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Abstract: Amorphous carbon nanotubes (aCNTs), synthesized through a low-temperature simple method have been decorated with chemically synthesized different zinc oxide (ZnO) nanostructures like nanocones and nanoflowers. The as-prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). It has been found that attachment of ZnO nanostructure can effectively enhance the field electron emission properties of the aCNTs. Modification with ZnO nanoflower-like structure can reduce the turn-on field of aCNTs from 8.91 to 3.64V/μm. The results have been explained in terms of increased roughness which in-turn led to large enhancement of the local electric field and thus facilitated electron emission from this hybrid emitter. [Copyright &y& Elsevier]

Abstract: a-C:F thin films with varying fluorine content were prepared by plasma CVD and the sputtering method as inorganic alignment layers for overcoming the disadvantages of conventional liquid crystal (LC) alignment layers. The material and structural properties were investigated by X-ray photoelectron spectroscopy, Fourier transform infrared absorption, and contact angle measurement. For elucidation of the liquid crystal alignment layers, LC cells with a-C:F films were fabricated, followed by examination of the textures of the LC and electro-optical characteristics. The fluorine concentrations of a-C:F films were controlled by changing the mixture gas ratio (R G) in CVD and applied power ratio (R P) in the sputter system. An increase in R G and R P led to increase fluorine incorporation, and the film microstructure changed from a diamond-like to a polymer-like structure. In addition, the sputtered a-C:F films showed a higher fluorination than the CVD sample since the PTFE target was only composed of CF2 functional groups. Surface composition influenced the surface energy of thin films and an extremely hydrophobic property was obtained in the case of fluorine-rich a-C:F films. LC orientations were observed in various compositions of a-C:F films, and the vertically self-aligned LC textures confirmed that a sputtered a-C:F film is a good candidate for an alignment layer without any post-treatment. [Copyright &y& Elsevier]

Abstract: Arrays of carbon nanotube (CNT) emitter dots with a diode structure were fabricated by screen printing and subsequent photolithographic patterning of a CNT paste. Two different types of raw CNTs, which were of narrow and wide distributions of lengths, were used in preparing the photosensitive CNT pastes. Field emission uniformity of the arrays of CNT emitter dots was characterized by statistically analyzing brightness data of individual dots. It seemed that the narrow length distribution of raw CNTs resulted in uniform heights of standing CNT emitters in dots, consequently giving rise to high emission uniformity over an area. [Copyright &y& Elsevier]

Abstract: To have insight to the atomistic process of graphitic ordering in tetrahedral amorphous carbon films which is induced by irradiation of high-energy electrons, the role of temperature in the graphitization was experimentally studied. The change of electron diffraction patterns before and after irradiation at room temperature indicated graphitic ordering, but irradiation at −170 °C resulted in disordering. Systematic measurements of the temporal evolution of electron energy loss spectra with irradiation at various elevated temperatures and data analysis based on the Johnson–Mehl–Avrami model yielded the activation energy for electron-stimulated ordering of as small as ∼0.09±0.01 eV. The most plausible model to account for all the experimental facts is the dissociative diffusion that is triggered by the electron-stimulated displacement of carbon atoms at the initial sites. [Copyright &y& Elsevier]

Abstract: A series of emission current measurements were taken from various types of multiwalled carbon nanotube (MWCNT) films in order to examine their stability for electron field emission. We found that the MWCNTs films grown by the catalytic thermal chemical vapor deposition (CVD) method exhibited much improved emission stability as compared to MWCNT films grown by the plasma-enhanced CVD (PECVD) method. We explain this difference of performance by referring to the graphitic order of these MWCNTs as detected by transmission electron microscopy and Raman spectroscopy. Results indicate that MWCNTs with high-order tubular structures demonstrate stable electron field emission. The best performing sample exhibits a constant current degradation of ∼3% per hour at an emission current density of ∼1 mJ/cm2. [Copyright &y& Elsevier]