Increasing Sputtering Pressure Research Articles

Fabrication of manganese oxide electrodes by radio frequency sputtering for electrochemical capacitors

Manganese oxide thin films were sputtered on graphite foils by radio frequency (RF) sputtering. At the 1,000th cycle of potential cycling, maximum mass specific capacitance of 341 F g−1 was obtained in 0.5 M LiCl and with optimum sputtering conditions (5 sccm of oxygen, 20 mTorr, and 70 W) as well as annealing temperature (150 °C). These show its high electrochemical stability and good mass specific capacitance at a higher sweep rate of 100 mV s−1. In addition, the higher the volume flow rates of oxygen, the larger the amount of trivalent manganese oxide and the higher the surface roughness, the higher the mass specific capacitance at lower volume flow rates of oxygen, but the amounts of trivalent manganese oxide were almost the same and the mass specific capacitance decreased due to decreasing surface roughness at higher volume flow rates of oxygen. Furthermore, the geometric specific capacitance increases with increasing sputtering pressure and power.

Composition, structure and magnetic properties of sputter deposited Ni–Mn–Ga ferromagnetic shape memory thin films

Polycrystalline Ni–Mn–Ga thin films were deposited by the d.c. magnetron sputtering on well-cleaned substrates of Si(1 0 0) and glass at a constant sputtering power of 36 W. We report the influence of sputtering pressure on the composition, structure and magnetic properties of the sputtered thin films. These films display ferromagnetic behaviour only after annealing at an elevated temperature and a maximum saturation magnetization of 335 emu/cc was obtained for the films investigated. Evolution of martensitic microstructure was observed in the annealed thin films with the increase of sputtering pressure. The thermo-magnetic curves exhibited only magnetic transition in the temperature range of 339–374 K. The thin film deposited at high sputtering pressure of 0.025 mbar was found to be ordered L2 1 austenitic phase.

Influence of sputtering parameters on the crystallinity and crystal orientation of AlN layers deposited by RF sputtering using the AlN target

Aluminum nitride (AlN) layers were grown on c-sapphire by radio frequency (RF) sputtering in plasma containing a mixture of argon and nitrogen gas using an AlN target. The influence of nitrogen gas fraction, RF power, and sputtering pressure on crystalline quality and growth rate as well as surface morphology were investigated. Crystalline quality improves as nitrogen gas fraction and RF power increase. The growth rate increases as the RF power increases and decreases as the sputtering pressure increases.

Study of photocatalytic activity of TiO2 thin films prepared in various Ar∕O2 ratio and sputtering gas pressure

In this study, various transparent TiO2 films were deposited on unheated glass-slide substrates by dc reactive sputtering technique. For one set of samples the ratio of Ar to O2 (GR) was varied from 9:1 to 6:4 for a fixed sputtering pressure of 0.8Pa, while for another set of samples the total working pressure was varied from 0.2to0.8Pa for a fixed GR of 7:3. The crystallographic and optical properties of TiO2 films were investigated in detail. The photocatalytic activity was evaluated by the measurement of decomposition of methanol under UV-visible irradiation. The structure of the TiO2 films, prepared with various GR, varied from amorphous to different crystalline phases. Similarly sputtering pressure variation induced change of crystalline phase and crystallinity of TiO2 films. The crystallinity improved greatly with decreasing sputtering pressure. The average transmittances of all of the TiO2 films were almost constant for wavelengths in the range of 900–380nm for GR-varied thin films. The optical transmission edge of the TiO2 films deposited at various sputtering pressure shifts toward low wavelength with higher sputtering pressure. The as-deposited TiO2 films successfully photocatalyzed methanol to CO2 and H2O, measured by Fourier transform infrared spectrometer. The decomposition efficiency of TiO2 films increased with increasing sputtering pressure. However, the photocatalytic efficiency of TiO2 films prepared at different GR did not show any regular dependence. The high photocatalytic activity of the sample prepared with GR=7:3 at sputtering pressure of 0.8Pa was tried to be explained by the effect of surface morphology and pure anatase crystalline phase.

