Oxygen Content In Films Research Articles

Effect of oxygen content on structural and transport properties in SrTiO 3− x thin films

SrTiO 3− x thin films with various oxygen vacancies were fabricated by laser molecular beam epitaxy. The out-of-plane and in-plane lattice constants of the films increase with increasing oxygen vacancies, which was attributed to the increase of Ti 3+ ions in the films. Ti 3+ ions are formed only in the film inner which is revealed from X-ray photoemission spectroscopy (XPS). With varying the oxygen content, a metal-to-semiconductor transition was observed. The oxygen contents in the films, determined from lattice parameters and XPS are very consistent with each other, which shows quasi-quantitative methods to measure oxygen content in thin films.

Chemical and microstructural study in radio frequency sputtered CdTe oxide films prepared at different N 2O pressures. Oxygen incorporation and film resputtering

CdTe oxide films were grown by radio frequency sputtering in Ar–N 2O plasma at different N 2O partial pressures. The film oxygen content determined by Auger electron spectroscopy ranged from 15 to 60 at.%. The free O 2 production during film deposition was monitored by in situ mass spectroscopy and it was found that it increases linearly over a critical N 2O pressure ~ 4.7 × 10 − 3 Pa alike the oxygen in the films. Film microstructure was studied by Raman spectroscopy and atomic force microscopy. Evidence of bands related to terminal Te–O vibrations was found in films prepared below the N 2O critical pressure, becoming predominant in films with higher oxygen content. The morphology and roughness evolution of the films confirm that they consist of a mixture of phases. Surface structures of the Ia-type and of the Ib-type were observed below and above the critical N 2O pressure. Eventually, ion bombardment process caused film resputtering.

Effect of nonuniform microstructure on magnetic switching behavior in CoCrPt–SiO2 perpendicular magnetic recording media

The effect of nonuniform microstructure on magnetic switching behavior for CoCrPt–SiO2 single layer media with oxygen contents (OCs) from 4% to 10% and recording layer thickness (tmag) from 2to27nm is investigated. Plan-view transmission electron microscopy images clearly show nonuniform microstructure of CoCrPt–SiO2 with OC=10% along the film thickness direction: poor grain isolation at a thin layer, excellent grain isolation at a medium layer, and formation of subgrains at a thick layer. The highest coercivity (Hc) is not observed on the medium with the best grain isolation. An initial CoPt layer with less grain isolation forms on top of Ru interlayer with increasing OC in films. It exhibits domain wall switching, resulting in significant incoherent switching. This is consistent with large magnetic activation volume at tmag⩽6nm. Other plausible incoherent switching mechanism for thicker layer media showing low Hc is likely due to formation of subgrains with less grain isolation.

Correlation Between Processing and Properties of Titanium Oxycarbide, TiCxOy, Thin Films

The main purpose of this work was to prepare of single layered TiCxOy thin films. The depositions were carried out from a TiC target by DC reactive magnetron sputtering, varying the oxygen flow. The presence of oxygen changes the film properties between those of titanium carbide and those of the corresponding titanium oxide. X-Ray diffraction (XRD) results revealed the occurrence of a face-centered cubic (TiC-type) phase, with a clear tendency toward amorphization at the highest oxygen contents. Chemical and structural features strongly influence the film properties, which were analyzed in detail as a function of the preparation conditions. Results indicate a systematic increase in resistivity and a decrease in hardness with the increase in the film's oxygen content.

Raman spectra and structural analysis in ZrO xN y thin films

Raman spectroscopy has been used as a local probe to characterize the structural evolution of magnetron-sputtered decorative zirconium oxynitride ZrO x N y films which result from an increase of reactive gas flow in the deposition. The lines shapes, the frequency position and widths of the Raman bands show a systematic change as a function of the reactive gas flow (a mixture of both oxygen and nitrogen). The as-deposited zirconium nitride film presents a Raman spectrum with the typical broadened bands, due to the disorder induced by N vacancies. The recorded Raman spectrum of the zirconium oxide film is typical of the monoclinic phase of ZrO 2, which is revealed also by X-ray diffraction. Raman spectra of zirconium oxynitride thin films present changes, which are found to be closely related with the oxygen content in films and the subsequent structural changes.

