Magnetron Technique Research Articles

Preparation and characterization of sputtered aluminum and gallium co-doped ZnO films as conductive substrates in dye-sensitized solar cells

Aluminum and gallium co-doped zinc oxide (GAZnO) films were deposited on borosilicate glass substrates by radio frequency (rf) magnetron technique. The effects of substrate temperature on the structural, optical and electrical properties of the sputtered films were investigated. X-ray diffraction measurement revealed mixed orientations for films prepared at low substrate temperatures, while films prepared at high temperatures were oriented mainly along the (002) direction. Optical transmittance data indicated that the transparency of all the films was above 80% within the visible spectrum, while the electrical resistivity and mobility were improved with increasing substrate temperatures reaching maximum values at 350°C. Finally, using GAZnO films prepared at 300°C and 350°C as transparent conductive substrates in a solar cell sensitized with a metal-free organic dye, light-to-electrical energy conversion efficiency of 3.5 and 3.7% under AM 1.5 irradiation (1000Wm−2 simulated sunlight) was recorded, respectively.

Optical constants of Er 2O 3-Al 2O 3 films studied by spectroscopic ellipsometry

Er 2O 3-Al 2O 3 film was deposited on the Si(001) substrate by radio frequency magnetron technique at room temperature. The sample was annealed at 450, 600 and 750 °C for 30 min in O 2 ambience, respectively. The optical constants were studied by spectroscopic ellipsometry for both the as-deposited and the annealed samples. The proper values of refractive index indicated that it could be a useful material for solar cells.

Optical fiber hydrogen sensor based on light reflection and a palladium-sliver thin film

Thin alloy films of palladium (Pd) and silver (Ag) are deposited onto glass substrates via the direct current (DC) magnetron technique. The hydrogen sensor probe consists of optical fiber bundle and Pd/Ag optical thin film. When the sensor is exposed to hydrogen, the refractive index of Pd/Ag optical thin layer will diminish and cause attenuation changes of the reflective light. It is observed that the thickness of Pd/Ag alloy layer can affect the hydrogen sensor signal. Under different substrate temperatures, several Pd/Ag samples are coated with different thicknesses of Pd/Ag alloy, and the results of a hydrogen sensor based on reflective light from the Pd/Ag alloy thin film are discussed.

Properties of zinc oxide at low and moderate temperatures

The properties of zinc oxide are examined as an analog of gallium nitride over a wide range of temperatures and possible applications. Its economic and environmental advantages are noted, as well as its radiation hardness, compared to group III nitrides. Methods for growing films and nanostructures with high crystal perfection are proposed. In particular, a magnetron technique for layer-by-layer growth of films is implemented which makes it possible to obtain high structural perfection and substantial thicknesses unattainable by several other methods. The feasibility of producing monochromatic UV radiation from films excited by short-wavelength radiation and electrons is demonstrated; this means that they may be useable as short-wavelength radiation sources. Efficient field emission by ZnO nanostructures and films is demonstrated and opens up the prospect of their use in vacuum microelectronics equipment. Nitrogen-doped ZnO films, in particular, have been used to fabricate a phototransistor with a sensitivity two orders of magnitude higher than conventional detectors. The physical basis for creating LEDs for different colors based on ZnO films and solid solutions with CdO is discussed. The importance of studying the physics and technology of zinc oxide-based devices is emphasized.

Study on the Energy Structure of Amorphous Antireflection Er<sub>2</sub>O<sub>3</sub> Films on Si(001) Substrates

Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. X-ray photoelectron spectroscopy, x-ray diffraction and atomic force microscopy show the Er2O3 films obtained are stoichiometric, amorphous, and uniform. The electronic structure is studied which shows a large energy gap value of the Er2O3 film, indicating Er2O3 film could be a promising antireflection coating for solar cells.

