Annealing and transport studies of suspended molybdenum disulfide devices

We fabricate suspended molybdenum disulfide (MoS 2 ) field effect transistor devices and develop an effective gas annealing technique that significantly improves device quality and increases conductance by 3–4 orders of magnitude. Mobility of the suspended devices ranges from 0.01 to 46 cm 2 V −1 s −1 before annealing, and from 0.5 to 105 cm 2 V −1 s −1 after annealing. Temperature dependence measurements reveal two transport mechanisms: electron–phonon scattering at high temperatures and thermal activation over a gate-tunable barrier height at low temperatures. Our results suggest that transport in these devices is not limited by the substrates, but likely by defects, charge impurities and/or Schottky barriers at the metal–MoS 2 interfaces. Finally, this suspended MoS 2 device structure provides a versatile platform for other research areas, such as thermal, optical and mechanical studies.

Fenglin Wang, Petr Stepanov, Mason Gray and Chun Ning Lau

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Electronic properties of single Ge/Si quantum dot grown by ion beam sputtering deposition

The dependence of the electronic properties of a single Ge/Si quantum dot (QD) grown by the ion-beam sputtering deposition technique on growth temperature and QD diameter is investigated by conductive atomic force microscopy (CAFM). The Si–Ge intermixing effect is demonstrated to be important for the current distribution of single QDs. The current staircase induced by the Coulomb blockade effect is observed at higher growth temperatures (>700 °C) due to the formation of an additional barrier between dislocated QDs and Si substrate for the resonant tunneling of holes. According to the proposed single-hole-tunneling model, the fact that the intermixing effect is observed to increase as the incoherent QD size decreases may explain the increase in the starting voltage of the current staircase and the decrease in the current step width.

C Wang, S Y Ke, J Yang, W D Hu, F Qiu, R F Wang and Y Yang

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Controlled coupling of a single nanoparticle in polymeric microstructure by low one-photon absorption—based direct laser writing technique

We investigated the coupling of a single nanoparticle (NP) into a polymer-based photonic structure (PS). The low one-photon absorption microscopy with a two-step technique allowed us first to accurately determine the location of a NP and then to embed it as desired into an arbitrary PS. The coupling of a gold NP and a polymer-based PS was experimentally investigated showing a six-fold photon collection enhancement as compared to that of a NP in unpatterned film. The simulation results based on finite-difference time-domain calculation method confirmed this observation and showed a 2.86-fold enhancement in extraction efficiency thanks to the NP/PS coupling.

M T Do, D T T Nguyen, H M Ngo, I Ledoux-Rak and N D Lai

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High-quality, single-layered epitaxial graphene fabricated on 6H-SiC (0001) by flash annealing in Pb atmosphere and mechanism

High-quality epitaxial graphene is produced on silicon carbide by flash annealing of 6H-SiC in a lead (Pb) atmosphere at ∼1400 °C for 30 s. Nearly three top bilayers of SiC are decomposed due to fast heating and cooling, and sublimation of Si atoms from SiC is retarded by the Pb atmosphere. The synergetic effects promote the growth of continuous single-layered graphene sheets on the SiC terraces, and a model is established to elucidate the effects and growth mechanism.

T W Hu, X T Liu, F Ma, D Y Ma, K W Xu and P K Chu

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Fabrication of electron beam deposited tip for atomic-scale atomic force microscopy in liquid

Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μ m silica bead at the cantilever end and fabricate a 500–700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having hig...

K Miyazawa, H Izumi, T Watanabe-Nakayama, H Asakawa and T Fukuma

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Photoelectrochemistry of n-type antimony sulfoiodide nanowires

In the presented work the photoelectrochemical properties of SbSI along with the electronic structure (i.e. conduction and valence band edge potentials as well as conductivity type) of sonochemically obtained nanowires are discussed for the first time. The spectroscopic investigations indicate interesting optical properties, including surface isotope effect and excitonic emission. The photoelectrochemical investigation of SbSI revealed the occurrence of the photoelectrochemical photocurrent switching effect. It may be defined as a change in photocurrent direction (generated at the illuminated semiconducting electrode immersed in electrolyte) due to an appropriate polarization of the electrode versus the reference electrode. It is often observed for semiconductors as a result of the reduction of molecular oxygen dissolved in the electrolyte. However, in the case of SbSI, the photocurrent switching was recorded regardless of the presence of molecular oxygen in the electrolyte, prob...

