Stabilizing the ferroelectric phase in HfO-based films sputtered from ceramic targets under ambient oxygen.

Thin film metal-insulator-metal capacitors with undoped hafnium oxide and a mixture of hafnium and zirconium oxides are prepared by sputtering from ceramic targets. The influence of the oxygen concentration while sputtering and of the zirconium concentration on the ferroelectric properties is characterized by electrical and structural methods. Depending on the ambient oxygen, the thin undoped hafnium oxide films show distinct ferroelectric properties.

Optimizing the Piezoelectric Strain in ZrO- and HfO-Based Incipient Ferroelectrics for Thin-Film Applications: An Ab Initio Dopant Screening Study.

HfO and ZrO have increasingly drawn the interest of researchers as lead-free and silicon technology-compatible materials for ferroelectric, pyroelectric, and piezoelectric applications in thin films such as ferroelectric field-effect transistors, ferroelectric random access memories, nanoscale sensors, and energy harvesters. Owing to the environmental regulations against lead-containing electronic components, HfO and ZrO offer, along with AlN, (K,Na)NbO- and (BiNa)TiO-based materials, an alternative to Pb(ZrTi)O-based materials, which are the overwhelmingly used ceramics in industry. HfO and ZrO thin films may show field-induced phase transformation from the paraelectric tetragonal to the ferroelectric orthorhombic phase, leading to a change in crystal volume and thus strain.