Table of contents

Resistive switching memory (ReRAM) has attracted much attention in recent times owing to its fast switching, simple structure, and non-volatility. Flexible and transparent electronic devices have also attracted considerable attention. We therefore fabricated an Al₂O₃-based ReRAM with transparent indium-zinc-oxide (IZO) electrodes on a flexible substrate. The device transmittance was found to be higher than 80% in the visible region (400–800 nm). Bended states (radius = 10 mm) of the device also did not affect the memory performance because of the flexibility of the two transparent IZO electrodes and the thin Al₂O₃ layer. The conduction mechanism of the resistive switching of our device was explained by ohmic conduction and a Poole–Frenkel emission model. The conduction mechanism was proved by oxygen vacancies in the Al₂O₃ layer, as analyzed by x-ray photoelectron spectroscopy analysis. These results encourage the application of ReRAM in flexible and transparent electronic devices.

The dipolar interaction of magnetic nanoparticles is of intense interest to engineer material self-assembly for anisotropic functional nanostructures. Here we report the solution synthesis of cobalt nanowires, where the one-dimensional nanowire formation is ultimately dependent on the magnetic dipolar interaction to realize in situ assembly of cobalt nanoparticles. The morphology transition of cobalt nanostructures is well controlled via the ligand-free synthesis and thermal decomposition of zero-valent cobalt precursor. This study provides a self-assembly approach to the development of anisotropic cobalt nanostructures and a better understanding of nucleation parameters, which are demonstrated to correlate strongly with the size and morphology of final cobalt nanowires. This approach may be extended to other magnetic materials for the control of their nanostructure and magnetic performance.

Uniformly aligned ZnO nanorod (NR) arrays grown on GaN quantum dots (QDs) as preferred nucleation sites are imperative for designing field emission emitters, ultraviolet photodetectors and light-emitting diodes for a wide range of new optoelectronic applications. In a recent study (2015 Nanotechnology26 415601), Qi et al reported a novel method of fabricating ZnO NRs arrays with uniform shape, the density of which is easily tunable by adjusting the density of GaN QDs. This approach opens a door to obtaining a combination of 0D and 1D structures for optoelectronic applications.

Graphene (Gr) is currently the object of intense research investigations, owing to its rich physics and wide potential for applications. In particular, epitaxial Gr on silicon carbide (SiC) holds great promise for the development of new device concepts based on the vertical current transport at Gr/SiC heterointerface. Precise tailoring of Gr workfunction (WF) represents a key requirement for these device structures. In this context, Günes et al (2015 Nanotechnology 26 445702) recently reported a straightforward approach for WF modulation in epitaxial Gr on silicon carbide by using nitric acid solutions at different dilutions. This paper provides a deep insight on the peculiar mechanisms of chemical doping of epitaxial Gr on 4H-SiC(0001), using several characterization techniques (Raman, UPS, AFM) and density functional theory calculations. The relevance of these findings and their perspective applications in emerging device concepts based on monolithic integration of Gr and SiC will be discussed.

We propose a facile and reproducible method, based on ultra thin porous alumina membranes, to produce cm² ordered arrays of nano-pores and nano-pillars on any kind of substrates. In particular our method enables the fabrication of conducting polymers nano-structures, such as poly[3,4-ethylenedioxythiophene]:poly[styrene sulfonate] (PEDOT:PSS). Here, we demonstrate the potential interest of those templates with controlled cell adhesion studies. The triggering of the eventual fate of the cell (proliferation, death, differentiation or migration) is mediated through chemical cues from the adsorbed proteins and physical cues such as surface energy, stiffness and topography. Interestingly, as well as through material properties, stiffness modifications can be induced by nano-topography, the ability of nano-pillars to bend defining an effective stiffness. By controlling the diameter, length, depth and material of the nano-structures, one can possibly tune the effective stiffness of a (nano) structured substrate. First results indicate a possible change in the fate of living cells on such nano-patterned devices, whether they are made of conducting polymer (soft material) or silicon (hard material).

Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for $t\;\gt$ 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm⁻¹. In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.

