Preparation And Study Of Low-dimensional Functional Nanomaterials

In recent years, low-dimensional nanomaterials have been attracted much attention due to their superior electrical, optical, magnetic, mechanical and thermal properties, as well as their potential applications in nanodevices, sensors and lasers. Against the background of the preparation and application of nanomaterials and with the emphasis of preparing low-dimensional nanomaterials, this paper reports on the latest progress in research of nanomaterials and our research achievements. Some main contents and innovations in this paper are listed as follows:I. Copper nitride thin films were prepared by reactive radio-frequency magnetron sputtering of pure Cu target on glass substrates with various N₂ flow rate. When the nitrogen flow rate increases, the deposition rate decreases and the lattice constant increases. The films have stronger texture along (100) direction when nitrogen flow rate increases. The films' surface was composed of tightly packed particles. The grain size changes from 26 to 16 nm when the nitrogen flow rate increases.II. The Cu₃N phase is very unstable, as it can be completely decomposed into Cu and N₂ through vacuum annealing at temperature of 200°C. The difference in reflectance between the as-deposited and thermally decomposed copper films demonstrates that the Cu₃N film has a high potential to be used as an optical recording media.III. The Hall coefficients of the films are demonstrated to be dependent on the nitrogen flow rate and the measuring temperature. Both the Hall coefficient and resistance of the Cu₃N films increase with the nitrogen flow rate at room temperature, while the Hall mobility and the carrier density of the films decrease. As the temperature changes from 100 K to 300 K, the Hall coefficient and the resistivity of the films decrease, while the carrier density increase and Hall mobility shows no great changes. The energy band gap of the films deduces from the curve of lnR_H vs. 1/T is 1.18-2.60 eV.IV. Wurtzite ZnS nanowires have been successfully prepared through hydrothermal method. The single crystalline ZnS nanowires preferentially grow along the [001] direction. Room-temperature photoluminescence curves of the as-synthesized ZnS nanostructures show four peaks that were analyzed by Gaussian fitting. V. Two-dimensional micrometer-sized single crystalline ZnS thin nanosheets were achieved on a large scale by the hydrothermal method. The ZnS nanosheets are growing along (001) direction and have a lateral dimension up to hundreds of microns and a thickness of 20-50nm. The room-temperature PL measurement reveals that the ZnS nanosheets have visible emissions of 518.2nm in the range of green corresponding to the bandgap emission of 3.65 eV.VI. Cobalt disulfide nanowire arrays have been synthesized by a novel method. The nanowires have apparently continuous, parallel, and ordered modality and the diameter is about 50 run. The XPS results indicate that the valence of cobalt is +2, and the sulfur is -1. The CoS₂ nanowires are anti-ferromagnetic material and the easy magnetization direction of nanowires is along the nanowire axes at room temperature. In the study of electrochemical properties, it is found that the reaction of cobalt disulfide is an intercalation reaction in the range of 1.6-3.0 V, while it is probable a redox reaction in the range of 0.02-1.6 V.VII. Fe₇S₈ nanowire arrays have been successful synthesized using the pulsed electrodeposition in the AAO template. The sample has a stable monoclinic-type superstructure of 4C-Fe₇S₈. The diameter of the Fe₇S₈ nanowires is about 50 nm and the product is single crystalline. The temperature variation of the magnetic susceptibility of the sample shows a ferromagnetic behavior with a transition temperature of～600 K.