Optical Constants of Al-Doped Er<sub>2</sub>O<sub>3</sub> Films Prepared by Radio Frequency Reactive Magnetron Sputtering

Al doped Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. X-ray diffraction and atomic force microscopy show the Al doped Er2O3 films obtained are amorphous and uniform. The optical constants are studied which shows a proper value of refractive index and a lower reflectivity, indicating it could be a usefully material for solar cells.

Structural and optical properties of Er 2O 3 films

Stoichiometric and amorphous Er 2O 3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er 2O 3 film in wavelength region of 400–1000 nm was between 1.6–1.7. The reflectivity of the Er 2O 3 films decreased greatly with respect to that from the uncoated Si substrates. The absorption coefficient of the Er 2O 3 film indicated that it had an energy gap larger than 4.5 eV. The obtained characteristics indicated that Er 2O 3 films could be promising candidates for anti-reflection coatings in solar cells.

Comparative study between zinc oxide elaborated by spray pyrolysis, electron beam evaporation and rf magnetron techniques

AbstractZinc oxide thin films have been fabricated by spray pyrolysis, reactive e‐beam, and rf magnetron sputtering techniques. Structural, optical, and electrical properties have been compared in order to clarify the characteristics of each technique. X‐ray diffraction measurements have shown that ZnO films deposited by reactive e‐beam evaporation reveal tensile stress and ZnO thin layers deposited by magnetron sputtering and spray pyrolysis reveal compressive stress. Raman studies confirm the results obtained with XRD. Concerning the electric resistivity studies, we have seen that the layers exhibiting tensile stress are conductors whereas the films exhibiting compressive stress leads to insulators materials. The optical transmittance shows that the film evaporated by e‐beam exhibits a maximum transmittance of over 60%, the film deposited by electrostatic spray pyrolysis exhibits a maximum transmittance less than 70% and the one fabricated by magnetron was found to have a maximum transparency less than 75%. Finally, the study of the surface morphology has shown that the most respected stoichiometry ratio between Zn and O was obtained using the e‐beam evaporation and sputtering techniques.

Influences of Target-to-Substrate Distance and DepositionTemperature on a-SiOx/Indium Doped Tin Oxide Substrate as aLiquid Crystal Alignment Layer

We present the structural, optical, and electrical properties of amorphous silicon suboxide (a-SiO ) films grown on indium tin oxide glass substrates with a radio frequency magnetron technique from a polycrystalline silicon oxide target using ambient Ar. For different substrate-target distances (d = 8 cm and 10 cm), the deposition temperature effects were systematically studied. For d = 8cm, oxygen content in a-SiO decreased with dissociation of oxygen onto the silicon oxide matrix; temperature increased due to enlargement of kinetic energy. For d = 10 cm, however, the oxygen content had a minimum between 150 C and 200 C. Using simple optical measurements, we can predict a preferred orientation of liquid crystal molecules on a- SiO thin film. At higher oxygen content (x > 1.6), liquid crystal molecules on an inorganic liquid crystal alignment layer of a-SiO showed homogeneous alignment; however, in the lower case (x < 1.6), liquid crystals showed homeotropic alignment.

Deposition and characterization of hybrid filtered arc/magnetron multilayer nanocomposite cermet coatings for advanced tribological applications

The demand for low-friction, wear and corrosion resistant components, which operate under severe conditions, has directed attention to advanced surface engineering technologies. The large area filtered arc deposition (LAFAD) process has demonstrated atomically smooth coatings at high deposition rates over large surface areas. In addition to the inherent advantages of conventional filtered arc technology (superhardness, improved adhesion, low defect density), the LAFAD technology allows functionally graded, multilayer, and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different metal vapor ion compositions. Further advancement is realized through a combinatorial process using a hybrid filtered arc–magnetron technique to deposit multilayer nanocomposite TiCrN + TiBC cermet coatings. Multiple TiCrN + TiBC coating architectures were reviewed for their ability to provide wear resistance for Pyrowear 675 and M50 steels used in aerospace bearing and gear applications. Coating properties were characterized by a variety of methods including SEM/EDS, HRTEM, and XRD. Wear results were obtained for high contact stress boundary lubricated sliding and advanced bearing simulation testing for wear performance under oil-off operating conditions. The best coating candidates demonstrated order of magnitude increases in resistance to sliding wear, and extended low friction operation during simulated oil-off events. Coating failure mechanisms were brittle in nature and suggestions are presented for the further optimization of TiCrN + TiBC coating architectures.

