Atomic Concentration Ratio Research Articles

Silicon carbonitride by remote microwave plasma CVD from organosilicon precursor: Physical and mechanical properties of deposited Si:C:N films

Silicon carbonitride (Si:C:N) films produced by the remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) using bis(dimethylamino)methylsilane as single-source precursor and hydrogen as an upstream gas for plasma generation, were examined in terms of their physical (density) and mechanical (hardness, elastic modulus, friction coefficient, and “plasticity index”) properties. The effect of substrate temperature (varied in the range of 30–400 °C) on the properties of Si:C:N films is presented. A reasonable compositional and structural dependencies of film properties were determined using, respectively, the XPS atomic concentration ratios N/Si and C/Si, as well as the relative integrated intensities of the IR absorption bands from the Si N and Si C bonds (controlled by deposition temperature), evaluated in the first part of this work. In view of their good mechanical properties, Si:C:N films seem to be useful coatings for improving surface mechanics of engineering materials.

Fabrication of SiO 2 microdisk arrays for optics and light trapping experiments

We present a simple silicon based microfabrication process that produces an array of SiO 2 microdisks using UV lithography. High-resolution SEM images of these structures indicate a smooth outer microdisk cavity surface. Photoemission measurements were performed at different spots on the microdisk and compared with measurements inside the cavity. A silicon to oxygen atomic concentration ratio of 1:2 obtained during depth profiling confirms that the entire microdisk is made up of stoichiometric SiO 2. In contrast, the inner cavity is mostly silicon with native oxide on top. We discuss the usefulness of SiO 2 microdisks in optics for light trapping experiments.

Electrical properties of ultra-thin oxynitrided layer using N 2O plasma in inductively coupled plasma chemical vapor deposition for non-volatile memory on glass

In this work, the silicon oxynitride layer was studied as a tunneling layer for non-volatile memory application by fabricating low temperature polysilicon thin film transistors on glass. Silicon wafers were oxynitrided by only nitrous oxide plasma under different radio frequency powers and plasma treatment times. Plasma oxynitridation was performed in RF plasma using inductively coupled plasma chemical vapor deposition. The X-ray energy dispersive spectroscopy was employed to analyze the atomic concentration ratio of nitrogen/oxygen in oxynitride layer. The oxynitrided layer formed under radio frequency power of 150 W and substrate temperature of 623 K was found to contain the atomic concentration ratio of nitrogen/oxygen as high as 1.57. The advantage of high nitrogen concentration in silicon oxide layer formed by using nitrous oxide plasma was investigated by capacitance–voltage measurement. The analysis of capacitance–voltage characteristics demonstrated that the ultra-thin oxynitride layers of 2 nm thickness formed by only nitrous oxide plasma have good properties as tunneling layer for non-volatile memory device.

Electron Diffraction study of Layer Structures in La-Mg-Ni Hydrogen Absorption Alloys

In order to improve the hydrogen absorption properties of the layer structure appearing at the nickel rich side of La-Mg-Ni alloy, appropriate amounts of Ni were replaced by some elemental atoms, Mn, Co and Al. The La0:8Mg0:2Ni3:4� xCo0:3(MnAl)x (0 < x < 0:4) alloy system was synthesized and crystal structures were investigated by electron microscopy. The atomic concentration ratio of (LaMg) to the other atoms was 3.7 in this system. The Pr5Co19-type structure (5:19H-structure) and the Ce5Co19-type structure (5:19R-structure) were found in this alloy system. Electron micrographs of these structures are presented in this paper. Structure analysis of the complex layer structure is demonstrated by careful observation of the electron diffraction pattern. [doi:10.2320/matertrans.MBW200631]

Effect of deposition conditions on the characteristics of ZnO–SnO 2 thin films deposited by filtered vacuum arc

ZnO–SnO 2 thin films were deposited on microscope glass substrates by filtered vacuum arc deposition system. The effects of deposition conditions on film characteristics were studied using cathodes prepared with three different ratios of atomic concentrations of Zn to Sn. The micro and the macro properties of the films were investigated as a function of cathode composition, arc current, background oxygen deposition pressure, and deposition time. X-ray diffraction analysis indicated that deposited films were amorphous, independent of the cathode composition. The atomic concentration ratio of Zn to Sn in the film as determined by XPS analysis were 33.9%: 10.6%, 43.9%: 3.8%, 44.7%: 4.7% for 50%: 50%, 70%: 30% and 90%: 10% Zn–Sn alloy cathodes, respectively. Film transmission in the visible was 70 to 90%, affected by interference effects. The maximal and minimal values of the refractive index n and the absorption coefficient k in the visible were 2.11 to 1.94 and 0.07 to 0.001, respectively. The optical band gap was in the range of 3.13 to 3.59 eV. All films were highly resistive independent of deposition conditions used.

