Preparation Of Metal Oxide Thin Films By Laser Assisted Chemical Solution Method

With the development of laser technology,laser annealing has been investigated as one of promising approach for material processing.This technology is 'essentially based on the photothermal and photochemical effect induced by high brightness and directional laser.It is consider as a promising avenue for low temperature,rapidly,localized and without substrate damage material manufacturing process.Chemical solution deposition(CSD)are superior to physical processes in terms of low costs,simplicity,vacuum free and scaling.Conventionally,the thermal treatment of films is conducted in a furnace in high temperature for forming crystalline films.This process is associated with issues such as high thermal power,high energy loss and long processing times.In addition,this process renders the compatibility of films with temperature sensitive substrates(eg.,Si,glass,alloy and flexible polymers).The laser-assisted chemical solution method combines the advantages of laser annealing and chemical solution deposition method to achieve a low temperature,low cost,short time and large area preparation of thin film materials.Metal oxide films have been utilized in dielectric capacitors,ferroelectric memories,piezoelectric sensors,multiferroic magnetoelectric devices,photocatalysis,gas sensors,transparent conductors,spintronics,field-effect transistors,infrared detectors,lithium-ion batteries,fuel cells and solar cells.Pulsed UV light is effective for the fabrication of metal oxide films,because oxides generally have a higher absorption of it.In this dissertation,metal oxide films are synthesized by laser assisted chemical solution deposition method.Several laser irradiation parameters are varied to optimize the performance of the films.The mechanisms of laser annealing are studied.The main contents of this paper are as following.1.The preparation of porous oxide films is achieved at room temperature using laser annealing.Fe3O4 has been recently received much attention as anodes in lithium ion batteries for high theoretical capacities.The large volume changes during charge/discharge,however,will lead to the serious degradation in performance,limiting the applications.Porous Fe3O4 thin films are successfully synthesized by a facile laser assisted chemical solution deposition(LACSD)method at room temperature in air.The average pore size of the films can be control by irradiation density.The porous Fe3O4 thin films show a high reversible capacity at a high current density of 2 C after 500 cycles.The developed LACSD method can provide a facile route to deposit porous oxide films.2.Transparent conducting film is crucial in electronic devices,while the high annealing temperature of it impede the development of flexibe electronics.The electronic transport performance of W-doped In2O3 thin flms was effectively improved though laser irradiation at room temperature.The maximum mobility of 9.81 cm2 V-1 s-1 is obtained,enabling a low resistivity of 2.88 × 10-3 ? cm.Moreover,the IWO thin film shows a high near-infrared region(NIR)transmittance.3.The electronic transport performance of Ga-doped ZnO thin flms was effectively improved though laser annealing at room temperature.After laser annealing at intensity of 110 mJ cm-2,the conducti-vity,carrier concentration and mobility increase by 30 times,3 times and 10 times respectively.The average transmittance of the thin film in visible region is above 94,5%.These results suggest that laser annealing is an effective way to improve the conductivity of transparent conductive films at room temperature.4.The epitaxial La0.7Sr0.3MnO3 films are successfully prepared by laser-assisted chemical solution method at a low substrate temperature.The metal-semiconductor and ferromagnetic-paramagnetic transition temperatures of the LSMO films can be modified by adjusting the laser energy density.The TIM and Tc of the LSMO films increased with an increase of the irradiation intensity from 60 to 90 mJ cm-2.On the other hand,the conductivity and magnetization are gradually enhanced with an intensity increase.This is attributed to the reduction of lattice defects,oxygen vacancies and the decline of Mn3+/Mn4+ratio in the films.