Electron Probe X-Ray Analysis of Nanofilms at Off-Normal Incidence of the Electron Beam

Abstract

The frontier of the electron probe X-ray spectral method in the determination of trace metal quantities on a silicon substrate is studied. The experimental data are acquired for ultrathin chromium films on a silicon substrate. It is shown that the signal-to-noise ratio significantly increases at a noticeable sample inclination (80°), which allows one to determine an extremely low (available by this approach) chromium content. The calibration curve for the inclined sample position is plotted using the Monte Carlo method. The surface concentration of chromium atoms (2.2 ± 0.4) × 10¹⁴ cm^–2 and the chromium detection limit (5 × 10¹³ cm^–2) are measured under the given experimental conditions. For the electron probe X-ray microanalysis of bulk samples, it is a record value. The equivalent weight of chromium at the aforementioned surface concentration is approximately 4 × 10^–18 g. The proposed technique requires no changes in the design of the device to be applied.