the enhanced interchain charge transport of CuPcTs doped PPy resulted in greatly enhanced conductivity and pseudocapacitance compared with pristine PPy.
Co-reporter:Lanlan Li, Yaqun Wang, Lijia Pan, Ye Shi, Wen Cheng, Yi Shi, and Guihua Yu
Nano Letters 2015 Volume 15(Issue 2) pp:1146-1151
Publication Date(Web):January 8, 2015
DOI:10.1021/nl504217p
The development of a scalable, low-cost, and versatile biosensor platform for the sensitive and rapid detection of human metabolites is of great interest for healthcare, pharmaceuticals, and medical science. On the basis of hierarchically nanostructured conducting polymer hydrogels, we designed a flexible biosensor platform that can detect various human metabolites, such as uric acid, cholesterol, and triglycerides. Owing to the unique features of conducting polymer hydrogels, such as high permeability to biosubstrates and rapid electron transfer, our biosensors demonstrate excellent sensing performance with a wide linear range (uric acid, 0.07–1 mM; cholesterol, 0.3–9 mM, and triglycerides, 0.2–5 mM), high sensitivity, low sensing limit, and rapid response time (∼3 s). Given the facile and scalable processability of hydrogels, the proposed conductive hydrogels-based biosensor platform shows great promise as a low-cost sensor kit for healthcare monitoring, clinical diagnostics, and biomedical devices.
Co-reporter:Min Qian;Yiming Pan;Fengyuan Liu;Miao Wang;Haoliang Shen;Daowei He;Baigeng Wang;Feng Miao;Xinran Wang
Advanced Materials 2014 Volume 26( Issue 20) pp:3275-3281
Publication Date(Web):
DOI:10.1002/adma.201306028
Co-reporter:Yaqun Wang, Ye Shi, Lijia Pan, Meng Yang, Lele Peng, Shi Zong, Yi Shi, and Guihua Yu
Nano Letters 2014 Volume 14(Issue 8) pp:4803-4809
Publication Date(Web):June 30, 2014
DOI:10.1021/nl5019782
Superhydrophobic surfaces are of immense scientific and technological interests for a broad range of applications. However, a major challenge remains in developing scalable methodologies that enable superhydrophobic coatings on versatile substrates with a combination of strong mechanical stability, optical transparency, and even stretchability. Herein, we developed a scalable methodology to versatile hydrophobic surfaces that combine with strong mechanical stability, optical transparency, and stretchability by using a self-assembled hydrogel as the template to in situ generate silica microstructures and subsequent silanization. The superhydrophobic coatings can be enabled on virtually any substrates via large-area deposition techniques like dip coating. Transparent surfaces with optical transmittance as high as 98% were obtained. Moreover, the coatings exhibit superior mechanical flexibility and robustness that it can sustain contact angles ∼160° even after 5000 cycles of mechanically stretching at 100% strain. The multifunctional surfaces can be used as screen filters and sponges for the oil/water separation that can selectively absorb oils up to 40× their weight.
Co-reporter:Chang Jin Wan, Li Qiang Zhu, Ju Mei Zhou, Yi Shi and Qing Wan
Nanoscale 2014 vol. 6(Issue 9) pp:4491-4497
Publication Date(Web):14 Feb 2014
DOI:10.1039/C3NR05882D
Ionic/electronic hybrid devices with synaptic functions are considered to be the essential building blocks for neuromorphic systems and brain-inspired computing. Here, artificial synapses based on indium-zinc-oxide (IZO) transistors gated by nanogranular SiO2 proton-conducting electrolyte films are fabricated on glass substrates. Spike-timing dependent plasticity and paired-pulse facilitation are successfully mimicked in an individual bottom-gate transistor. Most importantly, dynamic logic and dendritic integration established by spatiotemporally correlated spikes are also mimicked in dendritic transistors with two in-plane gates as the presynaptic input terminals.
