In situ and real-time monitoring of structure formation during non-reactive sputter deposition of lanthanum and reactive sputter deposition of lanthanum nitride

Bärbel Krause*, Dmitry S. Kuznetsov, Andrey E. Yakshin, Shyjumon Ibrahimkutty, Tilo Baumbach, Fred Bijkerk

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Lanthanum and lanthanum nitride thin films were deposited by magnetron sputtering onto silicon wafers covered by natural oxide. In situ and real-time synchrotron radiation experiments during deposition reveal that lanthanum crystallizes in the face-centred cubic bulk phase. Lanthanum nitride, however, does not form the expected NaCl structure but crystallizes in the theoretically predicted metastable wurtzite and zincblende phases, whereas post-growth nitridation results in zincblende LaN. During deposition of the initial 2-3 nm, amorphous or disordered films with very small crystallites form, while the surface becomes smoother. At larger thicknesses, the La and LaN crystallites are preferentially oriented with the close-packed lattice planes parallel to the substrate surface. For LaN, the onset of texture formation coincides with a sudden increase in roughness. For La, the smoothing process continues even during crystal formation, up to a thickness of about 6 nm. This different growth behaviour is probably related to the lower mobility of the nitride compared with the metal. It is likely that the characteristic void structure of nitride thin films, and the similarity between the crystal structures of wurtzite LaN and La2O3, evoke the different degradation behaviours of La/B and LaN/B multilayer mirrors for off-normal incidence at 6.x nm wavelength.

Original languageEnglish
Pages (from-to)1013-1020
Number of pages8
JournalJournal of applied crystallography
Volume51
DOIs
Publication statusPublished - Aug 2018

Keywords

  • UT-Hybrid-D
  • Nitrides
  • Sputter deposition
  • X-ray optics
  • Extreme UV
  • sputter deposition
  • extreme UV
  • nitrides

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