On the thickness scaling of ferroelectricity in Al0.78Sc0.22N films

Thickness scaling on ferroelectric properties of sputter-deposited poling-free Al0.78Sc0.22N films has been examined. The c-axis oriented films were confirmed by X-ray rocking curve measurements with a film as thin as 10 nm. Ferroelectric-type hysteresis and poling-free behaviors are observed from the capacitance measurements, even with a thickness of 20 nm. The remnant polarization (P r) shows a gradual degradation when the thickness is less than 35 nm. The switching (SW) cycle test reveals a wake-up effect for the film, especially for thick films of over 35 nm. A longer SW cycle of over 105 times can be obtained with thinner Al0.78Sc0.22N films around 20 nm at the cost of P r.