X-ray reflectivity characterization of thickness and mass density of α:CH films
Grazing-angle X-ray reflectivity(XRR) is described as an efficient,nondestructive means to measure the mass density of various amorphous carbon films down to the nanometer thickness range.Amorphous hydrogenated carbon films(α:CH films) are fabricated by low pressure plasma chemical vapor deposition method.The thickness of α:CH films is derived from XRR by the method of line fitting(according to the theory of modified Bragg equation) and by the period width(fringe space) of XRR.The mass density of the films is also derived from the critical angle of XRR based on the refractive theory.The results show that the thicknesses of films obtained by the two methods agree well,the average difference among them is only 5.5%.The mass density of the films' error obtained from the critical angle is 8%.