Research Interest

Piezoelectric materials 

There has been a growing research interest in the piezoelectric thin films due to their potential use in variety of microelectronic devices, which includes micro-electro-mechanical systems (MEMS). In MEMS technology, most of the devices are developed using the micromachined silicon structures. Combination of micromachined silicon with piezoelectric films has resulted in novel microdevices such as microactuators, microsensors and ultrasonic motors etc.  Pb(ZrxTi1-x)O3 known as PZT is identified as the ideal material to realize the above mentioned piezo-microdevices due to attractive properties such as  high piezoelectric coefficients, large remnant polarization and ease integration into micro systems.  Our research involves the synthesis and investigations of PZT thick films with the composition close to x@0.48, the so-called morphotropic phase boundary (MPB).

 

Figure1. Existence of MPB between tetragonal and rhombohedral phases of PZT system

 

Ferroelectric materials

 Electrical properties of bismuth titanate(BTO) based ferroelectric thin films have been widely studied because of its low processing temperature compatible with silicon based technology. Bismuth layer-structured ferroelectrics have the general formula of (Bi2O2)2+ (Ax-1BxO3x+1)2-, Where A can be Bi3+ and B can be Ti 4+. Thus the BTO consists of three perovskite-like units (Bi2Ti3O10)2-, sandwiched between bismuth oxide (Bi2O2)2+ layers. BTO has high leakage current and domain pinning due to defects leads to fatigue which prevent their FeRAM application. Partial substitution of volatile Bi ions in BTO by suitable trivalent rare-earth ions  could improve its ferroelectric and fatigue resistance properties. The fatigue free behavior of these films can be attributed to the enhanced stability of the oxygen in the Ti-O octahedron layer, which is caused by the substitution of stable rare-earth ions for the volatile Bi ions located near the Ti-O octahedron layer. Our current research is also focused on the fabrication and characterization of rare-earth modified BTO thin films by metal-organic  solution decomposition method.