Characterization of zirconium oxynitride films obtained by radio frequency magnetron reactive sputtering

Thin ZrN_xO_y films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon-oxygen-nitrogen mixture. The Φ_N2/Φ_{(Ar + N2 + O2)} ratio was varied in the range 2.5%-100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO₂, ZrN, ZrON and N-rich zirconium nitride which is correlated with the Φ_N2/Φ_{(Ar + N2 + O2)} values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution.     

Scaling behavior and structure transition of ZrO2 films deposited by RF magnetron sputtering

ZrO₂ thin films were deposited onto Si wafers and glass slides by reactive rf magnetron sputtering with varying conditions of substrate temperature (T_s). Structural analysis was carried out using high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The scaling behavior of the AFM topographical profiles was analyzed using one-dimensional power spectral density method (1DPSD). Morphological and structural evolution of ZrO₂ films have been studied in relation to T_s. With substrate temperatures ranging from RT to 550 °C, the structural transition of the films is a-ZrO₂ (below 250 °C) → m-ZrO₂ with a little a-ZrO₂ (450 °C) → m-ZrO₂ with a little t-ZrO₂ (550 °C). The roughness exponent α is 1.53 ± 0.02, 1.04 ± 0.01, 1.06 ± 0.05, 1.20 ± 0.03 for ZrO₂ thin films deposited at RT, 250 °C, 450 °C, and 550 °C, respectively. Quantitative surface characterization by spatially resolved 1DPSD analyses identified three different growth mechanisms of surface morphology for ZrO₂ thin films deposited at RT, 250∼450 °C and 550 °C. The evolution and interactions of surface roughness and microstructure are discussed in terms of surface diffusion, grain growth, and flux shadowing mechanisms.     

Hydrophilic properties of nano-TiO2 thin films deposited by RF magnetron sputtering

Microstructure and hydrophilicity of nano-titanium dioxide (TiO₂) thin films, deposited by radio frequency magnetron sputtering, annealed at different temperatures, were studied by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and water contact angle methods. It is found that the crystal phase transforms from amorphous to rutile structure with increase of annealing temperature from room temperature to 800 °C. It is also indicated that the organic contaminants on the surface of the films can be removed and the oxygen vacancies can be reduced by the annealing treatment. Annealed at the temperature below 300 °C, amorphous TiO₂ thin films show rather poor hydrophilicity, and annealed at the temperature range from 400 to 650 °C, the super hydrophilicity anatase of TiO₂ thin films can be observed. However, when the annealing temperature reaches 800 °C, the hydrophilicity of the films declines mainly derived from the appearance of rutile.     

Photocatalytic activity of TiO2 thin films deposited by RF magnetron sputtering

Nano-TiO₂ thin films were deposited on silicon and glass substrates by radio-frequency (RF) magnetron sputtering using TiO₂ ceramic target and characterized by X-ray diffractometer, X-ray photoelectron spectrometer, atomic force microscope, and ultraviolet-visible spectrophotometer. Photocatalytic activity was evaluated by light induced degradation of 5 ppm methyl orange solution using a high pressure mercury lamp as lamp-house. It was found that the film as deposited is polymorph, with energy gap of 3.02 eV, and can absorb visible light. The film was repeatedly used for six times in degradation of 5 ppm methyl orange, and the degradation rates of methyl orange solution are 36.566%, 33.112%, 32.824%, 32.248%, 30.521% and 28.794%, respectively. After ultrasonic treatment in de-ionized water for ten minutes, the degradation rate of methyl orange solution resumes to 33.975%.     

Characterization and photocatalytic activity of TiO2 thin films prepared by RF magnetron sputtering

TiO₂ nano-structured thin films were prepared by RF magnetron sputtering and annealed in ambient air for 1 h at 400, 600, 800, 1000, and 1200 °C, respectively. Their phase structure, surface topography, and energy gap were characterized by X-ray diffractometer, atomic force microscope, and fluorescence spectrometer. Photocatalytic activity of the films was evaluated by light induced degradation of methyl orange (C₁₄H₁₄N₃NaO₃S) solution using a high pressure mercury lamp as lamp-house. The relation of photocatalytic activity and annealed temperature was studied in detail. It is found that the crystal phase transforms from amorphous to anatase, and rutile structure with annealing temperature increasing from room temperature to 1200 °C. Energy gap varies with annealing temperature. Photocatalytic activity is dependent on energy gap and grain size. Suitable energy gap from 2.97 to 3.07 eV is favorable for creation of electronic-hole pairs that make the films show excellent photocatalytic activity.     

