Deposition of amorphous carbon nitride films using Ar/N2 supermagnetron sputter

Amorphous carbon nitride (a-CN_x) films were formed by supermagnetron sputter deposition using N₂ and/or Ar gases. Supplying rf power with a substrate-holding electrode (bias sputter) and lowering the gas pressure were found to be effective at decreasing the optical band gap and increasing the hardness. Nitrogen concentrations of bias sputtered films were about 32-35 mass% (30-100 mTorr). The a-CN_x films deposited for electron field emission showed a low-threshold electric field (E_TH). With the decrease of gas pressure, admixture of Ar to N₂ or the use of pure Ar, and the use of bias sputter, the E_TH of a-CN_x films largely decreased to 11 V/μm (30 mTorr Ar/N₂ bias sputter).     

Effect of composition and deposition parameters on optical properties of Ge25Sb15−xBixS60 thin films

The optical constants of the Ge₂₅Sb_15−xBi_xS₆₀ (0?x?15) chalcogenide films, either as-deposited or after being annealed at various temperatures have been computed in the spectral wavelength range 400-2400 nm from the transmittance and reflectance measurements of normally-incident light. With the increase in bismuth content, the optical energy gap (which is indirect) decreases, while the refractive index increases. The effects of film thickness, substrate type, deposition rate and γ-radiation on optical properties have been studied. The effect of thermal annealing on the growth characteristics and stability of the films has been studied using X-ray diffraction and scanning electron microscopy. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model.     

TixSiyN nanocomposites by cathodic arc plasma deposition

We have deposited Ti_xSi_yN nanocomposites by means of a custom-made cathodic arc evaporation system, using a TiSi 80/20 at% compound target in a reactive Ar-N₂ atmosphere. We have studied the influence of different process parameters, like the amount of nitrogen in the gas, the total pressure, the arc current or the deposition temperature, on the properties of the material. We have analysed the films by X-ray diffraction (XRD), which has allowed us to determine the optimum conditions to obtain TiN nanocrystals with a good degree of texture. We have found that a moderate increase in the deposition temperature leads to an improvement in the crystalline quality of the films; however, the results as to their hardness are not as good as we expected. We have not been able to confirm the existence of Si₃N₄ by Fourier-transform infrared (FT-IR) spectrometry measurements. Additionally, glow-discharge optical emission spectroscopy (GD-OES) analyses show a high amount of oxygen incorporated to the films (around 5.5 at%).     

Magnetron sputtering of TiOxNy films

This article reports on the characterization and preparation of N-doped titanium dioxide (TiO₂) films by reactive magnetron sputtering from Ti(99.5) targets in a mixture of Ar/O₂/N₂ atmosphere on unheated glass substrates. A dual magnetron system supplied by a dc bipolar pulsed power source was used to sputter the TiO_xN_y films. The amount of N in the TiO_xN_y film ranges from 5 to 40 at%. Its structure was measured using X-ray diffraction (XRD), the optical band gap was calculated from Tauc plots and the decrease of the water contact angle α_ir after the film activation by UV irradiation was investigated as a function of at% of N in the TiO_xN_y film. The yellow-coloured TiO_xN_y films with high (≈8 at%) amount of N exhibited a strong decrease of the band gap E_g down to 2.7 eV. A significant decrease of the water contact angle α_ir after UV irradiation has been observed for 2 μm thick transparent nanocrystalline (anatase+rutile) N-doped TiO₂ films containing less than 6 at% of N.     

The deposition and optical properties of Ge1−xCx thin film and infrared multilayer antireflection coatings

The effects of deposition parameters on the deposition rate, microstructure, and composition of Ge_1−xC_x thin films prepared by plasma enhanced chemical vapor deposition were studied and the films' infrared optical properties were investigated. The results show that the carbon content of these films increases as the precursor gas flow ratio of CH₄:GeH₄ increases, while the infrared refractive index of these films decreases from 4 to 2. The deposition rate increases with the radio-frequency power and reaches a constant value when the power goes above 60 W. Ge_1−xC_x/diamond-like carbon infrared antireflection coatings were prepared, and the transmittance of the coatings in the band of 8 to 14 μm was 88%, which is superior to that of Zinc Sulfide substrate by 14%.     

