Li and OH-Li Complexes in Hydrothermally Grown Single-Crystalline ZnO

Fourier-transform infrared spectroscopy (FTIR) and secondary-ion mass spectrometry (SIMS) have been employed to investigate the relation between the Li concentration and the strength of the 3577 cm−1 absorption line in five as-grown hydrothermal ZnO wafers. This line has previously been identified as a local vibrational mode of an OH molecule adjacent to a Li atom on the Zn-site. In this work, we show that the integrated absorption of the 3577 cm−1 line does not follow the variation in the total Li concentration between different wafers, providing evidence that the concentration is not the limiting factor for the formation of the 3577 cm−1 defect. It is speculated that the presence of inhomogeneously distributed Li along the direction of the c-axis, as revealed by SIMS depth profiling in three of the studied wafers, is related to trapping of Li by inversion domain boundaries (IDB). IDBs are expected to have high thermal stability, which may be associated with the high apparent thermal stability reported for the 3577 cm−1 line.