Epitaxial growth of Nd2Hf2O7(1 1 1) thin films on Ge(1 1 1) substrates by pulsed laser deposition

Nd2Hf2O7 (NHO) thin films have been epitaxially grown by pulsed laser deposition (PLD) on Ge(1 1 1) substrates. In situ reflection high-energy electron diffraction (RHEED) evolution of the (1 1 1)-oriented NHO during the deposition has been investigated and shows that the epilayer has a twin-free character with type-B stacking. Interfacial structure of NHO/Ge has been examined by high-resolution transmission electron microscopy (HRTEM). The results indicate a highly crystalline film with a very thin interface, and the orientation relationship between NHO and Ge can be denoted as (1 1 1)NHO//(1 1 1)Ge and image. Finally, twin-free epitaxial growth of NHO with type-B orientation displays temperature dependence and the type-B epitaxy is favored at high temperature.