Co-reporter:Songtao Zhang, Mingbo Zheng, Zixia Lin, Nianwu Li, Yijie Liu, Bin Zhao, Huan Pang, Jieming Cao, Ping He and Yi Shi
Journal of Materials Chemistry A 2014 vol. 2(Issue 38) pp:15889-15896
Publication Date(Web):30 Jul 2014
DOI:10.1039/C4TA03503H
Porous activated carbon with a ultrahigh specific surface area (3164 m2 g−1) and large pore volume (1.88 cm3 g−1) was prepared from waste litchi shells with channel-like macropores via a KOH activation method. The macroporous structure of litchi shells is believed to be conducive to distribute the activation agent, which enables sufficient activation. The as-prepared activated carbon was developed as a conducting framework for lithium–sulfur battery cathode materials. The resulting activated carbon/sulfur composite cathode possesses a high specific capacity, good rate capability, and long-term cycling performance. At 200 mA g−1 current density, the initial discharge capacity of the activated carbon/sulfur composite cathode with 60 wt% sulfur content is 1105 mA h g−1. At a current density of 800 mA g−1, the activated carbon/sulfur composite cathode shows 51% capacity retention over 800 cycles with a fade rate of 0.06% per cycle. The coulombic efficiency of the cell remains at approximately 95%. By adding LiNO3 in the electrolyte, the activated carbon/sulfur composite electrode tested at 800 mA g−1 shows a high coulombic efficiency (>99%). The activated carbon/sulfur composites exhibited similar capacity value and cycling trends with an increase in sulfur content from 60% to 68%. The good electrochemical performance can be attributed to the excellent structural parameters of the activated carbon. The ultrahigh specific surface area and large pore volume not only enhances the sulfur content but also ensures dispersion of elemental sulfur in the conducting framework, thereby improving sulfur utilization. The small nanopores of the activated carbon can effectively inhibit the diffusion of polysulfides during the charge/discharge process.
Co-reporter:Yu Wang, Lan Chen, Qijing Wang, Huabin Sun, Xizhang Wang, Zheng Hu, Yun Li, Yi Shi
Organic Electronics 2014 Volume 15(Issue 10) pp:2234-2239
Publication Date(Web):October 2014
DOI:10.1016/j.orgel.2014.06.024
•Organic semiconducting crystals were directly written by rollerball pens for OFETs.•A facile and rapid approach for the growth of solution-processed organic crystals.•High performance with μFET of 0.7 cm2/Vs and on/off ratio of 107 was obtained.•Solution flowing behavior benefits formation of crystals with large grain sizes.To deposit organic semiconducting crystals from solution, we propose the use of a rollerball pen as a simple and promising tool. These organic crystal grains of dioctylbenzothienobenzothiophene measured several hundred micrometers. The fabricated OFETs exhibited good device performance with a field-effect mobility (μFET) of 0.7 cm2/Vs and an on-off ratio of more than 107. Simulation results reveal that the flow behavior of solution from the pen refill tube to the substrate intrinsically enhances the formation of large organic crystals.Graphical abstract
Co-reporter:Yun Li, Chuan Liu, Michael V. Lee, Yong Xu, Xu Wang, Yi Shi and Kazuhito Tsukagoshi
Journal of Materials Chemistry A 2013 vol. 1(Issue 7) pp:1352-1358
Publication Date(Web):2012/12/07
DOI:10.1039/C2TC00384H
One of the major factors driving the fast growth of the semiconductor manufacturing industry is a steady decrease in production costs. For traditional semiconductors, most of the cost originates from infrastructure, equipment, and processing. In contrast with low-cost strategies involving organic semiconductors, the materials can easily become one of the greatest costs. Here, we demonstrate a simple and efficient fabrication process, which involves in situ purification via spin-coating from organic semiconductor/polymer blends, to eliminate the influence of impurities on the electrical properties of the semiconductor. Thus, we achieve the same performance using low-purity, low-cost materials for transistor arrays with patterned organic semiconducting crystals as that obtained from high-purity materials. The exclusion of impurities is attributed to the vertical phase separation and crystallization that occur during spin-coating, which produces purified organic semiconducting crystals. With this reduction in cost, our results can redirect organic electronics to seek the lowest purity and lowest cost material that still provides adequate performance, rather than simply using the highest purity and costliest materials.
Co-reporter:Zixia Lin, Mingbo Zheng, Bin Zhao, Lijia Pan, Lin Pu and Yi Shi
RSC Advances 2013 vol. 3(Issue 47) pp:24882-24885
Publication Date(Web):27 Sep 2013
DOI:10.1039/C3RA44177F
Mesoporous TiO2 interwoven with multilevel carbon networks was obtained by in situ self-assembly of TiO2 and P123 micelles within the nanospace of thermally exfoliated graphene. The nanocomposite exhibited excellent capacity retention and good rate capability as a material for lithium-ion battery anodes.
