Si doped zinc oxide (SZO, Si 3%) thin films are grown at low substrate temperature (T <= 150 degrees C) under oxygen atmosphere, using pulsed laser deposition (PLD). Si addition leads to film amorphization and higher densification. Hall effect measurements indicate a resistivity of 7.9 x 10(-4) Omega cm for SZO thin films deposited at 100 degrees C under optimized 1.0 Pa oxygen pressure. This value is in good agreement with optical resistivity simulated from the transmittance spectra. XPS measurements suggest more than one oxygen environment, and a Si oxidation state lying in between 2 and 3 only. As a matter of fact, the values of both measured and simulated carrier numbers are smaller than the ones expected, assuming that all Si cations in the ZnO matrix are at the 4(+) oxidation state. Finally, the differences in the electrical and optical properties of SZO thin films deposited both on glass and PET substrates confirm the strong dependency of the electronic properties to the film crystallinity and stoichiometry in relationship with the substrate nature. (C) 2011 Elsevier B.V. All rights reserved.