Determination of the hydrogen content in diamond-like carbon and polymeric thin films by reflection electron energy loss spectroscopy

A new non-destructive method to determine hydrogen content in diamond-like carbon and polymeric thin film materials is developed. The method relies on quantification of the intensity of elastic peak stemming from the backscattering of electrons with the hydrogen atoms present in the samples as measured by reflection electron energy loss spectroscopy. Low current primary electron beams of $\sim$ 1500 eV are used to minimize hydrogen desorption by electron bombardment and to provide enough energy separation between the elastic signals coming from hydrogen and other atoms (mainly C and O atoms) from the thin film materials. Quantitative analysis of the hydrogen content at the surface of diamond-like carbon thin films is achieved by using phenomenological sensitivity factors of hydrogen against the other atoms with reference to polymeric samples. The validity of the method is checked with elastic recoil detection measurements. A comparison is also made with data provided by infrared spectroscopy analysis of the same samples. We estimate that the error bar in the determination of hydrogen content in the samples is around 20% of the total hydrogen content