The influence of the chirality of semiconductor nanocrystals, CdSe/ZnS quantum dots (QDs) capped with L- and D-cysteine, on the efficiency of their uptake by living Ehrlich Ascite carcinoma cells is studied by spectral- and time-resolved fluorescence microspectroscopy. We report an evident enantioselective process where cellular uptake of the L-Cys QDs is almost twice as effective as that of the D-Cys QDs. This finding paves the way for the creation of novel approaches to control the biological properties and behavior of nanomaterials in living cells.

Although metal–metal oxide nanoparticles have attracted considerable interest as catalysts, they have attracted little interest in nanomedicine. This is likely due to the fact that metal oxide semiconductors generally require biologically harmful ultraviolet excitation. In contrast, this study focuses upon WO₃/Pt nanoparticles, which can be excited by visible light. To optimize the nanoparticles' catalytic performance, platinization was performed at alkaline pH. These nanoparticles destroyed organic dyes, consumed dissolved oxygen and produced hydroxyl radicals. 4T1 breast cancer cells internalized WO₃/Pt nanoparticles within the membrane-bound endo-lysosomal compartment as shown by electron and fluorescence microscopy. During visible light exposure, but not in darkness, WO₃/Pt nanoparticles manufacture reactive oxygen species, promote lipid peroxidation, and trigger lysosomal membrane disruption. As cells of the immune system degrade organic molecules, produce reactive oxygen species, and activate the lipid peroxidation pathway within target cells, these nanoparticles mimic the chemical attributes of immune effector cells. These biomimetic nanoparticles should become useful in managing certain cancers, especially ocular cancer.

Gaps with single-nanometer dimensions (<10 nm) between metallic nanostructures enable giant local field enhancements for surface enhanced Raman scattering (SERS). Monolayer graphene is an ideal candidate to obtain a sub-nanometer gap between plasmonic nanostructures. In this work, we demonstrate a simple method to achieve a sub-nanometer gap by dewetting a gold film supported on monolayer graphene grown on copper foil. The Cu foil can serve as a low-loss plasmonically active metallic film that supports the imaginary charge oscillations, while the graphene can not only create a stable sub-nanometer gap for massive plasmonic field enhancements but also serve as a chemical enhancer. We obtained higher SERS enhancements in this graphene-gapped configuration compared to those in Au nanoparticles on Cu film or on graphene–SiO₂–Si. Also, the Raman signals measured maintained their fine features and intensities over a long time period, indicating the stability of this Au–graphene–Cu hybrid configuration as an SERS substrate.

An optical functional film applicable to various lighting devices is demonstrated in this study. The phase separation of two immiscible polymers in a common solvent was used to fabricate the film. In this paper, a self-organized lens-like structure is realized in this manner with optical OLED functional film. For an OLED, there are a few optical drawbacks, including light confinement or viewing angle distortion. By applying the optical film to an OLED, the angular spectra distortion resulting from the designed organic stack which produced the highest efficiency was successfully stabilized, simultaneously enhancing the efficiency of the OLED. We prove the effect of the film on the efficiency of OLEDs through an optical simulation. With the capability to overcome the main drawbacks of OLEDs, we contend that the proposed film can be applied to various lighting devices.

By means of hybrid density functional theory (DFT) computations, we found that (Li,K)-codoped WO₃ shows a significantly enhanced near-infrared (NIR) absorption ability for smart windows, and investigated the influence of doping through the analysis of the electronic structures of pure and doped hexagonal WO₃. Furthermore, this codoped material, with a hexagonal tungsten bronze nanostructure, was successfully prepared via a simple one-step hydrothermal reaction for the first time. Transmission electron microscopy images showed that the as-prepared products possessed a nanorod-like morphology with diameters of about 5–10 nm. It was demonstrated that (Li,K)-codoped WO₃ presents a better NIR absorption ability than pure, Li-monodoped or K-monodoped WO₃, which is in good agreement with our theoretical predictions. The experiment and simulation results reveal that this enhanced optical property in NIR can be explained by the existence of high free electrons existing in (Li,K)-codoped WO₃.