Growth phenomena in room temperature pulsed laser deposited chromium and chromium nitride coatings

Oxygen is usually found as a contaminating species in chromium (Cr) and chromium nitride (CrNx) coatings grown by various PVD techniques (e.g. sputtering, arc evaporation). The current work shows that the high energetic pulsed plasma conditions in the Pulsed Laser Deposition (PLD) technique intensify the oxygen trapping in Cr and CrNx coatings and strongly influence their microstructure. Cr-based coatings were deposited by an industrially designed 4-beam PLD evaporation system at room temperature (25 °C) by using Nd:YAG laser radiation (wavelength: 1064 nm) for Cr target ablation in N2/Ar gas mixtures. Due to the decrease of the oxygen content in films of higher thickness the source of O2 was found to be the rest gas atmosphere after evacuation to pressures lower than 2×10−3 Pa. Coatings deposited from the pure metallic Cr targets in Ar rich atmospheres possess a very fine-grained α-Cr phase structure with strongly increased lattice parameters resulting from the exchange of Cr by O atoms on bcc lattice sites. In contrast, high N2 contents in the deposition atmosphere result in the predominant formation of rhombohedral Cr2O3 mixed with fcc CrN.

Evolution of the local structure in GaN:O thin films grown by ion‐assisted deposition with film thickness

AbstractOptical and optoelectronic properties of gallium nitride strongly depend on the synthesis procedure, which may be related to specific structural characteristics of GaN inherent to each preparation condition. Amorphous and nanocrystalline GaN films have been prepared by ion‐assisted deposition (IAD). The films prepared at 10−5 Torr for <50 min have shown exploitable optoelectronic properties, in spite of the high concentration of oxygen of these films (up to 25 at.%). We study here the evolution of the local structure around Ga atoms as the deposition time increases. Five IAD GaN films of thickness ranging between 140 and 450 nm on silicon substrates were analysed by x‐ray absorption fine structure (XAFS) at the Ga K‐edge. The first and second shells of neighbouring atoms are clearly identified in the radial distribution functions at approximately 1.9 and 3.2 Å, respectively. In all of the films, Ga seems to be tetrahedrally coordinated to four nitrogen atoms, some of which may be substituted by oxygen. For deposition times <50 min, analysis of both x‐ray adsorption near‐edge structure (XANES) and extended x‐ray adsorption fine structure (EXAFS) regions indicates that the material is highly amorphous. Above this threshold, a peak corresponding to the first coordination sphere of Ga atoms becomes discernible and increases in intensity for longer deposition times, indicating that the second shell of atoms is now more ordered. The pseudo Debye–Waller factor of the Ga shell is used for monitoring the average degree of amorphization in an ∼100 nm thick top layer, which seems to be related to the film oxygen content. The XAFS results are compatible with a layered distribution of crystallinity, as has been suggested previously for these films. Copyright © 2005 John Wiley & Sons, Ltd.

The Influence of Argon Pressure on the Properties of Sputtered Molybdenum Disulfide films

Sputtered molybdenum disulfide films having various density, internal stress, morphology, and impurities were produced by varying argon pressure, and the properties were investigated. The main results obtained are summarized as follows : A decrease of argon pressure brings the increase of the bulk density, compressive stress, and argon contents in films. However, the weight of films and stoichiometry are scarcely influenced by the argon pressure. The decrease of bulk density correlates with the proportion of voids in films. An increase of argon pressure brings the increase of the deposition rate, true density, and oxygen contents in films. The occurrence of compressive stresses and increase of true density correlate with the presence of entrapped argon in films. At least in the argon pressure range of 1.7 to 4 Pa, films with preferential orientation were obtained.

