Raman spectra and phonon modes of MgxZn1–xO alloy films
Abstract
Hexagonal MgxZn1–xO alloy layers with 0 ≤ x < 0.3 have been grown by plasma-assisted molecular beam epitaxy on sapphire (006) and Si (111) substrates. Their crystal structures are characterized by x-ray diffraction spectroscopy. The nonresonant and resonant Raman spectra were measured using 488 nm line from Ar+ laser, and 325 nm line from He-Cd laser by backscattering geometry. Four Raman modes (E2high, LO, TO, multiphonon processes) were observed in the nonresonant Raman spectra of hexagonal MgxZn1–xO with different Mg contents. The optical phonon frequencies were found to display one-mode behaviour for all the samples since no separate ZnO- and MgO-like modes were observed. The long-wavelength frequencies of ZnO-like optical phonons measured in the resonant Raman spectra can be expressed as linear functions of x. These behaviours can be explained within a modified random-element- isodisplacement model (MREI). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