Co-reporter:Mingbo Zheng, Danfeng Qiu, Bin Zhao, Luyao Ma, Xinran Wang, Zixia Lin, Lijia Pan, Youdou Zheng and Yi Shi
RSC Advances 2013 vol. 3(Issue 3) pp:699-703
Publication Date(Web):09 Nov 2012
DOI:10.1039/C2RA22702A
A continuous mesoporous iron oxide nanofilm was directly formed on graphene nanosheets through the in situ thermal decomposition of Fe(NO3)3·9H2O and was anchored tightly on the graphene surface. The lithiation-induced strain was naturally accommodated, owing to the constraint effect of graphene and the mesoporous structure. Hence, the pulverization of the iron oxide nanofilm was effectively prevented.
Co-reporter:Minmin Zhou, Shancheng Yan, Yi Shi, Meng Yang, Huabin Sun, Jianyu Wang, Yao Yin, Fan Gao
Applied Surface Science 2013 Volume 273() pp:89-93
Publication Date(Web):15 May 2013
DOI:10.1016/j.apsusc.2013.01.191
Abstract
Large-scale cadmium sulfide (CdS) nanorod arrays were successfully synthesized on several different substrates through solvothermal reaction. During the growth experiments, we observed that the adhesion strength of the CdS nanorod arrays to different substrates differed dramatically, causing some of the CdS coating being easily flushed away by deionized water (DI water). With doubts and suspicions, we seriously investigate the original morphology of all the substrates by using atomic force microscopy (AFM). The phase, morphology, crystal structure and photoelectric property of all the products were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and current–voltage (I–V) probe station. The growth mechanism of solvothermal reaction was proposed on the basis of all the characterizations. Our approach presents a universal method of liquid phase epitaxy of 1D material on a wide range of substrates of any shape.
Co-reporter:Zewen Zuo;Guanglei Cui;Yu Wang;Junzhuan Wang;Lin Pu
Chemical Vapor Deposition 2013 Volume 19( Issue 10-11-12) pp:363-366
Publication Date(Web):
DOI:10.1002/cvde.201307003
Abstract
The nucleation rate of hydrogenated microcrystalline silicon (µc-Si:H) films deposited by plasma-enhanced (PE)CVD on hydrogenated amorphous silicon (a-Si:H) substrates is investigated through structural and electrical characterization, with special attention paid to the initial growth stage of µc-Si:H films. It is found that the nucleation rate of µc-Si is dependent on the thickness of the a-Si:H substrate. The µc-Si:H film exhibits a rapid nucleation on a thin a-Si:H layer, leaving a thin incubation layer at the µc-Si/substrate interface. This substrate-thickness dependence of the nucleation rate is proposed to be correlated with the stress inside the a-Si:H layer. The high interfacial stress existing in the thin a-Si:H layer facilitates the formation of high concentration, strained Si-Si bonds, which are responsible for the rapid µc-Si nucleation. The thick a-Si:H layer relaxes the interfacial stress through the formation of islands in the Stranski-Krastanow (S-K) growth mode, while the intrinsic stress is still low, resulting in a long nucleation process allowing for the intrinsic compressive stress to be accumulated that is necessary for the µc-Si deposited on it.
Co-reporter:Xiangdong Ye, Zhouwei Yang, Jiabao Sun, Yi Zhao, Yi Shi
Microelectronic Engineering 2013 Volume 105() pp:46-50
Publication Date(Web):May 2013
DOI:10.1016/j.mee.2012.12.011
A method of fabricating the Au micro-pattern arrays on the flexible substrate is proposed, which consists of making Au patterns on the hard substrate by the conventional microfabrication process, and then transferring the Au patterns on the flexible substrate by a medium layer. The main advantage of the method is that the high-quality Au pattern arrays can be easily obtained on the flexible substrate. The high quality of Au patterns on the hard substrate can be guaranteed by the conventional microfabrication process, and meanwhile it is convenient to control the transfer conditions so as to bring no damage to Au patterns during transfer process. As a result, various Au micro-pattern arrays are fabricated on the flexible substrate with high fidelity.Graphical abstractHighlights► A method of fabricating Au micro-pattern arrays on flexible substrate is proposed. ► The method integrates the conventional microfabrication process with a transfer process. ► A model is established to analyze the transfer process. ► Various Au micro-patterns can be fabricated by the method with high fidelity.