Optical characterization of filtered vacuum arc deposited zinc oxide thin films

ZnO thin films, 100–250 nm thick, were deposited on microscope glass slides and UV fused silica (UVFS) substrates using a filtered vacuum arc deposition (FVAD) system, operating at room temperature (RT) and 200 A for 60 s. The cathode was prepared from 99.9% pure Zn metal and the oxygen background pressure during deposition was in the range 0.67–0.93 Pa. The films were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), optical transmission and spectroscopic ellipsometry. As-deposited ZnO films were found to be polycrystalline with c-axis orientation. The atomic concentration ratio of Zn to O in the film as determined by XPS analysis was stoichiometric. Film transmission in the visible was 70–90%. The maximum and minimum values of the refractive index n and the extinction coefficient k in the visible, for all samples, were 2.23 to 1.90 and 0.6 to approximately 0, respectively. The type of inter-band electron transition was found to be direct transition with optical band gap in the range of 3.25–3.42 eV.

Laser-induced breakdown spectroscopy for compositional analysis of multielemental thin films

The laser-induced breakdown spectroscopy technique is employed for compositional analyses of thin films produced by pulsed laser ablation of multielemental targets. Information about the atomic concentration of the chemical species from the irradiated target is inferred by means of the optical emission spectra of the plasma generated during laser ablation. The atomic concentration percentages and the atomic concentration ratios of the elements of Co-based magnetic alloy targets are deduced from the integrated intensities of selected emission lines of the alloy components. The experimental results show that Co atomic percentage concentration and C Si/C Co and C Cr/C Co atomic concentration ratios are in agreement with the corresponding values obtained by traditional compositional analysis techniques. On the contrary, Si atomic percentage concentration values are in disagreement, since the used emission lines have significant self-absorption values. Therefore, the work proves that laser-induced breakdown spectroscopy is adequate for elemental concentration measurements provided an accurate choice of the emission lines.

Strong composition-dependent variation of MCs + calibration factors in TiO x and GeO x ( x ≤ 2) films

The emission of MCs + secondary ions (M designates the analyte species) from TiO x (0.2 ≤ x ≤ 2) and GeO x (0.001 ≤ x ≤ 0.8) films under Cs + bombardment was examined. The relative calibration factors of OCs +/TiCs + and OCs +/GeCs + were determined and were found to depend pronouncedly on the O/Ti and O/Ge atomic concentration ratios. Specifically, with increasing oxygen content OCs + ions form much more efficiently (as compared to TiCs + or GeCs + ions), an enhancement amounting to more than a factor of 10 for the highest oxygen concentrations. Concurrently, the formation of TiOCs + or GeOCs + ions increases drastically. For both oxide systems, an empirical relation for the oxygen-concentration dependence of the relative calibration factors could be established.

Remote hydrogen microwave plasma chemical vapor deposition of silicon carbonitride films from a (dimethylamino)dimethylsilane precursor: Compositional and structural dependencies of film properties

The physical, optical, and mechanical properties of amorphous hydrogenated silicon carbonitride (a-Si:C:N:H) films produced by the remote hydrogen plasma chemical vapor deposition (RP-CVD) from (dimethylamino)dimethylsilane have been investigated in relation to their chemical composition and structure. The films deposited at different substrate temperature (30–400 °C) were characterized in terms of their density, refractive index, adhesion to a substrate, hardness, elastic modulus, friction coefficient, and resistance to wear predicted from the “plasticity index” values. The correlations between the film compositional parameters, expressed by the atomic concentration ratios N/Si and C/Si, as well as structural parameters described by the relative integrated intensities of the absorption IR bands from the Si–N, Si–C, and C–N bonds, and the XPS Si2p band from the Si–C bonds (controlled by substrate temperature) were investigated. On the basis of the results of these studies, reasonable compositional and structural dependencies of film properties have been determined.

