The angle-dependences of N-K emission intensity profile of hBN on polar angle θ and azimuth angle ϕ were examined. The θ-dependent N-K emission intensity profiles show different angle dependences in the top and the bottom region of valence band (VB). From the comparison with the theoretically calculated charge distributions, there was a clear relation between the θ-dependence and the corresponding charge distribution was confirmed. No ϕ-dependence of N-K profile was observed and confirmed by a simple calculation, which shows no ϕ-dependence is reasonable for three, four, six-fold symmetrical charge distribution with the same energy. Important factor is the angle θ between a specified axis of the extend/reduce of charge distribution and the detection direction. From the angle dependent B-K emission profile of Fe2B, the presence of the interlayer one-dimensional B-B bonding of pz orbital was assigned at the bottom of VB. For discussing the anisotropic charge distribution in materials other than graphite and hBN, an anisotropy index α(E) was proposed and evaluated for the present experimental data.
Terauchi et al. (Tue,) studied this question.