We successfully demonstrate the synthesis of lead zirconate titanate nanoparticles (PZT NPs) and a ferroelectric device using the synthesized PZT NPs. The crystalline structure and the size of the nanocrystals are studied using x-ray diffraction and transmission electron microscopy, respectively. We observe <100 nm of PZT NPs and this result matches dynamic light scattering measurements. A solution-based low-temperature process is used to fabricate PZT NP-based devices on an indium tin oxide substrate. The fabricated ferroelectric devices are characterized using various optical and electrical measurements and we verify ferroelectric properties including ferroelectric hysteresis and the ferroelectric photovoltaic effect. Our approach enables low-temperature solution-based processes that could be used for various applications. To the best of our knowledge, this low-temperature solution processed ferroelectric device using PZT NPs is the first successful demonstration of its kind.

We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.

Nanoimprint templates made of diamond-like carbon (DLC) and amorphous silicon carbide (SiC) thin films and fluorine-doped associated materials, i.e. F–DLC and F–SiC were investigated in the context of thermal nanoimprint lithography (NIL) with respect to their release properties. Their performances in terms of durability and stability were evaluated and compared to those of conventional silicon or silica molds coated with antisticking molecules applied as a self-assembled monolayer. Plasma-enhanced chemical vapor deposition parameters were firstly tuned to optimize mechanical and structural properties of the DLC and SiC thin films. The impact of the amount of fluorine dopant on the deposited thin films properties was then analyzed. A comparative analysis of DLC, F–DLC as well as SiC and F–SiC molds was then carried out over multiple imprints, performed into poly (methyl methacrylate) (PMMA) thermo-plastic resist. The release properties of un-patterned films were evaluated by the measurement of demolding energies and surface energies, associated with a systematic analysis of the mold surface contamination. These analyses showed that the developed materials behave as intrinsically easy-demolding and contamination-free molds over series of up to 40 imprints. To our knowledge, it is the first time that such a large number of imprints has been considered within an exhaustive comparative study of materials for NIL. Finally, the developed materials went through standard e-beam lithography and plasma etching processes to obtain nanoscale-patterned templates. The replicas of those patterned molds, imprinted into PMMA, were shown to be of high fidelity and good stability after several imprints.

We developed an effective graphene transfer method for graphene/silicon Schottky diodes on a wafer as large as 6 inches. Graphene grown on a large scale substrate was passivated and sealed with a gold layer, protecting graphene from any possible contaminant and keeping good electrical contact. The Au/graphene was transferred by the tension-assisted transfer process without polymer residues. The gold film itself was used directly as the electrodes of a Schottky diode. We demonstrated wafer-scale integration of graphene/silicon Schottky diode using the proposed transfer process. The transmission electron microscopy analysis and relatively low ideality factor of the diodes indicated fewer defects on the interface than those obtained using the conventional poly(methyl methacrylate)-assisted transfer method. We further demonstrated gas sensors as an application of graphene Schottky diodes.

Cross-stacked carbon nanotube (CNT) film is proposed as an additional built-in current collector and adsorption layer in sulfur cathodes for advanced lithium sulfur (Li-S) batteries. On one hand, the CNT film with high conductivity, microstructural rough surface, high flexibility and mechanical durability retains stable and direct electronic contact with the sulfur cathode materials, therefore decreasing internal resistivity and suppressing polarization of the cathode. On the other hand, the highly porous structure and the high surface area of the CNT film provide abundant adsorption points to support and confine sulfur cathode materials, alleviate their aggregation and promote high sulfur utilization. Moreover, the lightweight and compact structure of the CNT film adds no extra weight or volume to the sulfur cathode, benefitting the improvement of energy densities. Based on these characteristics, the sulfur cathode with a 100-layer cross-stacked CNT film presents excellent rate performances with capacities of 986, 922 and 874 mAh g⁻¹ at cycling rates of 0.2C, 0.5C and 1C for sulfur loading of 60 wt%, corresponding to an improvement of 52%, 109% and 146% compared to that without a CNT film. Promising cycling performances are also demonstrated, offering great potential for scaled-up production of sulfur cathodes for Li-S batteries.