Properties of dc magnetron sputtered Cu 2O films prepared at different sputtering pressures

The sputtering pressures maintained during the deposition of Cu 2O films, by dc reactive magnetron sputtering, influence the structural, electrical and optical properties. The crystalline orientation mainly depends on the sputtering pressure. The films deposited at a sputtering pressure of 4 Pa showed single-phase Cu 2O films along (1 1 1) direction. The electrical resistivity of the films increased from 1.1 × 10 1 Ω cm to 3.2 × 10 3 Ω cm. The transmittance of the films increased from 69% to 88% with the increase of sputtering pressure from 2.5 Pa to 8 Pa.

Influence of sputtering pressure on polarity distribution of aluminum nitride thin films

The authors have investigated the influence of sputtering pressure on the polarity distribution of aluminum nitride (AlN) films. They have found that sputtering pressure strongly influences the polarity distribution of AlN films prepared on molybdenum electrodes. The polarity distribution of the AlN films was observed by piezoresponse force microscopy. The polarity orientation is decided with respect to each fine grain constituting the AlN films, and polarity conversion from Al polarity to N polarity is observed with increasing sputtering pressure. The piezoelectric response of the films changes from +3.7to−4.4pC∕N with increasing sputtering pressure from 0.36to4.0Pa.

Microstructure and percolation threshold characteristics of reactive sputtered Au–TiO2 granular composite films

The Au/TiO2 composite films were prepared by using reactive co-sputtering technique. The size and shape of the embedded Au particles and the absorption spectra of the composite films were investigated by using SEM, XRD, and UV–VIS–NIR spectrophotometer, respectively. The average size of Au particles and the electrical conductivity decrease as the sputtering pressure increases. The normalized conductivity of the films deposited at five different pressures with the Au concentration in the range of 0.15–0.91 were measured. The percolation threshold increases from 0.21 to 0.90 as the sputtering pressure increases from 2×10−2Torr to 9.5×10−2Torr.

Stress evolution during and after sputter deposition of Cu thin films onto Si (100) substrates under various sputtering pressures

The stress evolution during and after dc magnetron sputter deposition of Cu thin films with thicknesses of 20 and 300 nm and deposited with a constant rate of 0.1nm∕s onto Si (100) substrates is studied for various sputtering pressures (0.05–6 Pa). The stress was determined by means of in situ wafer curvature measurements using an optical two-beam deflection method. To correlate the stress evolution with the microstructure development, microstructure investigations were performed by scanning electron microscopy, atomic force microscopy, and electron backscatter diffraction. The results show the transition from tensile to compressive stress with decreasing sputtering pressure at different stages of the deposition. The features of the stress evolution during the early stage of deposition can be ascribed to the Volmer–Weber mechanism. For thicker films, three regions of the sputtering pressure can be distinguished concerning their effect on the stress evolution. The transition from compressive to tensile stress was correlated with the evolution from a dense to an open microstructure and with increasing surface roughness by increasing sputtering pressure. The results of the stress and microstructure evolution are interpreted in the context of the mechanisms being discussed in the literature.

Dependence of Magnetic Properties on Sputtering Pressure for Fe–Al–O Alloy Films Made by Carousel-Type Sputtering

We have investigated the magnetic anisotropy and permeability of FeAlO films with Bs∼1.8 T and ρ∼1 µΩm. The films were prepared using a carousel-type sputtering system. Although an aligning magnetic field to induce uniaxial magnetic anisotropy was not applied to the substrates during deposition, the FeAlO films in the as-deposited state had uniaxial magnetic anisotropy. The anisotropy strongly depends on sputtering pressure. The direction of the magnetic anisotropy shifts 90° from the rotation direction to the radial direction of the substrate holder as the sputtering pressure increases. In the pressure range of 0.3–0.4 Pa, the measured µ–f properties are largely different from the theoretical one because of magnetic anisotropy dispersion. The anisotropy dispersion can be explained by a model with two orthogonal anisotropy components.