The structure and photoluminescence properties of ZnO/SiC multilayer film on Si substrate

ZnO/SiC multilayer film has been fabricated on a Si (111) substrate with a silicon carbide (SiC) buffer layer using the RF (radio frequency)-magnetron technique with targets of a ceramic polycrystalline zinc oxide (ZnO) and a composite target of pure C plate with attached Si chips on the surface. The as-deposited films were annealed at a temperature range of 600–1000°C under nitrogen atmosphere. The structure and photoluminescence (PL) properties of the samples were measured using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and PL spectrophotometry. By increasing the annealing temperature to 800°C, it is found that all the ZnO peaks have the strongest intensities, and the crystallinity of ZnO is more consistent on the SiC buffer layer. Further increase of the annealing temperature allows the ZnO and SiC layers to penetrate one another, which makes the interface between ZnO and SiC layer become more and more complicated, thus reduces the crystallinities of ZnO and SiC. The PL properties of a ZnO/SiC multilayer are investigated in detail. It is discovered that the PL intensities of these bands reach their maximum after being annealed at 800°C. The PL peaks shift with an increase in the annealing temperature, which is due to the ZnO and SiC layers penetrating reciprocally. This makes the interface more impacted and complicated, which induces band structure deformation resulting from lattice deformation.

Fabrication and characterization of stacked ZnO and ZnOGa2O3 layers for the realization of bulk acoustic wave resonated membranes

ZnOGa2O3 alloys have been deposited by electron beam co-evaporation technique below the piezoelectric radio frequency magnetron sputtered ZnO films, with the aim of reducing the compressive stress due to the piezoelectric zinc oxide elaborated by radio frequency magnetron technique. The structural characterizations of the Ga2O3 thin films show an amorphous structure. Co-evaporating gallium oxide with zinc oxide has improved the optical and structural qualities of the e-beam zinc oxide films. Thus, deposing compressive rf magnetron sputtered piezoelectric ZnO on tensile thin layers of ZnOGa2O3, has reduced the stress and improved the structural quality of the realized bulk acoustic wave resonators. The fabrication of less stressed ZnO resonators has permitted to liberate partially our membranes by attacking the silicon substrate on which the resonator is realized. Finally, hyper frequency characterizations have been done by a network analyzer to study the influence of the silicon substrate thickness on the piezoelectric activity.

Off-axis growth of AlN thin films by hollow cathode magnetron sputtering under various nitrogen concentrations

Amorphous and crystalline AlN thin films were deposited on Si (100) substrates by off-axis hollow cathode magnetron technique. The evolution of the crystalline orientation and the morphology of AlN thin films have been investigated depending on the nitrogen concentration. It has been demonstrated by using a combination of mass spectrometry, X-ray diffraction and atomic force microscopy techniques, that the film crystallinity and surface roughness are related with the nitrogen concentration. The results show that the monitoring of Al + and AlN + species by mass spectrometry proved to be an important new method to prescribe the plasma conditions for growing amorphous or crystalline films.

35 GHz compact radar using fan beam antenna array for obstacle detection

A 35 GHz, magnetron-based, compact pulse radar is presented. It contains some novel solutions of four electrically switched slot array antennas having fan beam patterns, solid-state modulator adaptive for the miniature magnetron and digital receiver techniques with advanced processing. It is designed for obstacle and rain detection for collision warning in helicopter applications.