The adsorption of small molecules (NH₃, N₂, H₂ and CH₄) on all-boron fullerene B₄₀ is investigated by density functional theory (DFT) and the non-equilibrium Green's function (NEGF) for its potential application in the field of single-molecular gas sensors. The high adsorption energies (−1.09 to −0.75 eV) of NH₃ on different adsorption sites of the B₄₀ surface indicate that NH₃ strongly chemisorbs to B₄₀. The charge transfer induced by the NH₃ adsorption results in a modification of the density of states (DOS) of B₄₀ near the Fermi level, and therefore changes its electronic transport properties. For all possible adsorption sites, the adsorption of NH₃ exclusively leads to a decrease of the conductance of B₄₀. Taking into consideration that the non-polar gas molecules (e.g. N₂, H₂ and CH₄) are only physisorbed and show negligible effect on the conductance properties of B₄₀, we would expect that B₄₀ can be used as a single-molecular gas sensor to distinguish NH₃ from non-polar gas molecules at low bias.

Haematite (α-Fe₂O₃) nanostructures were synthesized via a Pechini sol–gel method (PSG) and an electrospinning (ES) technique. Their texture and morphology were investigated by scanning and transmission electron microscopy. α-Fe₂O₃ nanoparticles were obtained by the PSG method, whereas fibrous structures consisting of interconnected particles were synthesized through the ES technique. The crystallinity of the α-Fe₂O₃ nanostructures was also studied by means of x-ray diffraction and Raman spectroscopy. Gas-sensing devices were fabricated by printing the synthesized samples on ceramic substrates provided with interdigitated Pt electrodes. The sensors were tested towards low concentrations of ethanol in air in the temperature range (200−400°C). The results show that the α-Fe₂O₃ nanostructures exhibit somewhat different gas-sensing properties and, interestingly, their sensing behaviour is strongly temperature-dependent. The availability of active sites for oxygen chemisorption and the diffusion of the analyte gas within the sensing layer structure are hypothesized to be the key factors responsible for the different sensing behaviour observed.

A new method of molecular detection in a metallic-semiconductor nanopore was developed and evaluated with experimental and computational methods. Measurements were made of the charging potential of the electrical double layer (EDL) capacitance as charge-carrying small molecules translocated the nanopore. Signals in the charging potential were found to be correlated to the physical properties of analyte molecules. From the measured signals, we were able to distinguish molecules with different valence charge or similar valence charge but different size. The relative magnitude of the signals from different analytes was consistent over a wide range of experimental conditions, suggesting that the detected signals are likely due to single molecules. Computational modeling of the nanopore system indicated that the double layer potential signal may be described in terms of disruption of the EDL structure due to the size and charge of the analyte molecule, in agreement with Huckel and Debye's analysis of the electrical atmosphere of electrolyte solutions.

In the present study, we report the electrochemical sensing property of multi-layer graphene nanobelts (GNBs) towards dopamine (DA). GNBs are synthesized from natural graphite and characterized by using techniques like field-emission scanning electron microscopy, atomic force microscopy and Raman spectroscopy. An electrochemical sensor based on GNBs is developed for the detection of DA. From the cyclic voltammetry and amperometry studies, it is found that GNBs possess excellent electrocatalytic activity towards DA molecules. The developed DA sensor showed a sensitivity value of 0.95 μA μM⁻¹ cm⁻² with a linear range of 2 μM to 0.2 mM. The interference data exhibited that GNB is highly selective to DA even in the presence of common interfering species like ascorbic acid, uric acid, glucose and lactic acid.

Low-temperature scanning gate microscopy (LT-SGM) studies of graphene allow one to obtain important spatial information regarding coherent transport such as weak localization (WL) and universal conductance fluctuations. Although fascinating LT-SGM results on pristine graphene prepared by mechanical exfoliation have been reported in the literature, there appears to be a dearth of LT-SGM results on chemical vapor deposition (CVD)-grown graphene whose large scale and flexible substrate transferability make it an ideal candidate for coherent electronic applications. To this end, we have performed LT-SGM studies on CVD-grown graphene wide constriction (0.8 μm), which can be readily prepared by cost-effective optical lithography fully compatible with those in wafer foundry, in the WL regime. We find that the movable local gate can sensitively modulate the total conductance of the CVD graphene constriction possibly due to the intrinsic grain boundaries and merged domains, a great advantage for applications in coherent electronics. Moreover, such a conductance modulation by LT-SGM provides an additional, approximately magnetic-field-independent probe for studying coherent transport such as WL in graphene and spatial conductance variation.

