RESUMO
Growth of organic semiconductor thin films on a two-dimensional template is affected by its properties and is not well understood. This growth process dictates a thin film's final morphology and crystal structure and is controlled by the interactions between ad-molecules and the template. Here, we report that the template's charge density determines the tuning of such interactions. We observe the dependence of pentacene nucleation on charge carrier density ng in graphene under an applied electric field and contact-doping and then deduce that the interaction energy EA between the ad-molecule and the graphene is related linearly to ng. This tunability of EA allows control of the pentacene crystals growth. We exploit these findings to demonstrate that graphene, in which ng is controlled, can be used to template pentacene thin films for improved optoelectronic properties, such as electrical conductivity and exciton diffusion length.
RESUMO
Realization of flexible electronics is an attractive challenge because of its great potential in many applications. However, the design of flexible and highly conductive metal electrodes has been a bottleneck for the fabrication of flexible devices because bulk metals are easily fractured when subjected to elongation or compression. Here, we demonstrate metal-ceramic nanolaminates as electrodes for flexible electronic devices. Insertion of ceramic layers, each with a thickness of a few nanometers, into an otherwise metal electrode significantly improved its strength and bending stability and only slightly reduced its electrical conductivity. Finally, we demonstrated that a touch screen panel fabricated with metal-ceramic nanolaminate electrodes was stable to 200 000 cycles of folding to a bending radius of 3 mm.
RESUMO
Although there is significant progress in the chemical vapor deposition (CVD) of graphene on Cu surfaces, the industrial application of graphene is not realized yet. One of the most critical obstacles that limit the commercialization of graphene is that CVD graphene contains too many vacancies or sp3 -type defects. Therefore, further investigation of the growth mechanism is still required to control the defects of graphene. During the growth of graphene, sublimation of the Cu catalyst to produce Cu vapor occurs inevitably because the process temperature is close to the melting point of Cu. However, to date few studies have investigated the effects of Cu vapor on graphene growth. In this study, how the Cu vapor produced by sublimation affects the chemical vapor deposition of graphene on Cu surfaces is investigated. It is found that the presence of Cu vapor enlarges the graphene grains and enhances the efficiency of the defect-healing of graphene by CH4 . It is elucidated that these effects are due to the removal by Cu vapor of carbon adatoms from the Cu surface and oxygen-functionalized carbons from graphene. Finally, these insights are used to develop a method for the synthesis of uniform and high-quality graphene.
RESUMO
A novel method is described for the direct growth of patterned graphene on dielectric substrates by chemical vapor deposition (CVD) in the presence of Cu vapor and using a solid aromatic carbon source, 1,2,3,4-tetraphenylnapthalene (TPN), as the precursor. The UV/O3 treatment of the TPN film both crosslinks TPN and results in a strong interaction between the substrate and the TPN that prevents complete sublimation of the carbon source from the substrate during CVD. Substrate-adhered crosslinked TPN is successfully converted to graphene on the substrate without any organic contamination. The graphene synthesized by this method shows excellent mechanical and chemical stability. This process also enables the simultaneous patterning of graphene materials, which can thus be used as transparent electrodes for electronic devices. The proposed method for the synthesis directly on substrates of patterned graphene is expected to have wide applications in organic and soft hybrid electronics.