Characterization of tungsten oxide films produced by reactive pulsed laser deposition

Tungsten oxide thin films have been prepared by reactive pulsed laser deposition (PLD). Substrate heat treatment and oxygen partial pressure during growth are correlated with Auger electron (AES), X-ray photoelectron (XPS), electron energy loss (EELS) and transmittance spectroscopies. Electronic and mass densities, composition and chemical states are strongly dependent of the deposition conditions. No significant change in the oxygen content in films as a function of substrate or annealing temperature is detected. However, the colored state turns out to be associated to the degree of chemical disorder in the samples, as evidenced by the peak shape of the W 4f transition. Also, the strength of a characteristic energy loss at 6–7 eV appears to be related to the presence of the colored state.

Optical absorption threshold of low pressure chemically vapor deposited silicon oxynitride films from SiCl 2H 2NH 3N 2O mixtures

Amorphous silicon oxynitride thin films were deposited on 4 inch (100) Si wafers in a conventional low pressure chemical vapor deposition reactor at 812 °C and 230 mTorr, using SiCl 2H 2NH 3N 2O gas mixtures. Depositions were carried out keeping the flows of SiCl 2H 2 and of NH 3 constants at 20 and 60 sccm, respectively, while that of N 2O was varying between 0 and 180 sccm. The optical properties of deposits were studied with the aid of the Forouhi–Bloomer model (Phys. Rev. B34, 7018 (1986)) for amorphous semiconductors. From the analysis of the optical spectra the complex refractive index of the films as well as their thicknesses were derived. Moreover, an approximate picture of the energetic distribution of the density of electronic states near the absorption threshold of these films was obtained. This picture was found to be consistent with theoretical calculations found in the literature for crystalline silicon nitride and oxynitride. Thus, the increase of oxygen content in films does not cause a shift of valence and conduction band towards lower and higher energies, respectively, but it implies rather an increase of the band gap and a decrease of the energetic distance between their centers of gravity due to the appearance of a local maximum near the top of the valence band. This maximum is due to the additive effect of the N 2 p and the O 2 p non-bonding orbitals. The study of optical properties provides also useful information regarding the presence of electronic states within the forbidden gap due to film defects, coherent with electrical measurements.

Investigation of the Effect of Hydrogen on the Passive Film on Iron by Surface Analysis Techniques

The effects of dissolved hydrogen on the thickness, structure, and composition of the passive film on iron formed in a boric/borate solution at pH 8.4 were investigated by Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), and nuclear reaction analysis (NRA). AES analysis showed that hydrogen decreases the film thickness and the oxygen content in the film, reduces the valence state of iron, and increases both the iron content in the film and the degree of deviation of the oxide in the passive film from its nominal chemical stoichiometry. The decrease in the oxygen content in the passive film was confirmed by NRA measurements. SIMS results showed that hydrogen charging increases the hydroxyl content in the passive film. These results provide very useful information for elucidating the mechanism by which hydrogen decreases the corrosion resistance of passive films and promotes pitting of iron. © 2003 The Electrochemical Society. All rights reserved.

Influence of the Oxygen Partial Pressure on the Composition and Optical Properties of Electron-beam Evaporated TiOx Films

Quantitative depth profiling and compositional analysis of oxygen in TiOx film deposited on K9 glass was carried out using the resonant elastic scattering 16O(α, α)16O at 3.045 MeV. By means of the resonance yield, the oxygen concentration in TiOx films as well as the oxygen-to-metal stoichiometry as a function of the depth probed can be deduced. TiOx films deposited by electron-beam evaporation at different oxygen partial pressures were analyzed, and it is shown that the oxygen concentration in the films is homogeneous. Oxygen partial pressure in the process of evaporation drastically affects the oxygen concentration in the films, and the refractive indices and the extinction coefficients of the films decrease with the increasing oxygen concentration in the films. Under our deposition conditions, we found that 1.6 × 10—4 Torr is the optimum value of oxygen partial pressure for forming TiO2 films by the electron-beam evaporation method. At this oxygen partial pressure, we can prepare an excellent band-pass filter.

