## 3 Results
### SXES Mapping of \(n\)-Type SrB\({}_{6}\)  
Figure 4a shows a BSE image of a piece of an \(n\)-type SrB\({}_{6}\) specimen prepared with a Sr-excess composition of Sr:B = 1:1. A spectral mapping procedure was performed with a probe current of 40 nA at an accelerating voltage of 5 kV. The specimen area in Figure 4a was divided into 20 \(\times\) 15 pixels of about 0.6 \(\upmu\)m pitch. Electrons of 5 keV, impinged on the SrB\({}_{6}\) surface, spread out inside the material via inelastic scattering of about 0.22 \(\upmu\)m in diameter,  
Figure 3: Back-scattering electron images of sintered SrB6 bulk specimens. The image of the \(p\)-type specimen is apparently inhomogeneous. Dark contrast regions could be Sr-deficient regions. (a) Sr:B = 1:1.\(n\)-type; (b) Sr:B = 1:6.\(n\)-type;(c) Sr:B = 1:12.\(p\)-type. Figure 2: (a) SXES-EPMA system used. The SXES spectrometer is composed of gratings and a CCD detector, which enables a parallel detection in a certain energy range. (b) B K-emission spectra of pure boron and boron compounds. Peak energy position (arrows) and shoulder structures (line) are different each other, reflecting different chemical bonding states owing to different crystal structures. which was evaluated by using [PERSON]'s equation [34]. The size, which corresponds to the lateral spatial resolution of the SXES measurement, is smaller than the pixel size of 0.6 \(\upmu\)m. SXES spectra were obtained from each pixel with an acquisition time of 20 s. Figure 4b shows a map of the Sr M\({}_{\zeta}\)-emission intensity of each pixel divided by an averaged value of the Sr M\({}_{\zeta}\) intensity of the area examined. The positions of relatively Sr-deficient areas with blue color in Figure 4b are a little different from those which appear in the dark contrast area in the BSE image in Figure 4a. This could be due to a smaller information depth of the BSE image than that of the X-ray emission (electron probe penetration depth) [35]. The raw spectra of the squared four-pixel areas A and B are shown in Figure 4c, which show a sufficient signal -o-noise ratio. Each spectrum shows B K-emission intensity due to transitions from VB to K-shell (1s), which corresponds to **c** in Figure 1, and Sr M\({}_{\zeta}\)-emission intensity due to transitions from N2,3-shell (4p) to M4,5-shell (3d), which corresponds to Figure 1d[36, 37]. These spectra intensities were normalized by the maximum intensity of B K-emission. Although the area B exhibits a slightly smaller Sr content than that of A in Figure 4b, the intensities of Sr M\({}_{\zeta}\)-emission of those areas in Figure 4c are almost the same, suggesting the inhomogeneity was small. When the amount of Sr in an area is deficient, the amount of the valence charge of the B\({}_{6}\) cluster network of the area should be deficient (hole-doped). This causes a shift in B 1s-level (chemical shift) to a larger binding energy side. This can be observed as a shift in the B K-emission spectrum to the larger energy side as already reported for Na-doped CaB\({}_{6}\)[20] and Ca-deficient n-type CaB\({}_{6}\)[21]. For making a chemical shift map, monitoring of the spectrum intensity from 187 to 188 eV at the right-hand side of the spectrum (which corresponds to the top of VB) is useful [20,21]. The map of the intensity of 187-188 eV is shown in Figure 4d, in which the intensity of each pixel is divided by the averaged value of the intensities of all pixels. When the chemical shift to the higher energy side is large, the intensity in Figure 4d is large. It should be noted that larger intensity areas in Figure 4d correspond with smaller Sr-M\({}_{\zeta}\) intensity areas in Figure 4c. The B K-emission spectra of areas A and B are shown in Figure 4e. The gray band of 187-188 eV is the  
Figure 4: (a) BSI image, (b) Sr M\({}_{\zeta}\)-emission intensity map, (c) spectra of areas A and B in (b), (d) chemical shift map of B K-emission, and (e) B K-emission spectra of A and B in (d). energy window used for making Figure 4d.