This study presents a new ultrathin SiC structure prepared by a catalyst free carbothermal method and post-sonication process. We have found that merging ultra-light 3D graphene foam and SiO together at high temperature leads to the formation of a complex SiC structure consisting of 3D SiC foam covered with traditional 1D nanowires. Upon breaking off, the 3D SiC was confirmed to be made from 2D nanosheets. The resulting novel 2D SiC nanosheets/nanoflakes were thoroughly investigated by using optical microscope, SEM, EDS, TEM, STEM, AFM, and Raman, which verified the highly crystallised structure feature. AFM results revealed an average thickness of 2–3 nm and average size of 2 μm for the flakes. This new SiC structure could not only actualise SiC usage for nano-electronic devices but is also expected to open new applications as well.

The core–shell nanostructures have the advantages of combining distinctive properties of varied materials and improved properties over their single-component counterparts. Synthesis approaches for this class of nanostructures have been intensively explored, generally involving multiple steps. Here, a general and convenient strategy is developed for one-step in situ synthesis of various carbon-encapsulated nanocrystals with a core–shell structure via a solid-state reaction of metallocene complexes with (NH₄)₂S₂O₈ in an autoclave at 200 °C. A variety of near-spherical and equiaxed nanocrystals with a small median size ranging from 6.5 to 50.6 nm are prepared as inner cores, including Fe₇S₈, Ni₃S₄ and NiS, CoS, TiO₂, TiO₂ and S₈, ZrO₂, (NH₄)₃V(SO₄)₃ and VO₂, Fe₇S₈ and Fe₃O₄, MoS₂ and MoO₂. The worm-like carbon shell provides exclusive room for hundreds of nanocrystals separated from each other, preventing nanocrystal aggregation. The synergistic effect of ammonium and a strong oxidizing anion on the electrophilic oxidation of metallocene complexes containing a metal–ligand π bond contributes to the carbon formation at low temperature. It is considered that the cyclopentadienyl ligand in a metallocene complex will decompose into highly reactive straight chain olefinic pieces and the metal–olefin π interaction enables an ordered self-assembly of olefinic pieces on nanocrystals to partially form graphitizable carbon and a core–shell structure. The high capacity, good cycling behavior and rate capability of Fe₇S₈@C and Ni₃S₄ and NiS@C electrodes are attributed to the good protection and electrical conductivity of the carbon shell.

Here, we report on the synthesis of MoS₂ nanosheets using a simple two-step additive-free growth technique. The as-synthesized nanosheets were characterized to determine their structure and composition, as well as their optical properties. The MoS₂ nanosheets were analyzed by scanning electron microscopy, transmission electron microscopy (TEM), including high-resolution scanning TEM imaging and energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL). The as-produced MoS₂ nanosheets are vertically aligned with curved edges and are densely populated. The TEM measurements confirmed that the nanosheets have the 2H-MoS₂ crystal structure in agreement with the Raman results. The XPS results revealed the presence of high purity MoS₂. Moreover, a prominent PL similar to mechanically exfoliated few and mono-layer MoS₂ was observed for the as-grown nanosheets. For the thin (≤50 nm) nanosheets, the PL feature was observed at the same energy as that for a direct band-gap monolayer MoS₂ (1.83 eV). Thus, the as-produced high-quality, large-area, MoS₂ nanosheets could be potentially useful for various optoelectronic and catalysis applications.

