Atomic layer deposition of piezoelectric materials: a timely review

Piezoelectric effect plays an important role in a variety of applications, such as sensors, nanogenerators and piezotronics. The performance of piezoelectric device is normally enhanced with increasing dimension of the piezoelectric layer and decreasing piezoelectric layer thickness. To meet the demand for producing superior piezoelectric films (as thin as 1 nm) with precise thickness and composition control, powerful fabrication techniques are essential. Atomic layer deposition (ALD) shows exceptional potential in preparing a wide range of materials with precise thickness control (due to its self-limiting growth nature at the Angstrom level) and capability of deposition on high aspect ratio surface. Here, we provide the introduction to ALD and highlight its unique features among other fabrication techniques, with reference to the state of the art on ALD preparation of different piezoelectric materials, including novel transition metal dichalcogenides (TMDs) and traditional Metal Oxides (MOs). Different ALD-related materials preparation strategies for the improvement of piezoelectricity are also discussed, together with future perspectives on the development of ALD-prepared piezoelectric materials. We believe ALD can enable wider applications of piezoelectricity due to its unique advantages.