Effect of Annealing Temperature and Dopant Concentration on the Surface Layer of Indium Doped Ba0.5Sr0.5TiO3 Thin Film

Abstract

Barium strontium titanate (Ba0.5Sr0.5TiO3) is one of the most important sensing materials for multi-function sensors. Basically, the sensing properties can be controlled by minor modification of the dopants. The purpose of this project is to fabricate barium strontium titanate (BST) and Indium doped barium strontium titanate (BIST) thin films using the chemical solution deposition (CSD) method with 1.00 M precursor. Indium was chosen to be doped into BST because indium was a well known chemical that been used in high performance device such as in the capacitors. The films were deposited by spin coating method with spinning speed at 3000 rpm for 30 seconds. The post deposition annealing of the films were carried out in a furnace at low temperature and high temperature for 1 hour in oxygen gas atmosphere. The surface roughness and grain size analysis of the grown thin films was characterized using atomic force microscope (AFM) at the analysis area of 250 nm x 250 nm. The rms surface roughness and the grain size of obtained BST and BIST thin films, are been discussed details in this project. When the annealing temperature increased, the rms value for the surface roughness and the grain size will decrease. Therefore, small rms value indicates the smoothness surface due to the ability of electron mobility. While, the longer the annealing time, the lower is the dielectric constant (mechanical properties). For the temperature at 240°C give the most homogenous surface. This can be proved in the Figure 4.12. For high temperature the result was too abnormal and can be concluded as unstable.