Mechanism Study Of The3D Porous Nanocrystalline TiO₂Thin-film By Atmospheric Pressure Radio Frequency Plasma Enhanced Chemical Vapor Deposition

Titanium dioxide has been widely studied in new energy resources and environment, due to its unique semiconductor structures.Porous thin film with unique sheet attached3D structure has been prepared in our lab by atmospheric pressure plasma enhanced gas phase chemical deposition. It is big in exposed high-energy surfaces, high in porosity, big in specific surface area. So it has broad application prospects in dye-sensitized solar cell and photocatalyst.Studying gas phase process as breakthrough point, by plasma diagnostic, collecting, characterizing and regulating the gas phase product, this paper find the sedimentation mechanism of the unique thin film and pointed out the direction about regulating the three-dimensional structures, improving the uniformity of thin film, and preparing large thin film.Firstly, with plasma emission spectroscopy, waveform of Ⅰ-Ⅴ and thermocouple, adequately diagnose the electron temperature, ion temperature, gas temperature, concentration of relevant particles and so on.Secondly, in order to intensive study the gas phase process, we collect and characterize the gas phase product. Researches show that the gas phase product is more than a dozen nanometers in size, sharp in size distribution. What is more, the consequence that gas phase product is crystallographic means that the spontaneous nucleation appears in the gas phase process. Introduce theory of charged nanoparticles to fully explain the growth mechanism of gas phase product, with the gas phase product are negatively charged, electrostatic field limits the gas phase products excessive growth. Fully illustrates the special of radio frequency atmospheric pressure plasma assisted deposition. The effect of power, residence time and the flow of O2on gas phase product composition and crystalline also has been studied.Lastly, present the growth mechanism of3D thin film based on the research results about gas phase process and the thin film growth process. The microcrystal from spontaneous nucleation process adsorbs on the substrate and became the growing point; When the other gas phase product contacts them, they will grow fast, cross will each other and the3D porous structure has been built. In this way, the new microcrystal continuously adsorbs and the3D porous structure grow one layer at a time to be the3D porous structure thin film. This is very meaningful in regulating the three-dimensional structures and preparing large3D porous structure thin film.