Graphene has attracted much interest in both academia and industry. The challenge of making it semiconducting is crucial for applications in electronic devices. A promising approach is to reduce its physical size down to the nanometer scale. Here, we present the surface-assisted bottom-up fabrication of atomically precise armchair graphene nanoribbons (AGNRs) with predefined widths, namely 7-, 14- and 21-AGNRs, on Ag(111) as well as their spatially resolved width-dependent electronic structures. STM/STS measurements reveal their associated electron scattering patterns and the energy gaps over 1 eV. The mechanism to form such AGNRs is addressed based on the observed intermediate products. Our results provide new insights into the local properties of AGNRs, and have implications for the understanding of their electrical properties and potential applications.
ZnO and Al-doped ZnO(ZAO) thin films have been prepared on glass substrates by direct current (dc) magnetron sputtering from 99.99% pure Zn metallic and ZnO:3 wt%Al2O3 ceramic targets, the effects of substrate temperature on the crystallization behavior and optical properties of the films have been studied. It shows that the surface morphologies of ZAO films exhibit difference from that of ZnO films, while their preferential crystalline growth orientation revealed by X-ray diffraction remains always the (0 0 2). The optical transmittance and photoluminescence (PL) spectra of both ZnO and ZAO films are obviously influenced by the substrate temperature. All films exhibit a transmittance higher than 86% in the visible region, while the optical transmittance of ZAO films is slightly smaller than that of ZnO films. More significantly, Al-doping leads to a larger optical band gap (Eg) of the films. It is found from the PL measurement that near-band-edge (NBE) emission and deep-level (DL) emission are observed in pure ZnO thin films. However, when Al was doped into thin films, the DL emission of the thin films is depressed. As the substrate temperature increases, the peak of NBE emission has a blueshift to region of higher photon energy, which shows a trend similar to the Eg in optical transmittance measurement.
Chemical Reviews,2015年115(11):5570–5603 ISSN：0009-2665
[Yang, Junliang] Cent S Univ, Sch Phys & Elect, Inst Super Microstruct & Ultrafast Proc Adv Mat, Changsha 410083, Hunan, Peoples R China.;[Yang, Junliang] Cent S Univ, Sch Phys & Elect, Hunan Key Lab Super Microstruct & Ultrafast Proc, Changsha 410083, Hunan, Peoples R China.;[Yan, Donghang] Chinese Acad Sci, Changchun Inst Appl Chem, State Key Lab Polymer Phys & Chem, Changchun 130022, Jilin, Peoples R China.;[Jones, Tim S.] Univ Warwick, Dept Chem, Coventry CV4 7AL, W Midlands, England.
[Yang, Junliang] Cent S Univ, Sch Phys & Elect, Inst Super Microstruct & Ultrafast Proc Adv Mat, Changsha 410083, Hunan, Peoples R China.
Molecular template growth (MTG) is a newly developed method for fabricating high-quality organic semiconductor thin films with controllable morphologies, molecular orientations, electronic structures, and interface properties to produce high-performance organic electronic and optoelectronic devices. There are several MTG methods with different molecular template materials and growth behaviors, including multiphenyl- and multithiophene-based MTG, and perylene-derivative MTG. Extensive research works have also revealed that Individualized methods for fabricating high-quality organic semiconductor thin films with controllable thin-film properties can be developed on the basis of specific understandings of the growth behaviors of organic semiconductor molecules and the desired device structures.
[He, Yuehui] Cent S Univ, State Key Lab Powder Met, Sch Phys Sci & Technol, Changsha 410083, Peoples R China.
Copper nanoparticles encapsulated by multi-layer graphene have been produced in large quantity (in grams) by metal-organic chemical vapor deposition at 600 degrees C with copper(II) acetylacetonate powders as precursor. The obtained graphene/copper shell/core nanoparticles were found to be formed by a novel coalescence mechanism that is quite different from the well-known dissolution-precipitation mechanism for some other graphene/metal (such as nickel, iron or cobalt) shell/core nanoparticles. Differential scanning calorimetry and thermogravimetric analyses showed that the copper nanoparticles encapsulated by multi-layer graphene with a thickness of 1-2 nm were thermally stable up to 165 degrees C in air atmosphere. Moreover, high-resolution transmission electron microscopy showed that the single-crystal copper nanoparticles, after exposure to air for 60 days, did not exhibit any sign of oxidation. (C) 2012 Elsevier Ltd. All rights reserved.
graphene;antidot lattices;bandgap;electronic structure;first-principles calculations;tight-binding model
The electronic structure of graphene antidot lattices (GALs) with zigzag hole edges was studied with first-principles calculations. It was revealed that half of the possible GAL patterns were unintentionally missed in the usual construction models used in earlier studies. With the complete models, the bandgap of the GALs was sensitive to the width W of the wall between the neighboring holes. A nonzero bandgap was opened in hexagonal GALs with even W, while the bandgap remained closed in those with odd W. Similar alternating gap opening/closing with W was also demonstrated in rhombohedral GALs. Moreover, analytical solutions of single-walled GALs were derived based on a tight-binding model to determine the location of the Dirac points and the energy dispersion, which confirmed the unique effect in GALs.
Sb2Se3 is a promising absorber material for photovoltaic cells because of its optimum band gap, strong optical absorption, simple phase and composition, and earth-abundant and nontoxic constituents. However, this material is rarely explored for photovoltaic application. Here we report Sb2Se3 solar cells fabricated from thermal evaporation. The rationale to choose thermal evaporation for Sb2Se3 film deposition was first discussed, followed by detailed characterization of Sb2Se3 film deposited onto FTO with different substrate temperatures. We then studied the optical absorption, photosensitivity, and band position of Sb2Se3 film, and finally a prototype photovoltaic device FTO/Sb2Se3/CdS/ZnO/ZnO:Al/Au was constructed, achieving an encouraging 2.1% solar conversion efficiency.