Study of ferroelectricity and related phenomena in the potassium nitrate: poly (vinyl alcohol) composite films

Abstract

Ferroelectric materials have attracted an immense interest due to their potential applications in microelectronics especially in nonvolatile memory devices such as ferroelectric random access memories (FeRAM), non volatile random access memories (NVRAMs) and dynamic random access memories (DRAMs) etc. Many ferroelectric materials, such as, barium titanate (BaTiO3), barium strontium titanate (BST), potassium dihydrogen phosphate (KDP), Lithium niobate (LiNbO3), lead zirconate titanate (PZT), strontium bismuth tantalate (SBT), strontium barium niobate (SBN) and tri-glycine sulphate (TGS) etc, have been studied in a variety of forms like, single crystal, pellet and thin film for the use of these materials in memory devices. There are many other applications of thin film ferroelectric materials as voltage tunable dielectric capacitor in resonators and filters. Also recently thin film ferroelectrics are finding increasing use in microelectronic mechanical systems (MEMS) in producing highly sensitive actuators and sensors with low noise. Generally, ferroelectric ceramics in film form are suitable for the microelectronic applications. The various fabrication methods such as sputtering, pulse laser deposition (PLD), metal organic chemical vapor deposition (MOCVD), chemical solution deposition (CSD), metal organic decomposition (MOD) and molecular beam epitaxy (MBE) have been employed to form ferroelectric films. These ferroelectric ceramics can also be produced in film form by dispersing these in polymer matrix. The ceramic-polymer composite materials are emerging as a new class of electronic and dielectric materials. The work in the thesis has been focused on the ferroelectric and switching properties of potassium nitrate (KNO3) and potassium nitrate - ammonium nitrate mixed system [(NH4)0.39K0.61NO3] composite films. The composite films of KNO3 and (NH4)0.39K0.61NO3 (NKN) have been produced with poly(vinyl alcohol) (PVA).