Investigation of hydrogenated microcrystalline silicon (muc-Si:H) thin films for solar cells deposited at very low substrate temperatures is motivated by further reduction of the energy budget and a possibility to use practical polymer substrates. We have applied the surface photovoltage (SPV) technique in an expanded spectral region (1.2-3 eV) to study transport properties of muc-Si:H thin films deposited at substrate temperatures between 35 and 200 degreesC. The application of the SPV technique revealed new phenomena of low-temperature muc-Si:H growth (e.g. formation of a bottom barrier for deposition temperatures below 100 degreesC, presence of a defective layer for deposition temperatures 75-200 degreesC) without performing any additional measurements. Good separation of top and bottom space charge regions was detected even for the sample thickness less than 0.5 mum. By increasing the deposition temperature, a transition from the amorphous to microcrystalline growth was crossed. However, it seems not to be sharp-the experimental data indicate at least three different growth regimes. (C) 2003 Elsevier B.V. All rights reserved.