Preparation and characterization of $Pb(Zr,Ti)O_3$ thin films by aerosol deposition

Abstract

Ferroelectric films are promising candidates for capacitor dielectrics in non-volatile memory devices due to the remanant polarization. Many of the ferroelectric materials are multi-metal oxide. Therefore, it is important to control the composition to produce ferroelectric films with good material quality. Aerosol deposition method has been investigated to be applied to prepare composition controlled ferroelectric films. Aerosol is a suspension of solid or liquid particles in a gas, usually air; a colloid. Precursor solution is atomized into droplets of micron size, transferred to the substrate, and deposited on it. Preparation of ferroelectric films of good quality has been reported, but the understanding on this process is scarce. In this study, the relationships between changes in aerosol condition and produced films are studied. Ultrasonic atomization is used to produce droplets. The mean size of the droplets are measured by particle size analyzer, which uses the optical principles. Lead acetate trihydrate ($Pb(OOCCH_3)_2ㆍ3H_2O) are dissolved in methanol and 2-methoxyethanol, respectively. These solutions are used as the model system. The mean sizes are in the range of 1-2㎛ and droplets are less than 10㎛ for all cases measured. The mean size decreases with solute concentration, and has power law relationship. A model that decribes the changes in droplet size, relative humidity, temperatures, is developed and used for computer simulation of droplet drying process. As droplet size decreases, solute concentration increases and solute begin to precipitate depending on their solubility. It is detrimental to produce uniform films. Less volatile solvent, low reactor wall temperature, high solute concentration, and high droplet number concentration favor small decrease in droplet size. The concentration profiles in the droplet at the end of simulation are uniform for all cases considered. This is due to the high relative humidity, which is characteristic in LSMCD...