Comparison of chromium nitride coatings deposited by DC and RF magnetron sputtering

Chromium nitride coatings were deposited by DC and RF reactive magnetron sputtering on AISI 304 stainless steels without substrate heating. A Cr₂N phase was formed in the RF sputtered coatings with a low N₂ flow content ranging within 30-50%. A NaCl type CrN_x phase was obtained by DC magnetron sputtering with different N₂ flow contents. The coating hardness increased with the increase of the N₂ flow content. When the coatings deposited with the same N₂ flow content were compared, the hardness of the RF sputtered CrN_x was higher than that of the DC sputtered CrN_x, which was mainly due to the distinct difference between the dense structure (RF process) and the porous structure (DC process). The RF sputtered CrN_x coatings showed an excellent adhesion strength as compared to the DC sputtered coatings. By selecting the deposition method and optimizing the N₂ flow content, CrN_x coatings with a preferred microstructure could be obtained, which would be a candidate material for research and applications in nano-science.     

Quantification of silver ion release, in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering

Surface treatments on biomaterials using several methods have greatly reduced the in vivo bacterial attachment, surface colonization and formation of biofilm. In this study, the effect of silver (Ag) ion release against in vitro antibacterial activity and cytotoxicity of 1-4wt% Ag doped titania (TiO₂) thin film coatings were evaluated. These coatings were deposited for 1-6 h onto stainless steel substrate (SS) using (radio frequency) RF magnetron sputtering technique. The coatings predominantly in the crystalline anatase phase were configured using X-ray Diffraction (XRD). Scanning electron microscopy (SEM) observation showed the presence of Ag-TiO₂ nanoparticles of less than 100 nm in all the coated surfaces confirming the formation of nanostructured coatings. An initial rapid release, followed by a sustained lower release of Ag ion concentration was measured between 0.45 and 122 ppb when all the coated substrates immersed in Phosphate Buffered Saline (PBS) for 1-10 days. The obtained concentration was less than the maximum toxic concentration for human cells; yet achieved antibacterial concentration, sufficient to kill or inhibit the growth of bacteria. In vitro cytotoxicity results have indicated that 1-4 wt% of Ag doped TiO₂ coatings had no adverse effect on mouse fibroblast proliferation, confirming its cytocompatibility. The antibacterial assessment was performed on 1 and 2 wt% Ag-TiO₂ coatings using Staphylococcus aureus (S. aureus) whereby significant antibacterial activity was observed in 2 wt% Ag-TiO₂ coatings.     

Microstructure and tribological behavior of WS2-Ag composite films deposited by RF magnetron sputtering

WS₂-Ag composite films were deposited on medium carbon steel substrate by RF magnetron sputtering method. The morphology and microstructure of the composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tribological behavior was investigated using a ball-on-disk tribometer in vacuum and in humid air. In the range of Ag content of the film from 4.2 at.% to 40.4 at.%, Ag phase dispersed in amorphous WS₂ matrix, and it changed from amorphous to crystalline structure with the increase of Ag content. The friction coefficients of composite films in humid air were lower and more stable than those of pure WS₂ film, and the environmental sensitivity of tribological behavior decreased obviously with the addition of Ag in the films. At the content of 16.2 at.% Ag, the composite film was dense and adherent, and exhibited excellent tribological performance both in vacuum and in humid air.     

