Unique Electronic Transport Properties Research Articles

Effect of the orientation of nitro group on the electronic transport properties in single molecular field-effect transistors

Molecular devices with nitro groups display unique electronic transport properties in experiments. By applying the non-equilibrium Green's function combined with density functional theory, we find that the orientation of the nitro group with respect to the backbone of the molecule has a crucial effect on the device performance and can show unusual experimental phenomena. Furthermore, molecular devices with a nitro group are sensitive to gate voltage and suitable for making effective single molecular field-effect transistors. These results provide an important theoretical support to experiments and the design of future molecular devices by using nitro groups.

Electronic Transport Properties of Assembled Carbon Nanoribbons

Graphitic nanowiggles (GNWs) are 1D systems with segmented graphitic nanoribbon GNR edges of varying chiralities. They are characterized by the presence of a number of possible different spin distributions along their edges and by electronic band-gaps that are highly sensitive to the details of their geometry. These two properties promote these experimentally observed carbon nanostructures as some of the most promising candidates for developing high-performance nanodevices. Here, we highlight this potential with a detailed understanding of the electronic processes leading to their unique spin-state dependent electronic quantum transport properties. The three classes of GNWs containing at least one zigzag edge (necessary to the observation of multiple-magnetic states) are considered in two distinct geometries: a perfectly periodic system and in a one-GNW-cell system sandwiched between two semi-infinite terminals made up of straight GNRs. The present calculations establish a number of elementary rules to relate fundamental electronic transport functionality, electronic energy, the system geometry, and spin state.

Photocatalytic studies of CdS nanoparticles assembled on carbon microsphere surfaces with different interface structures: from amorphous to graphite-like carbon

A rapid microwave-assisted method was used for the accurate coating of CdS nanoparticles on the surface of colloidal carbon microspheres to form C/CdS hybrid microspheres, which demonstrated enhanced visible-light-photocatalytic activity for the degradation of rhodamine B (RhB). To investigate the optimal photocatalytic synergistic effect, the above as-prepared of C/CdS hybrid microspheres were treated in a tube furnace by annealing at different temperatures (from 300 to 800 °C) in a N2 flow, which resulted in CdS nanoparticles assembled on different carbon layers (from amorphous to graphite-like carbon). The changes in FT-IR and Raman spectra that were caused by different interfaces were studied. Further, the synergic effect between CdS nanoparticles and different carbon layers, which influence the photocatalytic activity, was then investigated systematically. The results show that the photocatalytic activity of these samples was gradually enhanced as the calcination temperature increased. But compared to the sample without calcination, the photocatalytic activity decreases first and then increases. The combination of CdS and graphite-like carbon may be an ideal system to cause a rapid photoinduced charge separation and decreased possibility of recombination of electron–hole pairs by taking advantage of graphite-like carbon's unique electron transport properties, which increase the number of holes participating in the photooxidation process and enhance the photocatalytic activity.

Electron transport in graphene nanoribbons under a central potential modulation

We study electron transport in graphene nanoribbons (GNs) under a one-dimensional central potential. Two kinds of structures are considered: armchair-edged GN (AGN) where a central potential is applied on the central dimer chain, and zigzag-edged GN (ZGN) where a potential is applied on the central zigzag chain. Both nanoribbons show unique electronic structure and interesting transport properties under potential modulation. Without considering edge effect, a metallic AGN is still metallic after potential modulation. However, if the edge effect is considered, an AGN under potential modulation can be either semiconducting or metallic depending on the potential strength. The AGN transits from semiconducting to metallic and then to semiconducting again with the potential increase. As to ZGN, the potential on the central zigzag chain also greatly affect the quantum conductance. A ZGN will transit from metallic to semiconducting as the potential strength exceeds critical value. All transitions of AGN and ZGN are correlated with the localized state on the central potential chain which induces a quantum channel along the chain.

Monitoring electron-beam irradiation effects on graphenes by temporal Auger electronspectroscopy

Because of its unique electronic transport properties, graphene has attracted an enormousamount of interest recently. By using standard Auger electron spectroscopy andRaman spectroscopy, we have studied electron-beam irradiation effects on graphenedamage. We have shown that irradiation with an electron-beam can selectivelyremove graphene layers and induce chemical reactions, as well as possible structuraltransformations. We have also demonstrated the dependence of damage in graphene onelectron-beam dose. Our work provides ideas on how to optimize the experimentalconditions for graphene characterization and device fabrication. The results throw lighton how energy transfer from the electron beam to graphene layers leads to theremoval of carbon atoms from graphene layers and on the possibility of usingelectron-beam irradiation to locally induce chemical reactions in a controlled manner.

Material characteristics and applications of transparent amorphous oxide semiconductors

Transparent amorphous oxide semiconductors have unique electron transport properties, such as large electron mobility (10–50 cm2/Vs) and the absence of a Hall voltage sign anomaly, that are not seen in conventional amorphous semiconductors. This class of materials has been attracting much attention as a channel layer in thin-film transistors (TFTs) utilizing the above features along with the processing advantage that thin films can be deposited at low temperatures by conventional sputtering methods. The primary driving force for this trend is a rapidly emerging demand for backplane TFTs that can drive the next generation of flat-panel displays. This article reviews the recent advances in fundamental science of these materials and their TFT applications. Emphasis is placed on the view that high ionicity in chemical bonding and large spherical spread of unoccupied metal s orbitals in p-block metal oxides lead to the realization of electronic structures that are advantageous for n-channel TFT applications. Amorphous oxide semiconductors are compared with conventional hydrogenated amorphous silicon, which is used widely as the channel material for backplane TFTs in current liquid-crystal displays.

