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Herein, we present a simple design concept for a monomer that affords individually separated supramolecular polymer chains.

Novel device architectures are opening a new frontier of flexible organic electronics with high integration density, data processability and optical responsivity.

We report on magnetotransport in a high-quality graphene device, which is based on monolayer graphene (Gr) encapsulated by hexagonal boron nitride (hBN) layers, i.e., hBN/Gr/hBN stacks. In the vicinity of the Dirac point, a negative magnetoconductance is observed for high temperatures > ~ 40 K, whereas it becomes positive for low temperatures ≤ ~ 40 K, which implies an interplay of quantum interferences in Dirac materials. The elastic scattering mechanism in hBN/Gr/hBN stacks contrasts with that of conventional graphene on SiO2, and our ultra-clean graphene device shows nonzero magnetoconductance for high temperatures of up to 300 K.

International audience; The detection and quantification of Cs + in aquatic media are an environmental safety and public health matter, so far limited by the lack of rapid, low cost, low limit of detection and selective analytical tools. Herein we demonstrate the efficient fabrication of a novel electrolyte-gated organic field-effect transistor sensor for the Cs + detection in seawater based on the combination of two ultra-thin layers namely poly(3hexylthiophene) as semiconductor and a single lipids monolayer as dielectric. The latter is end-capped with a specific Cs + probe based on a calix[4]arene benzocrown ether to ensure the selectivity. Interestingly, we clearly evidence that by controlling affinity driven guest/host ion exchange, one can lift the general problem of selectivity encountered in all FET-based ion sensors, reaching a nearly perfect selectivity even in highly complex analyte solutions containing competitive ions, such as phosphate buffered saline solution or seawater. Such ultra-thin transistor structure exhibits, a limit of detection at the sub-femtomolar level which corresponds to a 5 folds' magnitude lower than Inductively Coupled Plasma Mass Spectroscopy, the most commonly used technic today. These results pave the way to a generalized monitoring of Cs + in complexed analytes.

International audience; An innovative novel interface has been designed and developed to be used as a potential active layer in chemically sensitive field-effect transistor (Chem-FET) sensor devices for the specific sensing of Cs +. In this study, the synthesis of a specific Cs + probe based on calix[4]arene benzocrown ether, its photophysical properties, and its grafting onto a single lipid monolayer (SLM) recently used as an efficient ultrathin organic dielectric in Chem-FETs are reported simultaneously. On the basis of both optical and NMR titration experiments, the probe has shown high selectivity and specificity for Cs + compared to interfering cations, even if an admixture is used. Additionally, attenuated total reflectance mode Fourier transform infrared spectroscopy was successfully used to characterize and prove the efficient grafting of the probe onto a SLM and the formation of the innovative novel sensing layer.

We report an optimized multi-step chemical vapor deposition process for growing MoS2 thin films. This process enables large-area processing, film patterning simply by using shadow masks, and precise control of the final thickness by changing the initial thickness of the first step of MoO3 film deposition. The structural characterization of the MoS2 films is performed with transmission electron microscopy and X-ray diffraction as a function of film thickness. MoS2 film with a thickness of 3 nm possesses a highly crystalline structure with a spacing of 0.62 nm. The crystallinity and orientation of the films are degraded with increased film thickness. Careful analysis by time-of-flight secondary ion mass spectroscopy reveals that a film with a thickness of 9 nm is not completely sulfurized, and unreacted MoO3 is left at the bottom of the film. These fundamental analyses coincide with the thickness dependence of thin-film transistor (TFT) performance. A TFT with the optimal film thickness of 3 nm achieves high performance, namely a carrier mobility of 0.57 cm2 V−1 s−1 and an on/off ratio of ~ 102.

Transition metal dichalcogenide MoS2 is a two-dimensional material, attracting much attention for next-generation applications thanks to rich functionalities stemming from its crystal structure. Many experimental and theoretical works have focused on the spin-orbit interaction which couples the valley and spin degrees of freedom so that the spin-states can be electrically controllable. However, the spin-states of charge carriers and atomic vacancies in devices have not been yet elucidated directly from a microscopic viewpoint. Here, we report the spin-states in thin-film transistors using operando electron spin resonance spectroscopy. We have observed clearly different electron spin resonance signals of the conduction electrons and atomic vacancies, and distinguished the corresponding spin-states from the signals and theoretical calculations, evaluating the gate-voltage dependence and the spin-susceptibility and g-factor temperature dependence. This analysis gives deep insight into the MoS2 magnetism and clearly indicates different spin-scattering mechanisms compared to graphene, which will be useful for improvements of the device characteristics and new applications. Identifying the properties of spin-states is crucial for understanding the possible magnetic applications of MoS2 thin-film transistors. Here, spin-states of conduction electrons and atomic vacancies in MoS2 are distinguished and investigated under device operation using electron spin resonance.

