Pyroelectric property of novel LiTa3O8 thin film prepared by sol-gel methods

Abstract

A novel sol-gel derived LiTa 3 O 8 film sample was prepared on the Pt/Ti/SiO 2 /Si(100) substrate using the lithium ethoxide and tantalum ethoxide as starting materials. The 0.2mol/L sol of LiTa 3 O 8 was prepared by reacting lithium ethoxide with tantalum ethoxide in 2-methoxyethanol and acetic acid in argon atmosphere to prevent humidity. The sol of LiTa 3 O 8 was firstly diluted to 0.1mol/L and then covered on the Pt/Ti/SiO 2 /Si(100) substrate to form wet film with the condition of the spin-coating speed of 3000~7000 r.p.m. for 30~60 second. Pyrolysis of the prepared wet film was carried out in oxygen atmosphere at temperature of 420~450oC for 2~5 min to remove the residual organics. Annealing of the prepared film was performed at temperature of 750~900oC for 2~4 min in the rapid thermal process furnace to crystallize the prepared film layer. More layers of LiTa 3 O 8 film can be added by repeating the spin-coating and pyrolysis steps prior to the final firing. It was found that up to 18 layers of LiTa 3 O 8 film sample can be deposited before the films begin to exhibit signs of cracking. The performance parameters such as orientation, surface morphology, grain size and thickness of the prepared LiTa 3 O 8 film sample were studied by XRD and SEM. The structure of the LiTa 3 O 8 film is similar to orthorhombic, different from LiTaO 3 film based on XRD pattern. The SEM micrograph reveals that the prepared LiTa 3 O 8 film sample is uniform, smooth and crack-free on the surface with a thickness of 1 µm after crystallized at 750oC. The pyroelectric property of the LiTa 3 O 8 film sample was measured by the home-made water-bath heating pyroelectric coefficient measurement system. The measurement result shows that the novel LiTa 3 O 8 film sample has pyroelectric property and its pyroelectric coefficient is 14.07μC/m 2 K after the sample is subjected to the DC poling of 6V, 15min. The experimental results verify the pyroelectric coefficient of the novel LiTa 3 O 8 film is smaller than that of 122.80μC/m2K of the LiTaO 3 film. The pyroelectric coefficient of the LiTa 3 O 8 film will be improved with the development of the prepared process and adopting higher poling voltage.