Technique to Measure the Density of Very Thin Carbon Films
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-16
This article describes a technique utilizing X-ray absorption principles to determine the density of thin carbon films. The technique involves the measurement of transmitivity of a soft X-ray line through the carbon film, and using the well-established equation I1=I0e-mpt, where I0 is the intensity of the radiation without the carbon film, I1 is the intensity of the radiation through the carbon film, m is the photoabsorption cross section, p the desired density, and t the independently measured thickness of the film. This method allows the use of the photoabsorption cross section values where the value is well determined and behaved (i.e., away from the absorption edge). A primary X-ray source, such as an end-window tungsten X-ray tube, may be used to excite the O-Ka line of a blank SiO2 substrate.