Raman active E-2 modes in aluminum nitride films

The vibrational spectrum of AlN thin films has been studied in recent years by theoretical and experimental methods, but there is still a lack of full knowledge of the Raman shift of the active E-2 modes of this material. Ear ly work by Carlone et al. [1] has indicated that the E-2 modes of AlN depos ited on Si occur at frequencies of 303cm(-1) and 426cm(-1). In the present study, Raman spectra of AlN deposited by magnetron sputtering on polished S i, quartz and BK7 substrates and also the Raman spectrum of pure Si, were c ompared to show that these peaks can actually be assigned as Raman peaks of Si, instead of AlN Raman peaks. We show that the Raman lines at 240cm(-1) and 650cm(-1) are the true AlN E-2 Raman peaks in agreement with calculated and experimental works reported in the literature that indicate the occurr ence of the low and high E-2 Raman modes of AlN in the ranges (228-252)cm(- 1) and (631-665)cm(-1), respectively. (C) 2001 Kluwer Academic Publishers.