Figure 4. Bi2Se3 thickness dependence.
(a) MSHG parameters were measured from samples of various Bi2Se3 thicknesses (1–10 QL). EuS thickness is fixed at 5 nm. Both (b) C(M)/A2 and (c) C(M)/A show a decreasing behaviour, possibly due to the increased bulk contributions and SHG absorption from thicker Bi2Se3 films. (d) Out-of-plane response φ(M⊥) for different Bi2Se3 thicknesses. In b–d error bars represent the uncertainties of least square fitting of data to the theoretical model.