68.3: Invited Paper: Transparent Amorphous Oxide Semiconductors for High Performance TFT

AbstractThis paper briefly describes unique electron transport properties of transparent amorphous oxide semiconductors (TAOS) for TFT performance along with our material design concept. Emphasized is essential importance of indium ion for emergence of high field effect mobility on the basis of recent results on electronic structure calculation on amorphous InGaZnO4.

Solution‐Based Synthetic Strategies for 1‐D Nanostructures

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5‐Substituted Tris(8‐quinolinolate) Aluminum(III) Complexes

The unique electron-transport and emissive properties of tris(8-quinolinolate) aluminum(III) (Alq(3)) have resulted in extensive use of this material for small molecular organic light-emitting diode (OLED) fabrication. So far, efforts to prepare stable and easy-to-process red/green/blue (RGB)-emitting Alq(3) derivatives have met with only a limited success. In this paper, we describe how the electronic nature of various substituents, projected via an arylethynyl or aryl spacer to the position of the highest HOMO density (C5), may be used for effective emission tuning to obtain blue-, green-, and red-emitting materials. The synthetic strategy consists of four different pathways for the attachment of electron-donating and electron-withdrawing aryl or arylethynyl substituents to the 5-position of the quinolinolate ring. Successful tuning of the emission color covering the whole visible spectrum (lambda=450-800 nm) was achieved. In addition, the photophysical properties of the luminophores were found to correlate with the Hammett constant of the respective substituents, providing a powerful strategy with which to predict the optical properties of new materials. We also demonstrate that the electronic nature of the substituent affects the emission properties of the resulting complex through effective modification of the HOMO levels of the quinolinolate ligand.

Ionic amorphous oxide semiconductors: Material design, carrier transport, and device application

Recently we have reported the room temperature fabrication of transparent and flexible thin film transistors on a polyethylene terephthalate (PET) film substrate using an ionic amorphous oxide semiconductor (IAOS) in an In2O3–ZnO–Ga2O3 system. These transistors exhibit a field effect mobility of ∼10cm2 (Vs)−1, which is higher by an order of magnitude than those of hydrogenated amorphous Si and pentacene transistors. This article describes a chemical design concept of IAOS, and its unique electron transport properties, and electronic structure, by comparing them with those of conventional amorphous semiconductors. High potential of IAOS for flexible electronics is addressed.

Self-Assembling Bipyridinium Multilayers

The identification of strategies to assemble nanostructured films with engineered properties on solid supports can lead to the development of innovative functional materials. In particular, the self-assembly of electroactive multilayers from simple molecular building blocks on metallic electrodes can offer the opportunity to regulate the exchange of electrons between the underlying substrate and solution species. In this context, we designed an experimental protocol to prepare electroactive films from bipyridinium bisthiols. Specifically, we found that a compound incorporating two bipyridinium dications at its core and terminal thiol groups self-assembles into remarkably stable multilayers on polycrystalline gold. The surface coverage of the resulting films can be regulated by adjusting the exposure time of the gold substrate to the bipyridinium solution. Control experiments with appropriate model compounds demonstrate that both bipyridinium dications as well as both thiol groups must be present in the molecular skeleton to encourage multilayer growth. The resulting films transport electrons efficiently from the electrode surface to the film/solution interface. Indeed, they mediate the reduction of Ru(NH(3))(6)(3+) in the electrolyte solution but prevent the back oxidation of the resulting Ru(NH(3))(6)(2+). Furthermore, these polycationic bipyridinium films capture electrostatically Fe(CN)(6)(4-) tetraanions, which can also be exploited to transport electrons across the interfacial assembly. In fact, electrons can travel through the bipyridnium(2+/1+) couples to redox probes in solution and then back to the electrode through the Fe(CN)(6)(4/3-) couples. Thus, our original approach to self-assembling multilayers can produce stable electroactive films with unique electron transport properties, which can be regulated with a careful choice of the anionic components.

Controlled Deposition and Applied Field Alignment of Single Walled Carbon Nanotubes for CNT Device Fabrication.

ABSTRACTCarbon nanotubes (CNTs) offer great potential for advanced sensing devices due to their unique electronic transport properties. However, a significant obstacle to the realization of practical CNT devices is the formation of controlled, reliable and reproducible CNT to metallic contacts. In this work, a procedure for the deposition and alignment of CNTs onto metallic electrodes using chemically functionalized lithographic patterns is reported. This method uses photo and electron beam lithography to pattern simple Cr/Au thin film circuits on oxidized Si substrates. The circuits are then re-patterned with a self-assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) to specify desired CNT locations between electrodes. The application of an electric field to the metallic contacts during the deposition of solution suspended single walled CNTs causes alignment of the CNTs in the field direction. This method consistently produces aligned CNTs in the defined locations.