Ferroelectric thin films BaTiO3 (BT), Ba0.5Sr0.5TiO3 (BST), PbZr0.5Ti0.5O3 (PZT) are well known dielectric material and have
been attractive for the applications such as capacitors and high density dynamic random access memory (DRAM) due to its high dielectric constant and high capacity of charge storage and ferroelectric solar cell. Thin films Ba0.5S0.5TiO3 (BST) and gallium doped BST (BGST) were successfully deposited by chemical solution deposition and spin coating method. To make BST precursor initially, 0.160 g barium acetate
, 0.131 strontium acetate , 0.355 g titanium isopropoxide {Ti<(CH3)2CHO>4, 99.99 %} and 1.25 ml 2-methoxyethanol , whereas to make BGST precursors initially, 0.060 g gallium oxide (Ga2O3, 99.9 %), 0.160 g barium acetate , 0.131 strontium acetate , 0.355 g titanium isopropoxide {Ti<(CH3)2CHO>4, 99.99 %} and 1.25 ml 2-methoxyethanol . Then using ultrasonic for 2 hours to get the clear liquid. It contained equivalent 1.00 M BST, BGST solution. The solution described above was applied on 15 mm x 15 mm surface p-type Si (100) substrates, then prepared by spin coating at angular velocity 3000 rpm for 30 seconds. The post deposition annealing of the films were carried out in a furnace at 200oC, 240oC, 280oC (low temperature) for 1 hour in oxygen gas atmosphere. The surface roughness and grain size analysis of the grown thin films are described by atomic force microscope (AFM) method at 5000 nm x 5000 nm area. Instead of tunneling current, an atomic force microscope (AFM) detects interatomic forces that occur between a cantilever probe tip and a substrate. Normal imaging forces are in the 1 - 50 nanonewton range and cantilever deflections of less than 0.1 nm can be detected (nanoscale). The rms surface roughness BGST thin films at 5000 nm x 5000 nm area are 0.632 nm, 0.564 nm, 0.487 nm for temperature 200oC, 240oC, 280oC, respectively, whereas the grain size (mean diameter) are 238.4 nm, 219.0 nm, 185.1 nm for temperature 200oC, 240oC, 280oC, respectively. In fact, to increase annealing temperature from 200oC to 280oC would result in decreasing the rms roughness and grain size. Therefore, rms roughness and grain size would have the strong correlation annealing temperature.