Reactive sputtering of SiO2-TiO2 thin film from composite Six/TiO2 targets

Coatings of SiO₂-TiO₂ films are frequently used in a number of optical thin film applications. In this work we present results from depositing films with variable Si/Ti ratios prepared by reactive sputtering. The different Si/Ti ratios were obtained by varying the target composition of composite single targets. Compared to co-sputtering this facilitates process control and composition uniformity of the films. Varying the oxygen supply during sputter deposition can result in films ranging from metallic/substoichiometric to stoichiometric oxides. Transmittance spectra of the different films are presented and the optical constants are determined from these spectra. Furthermore, the deposition process, films structure and composition of the films are discussed. The study shows that by choosing the right composition and working in the proper oxygen flow range, it is possible to tune the refractive index.     

Optical properties of amorphous, erbium-doped yttrium alumino-borate thin films

In this paper, we report on the optical characterizations of erbium-doped yttrium alumino-borate glassy thin films prepared by the polymeric precursor and sol-gel routes and the spin-coating technique. High quality planar waveguides were produced by a multilayer processing of Y_1−xEr_xAl₃(BO₃)₄ compositions with x = 0.02, 0.05, 0.10, 0.30, and 0.50. Their optical properties were investigated using transmission, photoluminescence, and m-lines spectroscopy, whereas high resolution scanning electron microscopy (HR-SEM) was applied to check film thickness and surface homogeneity. The refractive indices determined from transmission and m-lines spectroscopy are in good agreement just like the film thickness measured by HR-SEM and transmission spectroscopy. We observed low propagation losses, together with efficient photoluminescence emission for polymeric precursor thin films, involving low cost and environment friendly reactants.     

The properties of transparent semiconductor Zn1 − xTixO thin films prepared by the sol-gel method

Transparent semiconductor thin films of Zn_1 − xTi_xO (0 ≦ x ≦ 0.12) were deposited on alkali-free glass substrates by the sol-gel method. The effects of Ti addition on the crystallization, microstructure, optical properties and resistivity of ZnO thin films were investigated. The as-coated films were preheated at 300 °C, and then annealed at 500 °C in air ambiance. X-ray diffraction results showed all polycrystalline Zn_1 − xTi_xO thin films with preferred orientation along the (002) plane. Ti incorporated within the ZnO thin films not only decreased surface roughness but also increased optical transmittance and electrical resistivity. In the present study, the Zn_0.88Ti_0.12O film exhibited the best properties, namely an average transmittance of 91.0% (an increase of ~ 12% over the pure ZnO film) and an RMS roughness value of 1.04 nm.     

Overview about the optical properties and mechanical stress of different dielectric thin films produced by reactive-low-voltage-ion-plating

Thin films of Ta₂O₅, Nb₂O₅, and HfO₂ were deposited by reactive-low-voltage-ion-plating (RLVIP) on unheated glass and silicon substrates. The film thickness was about 200 nm. Optical properties as well as mechanical film stress of these layers were investigated in dependence of various deposition parameters, i.e. arc current and oxygen partial pressure. For an arc current in the range between 40 and 50 A and an oxygen partial pressure of at least 11 · 10^− 4 mbar good results were obtained. The refractive index and film thickness were calculated from spectrophotometric transmission data using the Swanepoel theory. For example at 550 nm wavelength the refractive index for thin RLVIP-Nb₂O₅-films was found to be n₅₅₀ = 2.40. The optical absorption was obtained by photo-thermal deflection spectrometry. For the investigated materials absorption coefficients in the range of k = 5 · 10^− 4 at 515 nm wavelength were measured. The mechanical film stress was determined by measuring the difference in bending of silicon substrates before and after the deposition process. For dense films, i.e. no water vapour sorption on atmosphere, the mechanical film stress was always compressive with values of some hundred MPa. In case of films deposited with higher arc currents (I_arc > 60A) and lower oxygen pressure (< 15 · 10^− 4 mbar) the influence of a post deposition heat treatment at 350 °C for 4 h on air was also investigated. For these films the properties could clearly be improved by such treatment. However, by using lower arc currents and higher oxygen partial pressure during the ion plating process, immediately dense and environmental stable films with good optical as well as mechanical properties could be achieved without post deposition heat treatment. All the results obtained will be presented in graphs and diagrams.     

SiOx-doped DLC films: Charge transport, dielectric properties and structure

In the present study, SiO_x-doped diamond-like carbon (DLC) films were synthesized by ion beam deposition on different substrates. Electrical properties, morphology and structure of the DLC films were investigated. Poole-Frenkel emission was the main carrier transport mechanism in all investigated metal-SiO_x-doped DLC-metal samples. Dielectric properties of the samples were dependent on both the bottom and top electrode metal. The trans-polyacetylene chain vibrations detected from the Raman spectra have been observed for all the SiO_x-doped DLC films. Different dielectric properties of the film deposited onto the different metal interlayers were explained both by different roughness of the metal films and by different structure of the ion beam-synthesized SiO_x-doped DLC films.     