Composite nanostructures consisting of porous NiO nanosheets on carbon nanotubes (CNTs) are fabricated using a facile and low-cost electroless plating method. The CNTs, modified by a polymer, are adopted as the template upon which porous Ni nanosheets are grown using electroless plating. This is followed by removal of the polymer layer and oxidation of the Ni by controlled thermal annealing. The effect of reductant concentration on the morphology of the NiO nanosheets is studied. The electrochemical characteristics of the nanostructures are measured using chronopotentiometry. Experimental measurements show that the NiO nanosheet covered CNT composite nanostructures exhibit a relatively high specific capacitance of 1177 F g⁻¹ at a discharge current density of 2 A g⁻¹, while retaining 89.2% of its initial capacitance at a current density of 2 A g⁻¹ after 1000 cycles.

Achieving the required control of dopant distribution and selectivity for nanostructured semiconducting building block is a key issue for a large variety of applications. A promising strategy is monolayer doping (MLD), which consists in the creation of a well-ordered monolayer of dopant-containing molecules bonded to the surface of the substrate. In this work, we synthesize a P δ−layer embedded in a SiO₂ matrix by MLD. Using a multi-technique approach based on time of flight secondary ion mass spectrometry (ToF-SIMS) and Rutherford backscattering spectrometry (RBS) analyses, we characterize the tuning of P dose as a function of the processing time and temperature. We found the proper conditions for a full grafting of the molecules, reaching a maximal dose of 8.3 × 10¹⁴ atoms/cm². Moreover, using 1D rate equation model, we model P diffusion in SiO₂ after annealing and we extract a P diffusivity in SiO₂ of 1.5 × 10¹⁷ cm² s⁻¹.

Obtaining topographic images of surfaces presenting terraces with heights in the nanometer and sub-nanometer range has become routine since the advent of atomic force microscopy (AFM). There remain however several open questions regarding the validity of direct topographic measurements. Here we turn to recent advances in AFM to correct the height of nanometric terraces by exploiting the four observables of bimodal AFM operated in the non-invasive attractive regime. We first derive expressions based on the van der Waals theory and then image model terraces in air in standard bimodal AFM while simultaneously correcting and decoupling the sources of loss/gain of height.

This study introduces a new class of heat transfer fluids by dispersing functionalised graphene oxide nanoparticles (GNPs) in ammonium and phosphonium-based deep eutectic solvents (DESs) without the aid of a surfactant. Different molar ratios of salts and hydrogen bond donors (HBD) were used to synthesise DESs for the preparation of different concentrations of graphene nanofluids (GNFs). The concentrations of GNPs were 0.01 wt%, 0.02 wt% and 0.05 wt %. Homogeneous and stable suspensions of nanofluids were obtained by high speed homogenisation and an ultrasonication process. The stability of the GNFs was determined through visual observation for 4 weeks followed by a centrifugal process (5000–20 000 rpm) for 30 min in addition to zeta potential studies. Dispersion of the GNPs in DES was observed using an optical microscope. The synthesised DES-based GNFs showed no particle agglomeration and formation of sediments in the nanofluids. Thermo-physical properties such as thermal conductivity and specific heat of the nanofluids were also investigated in this research. The highest thermal conductivity enhancement of 177% was observed. The findings of this research provide a new class of engineered fluid for heat transfer applications as a function of temperature, type and composition DESs as well as the GNPs concentration.

It is generally accepted that the nonlinear I–V characteristics for semiconductor nanostructures are mainly induced by the Schottky contacts or by the space charge limited transport mechanism. We perform I–V measurements on undoped and doped In–Zn–O compound nanobelts and confirm that their intrinsic non-ohmic transport behaviors are not caused by these mechanisms. A model based on the hopping assisted trap state electrons transport process is introduced to explain the nonlinear I–V characteristics and to extract their electrical parameters. An understanding of this trap-state influenced carrier transport can advance the progress of nanomaterials applications and enable us to distinguish their intrinsic transport behaviors from contact effects. The results also indicate that the material has good electrical properties and can be used as a potential substitute for In₂O₃.

We report a facile and large-scale fabrication of highly ordered one-dimensional (1D) indium phosphide (InP) nanopore arrays (NPs) and their application as photoelectrodes for photoelectrochemical (PEC) hydrogen production. These InP NPs exhibit superior PEC performance due to their excellent light-trapping characteristics, high-quality 1D conducting channels and large surface areas. The photocurrent density of optimized InP NPs is 8.9 times higher than that of planar counterpart at an applied potential of +0.3 V versus RHE under AM 1.5G illumination (100 mW cm⁻²). In addition, the onset potential of InP NPs exhibits 105 mV of cathodic shift relative to planar control. The superior performance of the nanoporous samples is further explained by Mott–Schottky and electrochemical impedance spectroscopy ananlysis.