Przemysław Kwolek, Kacper Pilarczyk, Tomasz Tokarski, Justyna Mech, Jakub Irzmański and Konrad Szaciłowski

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Crystalline ZnO/Amorphous ZnO Core/Shell Nanorods: Self-Organized Growth, Structure, and Novel Luminescence

The Journal of Physical Chemistry C

DOI: 10.1021/jp511783c

Saikumar Inguva, Sandeep Kumar Marka, Rajani K. Vijayaraghavan, Enda McGlynn, Vadali V. S. S. Srikanth and J.-P. Mosnier

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Mechanistic Insights into CO2 Activation via Reverse Water–Gas Shift on Metal Surfaces

The Journal of Physical Chemistry C

DOI: 10.1021/jp512962c

Luca Dietz, Simone Piccinin and Matteo Maestri

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Photoredox-active Dyads Based on a Ru(II) Photosensitizer Equipped with Electron Donor or Acceptor Polymer Chains: A Spectroscopic Study of Light-Induced Processes toward Efficient Charge Separation

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b00866

Joachim Kübel, Robert Schroot, Maria Wächtler, Ulrich S. Schubert, Benjamin Dietzek and Michael Jäger

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Au-Assisted Growth of Anisotropic and Epitaxial CdSe Colloidal Nanocrystals via in Situ Dismantling of Quantum Dots

Chemistry of Materials

DOI: 10.1021/cm504433y

Víctor Fernàndez-Altable, Mariona Dalmases, Andrea Falqui, Alberto Casu, Pau Torruella, Sònia Estradé, Francesca Peiró and Albert Figuerola

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Nitridomagnesosilicate Ba[Mg3SiN4]:Eu2+ and Structure–Property Relations of Similar Narrow-Band Red Nitride Phosphors

Chemistry of Materials

DOI: 10.1021/cm504604d

Sebastian Schmiechen, Philipp Strobel, Cora Hecht, Thomas Reith, Markus Siegert, Peter J. Schmidt, Petra Huppertz, Detlef Wiechert and Wolfgang Schnick

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Small ChangeGreat Effect: Steep Increase of Li Ion Dynamics in Li4Ti5O12 at the Early Stages of Chemical Li Insertion

Chemistry of Materials

DOI: 10.1021/cm504564k

Walter Schmidt, Patrick Bottke, Michael Sternad, Peter Gollob, Volker Hennige and Martin Wilkening

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Heteroplasmon Hybridization in Stacked Complementary Plasmo-Photonic Crystals

Nano Letters

DOI: 10.1021/nl504755d

Masanobu Iwanaga and Bongseok Choi

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Catalytically Activated Palladium@Platinum Nanowires for Accelerated Hydrogen Gas Detection

ACS Nano

DOI: 10.1021/acsnano.5b00302

Xiaowei Li, Yu Liu, John C. Hemminger and Reginald M. Penner

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A Multifunctional Polymer-Graphene Thin-Film Transistor with Tunable Transport Regimes

ACS Nano

DOI: 10.1021/acsnano.5b00050

Thomas Mosciatti, Sébastien Haar, Fabiola Liscio, Artur Cieselski, Emanuele Orgiu and Paolo Samorì

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Twin-Tail Surfactant Peculiarity in Superficial Fabrication of Semiconductor Quantum Dots: Toward Structural, Optical, and Electrical Features

The Journal of Physical Chemistry C

DOI: 10.1021/jp510428z

Deepika Jamwal, Gurpreet Kaur, Pankaj Raizada, Pardeep Singh, Dinesh Pathak and Pankaj Thakur

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One-pot synthesis of one-dimensional CdTe-cystine nanocomposite for humidity sensing

