Unique Variable-angle GI-XRF Capability

Introduction

An incident X-ray beam impinges upon the sample at a shallow angle resulting in virtually complete reflection of the excitation beam away from the silicon drift detector (Figure 1). This affords dramatically reduced background contributions in the measured energy dispersive X-ray fluorescence spectra. Furthermore, it is possible to obtain information depending on measuring depth with GI-XRF capability. 

Figure 1: TXRF principle

Measurement and results

In this example, a 25 nm nickel (Ni) thin film on a glass substrate was measured at two different incident angles: 0.02° and 0.40° (Figure 2). The results of the measurement are shown in Figure 3. Incident angle 0.02° is under condition of TXRF and then only the surface information is obtained. On the other hand, angle 0.40° is higher than the critical angle then it is possible to measure deeper area beneath the surface.

Figure 2: Nickel coated sample

Only Ni was strongly excited at 0.02° GI (Grazing Incidence) excitation condition (blue spectrum). However, elements included in the glass substrate are strongly exited at the higher 0.40° angle (red spectrum) because X-rays penetrate more deeply into the substrate. It is possible to change incident angle arbitrarily, and then the characterization of the solid surface can be done by using this function.

Figure 3:  Spectra of the Ni thin film (25 nm) for different incident angles