Structure Dependent Dielectric Properties of Transition Metal Oxide Nanostructures

Abstract

Submicron CMOS technology requires the replacement of SiO2 with high kdielectric materials as gate dielectrics to prevent leakage current and improve the device performance. Because on scaling down the device size, the thickness of SiO2 gate oxide films has to be reduced to few nanometer level which increases the leakage current. To prevent this, SiO2 has to be replaced with highk materials which provide equivalent oxide thickness required for sub-micron CMOS devices. High-k dielectrics can enhance the performance of transparent p-type metal oxide thin-film transistors (TFTs) in CMOS device. Reports reveal that SnO, CuxO and NiOx have been incorporated as p-type channels in transistors. However, fabrication of high-performance p-type metal oxide films are challenging due to deviation from stoichiometry which alters the electronic structure. The stoichiometry deviation due to point defects has to be controlled to improve the electrical performance of p-type metal oxide TFTs. Recent Investigations reveal that hole field-effect mobility and current ratio (Ion/Io f f ) is improved in p-type CuO TFTs based high-k dielectric. Besides, the operating voltage for this type of heterogeneous interfacial layer has been reduced drastically from 30 V to 3 V. The point defects in ZrO2 and NiO (p-type) nanostructures synthesized by solution based techniques can be tuned by surfactant. The nature of point defects induced by the surfactant determines the structure and electrical properties of ZrO2 and NiO nanostructure. In this context, the present thesis describes the influence of surfactant (PVP/CTAB), mineralizer (NH4OH/NaOH), crystallization and sintering temperature on structure and dielectric properties of zirconia nanostructures. Besides it also discuss the influence of surfactants (PVP/CTAB) on point defects, dielectric constant and carrier mobility in NiO nanostructures. Neutral polymeric surfactant PVP through its electrosteric effect is quiet efficient in slowing down the polymerization(abstract attached).