Low-temperature epitaxial growth of conductive LaNiO3 thin films by RF magnetron sputtering

Epitaxial growth of LaNiO₃ (LNO) thin films was successful on CeO₂/YSZ/Si(100), MgO(100) and SrTiO₃ (STO)(100) substrates by RF magnetron sputtering at 300 °C, although pulsed laser deposition requires 600 °C to prepare epitaxial LNO films according to the literature. Epitaxial LNO films deposited on CeO₂/YSZ/Si(100) and STO(100) had single orientation of LNO[100]//CeO₂[110]//YSZ[110]//Si[110]) and LNO[100]//STO[100], respectively. On the other hand, epitaxial LNO films deposited on MgO(100) had mixed orientations of LNO[100]//MgO[100] and LNO[100]//MgO[110]. The lattice parameter, composition and resistivity of the LNO thin films were strongly dependent on the substrate temperature. The minimum resistivity of LNO films was approximately 5×10⁻⁶ Ω m, which value almost agrees with the resistivity in the literature. It was found that the temperature to achieve minimum resistivity was 200 °C, irrespective of the type of substrate. The surface of the LNO films was smooth and flat.     

Tribological properties of Ti2N-Wx% coatings deposited by magnetron sputtering

Ti₂N-W_x% coatings with different tungsten contents were deposited using unbalanced magnetron sputtering technology. The microstructures and mechanical properties of Ti₂N-W_x% coatings have been characterized by SEM, X-ray diffraction (XRD), nanoindentation and adhesion techniques. The tribological performance of the coatings was investigated using an oscillating friction and wear tester under dry conditions. Indexable inserts with Ti₂N-W_x% coatings were applied to turning AISI 1045 steel material by a lathe. Micron-drills with Ti₂N-W_x% coatings were adopted in the ultra-high speed (10⁵ rpm) Printed Circuit Board (PCB) through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the tungsten content. Ti₂N-W_14% coated inserts showed the best wear resistance in 1045 steel turning and PCB through-hole drilling tests. The service life of a Ti₂N-W_14% coated tool is five times greater than that of an uncoated tool in PCB through-hole drilling test.     

反应磁控溅射沉积氧化铜薄膜及其电化学性能研究

以金属铜为靶材,氧气为反应气体,采用射频磁控溅射法在不同温度的不锈钢基片上制备了氧化铜薄膜电极.采用X射线衍射(XRD)和原子力显微镜(AFM)分别对薄膜的组成和形貌进行了表征分析.电化学测试表明,在基片温度为室温条件下沉积得到的薄膜电极比300℃基片温度沉积得到的薄膜电极首次放电容量高,达到785μAh/(cm2·μm),但循环100次后后者放电容量较高.用交流阻抗法测得锂离子在氧化铜薄膜中的扩散系数为2.46×10-15cm2/s.     

Characterization of electrolyte films deposited by using RF magnetron sputtering a 20 mol% gadolinia-doped ceria target

20 mol% Gd-doped ceria (20GDC) electrolyte films on poly-crystalline Al₂O₃ substrates were prepared by radio frequency (RF) magnetron sputtering from a 20GDC oxide target, which was made by the processes of colloidal dispersion-pressure casting-sintering. Material characteristics of the 20GDC oxide target and the deposited films before and after annealed at 900 °C for 2 h were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and conductivity measurements. Crack-free and dense 20GDC electrolyte films were observed by the deposition conditions of 200 W (RF power). Homogeneity tests revealed the chemical compositions (Ce and Gd) were uniformly distributed through the bulk of the target and the deposited films. 20GDC film with a comparable conductivity of 1.00 × 10^− 3 S/cm at 650 °C is higher than that of bulk yttria-stabilized zirconia (YSZ), but smaller than that of bulk GDCs (10GDC and 20 GDC). Sputtered-GDC films in this study can be also suggested to be used as the electrolyte films for solid oxide fuel cells (SOFCs) systems as compared to the well-known YSZ.     

Structural and optical investigation of sputter deposited hydrophobic chromium oxynitride films

Nanocrystalline chromium oxynitride films were deposited by reactive RF magnetron sputtering of metallic chromium target in argon and helium atmospheres. The paper deals with consequence of increase in oxygen partial pressure on structural, hydrophobic and optical properties of chromium oxynitride films. The film stoichiometry changes from CrN and Cr₂O₃ to only Cr₂O₃ with increase in oxygen partial pressure as evident from X-Ray Diffraction analysis in both cases. The average crystallite size decreases with increase in oxygen partial pressure for both gas atmospheres. The thickness calculated from transmission data and surface profilometer are in good harmony with each other. The deposited films are hydrophobic by nature and the contact angle of the films varies as a function of surface roughness. Surface energy of the films is inversely proportional to the observed contact angle values. As oxygen partial pressure increases, the optical properties: transmission and band gap values increases as determined by Ultraviolet-visible-Near Infrared spectrophotometer in both cases. This film can have potential applications as insulating, hydrophobic and corrosion resistant protective coatings.     