Influence of O 2 admixture and sputtering pressure on the properties of ITO thin films deposited on PET substrate using RF reactive magnetron sputtering

A systematic study of the growth of indium tin oxide (ITO) thin films on polyethylene terephthalate substrate was carried out using RF reactive magnetron sputtering. The effect of oxygen admixture to sputtering gas, sputtering pressure (4.5×10 −1 to 6.8×10 −1 Pa), RF power (30–50 W) and growth time (15–50 min) on the electrical and optical properties of ITO thin films was investigated. An indium tin alloy (90:10) of 99.999% purity was used as target. Deposition was carried out at room temperature. Cracks in the films were not observed. It is found that the increase in admixture of O 2 to Ar sputtering gas decreases the growth rate. A minimum value of resistivity (7×10 −3 Ω cm), decreases in the mobility, reduction in particle size, an average transmittance of ∼80% in UV–Vis range with carrier concentration of ∼5.9×10 19 atmos/cm 3 and mobility of ∼37 cm 2/V s was found with increasing O 2 admixture. The increase in sputtering pressure has less effect on growth rate, changes the distribution of particles with increase in their sizes, little variation in Sn/In ratio and a minimum resistivity of 1.9×10 −3 Ω cm. The increasing pressure results in improved transmittance to above 80%. Increase in RF power results in a minimum resistivity of 1.9×10 −3 Ω cm (at 50 W) and decreases the carrier mobility to 3.5 cm 2/V s. A linear increase in the film thickness with increase in optical transmittance to ∼85 is found with increasing growth time. It can be concluded that the film grown at 10% of O 2 admixture, 5.6×10 −1 Pa sputtering pressure and RF power of 50 W, can meet the requirement of a good transparent and conducting ITO film on polymer substrate.

Optimizing the giant magnetoresistance of NiFe/Cu/Co pseudo spin-valves prepared by magnetron sputtering

We study the dependence of magnetic and magnetotransport properties of NiFe/Cu/Co pseudo spin-valves on the pressure of the Ar sputtering gas during magnetron deposition. The giant magnetoresistance (GMR) ratio as a function of the sputtering pressure behaves nonmonotonically with a maximum of about 4% at an intermediate pressure of 0.87×10−2 mbar. Magneto-optic Kerr-effect measurements reveal different coercive fields and independent switching of the Co and NiFe layers. The structural characterization by x-ray scattering shows no significant pressure dependence. However, we observe by atomic force microscopy a variation of the grain structure with increasing sputtering pressure; the grain size first decreases and then the grains start clustering for highest pressures. The reduced coercive field and the lower GMR ratio indicate that the clustered grains have weaker magnetic pinning and increased spin-independent scattering.

Temperature dependence of magnetization reversal in TbFeCo films

The magnetization reversal process has been studied in a series of four TbFeCo films over the temperature range 300–460 K. The films were characterized by time decay, dynamic coercivity, Kerr imaging, and torque measurements. For a film with a sputter-etched SiN underlayer, the reversal process at low temperatures was dominated by nucleation followed by rapid domain wall motion. The low temperature relaxation curves for this sample were analyzed using a Fatuzzo model. At high temperatures, the Fatuzzo model did not apply. For the other films, with no etching, relaxation curves were logarithmic at all temperatures. All activation volumes increased with increasing temperature and decreased with increasing sputtering pressure. The magnetic anisotropy direction changed from perpendicular to in-plane as the argon sputtering pressure was increased.

Studies on photocatalytic activity and transmittance spectra of TiO 2 thin films prepared by r.f. magnetron sputtering method

Transparent TiO 2 thin films were obtained on microscope glass slides by r.f. magnetron reactive sputtering. The samples were investigated using X-ray diffraction (XRD), transmittance electron microscopy (TEM), UV-VIS-NIR spectrophotometer and coatings scratch testing. All the films were anatase phase and the particle size was in nanoscale. The photocatalytic properties of the samples were tested on the degradation of methylene blue dye solution. It was found that the photocatalytic activity increased with decreasing sputtering pressure. At the same time, the results indicate that the band gaps of the films all became larger than the bulk TiO 2 and the adhesion strength between the films and the substrates decreased with increasing sputtering pressure.

