Power and pressure effects upon magnetron sputtered aluminum doped ZnO films properties

In this work, polycrystalline aluminum doped zinc oxide (ZnO:Al) films with c-axis (002) orientation have been grown on glass and silicon substrates by RF (radio frequency) magnetron sputtering technique, at room temperature. A systematic study of the effect of sputtering deposition parameters (i.e. RF power and argon gas pressure) on the structural, optical and electrical properties of the films was carried out. We observed that, with increasing RF power the growth rate increased, while it decreased with increasing gas pressure. As mentioned above, the films were polycrystalline in nature with a strong preferred (002) orientation. The intrinsic compressive stress was found to decrease with both increasing RF power and gas pressure, and near stress-free film was obtained at 200 W RF power and 2 × 10^− 1 Pa gas pressure. The obtained ZnO:Al films, not only have an average transmittance greater than 90% in the visible region, but also have an optical band gap between 3.33 and 3.47 eV depending on the sputtering parameters. Moreover, a low value of the electrical resistivity (~ 1.25 × 10^− 3 Ω cm) was obtained for the film deposited at 200 W and 2 × 10^− 3 mbar.     

Preparation of amorphous FexSi(1 − x) film using unbalanced magnetron sputtering

The preparation of iron-silicon films was performed onto Si (100) substrates by microwave electron cyclotron resonance (ECR) plasma source enhanced unbalance magnetron sputtering. The compositions, microstructures and properties of films under different sputtering powers and annealing conditions were characterized by AES, GAXRD, TEM and absorption spectrum techniques. The results described that the amorphous iron silicon films can be easily prepared by unbalance magnetron sputtering. Even the Fe/Si ratio deviated far from 1:2, such as Fe/Si = 1:14.8 or 1:10, the amorphous iron silicon film with semiconductor properties can also be obtained, which suggests that the Fe/Si ratio is not the only factor to determine whether the samples have semiconducting properties in iron silicon amorphous. After annealing at 850 °C for 4 h, the microstructure of nanometer β-FeSi₂ embedded into amorphous Si still possesses semiconducting characteristics.     

Residual stress in polytetrafluoroethylene-metal nanocomposite films prepared by magnetron sputtering

In the present research we have evaluated residual stress as well as thermal stability of polytetrafluoroethylene (PTFE) and PTFE-based silver (Ag) nanocomposite films fabricated by dual magnetron sputtering. We used a RF magnetron system for sputtering PTFE, and a DC magnetron sputter source for metal. We have demonstrated that thin nanocomposite films of Ag/sputtered PTFE (thickness 800 to 1100 nm, Ag concentration 3.5 to 24.5%) deposited on silicon are stressed (6.24 to 12.2 MPa). The residual stress depends on the concentration of the nanoparticles. Pure sputter deposited PTFE films are under a small tensile stress, which becomes increasingly more compressive upon increasing the filling factor of the metallic nanoparticles. Depending on the concentration of nanoparticles, the residual stress is determined by a thermal component that is sensitive to temperature variation, even in the range of room temperature. In the evaluation of the thermal response of the nanocomposite-silicon system, both the changes in the thermal expansion coefficient as well as the elastic modulus of the nanocomposite with the concentration should be taken into account.     

Effect of post-deposition annealing on phase formation and properties of RF magnetron sputtered PLZT thin films

In this work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films by RF magnetron sputtering on platinized silicon (Pt/Ti/SiO₂/Si) substrate. Sputtering was done in pure argon at 100 W RF power without external substrate heating. X-ray diffraction studies were performed on the films to study the effect of post-deposition furnace annealing temperature and time on the perovskite phase formation of PLZT. Annealing at 650 °C for 2 h was found to be optimum for the preparation of PLZT films in pure perovskite phase. The effect of different annealing conditions on surface morphology of the films was examined using AFM. The dielectric, ferroelectric and electrical properties of these films were also investigated in detail as a function of different annealing conditions. The pure perovskite film exhibits better properties than the other films which have some fraction of unwanted pyrochlore phase. The remanent polarization for pure perovskite film was found to be ∼29 μC/cm² which is almost double compared to the films having mixed phases. The dc resistivity of the pure perovskite film was found to be 7.7 × 10¹⁰ Ω cm at the electric field of ∼80 kV/cm.     

