Polycrystalline LiNbO3 films on (001)Si substrate were grown by radio-frequency magnetron sputtering process at different sputtering conditions. X-ray diffraction analysis showed that films formed in Ar environment (P = 5.0 x 10(-1) Pa) having two-phase composition (LiNbO3, LiNb3O8) transformed into c-axes-oriented LiNbO3 films when Ar pressure declined up to P = 1.5 x 10(-1) Pa. This induced an increase in positive oxide charge and coercive field due to formation of defects in the LiNbO3 layer. Using Ar + O-2 reactive gas mixture led to decline in defect formation (positive oxide charge) and coercive field. Current-voltage and capacitance-voltage analyses demonstrated that barrier properties of the Si-LiNbO3 heterojunctions are affected by the plasma composition.