Naomi Pieczulewski

Effect of substrate miscut angle on critical thickness, structural and electronic properties of MBE-grown NbN films on c-plane sapphire

  1. Anand Ithepalli,
  2. Saumya Vashishtha,
  3. Naomi Pieczulewski,
  4. Qiao Liu,
  5. Amit Rohan Rajapurohita,
  6. Matthew Barone,
  7. Darrell Schlom,
  8. David A. Muller,
  9. Huili Grace Xing,
  10. and Debdeep Jena
We report the structural and electronic properties of niobium nitride (NbN) thin films grown by molecular beam epitaxy on c-plane sapphire with miscut angles of 0.5o, 2o, 4o, and 10o
towards m-axis. X-ray diffraction (XRD) scans reveal that the full width at half maximum of the rocking curves around the 1 1 1 reflection of these NbN films decreases with increasing miscut. Starting from 76 arcsecs on 0.5o miscut, the FWHM reduces to almost 20 arcsecs on 10o miscut sapphire indicating improved structural quality. Scanning transmission electron microscopy (STEM) images indicate that NbN on c-sapphire has around 10 nm critical thickness, irrespective of the substrate miscut, above which it turns columnar. The improved structural property is correlated with a marginal increment in superconducting transition temperature Tc from 12.1 K for NbN on 0.5o miscut sapphire to 12.5 K for NbN on 10o miscut sapphire.
arxiv pdf