Corrosion performance of thin hydrogenated amorphous carbon films prepared by magnetron sputtering

Hydrogenated amorphous carbon (a-CH_x) films were prepared by magnetron sputtering at different H₂/Ar gas flow ratios. Several sets of perpendicular magnetic recording disks with a-CH_x overcoats of 5 nm were prepared for accelerated environmental corrosion test. The corrosion spots on the disks and the corrosion products were analyzed using optical surface analyzer and time-of-flight secondary ion mass spectroscopy, respectively. Other techniques, such as Raman spectroscopy, atomic force microscopy nano-scratch and contact angle measurement, were used to characterize the properties of a-CH_x films. Compared to pure carbon overcoat, all the a-CHx overcoats have better corrosion resistance and higher polar component of surface free energy. The a-CH_x film with appropriate H content shows the highest scratching resistance, and the corresponding disk has the lowest corrosion area on the disk surface after the accelerated corrosion.     

Dielectric properties of amorphous BaTiO3 films deposited by RF magnetron sputtering

In the present paper, dielectric properties of a-BaTiO₃ films have been investigated as a function of frequency (10⁻¹ to 10⁵ Hz) and temperature (25–350 °C) using the dielectric spectroscopy technique. Relaxation and ac-conductivity processes were analyzed in order to study charge transport in the bulk and at the electrode-film interfaces. It seems that the oxygen vacancies play an essential role in both processes.     

Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering

Zinc sulfide [ZnS] thin films were deposited on glass substrates using radio frequency magnetron sputtering. The substrate temperature was varied in the range of 100°C to 400°C. The structural and optical properties of ZnS thin films were characterized with X-ray diffraction [XRD], field emission scanning electron microscopy [FESEM], energy dispersive analysis of X-rays and UV-visible transmission spectra. The XRD analyses indicate that ZnS films have zinc blende structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM data also reveal that the films have nano-size grains with a grain size of approximately 69 nm. The films grown at 350°C exhibit a relatively high transmittance of 80% in the visible region, with an energy band gap of 3.79 eV. These results show that ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se₂ solar cells.     

Influence of postdeposition annealing on the properties of ZnO films prepared by RF magnetron sputtering

ZnO films were prepared on unheated silicon substrate by RF magnetron sputtering technique. Postdeposition annealing of ZnO films in vacuum were found to improve film structure and electrical characteristics, such as dense structure, smooth surface, stress relief and increasing resistivity. Suitable annealing temperature also reduced loss factor. The correlation between annealing conditions and the physical structure of the films (crystalline structure and microstructure) was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The preferred annealing condition has been found to improve ZnO film characteristics for piezoelectric applications. An over-mode acoustic resonator using the ZnO film after annealing at 400 °C in vacuum circumstance for 1 h showed a large return loss of 42 dB at the center frequency of 1.957 GHz.     

Effect of Fe-doping on the structural,optical and magnetic properties of ZnO thin films prepared by RF magnetron sputtering

In this paper, we report the fabrication and systematic characterization of Fe Doped ZnO thin Films. Fe_xZn_1−x O (x=0<0.05) films were prepared by RF magnetron sputtering on Si (400) substrate. Influence of Fe doping on structural, optical and magnetic properties has been studied. The X-ray diffraction (XRD) analysis shows that Fe doping has affected the crystalline structure, grain size and strain in the thin films. The best crystalline structure is obtained for 3% Fe Doping as observed from Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). The magnetic properties studied using Vibrating Sample Magnetometer reveals the room temperature ferromagnetic nature of the thin films. However, changing the Fe concentration degrades the magnetic property in turn. The mechanism behind the above results has been discussed minutely in this paper.     

Microstructural and optical properties of Ta-doped ZnO films prepared by radio frequency magnetron sputtering

Ta-doped ZnO films with different doping levels (0–5.02 at%) were prepared by radio frequency magnetron sputtering. The effects of the doping amount on the microstructure and the optical properties of the films were investigated. The grain size and surface roughness first significantly decrease and then slowly increase with the increase of Ta doping concentration. Both the grain size and the root mean square (RMS) roughness reach their minimum values at the doping content of 3.32 at%. X-ray Diffraction (XRD) patterns confirmed that the prepared Ta-doped ZnO films are polycrystalline with hexagonal wurtzite structure and a preferred orientation along the (002) plane. X-ray photoelectron spectroscopy (XPS) analysis reveals that Ta exists in the ZnO film in the Ta⁵⁺ and Ta⁴⁺ states. The average optical transmission values of the Ta-doped ZnO films are higher than those of the un-doped ZnO film in the visible region. The band gap energy extracted from the absorption edge of transmission spectra becomes large and the near band edge (NBE) emission energy obtained from PL spectra blueshifts to high energy when the Ta doping content grows from 0 at% to 5.02 at%, which can be explained by the Burstein–Moss shift.     