Raman and XRD studies of Ge nanocrystals in alumina films grown by RF-magnetron sputtering

Germanium (Ge) nanocrystals (NCs) embedded in alumina thin films were produced by deposition on fused silica and silicon (111) substrates using radio-frequency (RF) magnetron sputtering. The films were characterised by both Raman and X-ray diffraction (XRD) spectroscopy. The deposition conditions were optimised in order to obtain crystalline Ge nanoparticles. In as-deposited films, the typical NC size was ∼3 nm as estimated by means of X-ray diffraction. Raman spectra taken from as-deposited films revealed both amorphous and crystalline semiconductor phases. Annealing was performed in order to improve the crystallinity of the semiconductor phase in the films. After a 1 h annealing at 800 °C the mean NC size estimated from the XRD data and Raman spectra increased to ∼6.5 nm. An increase in the crystallinity of the Ge phase was also confirmed by the Raman spectroscopy data.     

The structural and optoelectrical properties of TiON/Au/TiON multilayer films

Sandwich structures of TiON/Au/TiON (TAT) films were deposited on glass substrates via RF magnetron sputtering of TiON and DC magnetron sputtering of Au. The optoelectronic properties of the films were strongly influenced by the Au intermediate layer. The Au insert caused a deteriorated optical transmittance, while electrical conductivity was improved with an increased carrier density. The intermediate Au film was crystallized in TAT films, but this may not have affected the crystallinity of the TiON films.In this study, new transparent and conducting TAT films with a sheet resistance of 29 Ω/□ and 78% of optical transmittance at 550 nm wavelength were obtained without intentional substrate heating.     

Electroluminescence of as-sputtered silicon-rich SiOx films

Si-rich oxide films (SiO_x, 0 < x < 2) were synthesized by reactive magnetron sputtering of a single Si target in a gas mixture of argon and oxygen. Intense visible electroluminescence was observed from the as-deposited SiO_x film. The microstructure of the as-sputtered SiO_x films was characterized by Raman and X-ray photoelectron spectroscopy techniques. Nanoscale amorphous Si clusters formed in the as-sputtered films. The electroluminescence was attributed to the oxygen-deficient defect luminescent centres and the formation of the amorphous Si nanoclusters.     

Stress and structural studies of ZnO thin films on polymer substrate under different RF powered conditions

The ZnO films are deposited on flexible substrate Teflon by radio frequency (RF) magnetron sputtering. The structure and residual stress of the films are revealed by XRD analysis. We find that the increase of RF power results in the change in the nature of stress and the difference of the grain size in the ZnO films on Teflon substrate. This indicates the possibility of the stress relaxation by increasing the RF power. Considering the (002) orientation and the mechanical stress, we suggest that the ZnO film deposited at RF power of 200 W for 1 h is optimal.     

The selective growth of rutile thin films using radio-frequency magnetron sputtering

Using unbalanced radio-frequency (RF) magnetron sputtering crystalline rutile films were synthesised on glass substrates at (combined Ar and O₂) pressures of 0.4 Pa or less, at RF powers of 500 and 600 W with substrate to magnetron distances of 40 mm or longer. Anatase films were deposited at the greater pressure of 1.2 Pa (substrate to magnetron distance of 40 mm) or shorter substrate to magnetron distance of 20 mm (at 0.4 Pa). A mixture of anatase and rutile was formed at 0.5 Pa with all other conditions being as for those required for rutile or the power was reduced along with the substrate to magnetron distance (500 W and 20 mm). The crystallite sizes of rutile obtained were 1 - 3 nm. It is proposed that the greater the energy imparted to the substrate surface by the impinging positive species the greater the activation energy to crystalline phase formation that can be overcome. Hence the formation of rutile over anatase is favoured at greater power, longer magnetron to substrate distances and decreased pressure. Moreover, not only is it possible to control the phase of TiO₂ formed it appears to be possible to control the degree of oxygen non-stoichiometry in the rutile films formed. Smaller O₂ partial pressures, shorter substrate to magnetron distances and greater RF power are believed to produce an environment of reduced reaction of sputtered Ti species with O₂ and to result in the formation of non-stoichiometric rutile structures resulting in increased band gap energies and decreased refractive indices.     