Quantitative analysis of the oxygen content in TiO 2 films deposited by electron-beam evaporation using [formula omitted]O(α,α) [formula omitted]O resonant elastic scattering

The resonant elastic scattering 16 O(α,α) 16 O at near 3.045 MeV is applied to determine the oxygen concentration in oxide films. By means of the resonance yield, the oxygen concentration in TiO 2 films as well as the oxygen to metal stoichiometry as a function of the depth probed can be deduced. In this paper, TiO 2 films deposited by electron-beam (E-B) evaporation at different oxygen ambiences are analyzed using the method. Our experimental results demonstrate that the oxygen concentration in the films deposited by E-B evaporation is homogeneous, and oxygen pressure in the process of evaporation affects the oxygen concentration in the films drastically. Under our deposition conditions, we found that 1.6×10 −4 Torr is the optimum value of oxygen pressure for forming TiO 2 films by the E-B evaporation method. At this oxygen pressure, we have prepared excellent bandpass filters.

Discharge characteristics of MgO and MgOZrO 2 protective films prepared by electron beam evaporation

In order to improve both the operating voltage and the memory coefficient (MC) of a protective layer for AC plasma display panels, controlled amount of ZrO 2 was added to the pure MgO. The effects of the ZrO 2 addition on both the electrical properties ( V f and V s) and the microstructure of the Mg 2−2 x Zr x O 2 films deposited by e-beam evaporation were investigated. As the [ZrO 2/(MgO+ZrO 2)] ratio of the protective materials increased, the oxygen content in films increased, and the relative ratio of (200)/(111) also increased with overall peak shifting to lower angular diffraction positions. The firing voltage of the MgO–ZrO 2 protective films, when the [ZrO 2/(MgO+ZrO 2)] ratio was 0.1, was 5% lower than that of the conventional MgO protective films with higher MC.

Low-Pressure Chemical Vapor Deposition of Semi-insulating Polycrystalline Silicon Thin Films: I. Experimental Study and Proposal of New Kinetic Laws

In the case of the semi-insulating polycrystalline silicon (SIPOS) low-pressure chemical vapor deposition (LPCVD) process, the influence of the two most important operating parameters, gas inlet composition and process temperature, on the evolutions of the deposition rate and of the film oxygen content along the reactor load and on-wafer, has been experimentally studied. This set of experimental results was then used as a database to develop a new kinetic model, using a local numerical simulation code for LPCVD reactors, named CVD2. This new kinetic model certainly summarizes numerous poorly known gas phase and surface reactions involved in SIPOS deposition. Its validation has been successfully performed by comparison with specific experimental data, both along the load and on-wafer. An efficient mathematical tool is then available to better control and optimize the performances of SIPOS low-pressure deposition processes. © 2001 The Electrochemical Society. All rights reserved.

Influence of oxygen on the morphological and structural properties of Ti thin films grown by ion beam-assisted deposition

Ti thin films have been deposited on silicon wafers by electron beam evaporation of Ti powder with and without simultaneous assistance of argon ion bombardment (IBAD technique). We have investigated the influence of the oxygen content on both the morphological and mechanical properties of the films. We found that the oxygen content in the films is minimum when a Ti pre-evaporation treatment is performed just before the deposition process. Moreover, the concentration of oxygen (∼5 at.%) found in non-assisted films grown with Ti pre-evaporation is very similar to that measured in Ti films deposited with the assistance of argon ions with different bombardment energies. The influence of the ion-beam acceleration voltage and the incident angle on the film properties was also investigated. It was found that the film oxygen concentration is critical for determining both the material film morphological performance (best at lower oxygen contents) and the film hardness, which is maximum with high and low oxygen contents in non-assisted and ion-assisted films, respectively.

