The densification of SiO2 layer is reflected in the shape and position of the selleck inhibitor next two bands having maxima at about 620cm?1 and 800cm?1 [6, 14, 15]. The band with the maximum at about 670cm?1 can be correlated with strong line reported for coesite and having the maximum at 661cm?1 [13]. The bands placed around 1090cm?1 and 1200cm?1 are assigned to Si-O stretching vibration [14]. The last important feature of Raman spectrum recorded for SiO2 thin film is the absence of boson band observed for visible excitation in the case of bulk material [14]. It should be emphasized that boson band was not observed for bulk SiO2 in the case of deep ultraviolet excitation [8].The bands observed for HfO2 and placed above 1000cm?1 are much weaker than similar bands in SiO2 spectrum.

The most important difference between Raman scattering observed for silicon dioxide and hafnium oxide is the shape of the spectrum in the range between 300cm?1 and 930cm?1. In the case of SiO2 three separate bands can be recognized in the spectrum: the main band placed between 300cm?1 and 550cm?1, D2 band placed around 620cm?1 and a band ��800cm?1��. In the spectrum observed for HfO2 film the bands are merged in such a way that the main band placed between 300cm?1 and 550cm?1 has a tail extended to 930cm?1. In the case of the spectrum observed for the sample, as-deposited weak band placed around 800cm?1 can be recognized on this tail. The range 600cm?1�C700cm?1 contains no unambiguous band. The main band placed between 300cm?1 and 550cm?1 is similar for spectra recorded for SiO2 and HfO2 as-deposited films.

Let us compare Raman spectra of HfO2 recorded film after thermal treatment. In the case of the sample annealed at 400��C, only a small increase of the main band intensity is observed. No changes in the shape of the spectrum appear. Annealing at higher temperature (600��C and 800��C) leads to a significant increase of GSK-3 the Raman scattering intensity combined with changes of the shape of the spectrum. The following bands (maxima) appear in the spectra of Si/SiO2/HfO2 samples annealed at 600��C and 800��C: 320cm?1, 380cm?1, 600cm?1, 670cm?1. An additional relatively narrow band appears near the Si one-phonon line. The band is merged with ��520cm?1�� line, and its maximum is placed at about 490cm?1. The weak band placed around 800cm?1 becomes stronger, and its maximum shifts towards smaller values of Raman shift by about 10cm?1.