Substrate temperature effect on the SiC passivation layer synthesized by an RF magnetron sputtering method

This paper describes amorphous silicon carbide (a-SiC) film as an alternative material to silicon nitride (SiN) and silicon oxide (SiO₂) for the passivation layer of solar cells. We deposited the film on p-type silicon (100) wafers and glass substrates by RF magnetron sputtering using a SiC (99%) target. Structural and optical properties of the films were investigated according to the process temperature (room temperature, 300 °C, 400 °C, 500 °C and 600 °C). The structural properties were analyzed by Raman microscopy and XPS (X-ray Photoelectron Spectroscopy). The XPS showed that the content of SiC in the film is increased when the substrate temperature is higher. The optical properties of the films were examined by UV-visible spectroscopy and Ellipsometer. The optical characteristic measurement showed that the lowest refractive index of the film is 2.65. Also, using carrier lifetime measurement, we investigated the performance of SiC as the passivation layer. At the substrate temperature of 600 °C, we obtained a highest carrier lifetime of 7.5 μs.     

Enhanced characterization of ITO films deposited on PET by RF superimposed DC magnetron sputtering

Tin-doped indium oxide (ITO) films were deposited on polyethylene terephthalate substrates by RF superimposed DC magnetron sputtering using an ITO target composed of In₂O₃ (90 wt.%):SnO₂ (10 wt.%). The total sputtering power was maintained at 70 W and the power ratio of RF/(RF + DC) was varied from 0 to 100% in steps of 25%. The discharge voltage and deposition rate decreased with increasing RF/(RF + DC) power ratio. The ITO film deposited at a 50% RF portion of the total power showed the lowest resistivity (3.18 × 10^− 4 Ωcm), high transmittance (87.5%) and relatively good mechanical durability, which was evaluated using bending and scratch tests.     

The influence of electric field on the microstructure of nc-Si:H films produced by RF magnetron sputtering

Hydrogenated nanocrystalline silicon thin films were prepared by RF magnetron sputtering. Different bias fields (no bias-no ground, grounded and negative bias) were applied to the substrate. The effect of the ion bombardment on the structure, chemical and optical property were studied by Raman spectroscopy, X-ray diffraction, Rutherford backscattering (RBS) and optical transmission spectroscopy. The deposition rate and the optical bandgap decrease as the bias voltage increases from 0 to −50 V. The structural characterization indicates that compressive stress is developed in plane and tensile stress is induced in the growth direction. No significant variation on the chemical composition was observed.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3−δ thin film electrolyte deposited by RF magnetron sputtering on the porous anode support for IT-SOFC

Thin films of solid electrolyte La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) were deposited by RF magnetron sputtering onto porous La_0.7Sr_0.3Cr_0.5Mn_0.5O_3−δ (LSCM) anode substrates. The effects of substrate temperature, sputtering power density and sputtering Ar gas pressure on the LSGM thin film density, flatness and morphology were systematically investigated. RF sputtering power density of 7.8 W cm⁻², substrate temperature of 300 °C and sputtering Ar gas pressure of 5 Pa are identified as the best technical parameters. In addition, a three-electrode half cell configuration was selected to investigate the electrochemical performance of the thin film. The LSGM film deposited at optimum conditions exhibited a lower area specific ohmic resistance of 0.68 Ω cm⁻² at 800 °C, showing that the practicability of RF magnetron sputtering method to fabricate LSGM electrolyte thin film on porous LSCM anode substrates.     

A novel magnetron sputtering for flexible coatings as a function for production of high quality films

A novel sputtering technique combining the symmetric compressive magnets with cylindrical cathode has been developed to mass produce high-quality oxide and nitride films on plastic sheets. The discharge characteristics of our sputtering can supply about three times larger power efficiencies than that of the conventional magnetron sputtering. Moreover, in continuous dielectric sputtering experiments, the substrate temperature was kept lower than 60 °C. The refractive index of SiN_X and SiO₂ thin film at 500 nm is 1.86 and 1.46 respectively. Moreover, 4 layered anti-reflection coatings of silicon nitride and oxide films deposited on both sides of the PET sheet is achieved to fabricate, and the reflection less than 1% is realized in the range from 420 to 680 nm.     

Study on ZnO thin films deposited on sol-gel grown ZnO buffer by RF magnetron sputtering

ZnO thin films with preferential C-orientation and dense microstructure have been prepared using RF magnetron sputtering method by the insertion of a sol-gel grown ZnO buffer layer. The XRD results show that the C-orientation of the film deposited on ZnO buffer is obviously better than that deposited directly on lime-glass substrate. With an increase of the RF power from 100 to 380 W, C-orientation of the films with ZnO buffer improves and the grain size increases. When the RF power equals 550 W, the orientation of the film changes to (1 0 0) and the grain size decreases. The crystalline and microstructure quality of the films can be improved after annealing, however, the grain size is not much dependent on the annealing temperature in the range of 560-610 °C.     

