AC electrical conductivity of electron beam evaporated Cu-GeO2 thin cermet films

• Published in: Journal of materials science 2000-12, Vol.35 (23), p.5899-5905
• Main Authors: RAHMAN, M. H, AL-SAIE, A. M, BEYNON, J
• Format: Article
• Language: English
• Subjects: Cermets; Cermets, ceramic and refractory composites; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Cross-disciplinary physics: materials science; rheology; Dielectric loss; Electric contacts; Electrical properties; Electrical resistivity; Electron beams; Electronic transport in condensed matter; Equivalent circuits; Exact sciences and technology; Frequency ranges; Germanium oxides; Materials science; Migration; Other materials; Physics; Resistance; Specific materials; Temperature dependence; Thin films
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1026789215041

AC electrical properties of 410 nm think 30 at.wt% Cu-70 at.wt% GeO2 thin films are reported for the frequency range 104 to 106 Hz and temperature range 150 to 425 K. The loss tangent (tan δ) and the dielectric loss (∈′′/∈0) are found to show striking minima around a cut-off frequency ∼105 Hz. In the lower frequency range (≤105 Hz), σ1(ω) ∝ ωsTn is obeyed with s (0 to 0.51) increasing as a function of temperature and n (0.10 to 0.14) showing a very weak temperature dependence. In the higher frequency region (≥105 Hz), σ1(ω) and ∈′′/∈0 increase sharply leading to the quadratic behavior of σ1(ω) with s equal to 2. These processes are discussed by analyzing an equivalent circuit which shows that at lower frequencies, the effects of series resistance in leads and contacts can be neglected, while at higher frequencies such effect give rise to spurious ω2 dependance for the conductance. A weakly activated AC conductivity and a frequency exponent s that increases with increasing temperature suggest that the low frequency behavior originates from carrier migration by tunneling process.