Properties of titanium dioxide thin films grown by atomic layer deposition from TiCl4 and H2O on SiO2 substrates were
characterized using Raman spectroscopy and spectrophotometry methods. Raman spectroscopy revealed transformation
of the film structure from amorphous to anatase, to anatase/rutile mixture and then back to anatase with the increase of
deposition temperature from 100 to 680oC. Variations in the growth rate, refractive index and extinction index
accompanied these structural changes. Analysis of the transmission curves demonstrated that differently from
amorphous films, the crystalline films were optically inhomogeneous in the growth direction.
Atomic layer deposition (ALD) of SnO2 thin films from SnI4 and either H2O2 or O2 on the α-Al203(1 1- 2) substrates is
studied. Reactor temperature is varied from 100 to 750 °C. X-ray diffaction, x-ray reflection, x-ray fluorescence, x-ray
photoelectron spectroscopy, reflection high-energy electron diffraction, and UV-visible spectroscopy are used to obtain
the growth and structural data. The SnI4-H202 precursor pair brings forth the film growth even at temperatures as low as
100°C with a wholly amorphous outcome up to 150°C. For the pair SnI4-02, the films grown nearby the process
initiation temperature of 400°C are also amorphous. When the temperature is raised respectively above 250 and 500°C,
both pairs make epitaxial growth happen, generally in three-dimensional mode. Exceptionally, in a limited range of
grown thicknesses in the proximity of 50 nm, the growth from SnI4 and O2 at 750°C appears to be driven by the
predominantly two-dimensional nucleation, as the films grow extremely flat. The SnI4-02 precursor pair gives at 600-
750°C the highest growth per cycle of about 0.085 nm. The epitaxially grown tetragonal (cassiterite) films are (1 0 1)-
oriented. The iodine contamination in them is below 0.1%. All the film-substrate structures are highly transparent in the
visible region.
Atomic layer deposition of Al203 thin films on Si and Si02 substrates was investigated in the temperature range of 470-
1030 K. The films grown at 870-1030 K contained crystalline phase while those deposited at temperatures below 870 K
were amorphous. The growth rate was 0.03 nm per cycle at 1030 K but it increased with decreasing temperature and reached
0.13 nm per cycle at 470 K. The densities of crystalline films were 3660-3670 kg/m3 while those of amorphous films ranged
from 2820 to 3140 kg/m3. The refractive indices of crystalline films (1.75-1.77 at the wavelength of 500 nm) were
significantly higher than the refractive indices of amorphous films. A disadvantage of crystalline films compared with
amorphous films was somewhat higher surface roughness. Nevertheless, the extinction coefficient of the former films did not
exceed 0.004 at the wavelength of 500 nm. Excitation of crystalline films at the wavelengths shorter than 175 nm resulted in
a broadband photoluminescence peaking at 350-360 nm. The excitation spectrum indicated dominant excitation of this
emission via interband transition. The intrinsic absorption edges of 7.2 and 6.6 eV were estimated for crystalline and
amorphous films, respectively, from the long-wavelength edges of the excitation spectra measured at 10 K.
LaF 3 is presented as a possible high refraction index material for the interference coatings down to wavelength of 145 nm, if
well-purified. A material shows up a negative inhomogeneity. The optical parameters of evaporated LaF3 layers are
presented. The best mirrors based on LaF3-MgF2 system have a reflectivity up to 99% depending on absorption in layers.
The MgF2 layers were vacuum evaporated on fused silica substrates using a crystalline and a pressed sintered evaporation materials. The transition spectra of the specimens were recorded in the wavelength range 240 - 830 nm and changes in it monitored during storage of the specimens in atmosphere. The results were analyzed using an envelope method and a fitting of Lorentzian dispersion model with various number of parameters. A rise of the computed indices of refraction and absorption during storing in the air was seen. A heating in vacuum resulted in the temporal descending of refraction and rise of absorption indices. Fitting of the dispersion equation showed a drop of the absorption index moving from 4 to 7 fitting parameters in the red side of the spectra. On the blue side (UV) both indices rose moving from 4 to 5 parameters and descended again at 7 parameters. This shows a need of proper selection of the dispersion model for describing the real coatings. The negative values for the indices of absorption obtained by envelope method displayed the inhomogeneity of the refractive index in the fresh coatings.
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