Acenes and azaacenes lie at the core of molecular materials' applications due to their important optical and electronic features. A critical aspect is provided by their heteroatom multiplicity, which can strongly affect their properties. Here we report pyrazinacenes containing the dihydro-decaazapentacene and dihydro-octaazatetracene chromophores and compare their properties/functions as a model case at an oxidizing metal substrate. We find a distinguished, oxidation-state-dependent conformational adaptation and self-assembly behaviour and discuss the analogies and differences of planar benzo-substituted decaazapentacene and octaazatetracene forms. Our broad experimental and theoretical study reveals that decaazapentacene is stable against oxidation but unstable against reduction, which is in contrast to pentacene, its C-H only analogue. Decaazapentacenes studied here combine a planar molecular backbone with conformationally flexible substituents. They provide a rich model case to understand the properties of a redox-switchable pi-electronic system in solution and at interfaces. Pyrazinacenes represent an unusual class of redox-active chromophores. Acenes are a promising class of organic materials with distinctive electronic and optical properties. Here decaazapentacene and octaazatetracenes are prepared and their self-assembly behaviour at different oxidation states is analysed. Práce se zabývá studiem pyrazinacenů obsahujících dihydro-dekaazapentacenové a dihydro-oktaazatetracenové chromofory a porovnáním jejich vlastností při modelovém chování na oxidačním kovovém substrátu. Byla nalezena odlišná, na oxidačním stavu závislá konformační adaptace a samouspořádající se chování. Byly připraveny dekaazapentaceny a oktaazatetraceny a analyzováno jejich samoorganizující se chování v různých oxidačních stavech.

Gas sensors based on transition metal dichalcogenides (TMDCs) have attracted much attention from a new perspective involving light-assisted or gate-voltage operation. However, their combined roles as regards the gas sensing performance and mechanism have not yet been understood due to the lack of controlled studies. This study systematically investigates the oxygen sensor performance and mechanism of few-layer-thick rhenium disulfide (ReS2) field-effect transistors (FETs) under light illumination and gate biasing. As a result, a combination of light illumination and positive gate voltage enhanced the device responsivity over 100% at a 1% oxygen concentration, that is, the approach achieved a practical sensitivity of 0.01% ppm-1, which outperform over most of the reports available in the literature. Furthermore, the fabricated devices exhibited long-term stability and stable operation even under humid conditions, indicating the ability of the sensor device to operate in a real-time application. These results contribute to the development of versatile tunable oxygen sensors based on TMDC FETs., 6 main figures, 1 table, 5 supporting figures

Graphene/hexagonal boron nitride (hBN) moir\'e superlattices have attracted interest for use in the study of many-body effects and fractal physics in Dirac fermion systems. Many exotic transport properties have been intensively examined in such superlattices, but previous studies have not focused on single-carrier transport. The investigation of the single-carrier behavior in these superlattices would lead to an understanding of the transition of single-particle/correlated phenomena. Here, we show the single-carrier transport in a high-quality bilayer graphene/hBN superlattice-based quantum dot device. We demonstrate remarkable device controllability in the energy range near the charge neutrality point (CNP) and the hole-side satellite point. Under a perpendicular magnetic field, Coulomb oscillations disappear near the CNP, which could be a signature of the crossover between Coulomb blockade and quantum Hall regimes. Our results pave the way for exploring the relationship of single-electron transport and fractal quantum Hall effects with correlated phenomena in two-dimensional quantum materials.