Co-reporter:Nianwu Li, Mingbo Zheng, Hongling Lu, Zibo Hu, Chenfei Shen, Xiaofeng Chang, Guangbin Ji, Jieming Cao and Yi Shi
Chemical Communications 2012 vol. 48(Issue 34) pp:4106-4108
Publication Date(Web):22 Feb 2012
DOI:10.1039/C2CC17912A
Lithium–sulfur batteries have a poor rate performance and low cycle stability due to the shuttling loss of intermediate lithium polysulfides. To address this issue, a carbon–sulfur nanocomposite coated with reduced graphene oxide was designed to confine the polysulfides.
Co-reporter:Shenglong Xu;Jiawei Dong;Lijia Pan;Xifeng Que;Youdou Zheng
Nano Research 2012 Volume 5( Issue 5) pp:361-368
Publication Date(Web):2012 May
DOI:10.1007/s12274-012-0216-3
Co-reporter:Zewen Zuo, Yu Wang, Jin Lu, Junzhuan Wang, Lin Pu, Yi Shi, Youdou Zheng
Vacuum 2012 Volume 86(Issue 7) pp:924-928
Publication Date(Web):8 February 2012
DOI:10.1016/j.vacuum.2011.04.031
Microcrystalline silicon (μc-Si) films were deposited at a high rate and low temperature using jet-type inductively coupled plasma chemical vapor deposition (jet-ICPCVD), and the deposition rate, microstructure and electrical properties of the deposited films were investigated. It was demonstrated that a high deposition rate of over 20 nm/s can be achieved while maintaining high crystallinity and low dark conductivity. The deposition rate is well controlled by regulating the generation rate and transport of growth precursors. High crystallinity of the films results principally from hydrogen-induced chemical annealing. Furthermore, the excellent electrical properties benefit from the low oxygen content and/or low deposition temperature.Highlights► High deposition rate of μc-Si film was obtained at low temperature by jet-ICPCVD. ► High rate, high crystallinity, low dark conductivity can be simultaneously obtained. ► Deposition rate is controlled by the generation rate and transport of precursors. ► High crystallinity results principally from hydrogen-induced chemical annealing. ► Low deposition temperature and low oxygen content favor the low dark conductivity.
Co-reporter:Guangli Wang;Lijia Pan;Lin Pu;Jin Lv
Frontiers of Optoelectronics 2011 Volume 4( Issue 2) pp:146-149
Publication Date(Web):2011 June
DOI:10.1007/s12200-011-0156-7
The Ge/Si nanocrystals on ultra thin high-k tunnel oxide Al2O3 were fabricated to form the charge trapping memory prototype with asymmetric tunnel barriers through combining the advanced atomic layer deposition (ALD) and pulse laser deposition (PLD) techniques. Charge storage characteristics in such memory structure have been investigated using capacitance-voltage (C-V) and capacitance-time (C-t) measurements. The results prove that both the two-layered and three-layered memory structures behave relatively qualified for the multi-level cell storage. The results also demonstrate that compared to electrons, holes reach a longer retention time even with an ultra thin tunnel oxide owing to the high band offset at the valence band between Ge and Si.
Co-reporter:S. Y. Song;L. Pu;L. J. Pan;Z. Xu;Y. Shi;R. Zhang;Y. D. Zheng
Advanced Materials 2007 Volume 19(Issue 3) pp:
Publication Date(Web):29 JAN 2007
DOI:10.1002/adma.200790011
Polyaniline nanotubes can be synthesized through a chemical template method. The shape and major parameters of the tubes are precisely controlled by the reactive templates of MnO2 nanowires, which also act as the oxidative initiator for polymerization. The cover image shows an example where the rectangular tubes are cloned from the cryptomelane-phase MnO2, as reported on p. 461 by Shi and co-workers.
