in situ X-ray diffraction (XRD) measurements have been used to study the amorphous-to-crystalline transformation in hydrogenated amorphous silicon (a-Si:H) thin films deposited by DC-Magnetron Sputtering at 300degreesC. The a-Si:H layers of 2.85 mum thickness were solid phase crystallized (SPC) and the crystallization kinetic was studied from in situ XRD measurements and also by in situ electrical conductance measurements during isothermal annealing at 630degreesC. The apparition and the evolution of the (I 1 1) peak in the XRD spectra during the annealing of the layer permit to follow the SPC kinetic which is the same as the electrical conductance kinetic (G =f(t)) performed in the same annealing conditions as in the XRD experiment. Several isothermal annealings at different temperatures permit to extract the characteristic parameters of the crystallization from the G =f(t) evolutions. These parameters are the thermally activated crystallization characteristic time and its activation energy. (C) 2002 Elsevier Science B.V. All rights reserved.