A set of Si_1−xSn_x/Si(001) quantum wells (QWs) is grown by applying molecular beam epitaxy. The activation energies of holes in these QWs are studied by deep-level transient spectroscopy. It is observed that the holes activation energies increase monotonically with the Sn fraction (x). The valence band offset between pseudomorphic Si_1−xSn_x and Si obeys the dependence ${\rm{\Delta }}{E}_{{\rm{v}}}$ = 1.69x eV, while the offset between the average valence bands of unstrained Si_1−xSn_x/Si heterojunction was deduced and obeys the dependence ${\rm{\Delta }}{E}_{{{\rm{v}}}_{{\rm{av}}}}$ = 1.27x eV.

We unambiguously show that the signature of Te-rich bismuth telluride is the appearance of three new peaks in the Raman spectra of Bi₂Te₃, located at 88, 117 and 137 cm⁻¹. For this purpose, we have grown stoichiometric Bi₂Te₃ nanowires as well as Te-rich nanowires. The absence of these peaks in stoichiometric nanowires, even in those with the smallest diameter, shows that they are not related to confinement effects or the lack of inversion symmetry, as stated in the literature, but to the existence of Te clusters. These Te clusters have been found in non-stoichiometric samples by high resolution electron microscopy, while they are absent in stoichiometric samples. The Raman spectra of the latter corresponds to the one for bulk Bi₂Te₃. The intensity of these Raman peaks are clearly correlated to the Te content. In order to ensure statistically meaningful results, we have investigated several regions from every sample.

Some molecular dynamics simulations focusing on the interactions between graphene films and water droplets are carried out in this article to investigate the fluid–solid interfacial behavior of surface wettability. The wettability of an ideal graphene film is investigated at room temperature at the beginning of the simulations, then the influences of ambient temperature, surface fluctuation and charge density of the graphene film on the wetting behaviors of water droplets on the film are also discussed from three points of view, namely the interaction energy of the graphene and the water droplet, the mass density of water and the water contact angle on the graphene film. The simulation results indicate that the ideal graphene film is slightly hydrophobic and that both the ambient temperature and the fluctuation of the graphene film play a negative role during the wetting processes. The observations also show that, once charged, the wetting property of graphene changes massively, from slightly hydrophobic to super-hydrophilic.

Using a well-known galvanic displacement reaction, ∼25–40 μm long silver ribbons grown after mixing ∼50 nm copper particles with AgNO₃ solution were observed as a function of Ag⁺ concentration and their growth was characterized in real-time and in situ by evanescent wave (EW) microscopy. At low Ag⁺ concentration, chain-like structures consisting of both Ag and Cu were observed. When the sequence of mixing these two reactants was reversed, different Ag microstructures (platelets and dendrites) were formed and were also characterized by EW microscopy. Dependence of the morphology of all these microstructures on silver ion concentration was determined by EW microscopy in conjunction with scanning and transmission electron microscopy.

Graphene-organic hybrid thin films are promising candidates for use as advanced transparent electrodes and high-performance photodetectors. In this work, we fabricated hybrid thin film structures consisting of graphene and either tetraphenyl-porphyrin (H₂TPP) or metalloporphyrins such as aluminum (III) tetraphenyl-porphyrin (Al(III)TPP) and zinc tetraphenyl-porphyrin (ZnTPP). The optical and electrical characteristics of ultrathin photodetectors based on the graphene-organic hybrid layers were subsequently evaluated. A hybrid deposition system capable of both thermal evaporation and vapor phase metalation was employed to synthesize the tunable metalloporphyrin-based thin films. As a proof of concept, we successfully fabricated various graphene-based photodetectors via the simple and efficient vapor-phase metalation of porphyrin. This work may facilitate the development of new architectures for flexible graphene-organic devices.