The authors report on observations regarding thermal annealing of ZnO submicron crystals grown by radio-frequency magnetron sputtering. The surface optical (SO) and A 1(LO) phonons in the resonant Raman scattering spectra, upon sample annealing, exhibit blue- and red-shift, respectively. The blue-shift of the SO mode is strongly correlated with the intensity reduction of the A 1(LO) mode, which is an indication of the weakening of the surface electric field that was built by surface and near-surface defects via forming surface states. Photoluminescence measurements reveal defects annihilation in the ZnO crystallites that led to the surface states passivation, while the off-axis X-ray diffraction mappings provide evidence that the red-shift in the A 1(LO) mode originated from the anneal-induced crystal reorientations.