Element-specific structural analysis of Si/B₄C using resonant X-ray reflectivity. Corrigendum

Abstract

[786][787][788][789][790][791][792][793][794][795][796] are corrected.It has come to the authors' attention that the paper published by Nayak et al. (2015) contains the following errors: (i) an error in the calculated electron density contrast (i.e. fraction of electron density difference, Á / ) between the Si and B 4 C layers and (ii) a numerical error during conversion of the measured angular reflectivity to q z = 4 sin / . Regarding (i), Á / across the Si/B 4 C interface is 0.5%, not 0.05%. This Á / is still one order of magnitude lower than what can be measured using hard X-ray reflectivity (XRR). Regarding (ii), the reported q z range in Figs. 3-10 of the original article exceeds the actual measured angle. The original data files were modified by mistake and are not retrievable. To show that the proposed methodology and the conclusion drawn are not affected by the error in q z , fresh measurements on freshly prepared similar samples were performed.Three different samples were fabricated on Si wafers using electron beam evaporation with varying spatial position of the B 4 C layer (40 Å ) in the Si film (300 Å ). The B 4 C layer is at the top, middle and bottom of the Si film in samples S1, S2 and S3, respectively. A tungsten layer with thickness 10 Å is located between the substrate and the thin film. In the B 4 C layer, elementary boron is incorporated through co-deposition. The XRR profiles of the three samples, measured using a Cu K source, are nearly identical in nature [similar to Fig , for S1, S2 and S3, respectively. Thus, our original conclusion that XRR is not sensitive to the low-contrast Si/B 4 C interface (Á / =0.5%) still stands.The microstructural sensitivity of the resonant soft X-ray reflectivity (R-SoXR) to the low-contrast Si/B 4 C interface is demonstrated near the B K edge of B 4 C (Fig. 1a). R-SoXR measurements were done in s-polarization geometry using the Optics Beamline on the BESSY synchrotron (Sokolov et al., 2014). The enhanced scattering strength strongly modulates the R-SoXR owing to reflection from the Si/B 4 C interface (similar to Fig. 3 in the original paper). This provides experimental evidence for the sensitivity of resonant reflectivity to the spatial variation of position of a low-contrast interface structure.To obtain spectroscopic information on S1, R-SoXR measurements are performed across the B K edge of In S1 of the original paper the elementary boron was oxidized, but in the fresh sample S1 elementary boron is not oxidized. Similarly, in S2 and S3, we observed that only elementary boron is present in the B 4 C layer (similar to Fig. 5 of the original paper).The atomic percent of resonating element and the distribution were quantified near the B K edge of elementary boron for S1, S2 and S3. The fitting procedure of R-SoXR is similar to that described in the original paper. In S1, the optimized values for the thicknesses (roughnesses) of the Si and B 4 C layers are 294 Å (5 Å ) and 42 Å (13 Å ), respectively. A carbon-contaminated layer at the top of the B 4 C layer i...