Papers by Author: C. Wang

Abstract: In our paper, we induced the process of ZnO based thin film transistors (ZnO-TFTs) fabricated on the substrate of glass. The photolithographic plate designed for using in the ZnO-TFT devices fabrication process was shown in our paper. The ZnO-TFT devices were fabricated successfully, the Ion/off ratio is ~104.

Abstract: ZnO films were grown under different oxygen partial pressures by metal organic chemical vapor deposition on the substrates of Corning glass. We investigated the quality of the films by SIEMENS D8 X-ray diffractometer. The surface morphology of the films were observed by Digital Nanoscope ІІІa AFM with normal silicon nitride tip in the contact mode. The hall effect measurements were carried out with indium ohmic contact. The transmission spectrum of the films were measured. The transmission ratio is larger than 80% in the region above the wavelength of 385nm, and sharply decreased under 10% below the wavelength of 375 nm.

Abstract: We deposited ZnO films on Corning glass substrate by metal-organic chemical vapor deposition (MOCVD). We found the diffraction (002) peak at ~34.46°, indicating that the ZnO thin films were C-oriented. ZnO films were highly transparent with a transmission ratio larger than 85% in the visible range. The surface morphology of the films was observed by atomic force microscopy (AFM).

Abstract: Functional self-assembled structure with well-defined shapes and dimensions are of great current interest. Porphyrins are attractive building manifold patterning for these structures because of their electronic, optical, and catalytic properties. In this paper, we report a novel technique for the assembly patterning of polymers. An Electrospinning process was used to create patterning with diameter ranging from 3 μm to 4 μm and length of up to several hundred micrometers in the presence of Zinc Porphyrin. Scanning electron microscopy (SEM), UV- visible spectra and EDX spectra were used to characterize the patterning. The results indicated that the patterning depended on the concentration of Porphyrin and the operational conditions.

Abstract: Poly(vinyl alcohol) (PVA) nanofibers containing functional ZnS nanoparticles have been successfully prepared by electrospinning technique. The ZnS/PVA mixture solution for electrospinning was obtained by reacting Zn(Ac)2 with Na2S in the PVA aqueous solution. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses revealed that the morphology of the ZnS/PVA nanofibers consists of the dispersion of ZnS nanopaticles with cubic structure in PVA nanofibers. The coordinations between –OH and Zn2+ were characterized by infrared spectroscopy. The photoluminescence spectroscopy studies showed that the ZnS/PVA nanofibers had a strong blue-violet emission band at 450 nm, which may be associated with defect-related emission of the ZnS.

Abstract: The electrospinning technology has been used to fabricate organic nanofibers. As the nanofibers are aligned parallel and crossed, unique electrical and photonic properties are generated. Hereby, a frame of copper thread with a diameter of 0.8 mm was used to collect and align polymer nanofibers. SEM results showed that the nanofibers were parallel aligned between two copper threads. The crossed nanofibers arrays were obtained by layer-by-layer assembling on the parallel nanofibers. The influence factors, such as distance between two copper threads and collection time etc, were investigated.

Abstract: Polyaniline doped with camphorsulfonic acid (PANI.HCSA) nanofibers have been successfully prepared using “nanofibers template” via electrospinning. The PVA nanofibers were used as a template to get the PANI/PVA composite fibers. After removing the template by heat treatment, the PANI fibers were obtained. Scanning electron microscope (SEM) with the Energy Dispersive X-Ray Spectrometer software (EDX) and FT-IR spectra were used to characterize the composite fibers and the PANI.HCSA nanofibers. The average diameters of the composite fibers obtained and PANI fibers were 920 nm and 530 nm, respectively.

Abstract: The carbon-nanofibers carrying Ag nanoparticles (Ag/CNF) have been successfully obtained via electrospinning followed by calcination. For it, AgNO3/polyacrylonitrile (PAN) fibers were firstly prepared as an intermediate and then the intermediate was calcined at 600°C for 4h to transit the PAN nanofibers to the CNF and reduce AgNO3 to the Ag nanoparticles. Transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were used to characterize their morphologies and structures. The results show that the diameters of the Ag nanoparticles and CNF are 5 nm and 180 nm on the average, respectively. Most of the Ag nanoparticles were located on the surface of carbon nanofibers.

Abstract: The effects of an organic solvent on the electrospinning of water-soluble polyacrylamide with ultrahigh molecular weight were investigated. An organic solvent, DMF, was introduced to the polyacrylamide aqueous solution and subsequently, transparent spinning solutions were obtained. The spinning solution was electrospun at the voltage of 10 kV and the electrospun products were examined by scanning electron microscopy (SEM). Results indicated that all the electrospinning products including colloidal particles, beaded fibers and smooth fibers were fabricated in the DMF/H2O bi-component solvent and the morphology of electrospun products changed from smooth fiber to beaded fiber with the increasing amount of DMF used.

Abstract: The CdS/PVP fibers have been successfully prepared by electrospinning. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectra were used to characterize the structure. Results showed that the concentration of polymer solutions and the CdS amount in the solvent influenced the morphology and the diameter of the electrospun fibers. The electrospinning from CdS/PVP in ethanol produced a structure having a combination of fibers, ribbons, beads and an unexpected half hollow sphere (HHS) structure. When the weight ratio of CdS:PVP was kept at 1:1000, the morphologies of electrospun products changed from HHS, to beaded fibers and ribbons, to beaded fibers, and to bead-free fibers with the increasing of the PVP concentration.