Plasma-assisted Reactive Magnetron Sputtering Research Articles

Study of High Transmittance of SiO2/Nb2O5 Multilayer Thin Films Deposited by Plasma-Assisted Reactive Magnetron Sputtering

SiO2/Nb2O5 multilayer thin films were designed for the special application of an aviation lighting system emitting green light. For optical components in this system to meet requirements such as a high transmittance and durability, SiO2/Nb2O5 multilayer thin films of 60 individual layers were fabricated by a plasma-assisted reactive magnetron sputtering method. As a result, the transmittance spectra were confirmed to have a flat top surface and a square bandwidth. The transmittances of the SiO2/Nb2O5 multilayer thin films in the range of 500 nm to 550 nm was approximately 96.14%. The reason for high transmittance was attributed to the almost matching between the designed and fabricated SiO2/Nb2O5 multilayer thin films. It was found that there was little difference in the total thickness between the designed and fabricated SiO2/Nb2O5 multilayer thin films without interlayer diffusion. The surface roughness and hardness of the SiO2/Nb2O5 multilayer thin films on a glass substrate was 2.32 nm ± 0.19 nm and 6.6 GPa, respectively. These results indicate that SiO2/Nb2O5 multilayer thin films can be applied not only to the optical filters used in aviation lighting devices, but also to various optics applications because of high transmittance.

Deposition and characterisation of c-axis oriented AlScN thin films via microwave plasma-assisted reactive HiPIMS

In this work, we demonstrate that highly oriented c-axis aluminium scandium nitride (AlScN) piezoelectric thin films can be deposited via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS), without the necessity of substrate heating. A combination of in situ plasma diagnostics, i.e. time-of-flight mass spectrometry (ToF-MS), modified quartz crystal microbalance (m-QCM), and magnetic field measurements allowed to optimise the deposition conditions, in turn maximising the nitrogen supply and ionic flux at the substrate region, while maintaining stable discharge conditions. The AlScN thin films synthesised in this study were deposited as chemically gradient coatings with varying levels of scandium doping, and were characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Obtaining highly textured films was made possible with the addition of microwave plasma to the optimised HiPIMS discharge, where the wurtzite AlScN films (with up to 20 at. % Sc) exhibited a stronger texture in the (0002) orientation compared to films prepared without microwave plasma. Additionally, the use of a microwave plasma led to a significant decrease in oxygen content in the films and increase in nitrogen content, ensuring stoichiometric compositions. Based on the results mentioned above, it is expected that the AlScN thin films fabricated via MAR-HiPIMS would exhibit a strong piezoelectric response.

Microwave plasma-assisted reactive HiPIMS of InN films: Plasma environment and material characterisation

This work focuses on the low temperature fabrication process of InN thin films via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The influence of microwave plasma on the HiPIMS discharge process at various nitrogen flows and microwave powers was monitored and characterised through in situ diagnostics, including following HiPIMS I(V,t) curves, optical emission spectroscopy (OES), as well as performing time-resolved Langmuir probe and time-of-flight mass spectroscopy (ToF-MS) measurements. This was followed by the deposition of InN films via standard reactive HiPIMS (reference sample) and MAR-HiPIMS and their characterisation via X-ray diffraction (XRD), reflectometry (XRR), as well as scanning and transmission electron microscopy (SEM, TEM). It was found that the microwave plasma facilitates the dissociation/activation of nitrogen species and supplies seed electrons to the magnetron discharge plasma. Furthermore, the energy of the incoming ions was determined via ToF-MS, and it was possible to identify their plasma origin and temporal behaviour. The produced R-HiPIMS sample was highly metallic, with no nitride phase detected. The MAR-HiPMS film, however, was stoichiometric and exhibited (0002) direction texturing, with an optical bandgap of approx. 1.5 eV, electron concentration of 2.72 × 1020 cm−3 and electron mobility of 7.16 cm2V−1 s−1 (in the range for polycrystalline InN).

High-temperature tribological performance of the Si-gradually doped diamond-like carbon film

Silicon containing diamond-like carbon films is of value for engineering applications operating at the temperature above 200 °C. This work presents a Si-gradually doped diamond-like carbon film with increasing the Si content from outer layer to inner layer deposited by plasma-assisted reactive magnetron sputtering process. The microstructure, chemical bonding state and temperature-dependence tribological properties upto 500 °C of the film are investigated by using focused ion beam/transmission electron microscope (FIB/TEM), X-ray photoelectron spectroscopy (XPS) techniques and ball-on-disk tribometer, respectively. The results show that the as-deposited Si-gradually doped DLC film exhibit amorphous structure. The wear track tested at 500 °C are composed of carbon, SiO2 and silicon oxide. High-temperature tribological tests show that the friction coefficient values are 0.05 ± 0.01, 0.02 ± 0.004 and 0.09 ± 0.04, while the wear rates are 1.17 × 10−7 mm3/N·m, 1.65 × 10−7 mm3/N·m and 1.4 × 10−6 mm3/N·m at 300 °C, 400 °C and 500 °C, respectively. It is proposed that the improved high-temperature tribological properties of the Si-gradually doped DLC film benefit from its special composition structure that the inner layer with high Si content provides the required mechanical properties and the outer layer with low Si content reduces the friction coefficient as well as the wear rate.

