Conductimetry and impedance spectroscopy study of low pressure metal organic chemical vapor deposition TiNxOy films as a function of the growth temperature: a percolation approach

Titanium oxinitride thin films have been grown by low pressure metal organi c chemical vapor deposition (LP-MOCVD) using titanium isopropoxide. Ti(OCH( CH3)(2))(4) (TIP) and NH3 precursors in a growth temperature range from 450 to 750 degreesC on sapphire substrates. The electrical behaviour of these films was studied between 400 and 173 K. revealing three different behaviou rs, ranking from a hopping conductivity (450-500 degreesC) to a conducting one (700-750 degreesC), with a dual behaviour for the intermediate growth t emperatures. Moreover. at room temperature, both conductimetry and impedanc e spectroscopy highlighted a percolation behaviour, interpreted in terms of continuum percolation. The effective media theory equations led to the usu al percolation parameters (s, t, Phi (c)) and the difference between the va lues thus obtained and the expected ones was explained in terms of anisotro pic percolation occurring in the columnar film structure. (C) 2001 Elsevier Science B.V. All rights reserved.