Ta-doped SnO2 films with high conductivity and high optical transparency have been successfully fabricated using the rf-sputtering method, and their electrical transport properties have been investigated. All films reveal degenerate semiconductor (metal) characteristics in electrical transport properties. For the thick films (t∼1μm with t being the thickness) deposited in pure argon, the electron–phonon scattering alone cannot explain the temperature-dependent behaviors of resistivity, the interference effect between electron–phonon and electron–impurity scattering should be considered. For t≲36 nm films, both the conductivity and the Hall coefficient show a linear relation with the logarithm of temperature (ln⁡T) from ∼100 K down to liquid helium temperature. The ln⁡T behaviors of conductivity and Hall coefficient cannot be explained by the Altshuler-Aronov type electron–electron interaction effect but can be quantitatively interpreted by the electron–electron interaction effects in the presence of granularity. Our results not only provide strong support for the theoretical results on the electron–phonon–impurity interference effect, but also confirm the validity of the theoretical predictions of charge transport in granular metals in a strong coupling regime.

Spatially resolved reflectance close to the source is dependent on high-order optical parameters of the media. In order to investigate the influence of high-order parameters on the diffuse reflectance, we define sensitivities of the spatially-resolved diffuse reflectance to the second- and third-order optical parameters. The sensitivity denotes the relative change of diffuse reflectance due to a change in the optical parameter. Expressions of the sensitivities are derived from P3 approximation theory, and numerical analyses are performed. We show that the sensitivity changes with source-detector separation and reaches a maximum in the region between one transport mean free path and two transport mean free paths, and is positive in the region beyond one transport mean free path. The influence of third-order optical parameter on the diffusing reflectance can be ignored in comparison with the influence of second-order optical parameter.

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