We investigate a two-dimensional (2D) heterostructure consisting of few-layer direct bandgap ReS2, a thin h-BN layer and a monolayer graphene for application to various electronic devices. Metal-insulator-semiconductor (MIS)-type devices with two-dimensional (2D) van-der-Waals (vdW) heterostructures have recently been studied as important components to realize various multifunctional device applications in analogue and digital electronics. The tunnel diodes of ReS2/h-BN/graphene exhibit light tuneable rectifying behaviours with low ideality factors and nearly temperature independent electrical characteristics. The devices behave like conventional MIS-type tunnel diodes for logic gate applications. Furthermore, similar vertical heterostructures are shown to operate in field effect transistors with a low threshold voltage and a memory device with a large memory gate for future multifunctional device applications., Comment: 29 pages

Contributing to the need for new graphene nanoribbon (GNR) structures that can be synthesized with atomic precision, we have designed a reactant that renders chiral (3,1)-GNRs after a multistep reaction including Ullmann coupling and cyclodehydrogenation. The nanoribbon synthesis has been successfully proven on different coinage metals, and the formation process, together with the fingerprints associated with each reaction step, has been studied by combining scanning tunneling microscopy, core-level spectroscopy, and density functional calculations. In addition to the GNR’s chiral edge structure, the substantial GNR lengths achieved and the low processing temperature required to complete the reaction grant this reactant extremely interesting properties for potential applications., The project leading to this publication has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 635919), from ICT-FET EU integrated project PAMS (Agreement No. 610446), from the Spanish Ministry of Science and Competitiveness (MINECO, Grant Nos. MAT2013-46593-C6-01, MAT2013-46593-C6-2-P, MAT2013-46593-C6-4-P, MAT2013-46593-C6-6-P), FEDER, from the Basque Government (Grant Nos. IT-621-13, IT-756-13, and PI2015-042), from the World Premier International Center (WPI) for Materials Nanoarchitectonics (MANA) of the National Institute for Materials Science (NIMS), Tsukuba, Japan, and from JSPS Bilateral Open Partnership Joint Research Project.

Electrically reconfigurable organic logic circuits are promising candidates for realizing new computation architectures, such as artificial intelligence and neuromorphic devices. In this study, multiple logic gate operations are attained based on a dual-gate organic antiambipolar transistor (DG-OAAT). The transistor exhibits a Λ-shaped transfer curve, namely, a negative differential transconductance at room temperature. It is important to note that the peak voltage of the drain current is precisely tuned by three input signals: bottom-gate, top-gate, and drain voltages. This distinctive feature enables multiple logic gate operations with "only a single DG-OAAT," which are not obtainable in conventional transistors. Five logic gate operations, which correspond to AND, OR, NAND, NOR, and XOR, are demonstrated by adjusting the bottom-gate and top-gate voltages. Moreover, varying the drain voltage makes it possible to reversibly switch two logic gates, e.g., NAND/NOR and OR/XOR. In addition, the DG-OAATs show a high degree of stability and reliability. The logic gate operations are observed even months later. The hysteresis in the transfer curves is also negligible. Thus, the device concept is promising for realizing multifunctional logic circuits with a simple transistor configuration. Hence, these findings are expected to surpass the current limitations in complementary metal-oxide-semiconductor devices.

Organic multivalued logic circuits (OMVLs) have drawn tremendous attention due to their high data processability and simple fabrication techniques. However, OMVLs have so far been achieved only on rigid silicon substrates, and this limits their potential for broader applications. In this study, we develop an organic ternary inverter on plastic substrates. The inverters showed well-balanced ternary logic states with high voltage gain and low power consumption. Importantly, the devices exhibited stable operation even after 100 bending cycles, demonstrating high flexibility and reliability. This device has high potential to attain mechanical flexibility and data handling capability at the same time.

Highly oriented, multilayer molecular films of picene and dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) molecules with the long axis parallel to the substrate (parallel configuration, hereafter) were fabricated on their characteristic bulklike monolayer. These molecules form a dense monolayer with a bulklike molecular arrangement on metal surfaces such as Au(111), which allows further stacking of parallel molecules. Indeed, upon adsorption of picene and DNTT on these dense monolayers, growth of straight islands of multilayer without the dendritic layer was observed. Particularly, in the case of picene, one-dimensional islands with lengths over 100 μm were formed and aligned in 3-fold symmetric directions of the substrate, which was not observed in the case of DNTT. X-ray diffraction measurements revealed the presence of [201̅] and [211̅] planes and the absence of the [001] diffractions, indicating that the one-dimensional islands of picene indeed consist of parallel molecules. The formation of huge crystalline islands in the case of picene, in contrast to the case of DNTT, is likely induced by the stronger intermolecular force, as suggested from the calculation of the vibrational energy.