氧分压对RF磁控溅射ZrO2薄膜生长特性的影响

采用反应射频(RF)磁控溅射法在n型(100)单晶S基片上沉积了ZrO2膜,研究了氧分压与ZrO：薄膜的表面粗糙度和沉积速率、SiO2中间界层的厚度以及ZrO2薄膜的折射率之间关系。结果表明：随着氧分压增高,薄膜的沉积速率降低,表面粗糙度线性地增加;在低的氧分压情况下,Si基片表面的本征SiO2层的厚度增加幅度较小,在高的氧分压情况下,Si基片表面的本征SiO2层的厚度有较大幅度地增加;在O2／Ar混和气氛下,溅射沉积的ZrO2薄膜的折射率受氧分压的影响不显著,而在纯氧气气氛环境下,ZrO2薄膜的折射率明显偏低,薄膜的致密性变差。     

Electrical properties of AlNxOy thin films prepared by reactive magnetron sputtering

Direct current magnetron sputtering was used to produce AlN_xO_y thin films, using an aluminum target, argon and a mixture of N₂ + O₂ (17:3) as reactive gases. The partial pressure of the reactive gas mixture was increased, maintaining the discharge current constant. Within the two identified regimes of the target (metallic and compound), four different tendencies for the deposition rate were found and a morphological evolution from columnar towards cauliflower-type, ending up as dense and featureless-type films. The structure was found to be Al-type (face centered cubic) and the structural characterization carried out by X-ray diffraction and transmission electron microscopy suggested the formation of an aluminum-based polycrystalline phase dispersed in an amorphous aluminum oxide/nitride (or oxynitride) matrix. This type of structure, composition, morphology and grain size, were found to be strongly correlated with the electrical response of the films, which showed a gradual transition between metallic-like responses towards semiconducting and even insulating-type behaviors. A group of films with high aluminum content revealed a sharp decrease of the temperature coefficient of resistance (TCR) as the concentration ratio of non-metallic/aluminum atomic ratio increased. Another group of samples, where the non-metallic content became more important, revealed a smooth transition between positive and negative values of TCR. In order to test whether the oxynitride films have a unique behavior or simply a transition between the typical responses of aluminum and of those of the correspondent nitride and oxide, the electrical properties of the ternary oxynitride system were compared with AlN_x and AlO_y systems, prepared in similar conditions.     

Nanocomposite Al2O3–ZrO2 thin films grown by reactive dual radio-frequency magnetron sputtering

Crystalline alumina–zirconia nanocomposites have been synthesized at 450 °C and 750 °C with reactive magnetron sputtering using radio-frequency power supplies. The composition of the films ranged from pure alumina to pure zirconia as measured by ion beam techniques. Microstructural characterization showed the presence of monoclinic zirconia in the pure zirconia films and γ-alumina in the pure alumina films while the nanocomposites contained either an amorphous compound, γ-alumina, cubic zirconia or a mixture of these. The grain size was  5 nm for the nanocomposite compared to larger grains in the pure oxide films. Electron energy loss spectroscopy showed a clear progression from the pure alumina to the pure zirconia.     