An optical absorption and electron spin resonance study in hydrogenated amorphous carbon prepared by radio frequency sputtering

In this work, we investigated different hydrogenated amorphous carbon (a-C:H) films grown by radio frequency (RF) magnetron sputtering covering a large variety of films from polymer-like carbon (PLC) to diamond-like carbon (DLC). Photothermal deflection spectroscopy (PDS), transmission spectroscopy in the visible and near infrared (IR) region were combined with electron spin resonance (ESR) measurements. The optical absorption spectra were analysed assuming a distribution of two overlapping Gaussian bands near the Fermi level in order to deduce the density of states (DOS) at the Fermi level. From the DOS and the density of paramagnetic states a correlation energy for midgap states is derived.     

Steady-state and transient room-temperature photoluminescence of AlN films,prepared by RF magnetron sputtering

Near UV (363.8 nm, continuous radiation) and UV (248 nm, pulse radiation) laser excited photoluminescence (PL) has been measured for aluminum nitride films at room temperature. The films were deposited by the radio frequency sputtering of Al target in an argon–nitrogen–hydrogen (Ar:N₂:H₂) gas mixture. The PL peak energies are found to be influenced by deposition conditions such as gas mixture flow rates and substrate temperature. The steady-state PL is analyzed based on the microstructures and electron spectra of the films. The changes in the PL spectra across samples deposited under different conditions have been correlated to the variation in the electron density distribution. Transient PL signal measured after short (20–25 ns) pulse KrF laser excitation reveals a long PL decay lifetime of 160±25 μs.     

Structural and mechanical properties of CNx thin films prepared by magnetron sputtering

In an attempt to define the role of nitrogen in CN chemical bonding and in the formation of CN_x thin films, several coatings with a variable concentration of N₂ were grown onto (100) Si substrates using magnetron sputtering in N₂/Ar discharge. The chemical composition of the as-deposited films was investigated by means of Rutherford backscattering spectroscopy (RBS) and showed an [N]/[C] ratio up to 0.7. Raman and Fourier transform infrared (FTIR) spectroscopy were carried out to measure the optical vibration properties for studying the bonding state of nitrogen.By means of grazing incidence X-ray diffraction (XRD) and transmission electron microscopy (TEM) electron diffraction the structure of the deposited films was proven to be mainly amorphous containing small crystallites of CN_x compounds. Scanning tunneling microscopy (STM) shows the clusterlike surface of the films where the cluster size is characterized by scaling behaviour. The mechanical properties of the CN_x thin films adhering their substrates were investigated using the nanoindentation technique. From the load–displacement curve the hardness H and the Young's modulus E of the films were calculated.The relationships between deposition parameters and properties of CN_x films are shown and discussed. In particular, the influence of the applied r.f. power and the role of the N₂ partial pressure are demonstrated.     

The relationship between structure and mechanical properties of hydrogenated amorphous carbon films

There is increasing interest in the relations between Raman fit parameters and the mechanical properties of diamond-like carbon films. The present work describes these relations in hydrogenated diamond-like carbon films (a-C:H) deposited by an ion beam source operated at varied discharge voltages, i.e. kinetic carbon species energies. A number of highly distinct relations between Raman fit parameters and mechanical properties are identified for the a-C:H films investigated. For example the nanohardness (H) and reduced elastic modulus (E) increase almost linearly with an increase in full width at half maximum of the G-band (FWHM (G)). The film elasticity, expressed as H³/E² increases with increasing FWHM (G). In addition, H and E increase linearly with decreasing intensity ratio of the D-band and the G-band (I_D/I_G). H and E also increase with the G-band dispersion (Disp. (G)), i.e. the rate of change of the G-band position vs. excitation energy. Hydrogen contents in all films are approximately equal and range from 21.2 to 23.5 at.% over the entire set of investigated samples.     

磁控溅射制备非晶态WO_3薄膜的光催化性能

采用射频反应磁控溅射工艺在玻璃基片上沉积了非晶态WO3薄膜。通过光催化降解亚甲基蓝和罗丹明B溶液实验,研究了所制WO3薄膜的光催化活性和使用寿命。X射线衍射(XRD)分析表明:所制备的WO3薄膜为非晶态。光催化实验表明:紫外光照3h后,薄膜对亚甲基蓝和罗丹明B溶液的最大降解率分别为83.26%和72.73%。重复使用3次后,薄膜对亚甲基蓝的降解率保持在75%以上,7次使用后薄膜基本丧失光催化活性。采用去离子水超声处理30min的方法可使已失活薄膜对亚甲基蓝的降解率从20%恢复至81%。     

Mechanical and tribological properties of boron,nitrogen-coincorporated diamond-like carbon films prepared by reactive radio-frequency magnetron sputtering