Graphene superlattices have recently been attracting growing interest as an emergent class of quantum metamaterials. In this paper, we report the observation of nonlocal transport in bilayer graphene (BLG) superlattices encapsulated between two hexagonal boron nitride (hBN) layers, which formed hBN/BLG/hBN moir\'e superlattices. We then employed these superlattices to detect a long-range charge-neutral valley current using an all-electrical method. The moir\'e superlattice with broken inversion symmetry leads to a hot spot with Berry curvature accumulating at the charge neutral point (CNP), and it harbors satellites of the CNP. We observed nonlocal resistance on the order of 1 $\text{k}\Omega$, which obeys a scaling relation. This nonlocal resistance evolves from the quantum Hall effect but without magnetic field/time-reversal symmetry breaking, which is associated with a hot-spot-induced topological valley current. This study should pave the way to developing a Berry-phase-sensitive probe to detect hot spots in gapped Dirac materials with inversion-symmetry breaking., Comment: 9 pages, 3 figures

Multi-step chemical vapor deposition (CVD) is a synthesis method which is capable of producing a uniform, large area, and high-quality thin films. In this work, we report the effect of post-annealing on the structural and optical properties of few-layers (FL) MoS2 thin films synthesized by multi-step CVD. Based on atomic force microscopic image, the thickness of the MoS2 thin film is ∼3 nm, which is equivalent to five layers. After annealing at 900°C for 17 min, intensity of the A1g and [Formula: see text] Raman modes increased by ∼3 times while the full-width-at-half-maximum (FWHM)* reduced from ∼10 cm−1 to ∼7.5 cm−1 for A1g and from ∼13.6 cm−1 to ∼7.5 cm−1 for [Formula: see text]. Both of the as-grown and annealed samples showed X-ray (002) diffraction peak at 14.2° but the intensity was more prominent for the annealed sample. It was found that the annealed sample showed clear and distinct absorbance peaks at 666, 615, 448, 401, and 278 nm which correspond to the A, B, C, D, and E excitons, respectively. The results indicate that annealing significantly improved the optical and structural quality of the MoS2 film. Field-effect transistor based on annealed MoS2 thin film was fabricated and showed electron mobility of 0.21 cm2V−1s−1, on/off ratio of 1.3 × 102 and a threshold voltage of 0.72 V. Our work highlights the importance of high-temperature annealing in multi-step CVD to obtain a uniform and high-quality FL MoS2 thin films.

Future one-dimensional electronics require single-crystalline semiconductor free-standing nanorods grown with uniform electrical properties. However, this is currently unrealistic as each crystallographic plane of a nanorod grows at unique incorporation rates of environmental dopants, which forms axial and lateral growth sectors with different carrier concentrations. Here we propose a series of techniques that micro-sample a free-standing nanorod of interest, fabricate its arbitrary cross-sections by controlling focused ion beam incidence orientation, and visualize its internal carrier concentration map. ZnO nanorods are grown by selective area homoepitaxy in precursor aqueous solution, each of which has a (0001):+c top-plane and six {1–100}:m side-planes. Near-band-edge cathodoluminescence nanospectroscopy evaluates carrier concentration map within a nanorod at high spatial resolution (60 nm) and high sensitivity. It also visualizes +c and m growth sectors at arbitrary nanorod cross-section and history of local transient growth events within each growth sector. Our technique paves the way for well-defined bottom-up nanoelectronics., Semiconductor nanocrystals are potential nanoelectronic materials but often display nonuniform electric properties due to their anisotropic growths. Here, the authors report cross-sectional cathodoluminescence imaging of a single-crystalline ZnO nanowire to resolve its growth sectors with different carrier concentrations.