Electronic properties of boron-doped {111}-oriented homoepitaxial diamond layers

p-type diamond single crystal layers were grown by Microwave Plasma-enhanced Chemical Vapor Deposition (MPCVD) on {111}-oriented Ib-type diamond substrates. The variation of the gas-phase boron-to-carbon atomic concentration ratio from 0.1 ppm to 10 4 ppm led to solid state incorporations of boron ranging from the 8 × 10 15 cm − 3 to 3 × 10 21 cm − 3 . Low temperature cathodoluminescence spectra in the bandgap region are shown to yield a reliable estimate of the quality of the layers and of the neutral acceptor concentration up to the metal–insulator transition. Temperature-dependent resistivity and Hall effect measurements allow a discussion of the relevance of the various charge carrier scattering mechanisms.

Bacterial adhesion studies on titanium, titanium nitride and modified hydroxyapatite thin films

A qualitative study on adhesion of the oral bacteria Porphyromonas gingivalis on titanium (Ti), titanium nitride (TiN), fluorine modified hydroxyapatite (FHA) and zinc modified FHA (Zn-FHA) thin films is investigated. Ti and TiN thin films were deposited by DC magnetron sputtering and hydroxyapatite-based films were prepared by solgel method. The crystalline structure, optical characteristics, chemical composition and surface topography of the films were studied by XRD, optical transmission, XPS, EDAX and AFM measurements. The predominant crystallite orientation in the Ti and TiN films was along (002) and (111) of hcp and cubic structures, respectively. The Ti : O : N composition ratio in the surface of the Ti and TiN films was found to be 7 : 21 : 1 and 3 : 8 : 2, respectively. The atomic concentration ratio (Zn + Ca) / P in Zn-FHA film was found to be 1.74 whereby the Zn replaced 3.2% of Ca. The rough surface feature in modified HA films was clearly observed in the SEM images and the surface roughness (rms) of Ti and TiN films was 2.49 and 3.5 nm, respectively, as observed using AFM. The film samples were sterilized, treated in the bacteria culture medium, processed and analyzed using SEM. Surface roughness of the films was found to have least influence on the bacterial adhesion. More bacteria were observed on the TiN film with oxide nitride surface layer and less number of adhered bacteria was noticed on the Ti film with native surface oxide layer and on Zn-FHA film.

Ion beam mixing of Co/Fe multilayers: Magnetic and structural properties

[Co(7 nm)/Fe(7 nm)] 6 multilayers were electron-beam evaporated onto Si(100) substrates in ultrahigh vacuum and irradiated at room temperature with 200-keV Xe ions, leading to ion beam mixing within the Co/Fe multilayer, but not with the Si substrate. Irradiation-induced changes in structural and magnetic properties were characterized by means of Rutherford backscattering spectroscopy, X-ray diffraction and in-plane magneto-optical Kerr effect. Irradiation with 1 × 10 16 Xe ions/cm 2 induced Co/Fe intermixing to a 1 : 1 atomic concentration ratio (RBS) and the formation of the Fe 50Co 50 permendur phase in the intermixed zone (XRD). For lower ion fluences, the coercivity decreased strongly, but then increased slowly for higher fluences. The angular pattern of the relative remanence showed a perfect uniaxial anisotropy. The magnetic energy density was parametrized with the expression E s / M s ∝ ( K u1 / M s) sin 2( φ − φ 0) + ( K u2 / M s) sin 4( φ − φ 0), M s being the saturation magnetization and φ 0 the symmetry angle. The second-order term K u2 / M s was found to decrease strongly with increasing Xe fluence.

Remote nitrogen microwave plasma chemical vapor deposition from a tetramethyldisilazane precursor. 2. Properties of deposited silicon carbonitride films

The physical, optical, and mechanical properties of silicon carbonitride (Si:C:N) films produced by the remote nitrogen plasma chemical vapor deposition (RP-CVD) from tetramethyldisilazane have been investigated in relation to their chemical composition and structure. The films deposited at different substrate temperature (30–400 °C) were characterized in terms of their density, refractive index, hardness, elastic modulus, and friction coefficient. The correlations between the film compositional parameters, expressed by the atomic concentration ratios N/Si, C/Si, and N/C, as well as structural parameters described by the relative integrated intensities of the infrared absorption bands from the Si–N, Si–C, and SiMe units (controlled by substrate temperature) were investigated. On the basis of the results of these studies, reasonable structure–property relationships have been determined.

