Silicon dioxide films were grown using an atmospheric-pressure plasma jet that was produced by flowing oxygen and helium between two coaxial metal electrodes that were driven by 13.56 MHz radio frequency power. The plasma exiting from between the electrodes was mixed with tetraethoxysilane (TEOS), and directed onto a silicon substrate held at 115-350 °C. Silicon dioxide films were deposited at rates ranging from 20±2 to 300±25 nm min-1. The deposition rate increased with decreasing temperature and increasing TEOS pressure, oxygen pressure and RF power. For the latter two variables, the rate increased as follows: Rd∝P0.3O2(RF)1.4. Films grown at 115 °C were porous and contained adsorbed hydroxyl groups, whereas films grown at 350 °C were smooth, dense and free of impurities. These results suggest that the mechanism in the atmospheric pressure plasma is the same as that in low-pressure plasmas.

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Deposition of Silicon Dioxide Films with a Non-Equilibrium Atmospheric-Pressure Plasma Jet

The optical properties of the broad absorption region due to asymmetric stretching vibration of bridging oxygen in the amorphous structure of bulk SiO 2 were studied. The complex refractive index of thick densified chemical-vapour-deposited silicon oxide film was calculated and used further to obtain the dielectric response function of the sample. Vibrational modes were analysed by energy-loss functions for transverse and longitudinal optical phonons. In the 900–1300 cm −1 spectral region, three vibrational modes with well-resolved TO–LO phonon splitting were obtained. The phonon spectra appears as the smeared-out version of the crystalline counterpart, i.e. the α-quartz. The most intense phonon couple at 1064  (TO), and 1248 cm −1 (LO) has the smallest damping and appears to be more crystalline-like than the remaining two. The broad frequency distribution of lattice-like phonon lines gives rise to frequency-dependent damping where the phonons only purely feel each other and have different phonon decays.

Vibrational modes in amorphous silicon dioxide

This paper presents the optical characterization of Nd3+ lead silicate glasses (SiO2–Na2CO3–PbO–ZnO), synthesized by means of the fusion method. Absorption, luminescence, lifetime and Raman spectroscopy measurements were performed in order to determine the radiative properties of the glasses. The near infrared luminescence exhibited the typical Nd3+ bands, particularly the band at 1060 nm (4F3/2 → 4I11/2). The calculated branching ratios for the 4F3/2 level are: β (9/2) = 35%, β (11/2) = 55%, β(13/2) = 9.5% and β (15/2) = 0.5%. The estimated quantum efficiency was about 90%, based on comparison with the Judd Ofelt theory and experimental lifetime measurements.

Judd Ofelt calculation of quantum efficiencies and branching ratios of Nd3+ doped glasses

Silicon dioxide thin films are deposited on (100) silicon substrates at low pressure (5 mTorr), from O2/tetraethoxysilane (TEOS) helicon plasmas. The reactor is operated at 300 W radio frequency power without any intentional heating or biasing of the substrate. The samples are characterized using infrared spectroscopy, ultraviolet-visible ellipsometry, and complementary density measurements. Changes in film properties are observed varying the TEOS fraction in the gas mixture. Good quality SiO2 films, insensitive to postdeposition exposure to atmospheric water, are deposited for low TEOS fractions (<5%) in the mixture. As the O2 flow rate decreases, porous SiO2 and polymeric SiOxCyHz samples are successively obtained. Aging over 5 months of intentionally produced porous films has been investigated using Fourier-transform infrared spectroscopy. The 2900–3800 cm−1 OH absorption stretching band is quantitatively analyzed with three deconvolution bands. These films are hygroscopic and they show changes in the ...

Optical spectroscopic analyses of OH incorporation into SiO2 films deposited from O2/tetraethoxysilane plasmas

An organosilicon/silicon oxide (SiO x ) multilayered barrier structure was consecutively deposited onto the polyethylene terephthalate (PET) substrate by plasma-enhanced chemical vapor deposition (PECVD) using tetramethylsilane (TMS) monomer and TMS–oxygen gas mixture, respectively. The thickness of the SiO x film directly deposited onto the PET substrate was firstly designed to perform the best barrier property to water vapor permeation, which also possessed the optimal surface uniformity and Si O Si structural order. By insetting an adequate thickness of the organosilicon layer plasma-polymerized from TMS monomer between the SiO x film and PET substrate, the water vapor transmission rate (WVTR) was further improved. The residual internal stress of such organosilicon/SiO x barrier structure was significantly lower than that of a single SiO x film deposited directly on the substrate. The improvement on the structural quality and surface densification of the organosilicon/SiO x barrier structures was discussed and observed from their chemical bond configurations and surface morphologies. Accordingly, low water vapor permeation below the MOCON detection limit ( − 2  g/m 2 /day) was achievable from the PET substrate coated with the 6-pairs of the organosilicon/SiO x multilayered barrier structure by PECVD using the same monomer precursor.

Organosilicon/silicon oxide gas barrier structure encapsulated flexible plastic substrate by using plasma-enhanced chemical vapor deposition

We have investigated the strongest infrared absorption mode in silicon oxide films obtained at low temperatures (anodic and plasma oxides). The asymmetric stretching transverse mode of the Si-${\mathrm{O}}_{4}$ tetrahedra, centered at 1070 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, exhibits an interesting multiple-resonance structure on the high-energy side of the infrared spectrum. A transverse-optical (TO) mode at 1200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and a longitudinal-optical (LO) mode at 1150 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, both modes associated with a LO-TO frequency splitting, and another longitudinal-optical mode at 1250 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, associated also with a LO-TO splitting of the 1250- and 1070-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ peaks are also observed. An important increase in the intensity of the multiple-resonance feature, attributed to the water concentration present during the oxidation process, is observed. This effect is related to the increase in the short-range disorder in silicon oxide films attributed to OH and ${\mathrm{H}}_{2}$O incorporation during growth. In addition, x-ray-photoelectron-spectroscopy measurements reflect the influence of this short-range disorder on the O 1s and Si 2p core-level and valence-band spectra.

L. Galán

Papers

Disorder-induced vibration-mode coupling in SiO2 films observed under normal-incidence infrared radiation.