Deposition of magnesium hydride thin films using radio frequency reactive sputtering

Reactive sputter deposition of MgH_x thin films was performed using mixed hydrogen-argon plasma. This technique allows in-situ deposition of metal hydride films in contrast to the commonly applied ex-situ hydrogenation of metallic films. Partly transparent films were obtained and the formation of crystalline MgH₂ could be observed for thicknesses above about 200 nm. The formation of some metallic Mg in the films could not be avoided. Increased hydrogen loading by increased pressure, H₂:Ar ratio or reduced power produced films of porous structure that easily oxidise. More densely packed films remain stable for several months of air exposure. Post-deposition treatments in H-plasma showed evidence of hydrogenation of deposited films without the use of a catalysing capping film. Film properties are studied by X-ray diffraction, scanning electron microscopy and by optical and resistivity measurements.     

Mechanical and environmental properties of Ge1−xCx thin film

Ge_1−xC_x thin film was prepared by plasma-enhanced chemical vapor deposition (PECVD) using GeH₄ and CH₄ as precursors and its mechanical and environmental properties were investigated. The samples were measured by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectrum, FT-IR spectrometer, WS-92 testing apparatus of adhesion and FY-03E testing apparatus of salt and fog. The results show that the infrared refractive index of Ge_1−xC_x thin film varies from 2 to 4 with different x values. The adhesion increases with increasing gas flow ratio of GeH₄/CH₄ and decreases with increasing film thickness. The nanoindentation hardness number decreases with increasing germanium content. Three series films exhibit the best anti-corrosion property when the RF power is about 80 W, or substrate temperature is about 150 °C, or DC bias is about −100 V. Furthermore, increasing the gas flow ratio of GeH₄/CH₄ improves the anti-corrosion property of these films.     

Cd1−xMnxTe thin films deposited by close-spaced sublimation for application in solar cells

High-quality Cd_1−xMn_xTe polycrystalline films with (1 1 1) preferred orientation were deposited by close-spaced sublimation (CSS) method. The XRD and optical absorption analysis indicated that the band gap of the film was about 1.6 eV. The as-grown Cd_1−xMn_xTe films exhibit quite low photovoltaic performance when used to make cells with CdS as the hetero-junction partner. The effect of various post-deposition treatments with vapors of chlorine-containing materials (CdCl₂ and/or MnCl₂), in Ar or H₂/Ar ambient, on the properties of Cd_1−xMn_xTe cells was studied.     

Structure and dielectric properties of sputtered bismuth magnesium niobate thin films

The Bi_1.5MgNb_1.5O₇ (BMN) thin films were prepared on platinum coated sapphire by rf magnetron sputter deposition. Effects of substrate temperature, sputter pressure and O₂/(O₂ + Ar) mixing ratio on phase structures and dielectric properties of thin films were investigated. The results indicated that sufficiently high substrate temperature and low sputter pressure would facilitate the formation of cubic pyrochlore in BMN thin films. Meanwhile, the appropriate O₂/(O₂ + Ar) mixing ratio of sputter atmosphere was required. The deposited Bi_1.5MgNb_1.5O₇ cubic pyrochlore thin films with (222) oriented texture exhibited large tunability of ~ 50% at a maximum applied bias field of 1.5 MV/cm, with low dielectric loss of ~ 0.007. The temperature and frequency dependent dielectric measurements indicated that no noticeable dielectric dispersion was detected in BMN cubic pyrochlore thin films.     

Thermal stability of amorphous molybdenum trioxide films prepared at different oxygen partial pressures by reactive DC magnetron sputtering

