Preparation of solar selective absorbing coatings by magnetron sputtering from a single stainless steel target

This paper presents a method to prepare solar selective absorbing coatings by radio frequency magnetron reactive sputtering using a single stainless steel target. Stainless steel/stainless steel nitride (SS/SS-N) ceramic-metal composite (cermet) thin films were produced under varied nitrogen gas flow ratios. The solar selective absorbing films have good solar absorptance of 0.91 and thermal emittance of 0.06 at 82 °C. The refractive index (n) and extinction coefficient (k) of the cermet composite layers prepared in nitrogen and argon atmospheres were determined by spectroscopic ellipsometry. The films were also analyzed by different oscillator models. The results showed a significant transformation from metal to cermet as the nitrogen gas flow ratio was increased to 10%. As the nitrogen gas flow ratio was increased to 17.5%, the film became a dielectric layer that could be used as an anti-reflection layer, suitable as the outermost layer of the solar selective absorbing coatings. A theoretical solar absorptance of 0.92 was achieved by selecting an appropriate combination of three solar absorbing layers. The experimental results agreed well with the theoretical calculations. This study proved the possibility of preparing solar selective absorbing coatings with high solar absorptance by using a single stainless steel target.     

MoSx-Ta composite coatings on steel by d.c magnetron sputtering

Sputter-deposited MoS₂ films have been often used as dry lubricant in various industrial fields, such as space application and much attention has been paid to reduction of friction coefficient and improvement of mechanical properties in recent decades. One way to achieve this is to deposit a MoS₂ film doped with another metal. The MoS_x-metal films were found to be denser, more adhesive and more oxidation-resistant than pure MoS₂. In this study, MoS_x-Ta composite films were synthesized by Electron Cyclotron Resonance microwave source enhanced DC sputtering with different target powers. The effects of doping Ta on mechanical properties of MoS_x-Ta films were investigated. The morphology and structure of films were investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The microhardness was evaluated using microhardness test instrument, and the adhesion strengths were obtained using a scratch tester. The results showed that the S/Mo ratio was influenced by the dc sputtering target power. Typical MoS₂ (100) (103) (002) orientations were present in pure MoS_x films, but disappeared with the increase in doped Ta, with the S/Mo content ratios decreasing from 1.52 to 0.84, and the hardness increasing from 3.55 to 15.23 GPa. The roughness and surface topography, friction coefficient and adhesion were significantly affected by the Ta, Mo and S content. The content of doped Ta plays a dominant role on the change in the Mo/S ratio, thereby influencing the mechanical and tribological properties of the MoS_x-Ta composite films.     

Properties of 310S stainless steel coatings produced by unbalanced magnetron sputter deposition

310S stainless steel coatings were produced using unbalanced magnetron sputter deposition technique. Different deposition parameters (Ar working pressure and bias voltage) were used during coating operations. It was found that the 310S coatings have a ferritic (bcc) phase structure; and the lattice parameter varies with the bias voltage and Ar pressure. Ar pressure has an important effect on the coating hardness. As Ar pressure increases from 2.67 to 8.0 × 10⁻³ mbar (1 mbar = 0.75 Torr), there is an abrupt drop in coating surface hardness. This was explained with the formation of different coating microstructures according to the Thornton's model. With increasing Ar pressure, surface roughness increases, indicating that the coating surface becomes more complex.     

Corrosion behaviour of CrN/Cr multilayers on stainless steel deposited by unbalanced magnetron sputtering

This paper reports the results of the influence of bilayer period (Λ) and total thickness (f) on the corrosion resistance of magnetron-sputtered CrN/Cr multilayers. Corrosion tests were carried out by potentiodynamic polarization with 0.5 M H₂SO₄ + 0.05 M KSCN solution and electrochemical impedance spectroscopy (EIS) with 3% NaCl solution. Measurements were also taken on the uncoated substrate and hard chromium coatings for comparison. Multilayer microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and chemical composition was studied by energy dispersive X-ray analysis (EDX).The experiments showed that CrN/Cr coatings having lower bilayer period and lower thickness increased their efficiency as a barrier and improved the corrosion resistance of all coatings evaluated.     