Influence of process parameters on the structure and the properties of ZrO 2 coatings deposited by reactive pulsed magnetron sputtering (PMS)

Thin ZrO 2 layers in the thickness range between 100 and 150 nm were deposited by reactive pulsed magnetron sputtering (PMS). The influence of the sputtering Ar pressure and of the target to substrate distance on structure and properties of the films were investigated. The structure of the layers was determined by grazing angle XRD. At low sputtering pressure of 0.3 Pa, the low temperature stable monoclinic modification of ZrO 2 is deposited, while at a sputtering pressure of 3.5 Pa, the high-temperature cubic phase of ZrO 2 can be obtained. Atomic force microscopy investigations have shown that with higher sputtering pressures the roughness of the deposited layers is increased. The residual stresses were also drastically influenced by the sputtering pressure. In the layers deposited at low sputtering pressures of approximately 0.3 Pa very high compressive stresses of up to 1800 MPa are present. With further increase of sputtering pressure these high compressive residual film stresses were decreased down to low tensile stresses of approximately 150 MPa. After a storage time of 1 month in air only small changes in the film stress values were measured. The hardness and Young's modulus of the layers were determined by nanoindentation techniques at an indentation depth of 20 nm. The results show that with increasing sputtering pressure the hardness and the Young's modulus of the layers are decreased from approximately 12.3 to 6.2 GPa and from approximately 173 GPa to 150 GPa, respectively. The refractive index (at λ=550 nm) of the layer deposited at low sputtering pressure is 2.2. With increasing sputtering pressure the refractive index is shifted to 2.1. The thickness of a surface roughness layer calculated by effective medium approximation is increased with increasing sputtering pressure from 2.5 to 11.5 nm.

Properties of (Nb0.35, Ti0.15)xNi1−x thin films deposited on silicon wafers at ambient substrate temperature

We have studied the properties of (Nb0.35, Ti0.15)xN1−x films deposited by reactive magnetron sputtering at ambient substrate temperature, focusing in particular on the dependence of film properties on the total sputtering pressure. As the pressure increases we observe a transition in the film structure from the ZT to the Z1 structural zone according to the Thornton classification. In general, the superconducting transition temperature (Tc) and residual resistance ratio have a very moderate dependence on total sputtering pressure, while the film resistivity increases an order of magnitude as the sputtering pressure increases. A wide spectrum of material science techniques is used to characterize the films and to explain the relationship between the sputtering conditions and film properties. Transmission electron microscopy and x-ray diffraction analysis show that 160-nm-thick (Nb0.35, Ti0.15)xN1−x films consist of 20–40 nm grains with good crystallinity. Films sputtered under low pressures have a weak [100] texture, while films sputtered under high pressures have a distinct [111] texture. A stable chemical composition and reduction in film density as the sputtering pressure increases indicate that the change of resistivity in the ZT structural zone is due to a variation in the quenched-in vacancy concentration. In contrast voids on the grain boundaries and vacancies together produce the high film resistivities in the Z1 structural zone.

Effect of sputtering pressure on the structure and current-perpendicular-to-the-plane magnetotransport of Co/Ag multilayered films

Co/Ag multilayers have been sputter-deposited at pressures ranging from 0.86 to 10 mTorr, and magnetotransport measurements have been performed with the current both perpendicular to the plane (CPP) and in the plane (CIP) of the samples. X-ray-scattering studies indicate that the roughness of the interfaces is influenced by the presence of the Nb layers used to make electrical contact for the CPP measurements, as well as by the sputtering pressure. For samples deposited at higher sputtering pressures, the Nb contact layers also influence the low-temperature coercive field of the multilayers. The CPP-giant magnetoresistance is observed to decrease with increasing sputtering pressure and, in the case of the signal observed after cycling to above the saturation field, this decrease is found to come in roughly equal measure from an increase in the high field-saturated specific resistance and a decrease in the field-dependent specific resistance. Making use of the direct connection between microscopic physical parameters and experimental results available through the CPP geometry, we show that both of these changes arise primarily from increased scattering in both spin channels. We see very little, if any, evidence for a change in the spin-dependent scattering with sputtering pressure.

