Environmental gas impact on the emission volume of X-rays near the interface in the variable pressure scanning electron microscopy.

• The effects of the scattered electrons in the gas on the X-ray lateral resolution is characterized using two adjacent materials. The e-beam is scanned across the Al-Cu interface for various experimental conditions of energy and pressure. Under low pressures and high energies, the EDS profiles have the same sigmoid shape as those acquired in high-vacuum. For high pressures and low energies, the sigmoid shape becomes enlarged and flatter. These results show how the scattered electrons by the gas entities can modify the shape of the EDS profile, causing the degradation of the X-ray spatial resolution. In this paper, our previously developed model to account for the secondary X-ray fluorescence and absorption effects near the interface of two adjacent materials in a high-vacuum scanning electron microscope (Zoukel & Khouchaf, 2014) is adapted and extended to experimental conditions of low-vacuum mode (in the presence of a gaseous environment in the SEM analysis chamber). The position shifting effect of the two Gaussian peaks issued from the first derivative equation that can fit the experimental low-vacuum EDS profiles is investigated. The impact of the medium gas on the emission volume of secondary X-rays near the interface is qualitatively discussed. Water vapour and helium are successively used as gas environment, in order to link the resolution of microanalysis profiles with the effects of the X-ray fluorescence and absorption phenomenon. A close agreement between Monte Carlo simulation and experimental results is found. X-ray Al k lateral resolution as the gas is introduced inside the analysis chamber of the VP-SEM using two adjacent materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]