We have deposited boron- and/or nitrogen-incorporated DLC films by radio-frequency magnetron sputtering, and systematically investigated the structure and the mechanical and tribological properties. The N content in DLC films increased with increasing N₂ flow ratio [N₂/(Ar + N₂)], and it tended to be saturated at higher N₂ flow ratios. The N content further increased with an increase in the B content of the targets. The B/C ratios of the films were almost the same as those of the B-containing targets regardless of the N content. Scratch tests revealed that the adhesion strength of N-incorporated DLC films decreased with increasing N₂ flow ratio and the critical loads of B-incorporated films were lower than that of an unincorporated film. It was found that for B, N-coincorporated films there was an optimum N₂ flow ratio at which the critical load became a maximum value, which was higher than that of the unincorporated film. The optimum N₂ flow ratio increased with an increase in the B composition of the targets. The N-incorporated films peeled off during ball-on-plate friction tests. On the other hand, the B, N-coincorporated films showed good wear-resistant properties that the specific wear rates were lower than those of the unincorporated and B-incorporated films.     

直流溅射ITO薄膜光电性能研究

采用直流溅射法制备了高性能的ITO薄膜。结果表明,氧气分压比和衬底温度对薄膜的方阻、可见光透射率具有重要的影响。其最佳值分别为0.5/50和350℃;同时,随着膜厚的增加,薄膜的晶粒增大,导电率也相应降低。     

The optical and electrical properties of ZnO:Al thin films deposited at low temperatures by RF magnetron sputtering

Several ZnO:Al thin films have been successfully deposited on glass substrates at different substrate temperatures by RF (radio frequency) magnetron sputtering method. Effects of the substrate temperatures on the optical and electrical properties of these ZnO:Al thin films were investigated. The UV–VIS–NIR spectra of the ZnO:Al thin films revealed that the average optical transmittances in the visible range are very high, up to 88%. X-ray diffraction results showed that crystallization of these films was improved at higher substrate temperature. The band gaps of ZnO:Al thin films deposited at 25 ℃, 150 ℃, 200 ℃, and 250 ℃ are 3.59 eV, 3.55 eV, 3.53 eV, and 3.48 eV, respectively. The Hall-effect measurement demonstrated that the electrical resistivity of the films decreased with the increase of the substrate temperature and the electrical resistivity reached 1.990×10^?3 Ω cm at 250 ℃.     

Mechanical and tribological properties of TiC/amorphous hydrogenated carbon composite coatings fabricated by DC magnetron sputtering with and without sample bias

TiC/amorphous hydrogenated carbon (a-C:H) composite films were deposited by Ti DC magnetron sputtering using argon and acetylene as the carrier gas and precursor, respectively. The working pressure was maintained at 4 × 10^− 1 Pa and the composition of the films was modulated by controlling the partial pressure of acetylene. The composition and structure of the films were evaluated by X-ray photoelectron spectroscopy and glancing angle X-rays diffraction, whereas the hardness and elastic modulus values of the films fabricated using different sample biases were measured by nano-indentation. Ball-on-disk tribometry was used to measure the tribological properties, and secondary electron microscopy was used to analyze the wear tracks. The results show that the friction coefficients and wear rates do not vary significantly with the Ti concentrations when the Ti concentration is above 39.7 at.% or below 20 at.% but increase with increasing titanium concentrations between 20 at.% and 39.7 at.%. The wear mechanism depends on the relative amounts of TiC and a-C:H. At high Ti concentrations, the mechanism resembles that of TiC due to the thin a-C:H matrix surrounding the TiC grains. At low Ti concentrations, the mechanism is similar to that of DLC as the effects of the a-C:H matrix dominates over those of the TiC grains.     

Study of the thermal stability of carbon nitride thin films prepared by reactive magnetron sputtering

CN_x amorphous films have been prepared by reactive magnetron sputtering in a pure N₂ discharge. The films grown on NaCl have been characterised by Fourier transform infrared spectroscopy (IR), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). C/N atomic ratios have been determined by EELS with values in the range 2.0–1.2 for samples grown under different conditions. The thermal stability of the films upon heating in vacuum was followed ‘in situ’ at the transmission electron microscope by EELS. This study has been completed by a thermogravimetric and mass spectrometer analysis of evolved gases upon heating in nitrogen flow and vacuum, respectively. Under these conditions the films are stable up to 1023 K. Above this temperature the films decompose by elimination of nitrogen remaining a carbonaceous residue. The thermal stability of the films upon annealing in air was studied by following the evolution of the X-ray photoelectron spectroscopy (XPS) peaks during heating in air of films grown on steel. Deconvolution analysis of the XPS spectra allows to determine the evolution of the different type of bonds. In particular pure carbon in the films appears more reactive to oxygen than CN and C–N bonds.     