Co-reporter:L. J. Pan;L. Pu;Y. Shi;S. Y. Song;Z. Xu;R. Zhang;Y. D. Zheng
Advanced Materials 2007 Volume 19(Issue 3) pp:461-464
Publication Date(Web):29 JAN 2007
DOI:10.1002/adma.200602073
Polyaniline nanotubes are synthesized from manganese oxide templates (see figure and cover). Manganese oxide is used as the physical template and the chemical oxidative initiator for the aniline polymerization. The template can be removed after the reaction, as manganese oxide is reduced into soluble Mn2+ ions. Many morphologies of polyaniline structures, such as nanotubes, spherical tube brushes, and double-shell nanotubes, can be fabricated using this method.
Co-reporter:Bo Yan, Yi Shi, Lin Pu, Kuangji Zhang, Pin Han, Rong Zhang, Youdou Zheng
Materials Letters 2007 Volume 61(Issue 17) pp:3711-3714
Publication Date(Web):July 2007
DOI:10.1016/j.matlet.2006.12.086
In this work, we propose a novel method for obtaining high-density Ge-dots/Si multilayered heterostructures. The high-density self-assembled Ge dots are firstly grown on a-Si layer using low-pressure chemical vapor deposition (LPCVD), and then low-temperature recrystallized by Ni based metal induced lateral crystallization (MILC). According to optical micrograph, microprobe Raman spectroscopy and transmission electron microscopy (TEM) observations, it has been found that the Ni induced lateral crystallized Si film has large leaf-like grains elongated along the MILC direction with (110) preference. The strain shift of Ge dots reveals the formation of high quality interface between the crystallized Si and Ge dot.
Co-reporter:L. J. Pan;L. Pu;Y. Shi;T. Sun;R. Zhang;Y. O. Zheng
Advanced Functional Materials 2006 Volume 16(Issue 10) pp:
Publication Date(Web):12 JUN 2006
DOI:10.1002/adfm.200500543
Polyaniline (PAni) mesostructures have been synthesized under hydrothermal conditions. The mesostructures show different forms—fibers, dendrite fibers, textured plates, featureless plates, and spheres. The obtained morphologies are more sensitive to the concentration of the doping acid, HCl, than the reaction temperature. Similar morphological evolutions have also been observed in the cases of phosphoric (H3PO4) and fluoroboric (HBF4) acids. The measured results of UV-vis and Fourier transform IR spectroscopy, as well as X-ray diffraction data, suggest that the morphology evolution is related to the charged property and reactivity of the semiquinone radical cation on the main chain of PAni, formed by polymer doping. Hydrothermal synthesis by tuning the concentration of the doping acid provides a platform for understanding the nature of the polymerization and the fabrication of 1- and 2D conjugated polymers.
Co-reporter:Ye Shi, Jun Zhang, Lijia Pan, Yi Shi, Guihua Yu
Nano Today (December 2016) Volume 11(Issue 6) pp:
Publication Date(Web):December 2016
DOI:10.1016/j.nantod.2016.10.002
•Recent development of gel-based nanomaterials including carbon based gels, conductive polymer gels, ionic gels and inorganic gels is reviewed.•Electronically/ionically conductive gels build up a promising material platform for advanced energy applications.•Mechanisms for the improvement of electronic/ionic conductivity and mechanical strength of gel systems are discussed.•Perspectives for each type of energy gels are given.Energy conversion and storage systems with high efficiency have attracted great research interest in recent years. To improve the performance of energy devices, nanomaterials with delicately controlled structures and interfaces have been applied. However, low-dimensional nanomaterials suffer from inhomogeneous aggregation, severe re-stacking, and the formation of bottlenecks and poor contacts during the processing and assembly, thus hindering the transport of electrons or ions in energy devices. Gel materials, a special class of bio-inspired materials, are emerging as promising candidates to overcome the drawbacks of low-dimensional nanomaterials. The 3D nanostructured gel network promotes electron transport along the backbone while facilitating the diffusion of ions through hierarchical pores, as well as providing high surface area for interfacial reactions. In addition, the properties of gels can be facilely tuned, thereby further extending their applications and improving their performance.To date, various synthetic strategies have been developed for the preparation of gel materials, including carbon-based gels, conductive polymer gels, ionically conductive gels and inorganic gels. These gel materials have successfully served as electrode materials, electrolytes, self-supported current collectors, 3D binder systems, etc. in various kinds of energy conversion and storage applications, such as lithium ion batteries, supercapacitors, catalysts, and fuel cells. In this review, we summarize the synthesis of various electrically conductive gel materials, including carbon-based gels, conductive polymer gels, and ionically conductive gels and their applications in energy conversion and storage devices. We also provide the perspective on the future developments of these gel materials in energy-related fields.