Formation and characterization of Ag-deposited TiO2 nanoparticles by chemical reduction method

Abstract Modified TiO 2 suspensions were prepared by adding silver nitrate to the suspension such that the desired Ag/Ti atomic concentration ratio was obtained. Ag-deposited TiO 2 particles were formed by a chemical reduction method using a semi-batch reactor and were characterized. The photocatalytic disinfection of E. coli using the nanoparticles was also investigated.

Atomic oxygen profiles (80 to 115 km) derived from Wind Imaging Interferometer/Upper Atmospheric Research Satellite measurements of the hydroxyl and greenline airglow: Local time–latitude dependence

Hydroxyl and oxygen greenline nightglow observations from the Wind Imaging Interferometer (WINDII) are used to examine the local time–latitude variation of atomic oxygen in the mesopause region. Individual hydroxyl and greenline emission profiles from over 5 years of data are converted to oxygen mixing ratio (or concentration) profiles and then binned into local times, latitudes, and seasons. The two derived oxygen profiles from each emission are then combined into a single profile that spans a significant portion of the mesopause region (80 to 115 km). A technique developed earlier that addresses the altitude variability of the emission profiles is used. This level of agreement indicates a high degree of consistency in the radiance observations and in the photochemistry used to convert the emission rates to oxygen profiles. We demonstrate that the atomic oxygen concentration or mixing ratio profiles are very sensitive to local nighttime, and we display the manner in which they vary. The local time variation is primarily due to the tidal dynamics in the atmosphere. Comparisons between our atomic oxygen data set, a simple tidal model, and the TIME‐GCM show good agreement; however, the local time tidal structure of atomic oxygen from MSISE‐90 shows a 180° phase inconsistency. The measured local time oxygen variations vary with season and latitude, and we show that these oscillations are stronger under equinox conditions.

Dependence of zinc oxide thin film properties on filtered vacuum arc deposition parameters

The micro-properties (structure and composition) and macro-properties (electrical and optical properties) of zinc oxide thin films deposited on glass substrates using a filtered vacuum arc deposition system were investigated as a function of oxygen pressure (0.37–0.5 Pa) and arc current (100–300 A). The films were polycrystalline and the crystal plane orientation varied with the oxygen pressure and arc current, tending to be aligned parallel to the c-axis. The sizes of the crystallite grains were 10–35 nm. The films were found to be compressively stressed, with stress in the range of −2.5–0 GPa. The stress in any sample decreased as a function of arc current; however, its dependence on the pressure also depended on the applied arc current. The compressive stress in samples deposited with arc current in the range 100–150 A, decreased with the pressure from −2.5 to −1.5 GPa (0.37–0.5 Pa), whereas it increased with the oxygen pressure in samples deposited with arc current ranging from 200–300 A. The compressive stress in all samples deposited with the highest oxygen pressure (0.51 Pa) was in a relatively narrow range of −2.1 to −1.7 GPa.Film composition, determined by x-ray photoelectron spectroscopy, depended weakly on the deposition parameters. All samples had zinc excess, with a typical oxygen to zinc atomic concentration ratio of 0.7–0.8. Film thickness, in the range of 80–780 nm, depended linearly on both the deposition parameters.The electrical resistivity (ρ) of the films was in the range of (1–5) × 10−4 Ωm, depending weakly on the deposition parameters. The electrical resistivity of the films with larger grain size was higher than that of films with smaller grains, whereas it increased with film stress. The optical transmission of the films, expressed by the extinction coefficient, depended strongly on both the deposition parameters (arc current and oxygen pressure). The lowest extinction was obtained with films deposited with higher pressure (P ⩽ 0.5 Pa) and lower arc current (I ⩾ 200 A). The lowest extinction coefficient was ∼4 × 10−4 nm−1 in the visible and the near-IR range of the spectrum. Films with larger grain size and lower stress had a relatively larger extinction coefficient (∼8 × 10−3 nm−1).