The electrical stability and reliability of molybdenum disulfide (MoS2) thin film transistors (TFTs) were investigated by associating thickness-dependent structural defects with degradation mechanism. Patterned MoS2 films with different thicknesses were fabricated for use as transistor channels via the modified multi-step chemical vapor deposition method. X-ray photoelectron spectroscopic (XPS) analyses revealed that highly layered and stoichiometric MoS2 films of up to ∼3 nm thickness were formed around the surface, whereas Mo metal bonds were dominant around the bottom of the films (9 nm). Variations in transistor properties of the thus prepared MoS2 films were examined by applying positive and negative bias stress (PBS and NBS, respectively). The experimental data indicated that MoS2 TFTs with 3-nm-thick films exhibited stable behavior under both PBS and NBS conditions, whereas those with 9-nm-thick films exhibited clear shifts in electrical performance ( △ V t h △ μ s a t s ). These results, together with XPS analyses, revealed that the instability of the MoS2 TFTs under PBS is dominated by sulfur interstitials, whereas their instability under NBS is caused by oxygen vacancies and metallic Mo defects. Additional details about the correlation between the atomic structural defects, which are generated due to insufficient sulfurization of thick films, and the electrical instability of the MoS2 TFTs were discussed.

For most thin film structures, by changing the wavelength range to fit ellipsometric spectra, the values of the fitted parameters also change to a certain extent. The reason is that compared with the ellipsometric sensitivity many thin films are vertically non-uniform. In absorbing films with significant dispersion in the used wavelength range, the penetration depth of probing light can show large variations depending on the wavelength. Consequently, the value of a fitted parameter for a certain wavelength range is a weighted sum of structural information over different depth ranges corresponding to the different wavelengths. By changing the wavelength range, the range of penetration depths can be adjusted, and the fitted values can be plotted as a function of the probed depth range calculated directly from the determined or tabulated extinction coefficients. We demonstrate the results on deposited polycrystalline thin films. The advantage of this approach over the parameterization of structural properties as a function of depth is that the wavelength scan approach requires no parameterized depth distribution model for the vertical dependence of a layer property. The difference of the wavelength scan method and the vertical parameterization method is similar to the difference between the point-by-point and the parameterized dielectric function methods over the used wavelength range. The lateral structures strongly influence the ellipsometric response, as well. One of the most remarkable effects is when the lateral feature sizes approach the wavelength of the probing light. In this case the effective medium method is not valid any more, since scattering and depolarization occurs. By scanning the wavelength range, the limit wavelength of the onset of scattering can be found, and used for the determination of the corresponding critical lateral period length.

We report a didactic and simple example of the subtleness in the balance of intermolecular and molecule-substrate interactions and its effect on molecular self-assembly. The study is performed on two closely related molecular blends of copper phthalocyanines and pentacene, in each of which one of the two molecules is fluorinated. Reversing the fluorination brings about changes in the intermolecular hydrogen bonds, as well as in the interactions with the substrate. As a result, on Au(100) substrates one blend assembles into a crystalline structure, whereas the other, displaying weaker intermolecular interactions and a larger corrugation in the molecule-substrate interaction potential, results in a disordered layer. However, the difference between the two blend's structures vanishes when substrates with less corrugated interaction potentials are used. © 2014 American Chemical Society., This work was supported by the Spanish Grant Nos. MAT2010-21156-C03- and PIB2010US-00652 and the Basque Government Grant No. IT-621-13. J.M.G.-L. acknowledges support from the Spanish Ministry of Economy and Competitiveness under projects FIS2012-30996 and FIS2010-21282-C02-01 and from the ReLiable project funded by the Danish Council for Strategic Research-Programme Commission on Sustainable Energy and Environment (project no. 11-116792).

Model donor-acceptor assemblies at metal-organic interfaces, namely, fluorinated copper-phthalocyanines (F 16CuPC) and pentacene (PEN) assemblies on the Au(111) surface, have been the focus of the present study. A full picture of the crystallographic and electronic structure of PEN and F 16CuPC monolayers as well as of their 1:1 binary mixture on the Au(111) surface has been explored by means of a variety of surface-sensitive techniques, providing important information on the intermolecular and molecule-substrate interactions governing the self-assembly process. A long-range ordered donor-acceptor network is observed for the mixture as a result of the greatly enhanced intermolecular interaction via C-F···H-C hydrogen bonds. Interestingly, the new supramolecular structure involves changes in the electronic structure of the molecular components. In particular, the strongest changes are observed at the C and F atoms of the F 16CuPc, as opposed to the F 16CuPc N, Cu, or PEN C atoms. With the aid of theoretical calculations, such effects are found to be at least partially related to an upward shift in energy of the F 16CuPc molecular orbitals, concomitant with a molecule-to-metal charge donation, not from the HOMO, but deeper lying orbitals. © 2012 American Chemical Society., This work was supported by the Spanish MICINN (MAT2010-21156-C03-01, C03-03, PIB2010US-00652) and the Basque Government (IT-257-07). The SRC is funded by the National Science Foundation (award no. DMR-0084402). B.P.D. thanks the ICTP (Trieste) for travel funding. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 226716. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007- 2013) through the Integrated Infrastructure Initiative “European Light Sources Activities − Synchrotrons and Free Electron Lasers” (grant agreement no. 226716).