Mechanical properties of superhard TiB2 coatings prepared by DC magnetron sputtering

Superhard titanium diboride (TiB₂) coatings (H_v> 40 GPa) were deposited in Ar atmosphere from stoichiometric TiB₂ target using an unbalanced direct current (d. c.) magnetron. Polished Si (0 0 1), stainless steel, high-speed steel (HSS) and tungsten carbide (WC) substrates were used for deposition. The influence of negative substrate bias, U_s, and substrate temperature, T_s, on mechanical properties of TiB₂ coatings was studied. X-ray diffraction (XRD) analysis showed hexagonal TiB₂ structure with (0 0 01) preferred orientation. The texture of TiB₂ coatings was dependent upon the ion bombardment (U_s increased from 0 to −300 V) and the substrate heating (T_s increased from room temperature (RT) to 700 °C). All TiB₂ coatings were measured using microhardness tester Fischerscope H100 equipped with Vickers and Berkovich diamond indenters and exhibited high values of hardness H_v up to 34 GPa, effective Young's modulus E*=E/(1-ν) ranging from 450 to 600 GPa; here E and ν are the Young's modulus and Poisson's ratio, respectively, and elastic recovery W_e≈80%. TiB₂ coating with a maximum hardness H_v≈73 GPa and E*≈580 GPa was sputtered at U_s=−200 V and T_s=RT. Macrostresses of coatings σ were measured by an optical wafer curvature technique and evaluated by Stoney equation. All TiB₂ coatings exhibited compressive macrostresses.     

非织造基磁控溅射纳米银薄膜导电性能的研究

在室温条件下采用射频磁控溅射在丙纶(PP)、聚乳酸(PLA)熔喷非织造布表面生长纳米银(Ag)薄膜,并且用等离子体预处理样品进行对比。采用扫描电子显微镜(SEM)对其形貌进行表征,采用四探针测试仪对所制备的纳米薄膜的导电性能进行表征。研究溅射时间、孔隙率及孔径分布和等离子处理对非织造基纳米银薄膜的导电性能的影响。实验表明:随着反应溅射时间的增加,薄膜的方块电阻值下降,导电性能增加;孔径大小也影响薄膜的导电性能,随着孔径的增大,薄膜的导电性能降低;等离子体处理对织物表面进行刻蚀,增加了纤维的比表面积,提高了纤维的润湿性能,改善了织物的导电性能。     

Structure and mechanical properties of ZrO2 films deposited by gas flow sputtering

ZrO₂ films were deposited by reactive gas flow sputtering (GFS) where voltage is applied to a cyindrical hollow-cathode target from a DC source, the discharge being produced at relatively high sputtering pressure. In this system, secondary electrons form a major component of the total current flow and lead to heating of the substrate which in turn has an effect on the properties of deposited films. The present experiments were carried out under the following conditions: Ar gas flow rate of 200 sccm, O₂ flow rate FO₂ in the range between 0.003 and 1 sccm, and sputtering power (P_S) in the range of 50-800 W. The reults showed that the crystal structure of the films deposited for P_S below 200 W was monoclinic but for P_S above 400 W, the films included tetragonal cystals of stable structure formed at high temperature by the electron bombardment. The films were formed with grains of 20-100 nm in diameter in a porous structure. The mechanical properties of the films were determined by a nanoindentation technique. Martens hardness (H_M) of the porous films was found to be in the range between 220 and 330 MPa which is substantially less than that of films typically deposited by rf magnetron sputtering.     

Protective YSZ-based thin films deposited by RF magnetron sputtering

Protective Zr(Y)O_2−δ-based films sputter-deposited onto apatite-type lanthanum silicate ceramics were appraised for potential applications in solid oxide fuel cells with silicate-based solid electrolytes, where the performance may suffer from surface decomposition processes in reducing atmospheres. Dense and crystalline coatings were deposited using radio-frequency magnetron sputtering from an yttria-stabilized zirconia target. On the basis of microstructural analysis and profile measurements, a sputtering power of 300 W was selected in order to achieve deposition rates in the range 0.50-0.75 μm/h. The surface morphology studies using an atomic force microscope revealed typical film structures with small (<50 nm) grains. The polarization of model electrochemical cells with cermet anodes comprising Ni, yttria-stabilized zirconia and Ce_0.8Gd_0.2O_2−δ (50:30:20 wt.%), deposited onto the protective zirconia films, was found quite similar to that of copper-zirconia cermets without interlayers, suggesting that the electrochemical reaction is essentially governed by the oxygen anion transfer from zirconia phase and/or hydrogen oxidation in the vicinity of zirconia film surface.