the x ray count rates is then observed the change in x ray count rates is related to the effective landing energy thereby enabling the determination of the surface voltage also the amount of charge introduced is preferably tightly controlled by measuring the gun current and exposure time knowing the effect on the surface voltage through landing energy modeling for the measured x ray decay yields the change in charge with time as a result of the leakage current in the examples described herein the nitrogen line is used to measure both the n dose in the film and the current leakage at the same time in other embodiments an oxygen spectrometer is also used which provides another x ray detection element for the gate dielectric layers the oxygen count rates together with the nitrogen count rates tend to improve the accuracy of the measurement of the change in landing energy and thereby the remaining charge on the gate dielectric layer one major advantage of the methods according to the preferred embodiments of the present invention is that they can be used on production substrates this is possible because these methods can be implemented on a very small spot size such as the size of the gates of actual production devices and can be easily combined with compositional analysis of the ultra thin.