Fabrication of continuous ultrathin ferroelectric films by chemical solution deposition methods

摘要

The integration of ferroelectrics in nanodevices requires firstly the preparation ofhigh-quality ultrathin films. Chemical solution deposition is considered a rapid andcost-effective technique for preparing high-quality oxide films, but one that hastraditionally been regarded as unsuitable, or at least challenging, for fabricating filmswith good properties and thickness below 100 nm. In the present work we explore thedeposition of highly diluted solutions of pure and Ca-modified lead titanates to prepareultrathin ferroelectric films, the thickness of which is controlled by the concentrationof the precursor solution. The results show that we are able to obtain single crystallinephase continuous films down to 18 nm thickness, one of the lowest reported usingthese methods. Below that thickness, the films start to be discontinuous, which isattributed to a microstructural instability that can be controlled by an adequate tailoringof the processing conditions. The effect of the reduction of thickness on thepiezoelectric behavior is studied by piezoresponse force microscopy. The resultsindicate that films retain a significant piezoelectric activity regardless of their lowthickness, which is promising for their eventual integration in nanodevices, forexample, as transducer elements in nanoelectromechanical systems.