Microcrystalline silicon (mu c-Si) thin films were prepared by closed chamber-chemical vapour deposition with thicknesses between 5 and 360 nm. The cycle includes an a-Si:H layer deposition and a hydrogen-radical treatment step. The layer contains high crystalline fractions at high deposition rates. The films were characterized by field effect-scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Layers with a thickness up to 50 nm consist of an amorphous matrix with small spherical grains. Above 50 nm layer thickness the crystallites have a columnar morphology.