Elemental surface analysis at ambient pressure by electron-induced x-ray fluorescence

Abstract

The development of a portable surface elemental analysis tool, based on the excitation of characteristic x rays from samples at ambient pressure with a focused electron beam is described. This instrument relies on the use of a thin electron transmissive membrane to isolate the vacuum of the electron source from the ambient atmosphere. The major attributes of this instrument include rapid ͑several minutes͒ spectrum acquisition, nondestructive evaluation of elemental composition, no sample preparation, and high-to-medium ͑several hundreds m͒ spatial resolution. The instrument proof-of-principle has been demonstrated in a laboratory setup by obtaining energy dispersive x-ray spectra from metal and mineral samples.

Atomic spectrometry update. X-ray fluorescence spectrometry

“…Although X-ray excitation using radioactive sources or X-ray tubes is almost universally used in portable XRF instrumentation, an interesting 'proof-of-concept' instrument using focused electron excitation was described by Feldman et al 106 This instrument incorporated a thin electron transmissive membrane to isolate the vacuum of the electron source from the ambient atmosphere and was evaluated in the nondestructive analysis of metal and mineral samples to a spatial resolution of better than several hundreds of micrometres.…”

Single Wafer Surface Micromachined Field Emission Electron Source

“…Free electron sources are needed in many applications like e-beam based material analysis [1], ebeam lithography [2], displays, but also sensing devices like vacuum gauges [3] and flow sensors [4], etc. However, for handling stable electron emissions, high vacuum conditions are needed, which require complex (and thus expensive) systems.…”

“…A schematic configuration of such a micromachined electron source is showed in Figure 1. In [1] a device without reaction chamber has been presented. The cavity was fabricated by wafer bonding.…”

“…In the novel device reported here a sealed microcavity used as vacuum chamber, and a microfluidic device used as reaction chamber, have been integrated on a single substrate using an IC-compatible surface micromachining process. In comparison to the bonding technique [1] the thin film approach presented here allows to achieve field emission at voltages that are two orders of magnitude lower because of the reduced distance between emitters and electrodes. In addition, our solution eliminates the need of the second substrate, thereby avoiding issues in the bonding of processed wafers and decreasing the footprint of the devices.…”