Structure and high-temperature tribological properties of Pb-Cr-O composite films prepared by reactive magnetron sputtering

The formation of ternary composite oxides in a high-temperature environment has laid the foundation for the design of high-temperature wear-resistant self-lubricating film. A series of Pb-Cr-O films with different Cr contents were prepared by incorporating different ratios of Pb-Cr into a target in the reactive magnetron sputtering system. The results showed that the hardness of the Pb-Cr-O films is greatly improved compared to the pure Pb-O film. In addition, the Pb₂₉Cr₄O₆₇ film with the highest Cr content forms an amorphous structure due to the accumulation of Cr⁶⁺ at the grain boundary, which improves the H/E and H³/E² of the film. At 600 °C, in contrast with the single PbO lubricating phase formed by pure Pb₃₃O₆₇ film, the Pb₂₉Cr₄O₆₇ film forms a composite lubricating phase of Pb₅CrO₈ and PbO. This leads to a decreased wear rate as low as 7.2 × 10^?6 mm³N^?1m^?1 while maintaining low coefficient of friction comparable to pure Pb₃₃O₆₇ film. At higher temperature of 700 °C, Cr element in Inconel 718 matrix diffuses into the Pb-based oxide film and forms Pb₅CrO₈ phase similar to Pb₂₉Cr₄O₆₇ film, which improves the wear resistance of the Pb₃₃O₆₇ film while maintaining low friction coefficient of 0.15.     

Improved physical properties of Al-doped ZnO thin films deposited by unbalanced RF magnetron sputtering

Room temperature Al-doped ZnO (AZO) thin films with improved crystalline and optical properties were grown on normal glass substrates using unbalanced RF magnetron sputtering technique. To modify the plasma density towards the substrate and enhance the crystalline nature, an additional magnetic field ranging from 0 to 6.0 mT has been applied to the AZO target by proper tuning of solenoid coil current from 0 to 0.2 A respectively, which plays a significant role for controlling the physical properties of AZO films. The results from XRD studies indicate that all AZO films were composed of hexagonal wurtzite structure with better crystal quality through the applied magnetic field, ZnO (002) plane as a preferred growth. Furthermore, XPS studies suggested that symmetric chemical shifts in the binding energies for the Zn 2p and O1s levels with applied magnetic field. SEM analysis revealed the formation of a smooth, homogeneous and dense morphological surface with applied magnetic field. From AFM analysis, it was observed that the applied magnetic field strongly influenced the grain size and the films showed decreasing tendency in electrical resistivity. Films exhibited superior optical transmittance more than 94% in the visible region essentially due to the formation of better crystalline nature. The results indicate that improved band gap from 3.10 to 3.15 eV with additional magnetic field varied from 0 to 6.0 mT respectively.     

Structural effects of nanocomposite films of amorphous carbon and metal deposited by pulsed-DC reactive magnetron sputtering

The relationship between metal-induced (W, Mo, Nb and Ti) structures and the surface properties of Me–DLC thin films is discussed. Nanocomposite films were deposited on c–Si wafers by pulsed-DC reactive magnetron sputtering controlling the gas ratio CH₄/Ar. The sputtering process of metals such as Ti, Nb and Mo (unlike the tungsten) in the presence of methane shows a low reactivity at low methane concentration. The deposition rate and the spatial distribution of sputtered material depend of Z-ratio of each metal. The surface contamination of metal targets by carbon, owing to methane dilution, limits the incorporation of metals into DLC films according to an exponential decay. Results of electron probe microanalysis and X-ray photoelectron spectroscopy indicate a C rich Me/C composition ratio for low relative methane flows. According to the depth profile by secondary ion mass spectrometry, the films are systematically homogeneous in depth, whereas at high carbon contents they exhibit a metal-rich interfacial layer on the substrate. Moreover, high resolution transmission electron microscopy has evidenced important structural modifications with respect to DLC standard films, with marked differences for each Me/C combination, providing nanodendritic, nanocrystallized or multilayered structures. These particular nanostructures favour the stress decrease and induce significant changes in the tribological characteristics of the films. This study shows the possibilities of controlling the amorphous carbon films structure and surface properties by introducing metal in the DLC matrix.     

ZAO薄膜使用射频溅射法生长之参数的研究

以氧化铝锌陶瓷为溅射靶材,在氩气环境下,使用射频溅射法在玻璃基片上制备氧化铝锌(ZAO)薄膜。通过调节气体压强、基片温度、溅射功率制膜,得到以C轴(002)为选择取向的氧化锌薄膜。由XRD、原子力显微镜(AFM)等对薄膜进行分析。结果表明,制备薄膜的最佳条件为:溅射压强0.4 Pa,溅射功率200 W,基片温度300℃。