Electron dephasing processes in the thin and thick Ta-doped SnO2 films

We have systematically investigated the electron dephasing processes of the thin and thick Ta-doped SnO2 films. All samples exhibit electron transport characteristics of degenerate semiconductors. At low temperature T (below ∼70 K), the weak-localization-induced negative magnetoresistance (MR) is observed. For the thick films with the thicknesses of ∼300 nm, the observed MR can be well described by three-dimensional weak-localization theory. The electron dephasing rate 1/τφ varies linearly with T3/2, indicating that the electron–electron scattering dominates the electron dephasing process. This is different from the common observation that the electron–phonon scattering is the main dephasing process for electrons in three-dimensional disordered conductors. For the thin films with the thicknesses of ∼30 nm, the MR can be well described by two-dimensional weak-localization theory. By analyzing the electron dephasing rate as a function of T, we find that both large- and small-energy-transfer electron–electron scattering processes play an important role in the electron dephasing.