Chemical states of carbon in amorphous boron carbide thin films deposited by radio frequency magnetron sputtering

Boron carbide thin films were deposited by radio frequency (RF) magnetron sputtering and characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high resolution transmission electron microscopy. The results reveal that the structure of thin films deposited at substrate temperatures lower than 350 °C is amorphous. We found that there are four chemical states for carbon in amorphous boron carbide thin films deposited by RF magnetron sputtering. One is the segregated carbon in form of the graphitic inclusions in the thin film identified by Raman spectroscopy and Raman mapping using two strong peaks at ~ 1360 cm^− 1 and ~ 1590 cm^− 1, but the XPS results show that the graphitic inclusions do not connect to the substrate directly. On the surface the carbon forms C=O bonds characterized by the peak of C1s core level at 285.0 eV besides B-C bonds in the boron carbide with the peak of C1s being at 282.8 eV. The detailed analysis of B-C bonds in the boron carbide shows that there are two states for carbon atoms in B-C bonds: in the C-B-C models with C1s peak at 282.3 eV and in the icosahedra with C1s peak at 283.3 eV.     

Composition and optical properties of silicon nitride films grown on SiO2-glass and R-Al2O3 substrates by reactive RF magnetron sputtering

We have grown silicon nitride (Si₃N₄) films on SiO₂-glass and R-Al₂O₃ substrates by using reactive RF magnetron sputtering deposition methods with N₂ pure gas and N₂ + Ar mixture gas. The film composition, thickness and impurities have been examined by ion beam analysis. It is shown that the films have stoichiometric composition and are free from Ar contamination, when N₂ gas was used for the film deposition. Effects of impurities on the film properties, e.g., optical properties will be discussed.     

Influence of RF power on the electrical and mechanical properties of nano-structured carbon nitride thin films deposited by RF magnetron sputtering

Nano structured carbon nitride thin films were deposited at different RF powers in the range of 50 W to 225 W and constant gas ratio of (argon: nitrogen) Ar:N₂ by RF magnetron sputtering. The atomic percentage of Nitrogen: Carbon (N/C) content and impedance of the films increased from 14.36% to 22.31% and 9 × 10⁻¹ Ω to 7 × 10⁵ Ω respectively with increase in RF power. The hardness of the deposited films increased from 3.12 GPa to 13.12 GPa. The increase in sp³ hybridized C-N sites and decrease of grain size with increase in RF power is responsible for such variation of observed mechanical and electrical properties.     

Fabrication of high frequency ZnO thin film SAW devices on silicon substrate with a diamond-like carbon buffer layer using RF magnetron sputtering

Diamond-like carbon (DLC) film is a promising candidate for surface acoustic wave (SAW) device applications because of its higher acoustic velocity. A zinc oxide (ZnO) thin film has been deposited on DLC film/Si substrate by RF magnetron sputtering; the optimized parameters for the ZnO sputtering are RF power density of 0.55 W/cm², substrate temperature of 380 °C, gas flow ratio (Ar/O₂) of 5/1 and total sputter pressure of 1.33 Pa. The results showed that when the thickness of the ZnO thin films was decreased, the phase velocity of the SAW devices increased significantly.     

Stress and texture in HIPIMS TiN thin films

Titanium nitride (TiN) films in the thickness range of 0.013 µm to 0.3 µm were grown by high power impulse magnetron sputtering (HIPIMS) on silicon substrates in two deposition modes: a) the substrate was grounded and b) − 125 V bias was applied to the substrate. On the films we performed microstructure-, film texture- and film stress-analysis. The films deposited under − 125 V bias experienced a more energetic ion bombardment than the films deposited on grounded substrates. This difference in ion bombardment energy is reflected in the different microstructure. In contrast to previous results for TiN films grown by conventional reactive magnetron sputtering, we observe no major film stress gradient for increasing film thicknesses. We explain this observation from the absence of a 200-to-111 texture crossover during film growth.A moderate ion bombardment leads to TiN films with (111) texture, while an intense ion bombardment leads to films with (001) texture (Greene et al.; Appl. Phys. Lett. 67 (20) 2928-2930 (1995)). At the same time (001) oriented grains are much more susceptible to compressive stress generation by ion bombardment than (111) oriented grains.