Raman scattering study of zinc blende and wurtzite ZnS

We have conducted an experimental and theoretical study on first- and second-order Raman scattering of zinc blende and wurtzite ZnS. Based on the calculated phonon band structure, phonon density of states, and symmetry selection rules, we have clearly identified for the first time the origins of these vibration modes in the second-order Raman spectra from these two polymorphs. For zinc blende ZnS, it is found that the previously estimated frequency of the LA mode at X point in the Brillouin-zone boundary is much smaller than the value obtained from other experiments and our calculation. Considering the involvement of LA phonon at X point, we reassign the second-order Raman active modes and some other modes which have not yet been understood so far. This work clarifies some of the controversial Raman mode assignments in zinc blende and wurtzite ZnS.