Chromium nitride/niobium nitride nano-scale multilayer coatings deposited at low temperature by the combined cathodic arc/unbalanced magnetron technique

CrN/NbN nano-scale multilayered coatings have been successfully grown at a deposition temperature of 250 °C. The coatings have been grown by the combined cathodic arc/unbalanced magnetron technique (Arc Bond Sputter) and were deposited at two different thicknesses namely ∼1.0 and ∼3.0 μm at bias voltages UB between −75 and −150 V. In all cases the stresses were compressive and increased from −4.4 GPa at UB=−75 V to −9.5 GPa at UB=−150 V. Coatings in all cases developed a pronounced {111} texture that tended to a maximum at a bias voltage of −95 V. The experiments indicated that the {111} texture developed by a competitive growth mechanism from a randomly oriented or {100} initial starting texture. Measurements of coefficients of friction and sliding wear show a decrease in the coefficients of friction and sliding wear with increasing bias voltage. The coefficient of friction decreases from μ=0.7 at UB=−75 V to μ=0.5 at UB=−150 V while in parallel the coefficient of sliding wear decreased by an order of magnitude from 1.3×10−14 at UB=−75 V to 2.8×10−15 at UB=−150 V. These decreases in coefficients of friction and sliding wear appear to mirror the increases in intensity of the {111} texture. The adhesion as measured by scratch test shows a distinct maximum of 72 N at a bias voltage UB of −95 V, which is a remarkably high value for a low temperature process in a coating with a compressive stress of −5.4 GPa.

The role of the growth defects on the corrosion resistance of CrN/NbN superlattice coatings deposited at low temperatures

CrN/NbN nano-scale multilayered coatings have been successfully deposited at a temperature of 250 °C on 304 stainless steel substrates by the combined cathodic arc/unbalanced magnetron technique (Arc Bond Sputter) with a thickness typically 3.0 μm at bias voltages UB of −75 and −95 V. The microstructure and surface morphology of the coatings were examined in the as-deposited and corroded condition using an environmental scanning electron microscope (ESEM) in the gaseous secondary electron mode. The corrosion resistance of the coatings was determined by a potentiodynamic polarisation measurement in a 3% NaCl solution open to air at room temperature. In the ESEM images defects could be observed on the surface of the coatings and the number of these defects decreased with increasing bias voltage. ESEM images of the as-deposited coatings showed that microstructure adjacent to growth defects is under dense. These defects have been shown to be sites for preferential corrosive attack However, even with these drawbacks the corrosion resistance as-measured by potentiodynamic polarisation was shown to be superior to that of the uncoated 304 stainless steel substrate, whilst the corrosion resistance of the CrN/NbN nano-scale multilayered coatings increased with increasing bias voltage. In all cases the corrosion resistance was inferior to similar CrN/NbN nano-scale multilayered coatings deposited at higher temperatures of 450 °C.

Influence of power on the structure and mechanical properties of TiN coatings deposited by rf magnetron

Nitrides of transition metals, such as Ti, attract significant interest since they find a wide field of applications ranging from cutting tools to electronic device applications. Titanium nitride is broadly used as a hard protective coating for tribologic applications and for high temperature structural materials. In this work we present the results obtained in the growth of the titanium nitride (TiN) thin films in reactive phase by rf magnetron technique on AISI 420 steels. The depositions of TiN were carried out at a pressure of 7 × 10–3 mbar in an atmosphere of N2 and Ar; we took as study parameter the incident power on the target of Ti (99.9). The films were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The study of XRD showed that films grown with power at 200 W are polycrystalline, while films grown between 350 W and 750 W built the (111) plane of the TiN phase in predominant form and at 800 W there is a change of the growth direction to the (200) plane. The analysis of the Energy Dispersive X-ray Spectroscopy (EDXS) indicated that the films grew stoichiometrically. On the other hand, the hardness tests determined that the films have micro-hardness with values that increased with the power applied to the target; the highest value was 2300 Knoops for the films grown at 500 W. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Comparison of microstructure and mechanical properties of chromium nitride-based coatings deposited by high power impulse magnetron sputtering and by the combined steered cathodic arc/unbalanced magnetron technique

