Short tubes with diameters of the order of 200 nm were drilled into silicon nitride (Si3N4) membranes of 200 nm thickness by focused ion beam technology and examined as leak elements for vacuum technology applications. These nano-holes exhibit molecular flow in the pressure range from high vacuum up to 10 kPa and can therefore be used as predictable leak elements for any non-condensable gas species. The geometrical dimensions were determined by SEM, STEM and AFM techniques. By Direct Simulation Monte Carlo method the conductances of these short tubes were calculated from the measured dimensions. The calculated conductance agreed with the value measured by comparison with a primary gas flowmeter within their respective uncertainties.
Ierardi, V., Becker, U., Pantazis, S., Firpo, G., Valbusa, U., & Jousten, K. (2014). Nano-holes as standard leak elements. Measurement: Journal of the International Measurement Confederation, 58, 335–341. https://doi.org/10.1016/j.measurement.2014.09.017