Ferroelectric properties of HfO_2 nanodots with a diameter smaller than 10 nm deposited on an ITO bottom electrode

摘要

HfO_2 nanodots and epitaxial HfO_2 thin films with ferroelectric properties were grown on yttria-stabilized zirconia substrates with indium tin oxide bottom electrodes via a pulsed laser deposition (PLD) method. The crystallinity and ferroelectric properties of the epitaxial HfO_2 thin films were analyzed to compare ferroelectric properties resulting from crystallinity and the strained structure of HfO_2 nanodots. Using the total number of PLD pulses as a control, it was possible to grow HfO_2 nanodots with diameters of 7, 12, and 20 nm and heights of 4.9, 7.8, and 14.8 nm. Based on the d_(33) piezoelectric hysteresis loops and polarization switching phenomena, it was confirmed that the HfO_2 nanodots exhibited good ferroelectric properties even for scaling of less than 7 nm in diameter. The observation of the piezoelectric d_(33) hysteresis loop of the HfO_2 nanodots and epitaxial HfO_2 thin films revealed that HfO_2 nanodots had improved ferroelectric properties due to the size effect.