Investigation On Preparation And Photophysical And Chemical Properties Of Bismuth Vanadium (0k0) Single Crystal Surface Film

With the development of society,energy shortage and environmental pollution have become increasingly serious.Searching for a new type of clean energy has become a hot topic of research today.The use of photocatalysts as a medium for production of sustainable clean energy,and the efficient degradation of pollutants has become one of the main research topics.The photocatalyst TiO₂ has many advantages,such as being cheap,non-toxic,and chemically stable.However,it has many disadvantages such as large optical band gap,high electron-hole recombination rate,and it can only absorb the ultraviolet part of the solar light.While visible light accounts for a large proportion of solar energy,How to construct an efficient visible light responsive catalyst has become a major research direction.At present,there are two main researches.On the one hand,doping and modification of TiO₂ broadens its optical absorption range,on the other hand,searches for new photocatalyst with a suitable optical gap.The new ferroelectric materials of the new bismuth layered perovskite structure have many excellent properties,such as ferroelectric,excellent dielectric properties,fatigue resistance,lead-free and environmentally friendly,and have many applications in film capacitance,electro-optical devices,etc.There are also many applications,and most have good visible light response.Barium vanadate as a lanthanum-layered perovskite material has received extensive attention from researchers.At present,many achievements have been made in the study of bismuth vanadium powder:1?Samples of different grain size,structure and morphology can be obtained by a variety of preparation methods.2?Structure and photocatalytic performance of samples with or without surfactant,3?Influence of the modification on photocatalysts?metal/metal ions,non-metal ions,heterojunctions with other semiconductors,etc.?.Although many aspects have been involved in the study of powder,there are still some vague aspects in their mechanistic studies,such as the inability to specify the distribution and source of the photogenerated carrier on the different crystal faces,as well as the growth of the bismuth vanadium single crystal film on the substrate.For these reasons,thin films with specific crystal planes were prepared by PLD technology,and their growth mechanism and photocatalytic properties were studied in detail.In this paper,a series of thin film samples were prepared by pulsed laser deposition?0k0?,the use of the highest lattice matching YSZ?001?single crystal as a substrate,and a series of thin film samples were prepared by controlling the substrate temperature,target and deposition time,etc.A series of thin film samples were prepared under the conditions,and detailed photophysical and photocatalytic properties of the prepared samples were studied.There are mainly the following research contents:?1?The monoclinic yttrium vanadate single crystal epitaxial thin films were successfully deposited on the YSZ?001?substrate by pulsed laser deposition.The following variables were mainly prepared samples:1?substrate temperature,2?target material,3?deposition time.?2?A series of film samples were prepared and characterized by XRD,AFM and Raman.It is found that as the substrate temperature increases,the yttrium vanadate single crystal thin film deposited on YSZ?001?gradually approaches the stoichiometric ratio of 1:1.When the substrate temperature is 680^oC and the target is 6:1,the pure phase?0k0?single crystal film can be prepared stably.At the same time,the composition of the sample in the process of temperature variation is analyzed.?3?The photocatalytic performance of samples prepared at different substrate temperatures was tested with Rhodamine B?10mg/L?as the target degradation product.Samples were irradiated with a 300W xenon lamp at a distance of 15cm from the sample.The photocatalyst was deposited at a deposition temperature of 680^oC,The best degradation effect is achieved with a degradation rate of 16.4*10^-3 min^-1.The characterization of the samples shows that the crystal grains were even and smooth on the topography,the grain boundaries were clearly distinguished,and the number of small-sized crystal nuclei was small.From the XPS,the deep level between 10-18 eV was obtained as compared with that of the previous vanadium vanadate.The polycrystalline sample deposited on the quartz substrate shows a significant change.The silver deposition experiments of in-situ silver niobate silver nanoparticles and barium vanadate monocrystalline films were investigated..?4?A series of samples were prepared by changing the different deposition time.The sample was scanned by atomic force microscopy.The growth mode of the film was a three-dimensional island growth.The crystal nuclei grew continuously as the deposition time progressed,When the growth was longitudinal to 200 nm,the sample will remain stable and grow horizontally and will be made in the sample.The sample preparation time will be extended to 60 minutes,the lateral growth did not grow indefinitely,and finally did not get continuous film.