Tetragonally strained crystal structure and ferroelectric properties of epitaxial PbTiO3 thin films grown on single-crystal Rh substrates

Highlights: • The tetragonally strained PbTiO₃ thin films on Rh substrates showed improved ferroelectric and piezoelectric properties. • The crystallinity of the PbTiO₃ thin films have been improved due to layer-by-layer growth mode. • The band gap of the PbTiO₃ is increased by the tetragonally strained. • Ferroelectricity and leakage current characteristics improve as the band gap of PbTiO₃ increases. To form tetragonally strained PbTiO₃ (PTO) thin films, PTO thin films were deposited on single-crystal Rh substrates using pulsed laser deposition (PLD). Reducing the PLD deposition rate could further increase the tetragonal strain of the PTO thin films, improve the crystallinity due to the layer-by-layer growth of the films, and improve their ferroelectric and piezoelectric properties. From the time-dependent ferroelectric switching current curves of the PTO capacitors, it was confirmed that the switching speed of the ferroelectric polarization increases as the crystallinity of the thin film improves. In particular, it was confirmed that the band gap could be increased due to the tetragonal strains formed by the lattice misfit between PTO and Rh, which supports the good leakage current characteristics of the PTO films with relatively large tetragonal strains.