Growth of poly- and single-crystal ScN on MgO(001): Role of low-energy N{sub 2}{sup +} irradiation in determining texture, microstructure evolution, and mechanical properties
- Department of Materials Science, Coordinated Science Laboratory, and Materials Research Laboratory, University of Illinois, 1101 West Springfield Avenue, Urbana, Illinois 61801 (United States)
- Department of Physics, Thin Films Division, Linkoeping University, S-581 83 Linkoeping (Sweden)
ScN layers, 345 nm thick, were grown on MgO(001) substrates at 750thinsp{degree}C by ultrahigh-vacuum reactive magnetron sputter deposition in pure N{sub 2} discharges at 5 mTorr. The N{sub 2}{sup +} to Sc ratio incident at the substrate and growing film was maintained constant at 14, while the ion energy E{sub N{sub 2}{sup +}} was varied from 13 to 50 eV. All films were stoichiometric with N/Sc ratios of 1.00{plus_minus}0.02. However, microstructural and surface morphological evolution were found to depend strongly on E{sub N{sub 2}{sup +}}. The nucleation and initial growth stages of ScN films deposited with E{sub N{sub 2}{sup +}}=13thinspeV are dominated by the formation of 111- and 002-oriented islands, but preferred orientation rapidly evolves toward a purely 111 texture by a film thickness of {approx_equal}50thinspnm as 002 grains grow out of existence in a kinetically limited competitive growth mode. In distinct contrast, films deposited with E{sub N{sub 2}{sup +}}=20thinspeV grow in a cube-on-cube epitaxial relationship with the substrate and exhibit no indication of 111-oriented grains, even in the earliest stages. Increasing E{sub N{sub 2}{sup +}} to 50thinspeV still results in epitaxial layers, but with high in-plane compressive stress and the presence of N{sub 2} gas bubbles. All epitaxial layers contain rectangular nanopipes {approx_equal}1thinspnm wide and aligned along the growth direction. The nanopipes result from atomic shadowing near the bottom of a periodic array of surface cusps which form along orthogonal {l_angle}100{r_angle} directions due to kinetic roughening during growth. The hardness H and elastic modulus E of the epitaxial ScN(001) layer grown with E{sub N{sub 2}{sup +}}=20thinspeV are 21.1{plus_minus}1.1 and 356{plus_minus}18thinspGPa, respectively. H and E increase (decrease) with increasing (decreasing) E{sub N{sub 2}{sup +}}. {copyright} {ital 1998 American Institute of Physics.} thinsp
- OSTI ID:
- 664663
- Journal Information:
- Journal of Applied Physics, Vol. 84, Issue 11; Other Information: PBD: Dec 1998
- Country of Publication:
- United States
- Language:
- English
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