Electrochemical behaviour of chromium nitride coatings with various preferred orientations deposited on steel by unbalanced magnetron sputtering

Abstract

Chromium nitride coatings Cr₂N(111) and preferred orientations of CrN(111) and CrN(200) were successfully deposited on AISI 304 stainless steel by an unbalanced magnetron sputtering method. The electrochemical corrosion properties of the deposited films were studied in a 0·5M H₂SO₄ + 1M NaCl aqueous solution at ambient temperature by electrochemical measurements, including the corrosion potential E _corr, linear polarisation, potentiodynamic polarisation and electrochemical impedance spectroscopy. The structural characterisation and surface morphology were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. The experimental results indicated that the CrN(200) coating possesses the best corrosion resistance property, followed by the CrN(111) coating, while the Cr₂N coating has the least resistance among the three types of CrN(111), CrN(200) and Cr₂N(111) coatings. The porosity, corresponding to the ratio of the polarisation resistance of the uncoated and the coated substrates, was higher in the Cr₂N(111) coating than in the other CrN coatings. The CrN(200) coating had a dense microstructure almost without porosity. The void defects of CrN(111) and Cr₂N(111) coatings are responsible for the decrease in corrosion protection.     

Topography and microstructure of Cu-Sn coatings deposited by magnetron sputtering

The topographical and microstructural features of Cu-Sn coatings deposited by magnetron sputtering using alloy target of Cu-7.8%Sn and Cu-74%Sn onto ferritic stainless steel substrates with a temperature gradient were investigated by means of optical and scanning electron microscopy.Depending on the substrate temperature the alloy film forms by a vapour → solid process or a vapour → liquid process with solidification after substrate cooling. In between a mixed mechanism of vapour → liquid → solid occurs during condensation in the temperature ranges 990–1170 K and 460–790 K for coatings deposited by sputtering of Cu-7.8%Sn and Cu-74%Sn targets respectively.The copper-rich condensate formed in the temperature range 370–1220 K consists of a single-phase α solid solution of tin in copper. Its lattice parameter decreases with increasing temperature mainly because of the decreasing tin content.The film obtained by sputtering a Cu-74%Sn target has a two-phase η′-Cu₆Sn₅ plus tin structure independently of the deposition temperature.     

Mo/SiO2 nanocomposite films for optical coatings prepared by vacuum magnetron sputtering

The embedding of metallic nanoparticles in the traditional optical materials (e.g. SiO₂) gives us the possibility to create new optical materials. Metallic particles of nanometric dimensions can be transparent in wide spectral ranges of light. The incorporation of nanocrystal inclusions in such nanocomposites provides the benefit of targeted manipulations of their macroscopic optical response. In this paper we present the possibility to create, using vacuum deposition methods, the nanocomposite coatings with fairly small refractivity.     

Oxidation behavior of Ti-B-C-N coatings deposited by reactive magnetron sputtering

Quaternary Ti-B-C-N coatings with different carbon concentrations are deposited on high-speed steel substrates by reactive magnetron sputtering. The oxidation behavior between 300 and 800 °C under ambient conditions is studied by scanning electron microscopy, high-resolution transmission electron microscopy, Vickers micro-hardness, and X-ray diffraction. The Ti-B-C-N coatings with smaller carbon contents have better oxidation resistance and the oxidation process can be divided into two stages: low-speed oxidation below 700 °C and high-speed oxidation above 700 °C. An oxidation mechanism is proposed to explain the relationship between the reaction with oxygen and observed oxidation behavior.     

The production of porous and chemically reactive coatings by magnetron sputtering

High surface area materials can have a number of applications including use as pyrophoric devices, sensors, laser mirrors, filters, thermal barriers and catalysts. The aim of this work was to deposit highly porous thin films capable of undergoing a spontaneous pyrophoric reaction and igniting a suitable substrate material. Magnetron sputtering was the chosen deposition technique as it enables reproducible deposition of coatings, with closely controlled, almost uniform, thickness and morphologies over extended surfaces.A number of magnetron magnetic configurations were investigated and deposition conditions were varied in order to control the surface area of the films and, thereby, optimise the pyrophoric behaviour. As a consequence, pyrophoric coatings were produced with ignition temperatures dependent on the deposition conditions and substrate material/topography. When deposited on combustible substrates, these coating/substrate systems formed simple pyrotechnic devices in a one-stage process. The main thermal signal emitted by these devices was dependent on the substrate material only.     

Functional properties of ceramic-Ag nanocomposite coatings produced by magnetron sputtering

In recent years, the use of nanocomposite materials to functionalize surfaces has been investigated, taking advantage of the complementary properties of the nanocomposite constituents. Among this family of materials, ceramic-Ag coatings have been widely studied due to the large variety of functionalities that silver possesses and the possibility of tuning the coating’s practical features by selecting the proper matrix to support this noble metal. Therefore, this review focuses on the effects of silver nanoparticles on the functional properties of ceramic-Ag nanocomposites. The chemistry, structure, morphology and topography of the coatings are analyzed with respect to the changes produced by the silver nanoparticles’ distribution, amount and sizes and by altering production process variables. To offer a clear understanding of the functionalities of these materials, the optical, electrical, mechanical, tribological, electrochemical and biological properties reported in the last decade are reviewed, focusing on the ability to tune such properties by modifying the silver distribution, morphology and composition. In particular, the surface plasmon resonance, self-lubricating ability and antibacterial effect of silver are covered in detail, establishing their correlation with factors such as silver diffusion, segregation and ionization.     

