A. Woollam, USA) was used.2.2. Data Analysis Mathematical pretreatment of the data included off-set and cosmic ray removal, baseline correction and intensity normalization. As a normalization condition, the intensity of one-phonon silicon line ��520cm?1�� which is equal to 1 was chosen. The pretreatment was done with Grams 8 (Thermo Scientific, USA) program. The spectra measured for high-�� materials selleck bio were compared with data obtained for SiO2 layer.3. Results3.1. Spectroscopic EllipsometryThe following samples: Si/SiO2, Si/SiO2/HfO2 (as-deposited), Si/GdSiO and Si/LaLuO3 were characterized by means of spectroscopic ellipsometry prior to Raman investigation. Other samples containing HfO2 layer were too small for these measurements. The main features: refractive index for 300nm and thicknesses of the samples, are collected in Table 1.

The values of refractive index measured for thin silicon dioxide film are similar to the data of bulk material reported in the literature [11]. All high-�� materials have significantly larger optical density. The last column of Table 1 presents the thicknesses of the samples.Table 1Refractive indices obtained for excitation wavelength equal to 300nm and film thicknesses measured by means of spectroscopic ellipsometry for silicon dioxide, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide.3.2. Raman StudyFigure 1 presents the data collected for Si/SiO2 sample. Black solid line marks measured spectrum and red dashed line designates fitted Lorentzian profile modeling one-phonon silicon line.

The following bands can be recognized in the spectrum (except Si line ��520cm?1��):weak band with maximum at about 230cm?1;relatively strong band spread from 300cm?1 to one-phonon Si line (~550cm?1);band with two maxima at about 630cm?1 and 670cm?1;broad band with maximum at about 810cm?1;strong band spread from 930cm?1 to 1030cm?1;two weak bands with maxima at about 1090cm?1 and 1200cm?1.Figure 1 Raman spectrum measured for Si/SiO2 sample, excitation wavelength 266nm. Black solid line represents measured data; dashed red line represents fitted Lorentzian profile modeling one-phonon Si line.Raman spectra measured for silicon wafers covered with HfO2 are presented in Figure 2. Raman spectra recorded for HfO2 are similar to the data measured for SiO2 layer.

The two most important common features observed for both dielectric materials can be recognized without detailed analysis:the absence of the so-called boson band;the presence Brefeldin_A of the band between 930cm?1 and 1030cm?1 assigned in the literature to multi-phonon scattering generated in Si substrate [9].The intensity of the Raman scattering observed for HfO2 layer is 2 �� 3 times larger than the intensity recorded for SiO2 film. This comparison is done for normalized spectra.