Conventional epitaxy of NiO thin films on muscovite mica and c-Al2O3 substrates

• Thickness variation of highly oriented (111) NiO films at 300 °C and 400 °C. • The thickest film at 400 °C showed reduced d-spacing, nearing the bulk value. • NiO film exhibits fiber texture on Si(100), while twin domain epitaxy is observed on c-sapphire. • NiO films on muscovite mica(001) show conventional epitaxy. Fiber-textured and epitaxial NiO thin films were deposited on Si(100), c-Al 2 O 3 , and muscovite mica(001) substrates using reactive magnetron sputtering at substrate temperatures of 300 °C and 400 °C, to investigate the effect of film thickness and substrate temperature on epitaxial growth of NiO films. The as-deposited films exhibited a face-centered cubic structure with a larger lattice constant, attributed to strain induced during the sputtering process. With an increase in substrate temperature to 400 °C, the d-spacing decreased due to strain release, approaching the NiO bulk value for the thickest film. The NiO film grown on Si(100) displayed fiber texture. On c-plane sapphire, NiO thin films exhibited twin domains and three-fold symmetry, consistent with expected crystallographic orientation relationship for NaCl-structured materials on sapphire: ( 111 ) N i O ∥ ( 0001 ) A l 2 O 3 and [ 0 1 ¯ 1 ] N i O ∥ [ 1 ¯ 010 ] A l 2 O 3 , [ 01 1 ¯ ] N i O ∥ [ 10 1 ¯ 0 ] A l 2 O 3 . On muscovite mica(001) substrates, the observed epitaxial shows that the mechanism is conventional epitaxy, rather than van der Waals epitaxy, consistent with the epitaxial growth of the non-layered non-van-der-Waals compound NiO. The epitaxial relationship was identified as of ( 111 ) N i O ∥ ( 001 ) M i c a and [ 0 1 ¯ 1 ] N i O ∥ [ 010 ] M i c a , [ 01 1 ¯ ] N i O ∥ [ 0 1 ¯ 0 ] M i c a .