Role of abnormal grain growth on the ferroelectric properties of SrBi2Ta2O9 thin films fabricated by R.F. Magnetron sputtering

With increasing sputtering pressure and post-annealing temperature, uniform rodlike grains were obtained through bimodal grain size distribution. But, (00l) peaks of SrBi2Ta2O9 thin films were increased. Improvement of electrical properties is expected by removing the abnormal grain growth and c-axis oriented SrBi2Ta2O9.

Development of x-ray mask fabrication process using w-sputtering

Properties of DC magnetron sputter-deposited W and WNx absorber films were investigated for x-ray mask applications. Low stress film (5 x 108 dyne/cm2 tensile stress) is difficult to obtain with pure Ar gas as the film stress changes from highly compressive to highly tensile with pressure change. The variation of stress with pressure is significantly reduced with N2/Ar mixture gas, and a reasonable tensile stress and stress stability were obtained with 5% N2 at 3.5 mTorr. Film density decreases with increasing sputtering pressure and N2/Ar + N2 ratio. XRD patterns for films deposited at 3.5 mTorr show crystalline α-W structure for Ar sputtered film but amorphous structure for 5% N2-sputtered film. Surface smoothness is very good at 5% N2 but further increase of N2/Ar+N2 ratio results in a surface roughening and this is also confirmed by TEM analysis. At this sputtering condition (5% N2, 3.5 mTorr), film stress stability during air-exposure and annealing was also superior, suggesting a optimum process condition for W-based absorber films.

Raman spectroscopic studies on Sb nanoparticles in SiO 2 matrix prepared by rf-cosputtering technique

Antimony nanoparticles in SiO 2 matrix were prepared by rf-cosputtering method. We report the effect of substrate temperature, sputtering power, sputtering pressure, weight of antimony during sputtering and sputtering time on average size of the particle as studied by Raman spectroscopic technique. The first-order Raman lineshape has been analyzed by confined optical modes and the average size of the particle has been estimated from this analysis. We found that the average size of the particle increases with increase in substrate temperature and sputtering power, while it decreases with increase in sputtering pressure and weight of antimony during sputtering. The average size of the particle does not change with sputtering time. The Raman lineshape of antimony particles embedded in SiO 2 matrix also does not change with annealing till 250 °C for 48 h. We have discussed the growth process of the particles in this system.

Effect of sputtering pressure of Pd underlayer on the perpendicular magnetic anisotropy in Co/Pd multilayered thin films

The magnetic properties of Co/Pd multilayers, in particular the perpendicular magnetic anisotropy, have been analyzed as a function of the sputtering pressure of Pd underlayer. With an increase of sputtering pressure of the underlayer from 6 mTorr to 25 mTorr, perpendicular coercivity of the multilayers increased with a slight decrease of saturation magnetization, and the increment of the coercivity was larger for the films with thinner cobalt layers. From the anisotropy analysis, it was found that the interface anisotropy energy decreased from 0.390 erg/cm/sup 2/ to 0.255 erg/cm/sup 2/ because of the interface roughening of the multilayers, which was mainly responsible for the decrease of perpendicular anisotropy, while the volume anisotropy energy increased from -11.37/spl times/10/sup 6/ erg/cm/sup 3/ to -7.90/spl times/10/sup 6/ erg/cm/sup 3/. The abnormally large intrinsic volume anisotropy energies of the multilayers with thin cobalt layers (<7 /spl Aring/) appears to suggest the noticeable contribution of magnetoelastic effect to the perpendicular anisotropy of the films.