Metal–insulator transition temperature dependence on lead and oxygen content in La1−xPbxMnO3±y thin films

Preparation of the manganese oxide films with high Curie temperature (TC) above room temperature (RT) is essential for developing multilayered devices that work at RT. We have fabricated La1−xPbxMnO3±y (LPMO) thin films on LaAlO3–Sr2AlTaO6 (001) single-crystal substrates using a pulsed-laser ablation deposition method. Their metal–insulator transition temperature (TRmax), which nearly equals TC, is investigated as a function of the lead (Pb) and oxygen contents contained. The results in the following were obtained. X-ray diffraction indicates growth of epitaxial films with (001) orientation. Samples with high TRmax∼370 K can be prepared in deposition conditions with a substrate temperature (TS) of 600 °C and an oxygen pressure (PO) not less than 0.4 Torr. The TRmax decreases with increasing TS or decreasing PO. The former decrease in the TRmax is shown by electron-probe microanalysis to be ascribed to evaporation of Pb from the films at high TS. On the other hand, it is inferred that the latter decrease is due to a reduction in oxygen content in the films. The reduction of Pb and oxygen contents in the LPMO films, respectively, leads to a decrease in the number of conduction electrons and, consequently, results in a TRmax decrease of the films.

Resistivity and oxygen content of indium tin oxide films deposited at room temperature by pulsed-laser ablation

Transparent, conductive indium tin oxide (ITO) films were fabricated by pulsed-laser deposition on substrates held at room temperature. We investigated the relationship between electrical/optical properties of the films and the material stoichiometry, measured by Rutherford backscattering. The lowest resistivity films (∼4×10−4 Ω cm) have excessive oxygen compared with the stoichiometric composition ITO. After annealing in argon at 400 °C for 1.5 h, the oxygen-to-(indium+tin) ratio approaches the stoichiometric composition of 1.5 and resistivities of annealed samples are ∼2.5×10−4 Ω cm. The room-temperature ITO resistivity dependence on chamber gas pressure is explained in terms of a gas-dynamic model and oxygen content of the film.

Quantitative analysis of the oxygen content in BaTiO 3 films deposited by PLD using 16O( α, α) 16O resonant elastic scattering

The resonant elastic scattering 16O( α, α) 16O at near 3.045 MeV is a very powerful tool for determining the oxygen concentration in oxide films. The resonance yield can be transformed into the stoichiometric ratio of oxygen to Ba–Ti as a function of the probed depth. By means of the resonance yield, we can obtain the oxygen concentration in BaTiO 3 films. In this work the method was used to analyze the oxygen concentration of the BaTiO 3 films deposited by pulsed laser deposition (PLD) at different oxygen ambience. Our experimental results demonstrate that the oxygen concentration in the films deposited by PLD is homogeneous, and the effect of oxygen pressure in the process of deposition on the oxygen concentration in the films is very significant. It is shown in our experiment that 20 Pa is the lowest value of oxygen pressure for forming optimum BaTiO 3 films by the PLD method.

Plasma characteristics at off-axis high pressure magnetron YBa2Cu3O7−δ sputtering

Plasma characteristics at high pressure YBa2Cu3O7−δ reactive magnetron sputtering were investigated with a probe technique and in situ film resistance measurements. The experimental features of probe measurements in oxygen plasma are discussed. Electron energy distribution is the sum of two Maxwell distributions with kTe≈1.5 eV and kTe≈0.3 eV. N2O addition to a gas mixture results in the generation of negative ions with a density virtually equal to the density of positive ions. The energies of ions, impinging the film surface under film biasing, are discussed in collisionless and drift approximations. Low energy ion bombardment of the film surface at temperatures ≈400 °C results in a reduction of film oxygen content.