Thin films of MoO₃ were prepared on quartz and Si (1 0 0) substrates by reactive dc magnetron sputtering of a Mo target in an oxygen and argon atmosphere. The structural and optical changes induced in the films due to post-growth annealing have been systematically studied by Rutherford backscattering (RBS), X-ray diffraction (XRD), X-ray reflectivity (XRR) and by optical methods. RBS studies reveal no change in composition of the films upon annealing at high temperatures. Grazing angle XRD studies show that the as-deposited films are amorphous and crystallize to β-MoO₃ phase with small contribution of α-MoO₃ upon annealing at 300 °C. The film prepared at 0.40 Pa transforms to α-MoO₃ upon annealing at 650 °C, while the film deposited at 0.19 Pa still has some β-MoO₃ phase contribution. XRR measurements reveal that the film thickness decreases upon annealing with simultaneous increase of film density. The surface roughness of the films strongly increases after crystallization. The contraction of the film deposited at 0.40 Pa is much greater than the contraction of the film prepared at 0.19 Pa. The mass variation of the film deposited at 0.19 Pa and that deposited at 0.40 Pa are completely different. The optical properties of MoO₃ films deposited at 0.19 and 0.40 Pa are changed strongly by annealing.     

Characteristics of stacked CuInS2 and CuGaS2 layers as determined by the growth sequence

CuInS₂ and CuGaS₂ thin films have been prepared sequentially from elemental evaporation sources onto conventional soda lime glass substrates heated at 350 °C during the deposition process. The gradient in the structure and composition of the stacked layers has been investigated for the two possible growth sequences. Structural depth profiling and crystallographic phase analysis were performed by grazing incidence X-ray diffraction. The atomic distribution in the films depth was analyzed by X-ray photoelectron spectroscopy combined with sputter etching. Formation of the quaternary compound CuIn_1 − xGa_xS₂, with a high Ga content x > 0.80, has been detected with different distribution depending on the growth sequence.     

Transfer of molybdenum sulphide coating material onto corundum balls in fretting wear tests

Transfer films on corundum balls from sulfur deficient molybdenum disulfide (MoS_x) coatings with different crystallographic orientations were investigated after fretting tests performed in ambient air of different humidity levels. The morphology of wear tracks on MoS_x coatings and of transfer films on corundum balls were investigated by light optical microscopy with Normarski contrast. The thickness of transfer films was measured by scanning white light and optical phase-shifting interferometry, and their composition was analyzed by X-ray photoelectron spectroscopy. The effect of relative humidity in fretting tests on the composition of the transfer films as well as the effect of the transfer film on the tribological performance of MoS_x coatings in fretting wear tests is discussed.     

Interaction of reducing gases with tin oxide films prepared by reactive evaporation techniques

SnO_2−x films were prepared by reactive thermal and e-beam evaporation of Sn on alumina substrates and by post deposition thermal treatment. X-ray diffraction measurements found that films are tin dioxide (SnO₂) phase with small amounts of SnO phase. The surface conductivity of films was measured in air and in presence of H₂S, H₂ and C₂H₅OH vapors at four sensor operating temperatures of 433-493 K. The resistance of SnO_2−x films decreases on exposure to H₂S but shows no change with hydrogen and ethanol. H₂S response decreases with rise in sensor temperature while both response and recovery times improve. H₂S signal enhances with increase in resistivity of SnO_2−x coatings. Our experiments conclude that increase in film conductance is due to chemical reaction between H₂S and SnO_2−x surface and there is little or no role of interaction of gas molecules with surface adsorbed charged oxygen species.     

A simple approach of preparing amorphous SiOx film on aluminum substrate

A kind of silicon oxide (SiO_x) film was grown on aluminum substrate by low temperature-atmospheric pressure chemical vapor deposition (CVD). The film thickness, changed with the procession temperature and time, and source gaseous ratio, were studied. The optimized procession parameters were determined. The film section morphology was investigated by the scanning electronic microscopy (SEM) and result shows that the SiO_x film is bound firmly to the aluminum substrate without any crack or gap. The reason of the excellent combination was also discussed. The X-ray diffraction technology (XRD) and transmission electronic diffraction technology (TED) demonstrate that the SiO_x film is basically amorphous with a little crystalline area in it.     

Determination of optical constants of Cd1−xZnxTe thin films by spectroscopic ellipsometry

The optical response of vacuum-evaporated Cd_1−xZn_xTe thin films in the 1.5-5.6 eV photon energy range at room temperature has been studied by spectroscopic ellipsometry. The films of Cd_1−xZn_xTe (x=0.04) were deposited at room temperature onto well-cleaned glass substrates of film thickness 450 nm. The measured dielectric-function spectra reveal distinct structures at energies of the E₁, E₁+Δ₁ and E₂ critical points corresponding to the interband transitions. Dielectric related optical constants such as complex refractive index, the absorption coefficients and the normal incidence reflectivity, are presented. Results are in satisfactory agreement with the calculations over the entire range of the photon energies.