Comment on "Twin symmetry texture of energetically condensed niobium thin films on sapphire substrates (a-plane Al2O3)" [J. Appl. Phys. 110, 033523 (2011)]

TL;DR

This paper critiques a previous study on niobium thin films on sapphire, identifying errors in the original analysis that invalidate its claims about the crystal structure and epitaxy relationship.

Contribution

It clarifies the correct crystallographic structure and orientations, correcting the previous misinterpretations in the literature.

Findings

Original claims about new epitaxy relationship are invalidated.

Errors in x-ray diffraction analysis were identified and corrected.

The crystal structure of sapphire was mischaracterized in the original study.

Abstract

In their recent publication, Zhao et al. [J. Appl. Phys. 110, 033523 (2011)] claim to have found a new three-dimensional relationship for niobium-on-sapphire epitaxy. However, two critical errors were made in the analysis of x-ray diffraction measurements. The crystal structure of sapphire (alpha-Al2O3) was erroneously cited as hexagonal close-packed, and crystallographic orientations of sapphire were misidentified. Correcting these errors, one finds their claim unjustified.