We examined the transistor properties of an N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8)/quaterrylene (QT) heteromolecular layer, in which the highly ordered molecular layers were stacked on the monolayer level. Ambipolar behavior was clearly observed when behaving as a field effect transistor (FET). The field effect mobilities and threshold voltages were evaluated to gain an insight into the injection and transport of the carriers. The obtained carrier mobilities for holes and electrons were calculated to be 3.6 × 10−3 and 2.7 × 10−2 cm2 V−1 s−1, respectively. These values are comparable to those of the respective FET behaviors of QT (p-channel) and PTCDI-C8 layers (n-channel), indicating that a well-defined heteromolecular interface is an essential factor for improving carrier transport in ambipolar FETs. On the other hand, in the PTCDI-C8 layer, a marked shift from 5 to 61.6 V was observed in the threshold voltage for electron transport. We concluded this drastic change in threshold voltage to be due to the presence of hole carriers in the underlying QT layers. This finding demonstrates the potential to manipulate threshold voltage according to the electronic states of the underling layer without disturbing carrier transport.

The temperature dependences of the photoluminescence (PL) spectra of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8)/Quaterrylene (QT) heteromolecular thin film and neat-PTCDI-C8 thin film were investigated to elucidate the effects of a heteromolecular interface on exciton relaxation and recombination processes. The PL spectra were deconvoluted into six components related to Frenkel, two charge-transfer (CT), and excimer exciton states. With the heteromolecular thin film, we found the behavior of the CT excitons to be intriguingly different in terms of luminous efficiency and temperature dependence from that of the Frenkel exciton. In this Letter, we provide detailed analyses of the exciton relaxation and recombination processes at a heteromolecular interface.

Self-assemble monolayers of binary molecules were studied by scanning tunneling microscopy. Di-indenoperylene (DIP) and fluorinated copper-phthalocyanine (F16CuPc), which are p-type and n-type organic semiconductors respectively, were co-deposited in ultra-high vacuum on Au(111) and Cu(111) surface. STM observation exhibited the molecules formed well-ordered intermixed monolayer on the metal surfaces. Theoretical calculation revealed C-F…H bonding between neighboring F16CuPc and DIP was a dominant force for the ordered phase formation. Orientation, alignment and domain formation were determined by balancing molecule-substrate interaction as well as such intermolecular interaction, and as a consequence showed dependency on the metal substrates and ratios of the molecules. Thus, the ordered phases were formed only at certain molecular ratios and were named as “molecular alloys” after those of inorganic materials.

Poly(vinyl chloride) (PVC) powder and commercial rigid PVC pipe were dechlorinated hydrothermally in the presence of alkalis such as ammonia, sodium hydroxide, and potassium hydroxide in a semi-batch flow reactor, with comparison to dechlorination using water alone. Aqueous ammonia was the most effective among these solvents. Dechlorination with aqueous ammonia proceeded in three stages: initial incubation, major dechlorination, and slow dechlorination. In the initial stage the rates were very slow and scarcely affected by temperature or ammonia concentration. In the second stage extensive dechlorination took place, and the rates were affected by temperature and ammonia concentration. These higher rates were found to be significantly influenced by swelling, not alkalinity, when these various alkalis solvents were compared. In the last stage the rates were slower than in the previous stage, and were not significantly dependent on temperature or ammonia concentration.