一种双真空室结构磁控溅射台的研制

本文研制了一种较高档的磁控溅射镀膜设备,用于微电子器件规模化生产过程中的基片表面镀膜.该设备采用双真空室结构,使溅射室始终维持较高的真空度和洁净度,提高镀膜质量和镀膜效率.环绕溅射室设计了3个直流靶和1个射频靶,能够溅射金属膜、介质膜、混合物和化合物薄膜.文中详述了该设备的设计原理、总体结构及工艺控制方法.该磁控溅射台已开发成功并投入使用,替代了同类进口设备.     

Introduction of helium into metals by magnetron sputtering deposition method

High concentration helium, up to 16 at.%, was introduced into Ti films through magnetron sputtering method in a He/Ar complex atmosphere. The introduced helium distributes homogeneously in the films and mainly forms small helium bubbles. Helium thermodesorption experiments were carried out, from which it was found that the thermodesorption properties of the introduced ⁴He are similar to those of radiogenic ³He in titanium tritides. Titanium alloy films containing helium were also prepared through this way and a comparison of thermodesorption properties was made between them and Ti–He films.     

Characterization of thermoelectric properties of layers obtained by pulsed magnetron sputtering

The pulsed magnetron sputtering technique was applied for the preparation of layers of Bi₂Te₃ and Sb₂Te₃. Target materials were synthesized in evacuated quartz ampoules by melting elemental powders mixed in stoichiometric proportions. The structure and microstructure of targets and prepared films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Thermoelectric properties were defined by the Seebeck coefficient and electrical conductivity measurements in the temperature range 320-430 K. The layers were deposited at various powers (0.09-0.20 kW) and currents (0.07-0.16 A) at an argon pressure of about 3.0 Pa. The efficiencies of thermoelectric power obtained for bismuth telluride and antimony telluride were 2-4×10⁻⁴ and 2-6×10⁻³ W K⁻² m⁻¹, respectively. The synthesized materials were used for the fabrication of thermoelectric couples with Bi₂Te₃ as the n-type material and Sb₂Te₃ as the p-type material. The thermocouples were annealed under vacuum to obtain optimum thermoelectric properties. The Seebeck coefficient of thermocouples was evaluated by a Seebeck scanning microprobe [Platzek D, Karpinski G, Stewie C, Muchilo D, Müller E. Proceedings of the second European conference on thermoelectrics, Poland, Cracow, September 15-17, 2004].     

磁控反应溅射不锈钢表面制备纳米TiO2薄膜及光催化活性研究

不锈钢箔片上溅射沉积25nm的钛底膜后,在工作真空0．9Pa．O2、Ar分压比1：6．基体温度270～280℃的条件下,用直流磁控反应溅射法制备了厚度约300nm的TiO2薄膜,并在420℃的氧气氛下进行热处理。XRD分析看出,薄膜为TiO2锐钛矿和金红石复合晶型。测算表明TiO2复合晶中锐钛矿质量含量约64％,其晶粒尺寸约14nm。用“弯曲法”测试表明,膜基结合力强。由对苯酚溶液的降解实验看出,制备光催化薄膜具有较好的光催化活性。     

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.     

Corrosion behaviour of decorative and wear resistant coatings on steel deposited by reactive magnetron sputtering - Tests and improvements

Depositions of decorative and wear resistant single layer coatings like TiN, Ti(B,N), CrN, NbN, NbON, (Ti,Mg)N and multilayer coatings like Cr/CrN, Nb/NbN, CrN/NbN and NbN/Nb-C:H were performed using reactive magnetron sputtering. The corrosion behaviour of the coated high speed steel substrates was studied in sodium chloride containing media by open-circuit-potential measurements, potentiodynamic corrosion tests and salt spray tests. Up to now, the best improvements with respect to the corrosion resistance in salt spray tests could be obtained for the system (Ti,Mg)N/high speed steel.     

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.     

Comparative analysis of Cr-B coatings deposited by magnetron sputtering in DC and HIPIMS modes

Surface coatings of the Cr-B system have been obtained by magnetron sputtering in the DC and high-power impulse (HIPIMS) regimes. It is established that the passage from the DC regime to HIPIMS leads to suppression of the columnar grain growth and a twofold increase in the resistance of coatings to plastic deformation, while the plasticity index and hardness of coatings increase by 29 and 18%, respectively.