Unusual tilted growth and epitaxial relationship of NaCl B1-structured NiO and CrN on r-plane Al2O3

Epitaxial NiO and CrN thin films were deposited on a single-crystal A l 2 O 3 ( 1 1 ¯ 02 ) (r-plane sapphire) using magnetron sputtering. The two materials were intentionally deposited into two different deposition chamber designs and under different conditions (temperature, pressure, gases, and energy of sputtered particles). Despite the differences in the deposition condition and material system, both materials had the same feature with uncommon tilted epitaxial growth. Through an in-depth x-ray diffraction analysis of the NaCl (B1)-structured materials on r-plane sapphire, the full twin domain epitaxial relations were determined and can be described as ( 110 ) NaCl ( B 1 ) ∥ ( 4 4 ¯ 03 ) A l 2 O 3 and [ 1 1 ¯ 2 ] NaCl ( B 1 ) ∥ [ 1 ¯ 1 ¯ 20 ] A l 2 O 3. This relationship differs from the previously observed orientation of ( 100 ) NaCl ( B 1 ) ∥ ( 1 1 ¯ 02 ) A l 2 O 3 and [ 100 ] NaCl ( B 1 ) ∥ [ 10 1 ¯ 0 ] A l 2 O 3. These results are of general relevance for the growth of the extended NaCl (B1)-structured cubic material family onto a r-plane sapphire substrate where similar epitaxial growth can be expected.