Growth and Rutherford backscattering spectrometry study of direct current sputtered indium oxide films

In 2O 3 thin films were grown by direct current reactive sputtering. Structural investigations using X-ray diffraction and transmission electron microscopy confirmed the single-phase and polycrystalline nature of the films. Rutherford backscattering spectrometry study of the interface of In 2O 3 films with Si indicated the formation of ∼20 nm thick intermediate region consisting of silicon, oxygen and indium. Annealing at 875 K in oxygen atmosphere led to an increase in interface layer thickness. Broadening of the interface and diffusion of silicon into In 2O 3 were observed in films annealed in argon at 875 K. Oxygen-to-indium atomic concentration ratio in the as-grown films was ∼1.44, which was found to vary depending upon the annealing conditions. However, films deposited over Si/SiO 2 showed a sharp interface between the In 2O 3 film and SiO 2.

Pervaporation separation of water + isopropanol mixtures using novel nanocomposite membranes of poly(vinyl alcohol) and polyaniline

Novel nanocomposite polymeric membranes containing nanosized (30–100 nm) polyaniline (PANI) particles dispersed in poly(vinyl alcohol) (PVA) were prepared and used in the pervaporation separation of water–isopropanol feed mixtures ranging from 10 to 50 mass% of water at 30 °C. Of the three nanocomposite membranes prepared, the membrane containing 40:60 surface atomic concentration ratio of PANI:PVA produced the highest selectivity of 564 compared to a value of 77 observed for the plain PVA membrane. Flux of the nanocomposite membranes was lower than those observed for the plain PVA membrane, but selectivity improved considerably. Membranes were characterized by differential scanning calorimetry, dynamic mechanical thermal analyzer, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The highest selectivity with the lowest flux was observed for 10 mass% water containing feed mixture. Flux increased with increasing amount of water in the feed, but selectivity decreased considerably. These results were attributed to the acid-doped PANI particles in the PVA membrane as a result of change in the micromorphology of the nanocomposite membranes. In addition, molar mass between cross-links and fractional free volume of the membranes are responsible for the varying membrane performance. Temperature effect on permeability was investigated for 10 mass% water containing feed with the membrane containing higher concentration of PANI particles, the presence of which could be responsible for varied effect of water permeation through the membrane. Membranes of this study could remove as much as 98% of water from the feed.

Effect of annealing on the magnetic, transport, and electronic properties of electron-beam evaporated Fe∕Al multilayers

The effect of FeAl phase formation on magnetic, transport, and electronic properties of electron-beam evaporated Fe∕Al multilayer samples (MLS), with an overall atomic concentration ratio of Fe:Al=1:1, have been investigated and reported in the present paper using magneto-optical Kerr effect, four-probe resistivity, and valence-band photoelectron spectroscopy techniques. Grazing incidence x-ray diffraction results show that after annealing at 700 K, all the peaks due to Al disappear and those of Fe are slightly shifted with the appearance of new peak at 2θ=31.22° indicating the formation of new crystalline B2FeAl intermetallic phase. The magnetization measurements at this temperature show a large increase in coercivity (Hc) from 21 Oe to 90 Oe, saturation field (Hs) from 80 to 430 Oe, and drastic reduction in magnetization intensity as compared to as-deposited multilayer sample, indicating the precipitation of nonmagnetic B2FeAl phase at the interface. Resistivity increases linearly with temperature and found a maximum at this particular temperature. The corresponding valence-band photoemission measurements carried out on these MLS using hν=134eV, show that after annealing, the binding energy values of Fe 3d band are shifted towards lower binding energy with corresponding increase in Fe 3d and decrease in Al 3s density of states. These observed changes in the magnetization, resistivity, and valence band behavior after annealing are, therefore, attributed to the transfer of valence Al 3p and Al 3s electrons to minority 3d orbital of Fe, suggesting the strong hybridization of sp-d state at Fermi level forming B2FeAl intermetallic phase at the interface.

Thermally induced changes in magnetic, transport and electronic properties of Fe/Al multilayers

The effect of thermal annealing on the magnetic, transport and electronic properties of electron beam evaporated Fe/Al multilayer samples (MLS), with an overall atomic concentration ratio of Fe/Al 1:1, have been investigated. The grazing incidence X-ray diffraction, resistivity and valance band photoemission measurements indicates the formation of sub-stoichiometric B2 FeAl intermetallic phase at the interface for the MLS annealed at higher temperatures. The corresponding magnetization measurements show large increase in coercivity and drastic reduction in magnetization values. The observed magnetization behaviour in each case is interpreted in terms of their structural and electronic properties changes induced due to the annealing treatment.