Co-reporter:Nianwu Li, Mingbo Zheng, Hongling Lu, Zibo Hu, Chenfei Shen, Xiaofeng Chang, Guangbin Ji, Jieming Cao and Yi Shi
Chemical Communications 2012 - vol. 48(Issue 34) pp:NaN4108-4108
Publication Date(Web):2012/02/22
DOI:10.1039/C2CC17912A
Lithium–sulfur batteries have a poor rate performance and low cycle stability due to the shuttling loss of intermediate lithium polysulfides. To address this issue, a carbon–sulfur nanocomposite coated with reduced graphene oxide was designed to confine the polysulfides.
Co-reporter:Yun Li, Chuan Liu, Michael V. Lee, Yong Xu, Xu Wang, Yi Shi and Kazuhito Tsukagoshi
Journal of Materials Chemistry A 2013 - vol. 1(Issue 7) pp:NaN1358-1358
Publication Date(Web):2012/12/07
DOI:10.1039/C2TC00384H
One of the major factors driving the fast growth of the semiconductor manufacturing industry is a steady decrease in production costs. For traditional semiconductors, most of the cost originates from infrastructure, equipment, and processing. In contrast with low-cost strategies involving organic semiconductors, the materials can easily become one of the greatest costs. Here, we demonstrate a simple and efficient fabrication process, which involves in situ purification via spin-coating from organic semiconductor/polymer blends, to eliminate the influence of impurities on the electrical properties of the semiconductor. Thus, we achieve the same performance using low-purity, low-cost materials for transistor arrays with patterned organic semiconducting crystals as that obtained from high-purity materials. The exclusion of impurities is attributed to the vertical phase separation and crystallization that occur during spin-coating, which produces purified organic semiconducting crystals. With this reduction in cost, our results can redirect organic electronics to seek the lowest purity and lowest cost material that still provides adequate performance, rather than simply using the highest purity and costliest materials.
Co-reporter:Songtao Zhang, Mingbo Zheng, Zixia Lin, Nianwu Li, Yijie Liu, Bin Zhao, Huan Pang, Jieming Cao, Ping He and Yi Shi
Journal of Materials Chemistry A 2014 - vol. 2(Issue 38) pp:NaN15896-15896
Publication Date(Web):2014/07/30
DOI:10.1039/C4TA03503H
Porous activated carbon with a ultrahigh specific surface area (3164 m2 g−1) and large pore volume (1.88 cm3 g−1) was prepared from waste litchi shells with channel-like macropores via a KOH activation method. The macroporous structure of litchi shells is believed to be conducive to distribute the activation agent, which enables sufficient activation. The as-prepared activated carbon was developed as a conducting framework for lithium–sulfur battery cathode materials. The resulting activated carbon/sulfur composite cathode possesses a high specific capacity, good rate capability, and long-term cycling performance. At 200 mA g−1 current density, the initial discharge capacity of the activated carbon/sulfur composite cathode with 60 wt% sulfur content is 1105 mA h g−1. At a current density of 800 mA g−1, the activated carbon/sulfur composite cathode shows 51% capacity retention over 800 cycles with a fade rate of 0.06% per cycle. The coulombic efficiency of the cell remains at approximately 95%. By adding LiNO3 in the electrolyte, the activated carbon/sulfur composite electrode tested at 800 mA g−1 shows a high coulombic efficiency (>99%). The activated carbon/sulfur composites exhibited similar capacity value and cycling trends with an increase in sulfur content from 60% to 68%. The good electrochemical performance can be attributed to the excellent structural parameters of the activated carbon. The ultrahigh specific surface area and large pore volume not only enhances the sulfur content but also ensures dispersion of elemental sulfur in the conducting framework, thereby improving sulfur utilization. The small nanopores of the activated carbon can effectively inhibit the diffusion of polysulfides during the charge/discharge process.
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