Sub-monolayer detection by electron microprobe analysis

Quantitative determinations of A1, Ti, Ag and Au deposits down to 10−3 monolayers thickness on thin carbon substrates have been performed by electron micro-probe analysis with spatial resolution better than 2 μm. A linear relationship between characteristic x-ray intensity and nominal deposit thickness is shown between 10−3 and 10+2 monolayers. The lower detection limit was investigated as a function of the electron energy. Experimental results are compared with theory. Relations and references are given which enable one to estimate the sensitivity of the method for other substrate-deposit combinations.