AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS+EM+SC-ThA

Paper SS+EM+SC-ThA9
Metal/Semiconductor Phase Transition in CrN Grown by Molecular Beam Epitaxy and Scanning Tunneling Microscopy

Thursday, November 18, 2004, 4:40 pm, Room 210C

Session: Compound Semiconductor Growth and Surface Structure
Presenter: C. Constantin, Ohio University
Authors: C. Constantin, Ohio University
M.B. Haider, Ohio University
A.R. Smith, Ohio University
Correspondent: Click to Email
Considerable interest has been of late in transition metal nitrides thin films/surfaces, which have both magnetic and electronic properties with potential applications in spintronics. CrN is a particularly interesting case, having a known correlation of structural and magnetic transition from a B@sub 1@ NaCl-paramagnetic to an orthorhombic-antiferromagnetic at T@sub Neel@=273-286K@footnote 1@. However,the reported electronic properties of CrN are controversial, and there has been no consensus whether the material is a metal or a semiconductor@footnote 2,3@. In this study, CrN is grown on MgO(001) at a substrate temperature of 450°C by a novel molecular beam epitaxy method for obtaining smooth surfaces. Bulk measurements reveal that the films are single crystal, and stoichiometric. The 1x1 face-centered cubic (fcc) surface structure is clearly distinguishable as obtained (for the first time) in room temperature atomic resolution scanning tunneling microscopy. In addition to the atomic resolution, long-range topographic distortions [LTD] are also seen on the surface, as also observed for the semiconductor ScN (001)@footnote 3@ and other nonpolar III-V surfaces. LTDs are characteristic of semiconductor surfaces, and are related to localized charge accumulation from impurities. Resistivity was measured from 77 to 450K; metallic behavior is found up to 260K (in contrast with some earlier reports) and semiconductor behavior above 285K. The bandgap obtained from resistivity data,71±0.315meV, agrees with the tunneling spectroscopy of the surface which show a very small gap. Consistent results have now emerged in which CrN has a semiconductor-metal phase transition corresponding to its magnetic transition. @FootnoteText@ @footnote 1@ A. Filippetti et.al, Phys. Rev. B 59, 7043 (1999)@footnote 2@J. D. Browne et.al, Phys. Status Solidi 1, 715 (1970)@footnote 3@P. S. Herle et.al, J. Solid State Chem. 134, 120 (1997)@footnote 4@H. A. Al-Brithen et.al, submitted to Phys. Rev. B.