Sliding, abrasive, and impact wear tests were performed on chromium nitride (CrN)-based coatings deposited on mirror-polished M2 high speed steel substrates by the novel high power impulse magnetron sputtering (HIPIMS) utilising high peak cathode powers densities of 3000 W cm −2. The coatings were compared to single layer CrN and multilayer superlattice CrN/NbN coatings deposited by the arc bond sputtering (ABS) technique designed to improve the coating substrate adhesion by a combined steered cathodic arc/unbalanced magnetron (UBM) sputtering process. The substrates were metal ion etched using non-reactive HIPIMS or steered cathodic arc at a substrate bias voltage of −1200 V. Subsequently a 2- to 3-μm thick CrN or CrN/NbN coating was deposited by reactive HIPIMS or UBM. No bias was used during the HIPIMS deposition, while the bias during UBM growth was in the range 75–100 V. The ion saturation current measured by a flat electrostatic probe reached values of 50 mA cm −2 peak for HIPIMS and 1 mA cm −2 continuous during UBM deposition. The microstructure of the HIPIMS coatings observed by transmission electron microscopy was fully dense in contrast to the voided columnar structure observed in conventional UBM sputtered CrN and CrN/NbN. The sliding wear coefficients of the HIPIMS CrN films of 2.3×10 −16 m 3 N −1 m −1 were lower by a factor of 4 and the roughness of the wear track was significantly reduced compared to the UBM-deposited CrN. The abrasive wear coefficient of the HIPIMS coating was 2.2×10 −13 m 3 N −1 m −1 representing an improvement by a factor of 3 over UBM deposited CrN and a wear resistance comparable to that of the superlattice CrN/NbN. The adhesion of the HIPIMS deposited CrN was comparable to state-of-the-art ABS technology.

Formation and thermal stability of the skutterudite phase in films sputtered from Co 20Sb 80 targets

The formation process of the skutterudite phase in both binary and iron-doped films prepared from non-stoichiometric Co 20Sb 80 targets was investigated by means of DTA, XRD, and transport measurement techniques. The results of the measurements allowed us to determine the influence of iron incorporation on the thermal behavior of the Co–Sb-based skutterudite phase. The films prepared by a DC magnetron technique on substrates kept at room temperature were amorphous in the as-deposited state. The crystallization of the skutterudite structure was found to occur exothermally on heating at temperatures near 145 and 153 °C for iron-containing and binary films, respectively. Antimony as a secondary phase was established from XRD measurements after the crystalline structure formation. The transport properties, resistivity and thermopower, of the as-grown films are highly sensitive to the phase formation process. The temperature behavior of these properties during the first measuring cycle is in good agreement with DTA and XRD data showing that these techniques can be valuable instruments to investigate the phase formation. The transport properties as well as the lattice parameters of as-grown films exhibit a permanent modification during thermocycling. The films are sensitive to oxygen at elevated temperatures. Iron incorporation lowers the thermal stability of the films in air. The mechanisms of formation and stability of the skutterudite phase are discussed.

Reactive Sputtering of Nanostructured WCx

ABSTRACTNanostructured WCx thin films were reactively sputtered in argon-methane plasma. A DC planar magnetron with a pure tungsten target was used. Films were deposited on glass, quartz, silicon and sapphire substrates at temperatures up to 700 °C. The carbon content in the film was varied by changing the partial pressure of methane. The carbon content in the films was analyzed by using X-ray Photon Spectroscopy (XPS) and Rutherford Backscattering Spectroscopy (RBS).The effect of temperature on the grain size was studied using Transmission Electron Microscopy (TEM). The target poisoning behavior was studied by measuring the target current. The critical methane concentration at which the metal – poison mode transition occurs was measured to be around 42% of CH4 in Ar. This transition is characterized by a sharp fall in the target current. The hysteresis in the target current can also be attributed to target poisoning. In this paper we describe the effects of film growth parameters on the film composition. We also discuss an alternate sputtering technique, hollow cathode sputtering, and the advantages of this technique over the conventional planar magnetron technique.