Haining Cui

Microstructure study of indium tin oxide thin films by optical methods

Abstract ITO (Indium-tin-oxide) thin films were obtained by a DC magnetron sputtering for different thicknesses at room temperature. The thickness, microstructure, surface roughness (δ), refractive index (n), energy band gap (Eg) and the sheet resistance of the ITO films were investigated by the transmission, absorption, specular and diffuse reflection spectra in the range of UV–Vis–NIR. The surface roughness was studied by atomic force microscopy (AFM) and by spectra data calculation. The film microstructure and thickness were investigated by scanning electron microscopy (SEM). The δ was in the range of 11.3–12.4xa0nm. The calculated Eg values explained that the ultra-fine particles within the film changed with deposition conditions. The investigation showed that initially the obtained ITO film grows preferably in a packed particle structure with an average grain size of 50xa0nm.

The structure, morphology and photocatalytic activity of graphene–TiO2 multilayer films and charge transfer at the interface

Graphene–TiO2 multilayer films were prepared using plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering. Inserting graphene into TiO2 induced significant enhancement of the TiO2 Raman signal, which was mainly based on the charge transfer between TiO2 and graphene. The insertion of graphene also greatly affected the surface morphology of the TiO2 films, leading to increased specific surface area. The adsorption capacity and UV photocatalytic activity of the samples were investigated in the process of methyl orange (MO) decomposition and it was found that graphene–TiO2 multilayer films exhibited improved photodegradation efficiency compared to pure TiO2 films.

Carbon dot/polyvinylpyrrolidone hybrid nanofibers with efficient solid-state photoluminescence constructed using an electrospinning technique

Carbon dots (CDs) are the promising candidates for application in optoelectronic and biological areas due to their excellent photostability, unique photoluminescence, good biocompatibility, low toxicity and chemical inertness. However, the self-quenching of photoluminescence as they are dried into the solid state dramatically limits their further application. Therefore, realizing efficient photoluminescence and large-scale production of CDs in the solid state is an urgent challenge. Herein, solid-state hybrid nanofibers based on CDs and polyvinylpyrrolidone (PVP) are constructed through an electrospinning process. The resulting solid-state hybrid PVP/CD nanofibers present much enhanced photoluminescence performance compared to the corresponding pristine colloidal CDs due to the decrease in non-radiative recombination of electron-holes. Owing to the suppressed self-quenching of CDs, the photoluminescence quantum yield is considerably improved from 42.9% of pristine CDs to 83.5% of nanofibers under the excitation wavelength of 360 nm. This has great application potential in optical or optoelectronic devices.

Photoluminescence enhancement of carbon dots induced by hybrids of photonic crystals and gold–silver alloy nanoparticles

Carbon dots are attracting worldwide interest owing to their unique optical properties and great potential for application. However, orange/red emission carbon dots are still rare and exhibit relatively low efficiency. In this work, we present a novel strategy to enhance the fluorescence intensity of orange carbon dots, by synergistically manipulating an electromagnetic field through opal photonic crystals and the localized surface plasmon resonance of a metal structure. An optimum intensity enhancement of 25-fold was obtained for a modulated sample of PMMA opal photonic crystals and 53-fold for PMMA opal photonic crystals/Au–Ag alloy plasmon hybrids. The local electromagnetic field distribution for the PMMA opal photonic crystals/Au–Ag hybrid is calculated by the finite difference time domain method. Furthermore, a fingerprint identification system based on synergistic modulation is realized in the composite system, which provides novel insights into the potential applications of carbon dot films.

Solution-grown method of CdS film by ultrasonical colloid chemistry deposition technique

A technique called ultrasonical colloid chemistry deposition (UCCD) has been used to produce bar-shaped ultrafine particles (UFP) cadmium sulphide films. UV-visible spectra and electron micrographic characterization results are presented and discussed. The thin films were analyzed by means of grazing incidence X-ray diffraction (GIXD) and X-ray diffraction (XRD). Detailed results about the amorphous characterization of the films during room temperature growth and post annealing are given.

ZnO/Cu2S/ZnO Multilayer Films: Structure Optimization and Its Detail Data for Applications on Photoelectric and Photocatalytic Properties

Monolayer Cu2S and ZnO, and three kinds of complex films, Cu2S/ZnO, ZnO/Cu2S, and ZnO/Cu2S/ZnO, were deposited on glass substrates by means of radio frequency (RF) magnetron sputtering device. The impact of the thickness of ZnO and Cu2S on the whole transmittance, conductivity, and photocatalysis was investigated. The optical and electrical properties of the multilayer were studied by optical spectrometry and four point probes. Numerical simulation of the optical transmittance of the multilayer films has been carried out in order to guide the experimental work. The comprehensive performances of the multilayers as transparent conductive coatings were compared using the figure of merit. Compared with monolithic Cu2S and ZnO films, both the optical transmission property and photocatalytic performance of complex films such as Cu2S/ZnO and ZnO/Cu2S/ZnO change significantly.