Modern field-effect transistors or laser diodes take advantages of band-edge structures engineered by large uniaxial strain εzz, available up to an elasticity limit at a rate of band-gap deformation potential azz (= dEg/dεzz). However, contrary to aP values under hydrostatic pressure, there is no quantitative consensus on azz values under uniaxial tensile, compressive, and bending stress. This makes band-edge engineering inefficient. Here we propose SEM-cathodoluminescence nanospectroscopy under in situ nanomanipulation (Nanoprobe-CL). An apex of a c-axis-oriented free-standing ZnO nanorod (NR) is deflected by point-loading of bending stress, where local uniaxial strain (εcc = r/R) and its gradient across a NR (dεcc/dr = R(-1)) are controlled by a NR local curvature (R(-1)). The NR elasticity limit is evaluated sequentially (εcc = 0.04) from SEM observation of a NR bending deformation cycle. An electron beam is focused on several spots crossing a bent NR, and at each spot the local Eg is evaluated from near-band-edge CL emission energy. Uniaxial acc (= dEg/dεcc) is evaluated at regulated surface depth, and the impact of R(-1) on observed acc is investigated. The acc converges with -1.7 eV to the R(-1) = 0 limit, whereas it quenches with increasing R(-1), which is attributed to free-exciton drift under transversal band-gap gradient. Surface-sensitive CL measurements suggest that a discrepancy from bulk acc = -4 eV may originate from strain relaxation at the side surface under uniaxial stress. The nanoprobe-CL technique reveals an Eg(εij) response to specific strain tensor εij (i, j = x, y, z) and strain-gradient effects on a minority carrier population, enabling simulations and strain-dependent measurements of nanodevices with various structures.

We have applied simultaneous horizontal and vertical bias to a single molecule (2 nm(2)) in an ordered and disordered matrix to virtually isolate and tune its property without taking it out physically from its environment. Using a dedicated electrode system, we have locally tuned nanoscale properties vertically by STM, while stabilizing its environment by applying a global electric field horizontally. Using this technique, we report tuning of molecular conformations in room temperature, whose evolution of states has been statistically investigated. We have also shown control on switching of a few selected conformations by applying dual bias simultaneously. As we avoid any direct injection of charge into the system via electrode contact, this technique could be used as a generalized method to tune phenomena evolved in an environment of weak interaction from a large distance without destroying the property.

The main aims of this study were to explore a new technique for growing molecular nanocrystals and to examine their optical properties. To grow nanocrystals, we applied a vacuum evaporation technique. Small perylene nanocrystals (ca. 200 nm) at a high density (7.6 μm-2) were produced by ultra-rapid evaporation on a pattern-indented Si surface. A perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) buffer layer was found to be effective for further downsizing of the nanocrystals and for preserving their fluorescence properties originating from the nanoscale size effect. [DOI: 10.1380/ejssnt.2006.69]

In order to produce dome-shaped Ge dots with small size and high density, C submonolayers (C-SMLs) were incorporated at the interface between Ge wetting layers and Ge dots. The C atoms are considered to induce a local strain field by forming Ge–C bonding. Such strain field enhanced dome formation even at low temperature (

Recent progress in photoactive organic field-effect transistors (OFETs) is reviewed. Photoactive OFETs are divided into light-emitting (LE) and light-receiving (LR) OFETs. In the first part, LE-OFETs are reviewed from the viewpoint of the evolution of device structures. Device performances have improved in the last decade with the evolution of device structures from single-layer unipolar to multi-layer ambipolar transistors. In the second part, various kinds of LR-OFETs are featured. These are categorized according to their functionalities: phototransistors, non-volatile optical memories, and photochromism-based transistors. For both, various device configurations are introduced: thin-film based transistors for practical applications, single-crystalline transistors to investigate fundamental physics, nanowires, multi-layers, and vertical transistors based on new concepts.

We propose a multistep procedure for Ge dot growth on Si (1 0 0) substrates. This procedure includes (i) sub-monolayer C deposition on a Ge wetting layer or a Ge surface, (ii) Ge deposition at low temperature and (iii) post-annealing after Ge and C deposition for controlling size, structure and density of the Ge dots. The main effect of C on Ge wetting layer was to enhance a structure transition of the Ge dot. Meanwhile, C on the Ge surface was found to suppress a structure modification of the Ge dots against post-annealing. The structure of Ge layers deposited at low temperature was readily modified upon post-annealing. By combining these procedures and optimizing experimental conditions, 10 nm-sized Ge dots with a high number density in the order of 10 11 cm −2 were successfully grown on the Si (1 0 0) substrate.