Quantum dot (QD)-incorporated one-dimensional (1D) nanocomposites offer great application potential. However, a facile one-step synthesis of the nanocomposites and fabrication of their free-standing film for sensing has not been accomplished. Herein a rod-shaped nanocomposite is one-pot synthesized via an L-cysteine-assisted hydrothermal approach, in which synthesis parameters including L-cysteine amount, temperature and reaction duration are tailored to control the composite nanostructures. CdTe nanocrystals are incorporated into the L-cystine matrices to form the nanorods, which tangle each other to network an intact film structure via a simple drying process. The free-standing CdTe-cystine nanorod film is directly utilized as a humidity sensor. This work provides a one-pot synthesis approach to grow 1D CdTe incorporated nanocomposites, demonstrating their great potential in film sensing applications.

Zhisong Lu, Jing Wang, Jiale Xie and Chang Ming Li

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ZnS nanoparticles well dispersed in ethylene glycol: coordination control synthesis and application as nanocomposite optical coatings

The study of the preparation and application of ZnS nanoparticles (NPs) has been one of the most prominent hotspots in the domain of semiconductor NPs. The ZnS NPs usually exist in two crystallographic forms: zinc blende (cubic) and wurtzite (hexagonal). However, controlled preparation of ZnS NPs with specified crystallographic forms is still a difficult problem. Herein, zinc blende type ZnS NPs have been prepared by coordination control with diethanolamine (DEA) in ethylene glycol (EG). The prepared ZnS NPs can be well dispersed in EG without precipitation. The effect of DEA on the crystal form of the ZnS NPs was studied. We conclude that in EG, when no strong coordinating agent exists for the zinc ion, hexagonal crystal ZnS nanoparticles may be obtained, while coordinating agents such as acetate and DEA coordinated with the zinc(II) ion can inhibit the formation of the hexagonal ZnS crystal nucleus and the more stable zinc blende can be obtained. Moreover, transparent nanocompo...

Yuanrong Cheng, Zhe Lin, Hao Lü, Liang Zhang and Bai Yang

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Electronic and magnetic properties of boron nitride nanoribbons with square–octagon (4 | 8) line defects

The electronic and magnetic properties of boron nitride nanoribbons (BNNRs) with square–octagon (4 | 8) line defects (LD-(4 | 8)), parallel to their edges, have been investigated by first-principles calculations. It is found that the zigzag type LD-(4 | 8) BNNR with boron terminated edges is an antiferromagnetic (AFM‘ + − + −’) insulator with an indirect bandgap, but that with nitrogen terminated edges has two degenerate ground states with the same energy, among which one is ferromagnetic (FM ‘ + + + +’) half-metallic and the other is AFM ‘ + + − −’ metallic. In contrast, it is more interesting to find that the bare and fully-hydrogen terminated armchair edge BNNRs with unsymmetric (4 | 8) line defects have an indirect and direct gap, respectively, both of which show a characteristic three family oscillation behavior, depending only on the ribbon width in its narrower part, but not the whole BNNR’s width. Finally, the stabilities of a two-dimensional h-BN sheet with a zigzag or a...

Yang Han, Rui Li, Jian Zhou, Jinming Dong and Yoshiyuki Kawazoe

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Immobilization of individual nanotubes in graphitic layers for electrical characterization

A simple route is followed to produce an abundance of individual carbon nanotubes (CNTs) immobilized in graphitic layers to counter the challenge of locating individual CNTs and restrict the lateral displacement of CNTs due to the high electrostatic force exerted by a scanning tunnelling microscope tip for electrical characterization. Graphitic layers are selected for the embedding matrix as graphite and the nanotubes have a similar work function and hence would not perturb the electrical configuration of the nanotube. Solvent mediated exfoliation of graphite layers to insert the nanotubes was preferred over oxidative expansion, as oxidation could perturb the electrical configuration of graphite. During the exfoliation of graphite the optimized amount of nanotubes was introduced into the medium such that an individual nanotube could be immobilized in few-layer graphene followed by precipitation and centrifugation. The dose and the time of sonication were optimized to ensure that ...

Debmalya Roy, Neeru Tiwari, K Mukhopadhyay and A K Saxena

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