Improving high temperature tribological performances of Si doped diamond-like carbon by using W interlayer

Diamond-like carbon films (DLC) with different silicon contents combined with W interlayer are deposited by plasma-assisted reactive magnetron sputtering. The structures and high-temperature tribological properties of the films are investigated. The results reveal that the pure DLC film is worn out at 400 °C because of graphitization, while the Si-DLC film with Si content of 4.56 at.% keeps low friction coefficient (0.2–0.05) at high temperature up to 500 °C. The 14.56 at.% Si-DLC film failed at 500 °C induced by the formation of SiO2. The improved high-temperature tribological performance of the 4.56 at.% Si-DLC film is attributed to the tribochemistry of W interlayer at 500 °C which formed a film composed of tungsten oxides and carbide.

High-performance thin-film optical filters with stress compensation.

We present a thorough description of high-performance thin-film optical filters with high flatness. These components can combine several tens or hundreds of layers and are manufactured using plasma-assisted reactive magnetron sputtering. Stress compensation is achieved using dual-side coatings with appropriate spectral function. Examples are described of highly reflecting mirrors at 515 nm with 15 nm flatness peak-to-valley up to and over 75 mm diameter aperture, narrow bandpass filters, and filters with broadband controlled transmission.

Effects of post-deposition plasma treatments on stability of amorphous InGaZnOx thin-film transistors prepared with plasma-assisted reactive magnetron sputtering

Effects of post-deposition plasma treatments on the stability of amorphous InGaZnOx thin-film transistors (TFTs) prepared with plasma-assisted reactive magnetron sputtering were investigated. The temporal evolution in the electrical characteristics of as-deposited IGZO TFT and post plasma treated IGZO TFT that passed over 400 d after fabrication and were kept under 40% humidity at room temperature were measured, resulting in which no change in the electrical characteristics of post plasma treated IGZO TFT with mobility of 40 cm2 V−1 s−1 were observed. Positive-current-bias instability in post plasma treated IGZO TFTs was examined together with as-deposited IGZO TFTs. The results indicated that the stabilities of electrical characteristics caused by the positive bias stress is primarily attributed to defects in the bulk a-IGZO region for as-deposited IGZO TFTs. The stabilities of electrical characteristics in post plasma treated IGZO TFTs were considerably improved compared to that of as-deposited IGZO TFTs. From these results, it was shown that the post plasma treatment is considered to be effective for improving the stability of IGZO TFTs as well as conventional thermal annealing.

Low-temperature formation of c-axis-oriented aluminum nitride thin films by plasma-assisted reactive pulsed-DC magnetron sputtering

The low-temperature formation of c-axis-oriented aluminum nitride thin films was demonstrated by plasma-assisted reactive pulsed-DC magnetron sputtering. The effects of the duty cycle at the pulsed-DC voltage applied to the Al target on the properties of AlN films formed via inductively coupled plasma (ICP)-enhanced pulsed-DC magnetron sputtering deposition were investigated. With decreasing duty cycle at the target voltage, the peak intensity of AlN(0002) increased linearly. The surface roughness of AlN films decreased since there was an increase in film density owing to the impact of energetic ions on the films together with the enhancement of nitriding associated with the relative increase in N radical flux. The improvement of both the crystallinity and surface morphology of AlN films at low temperatures is considered to be caused by the difference between the relative flux values of ions and sputtered atoms.

Complex optical interference filters with stress compensation for space applications

We present hereafter a study of complex bandpass optical interference filters with central wavelengths ranging in blue region or in the near infrared. For these applications, the required functions are particularly complex as they must present a very narrow bandwidth as well as a high level of rejection over a broad spectral range. Moreover, these components must have a good flatness meaning that the stress induced by the different layers has to be taken in account in the filter design. We present a thorough study of these filters including their design, fabrication using Plasma Assisted Reactive Magnetron Sputtering (PARMS) and characterization. Excellent agreement between experimental and theoretical spectral performances associated with a final sag of 326 and 13 nm, and uniformity from −0.05 to 0.10 and −0.10 to 0.20% are demonstrated for the two manufactured filters.

Al-Si-N/a-SiN:H thin-film coating for polycarbonate glazing applications

To improve the scratch resistance and UV weatherability of polycarbonate (PC), a protective layer consisting of a transparent Al-Si-N thin film of high hardness and a UV-blocking a-SiN:H (hydrogenated amorphous Si-N) thin film was studied using inductively coupled plasma-assisted reactive magnetron sputtering at room temperature. Transparent and hard Al-Si-N thin films with Si contents of 5-45 at% were deposited and characterized. Further, to protect PC from UV radiation below 300 nm in wavelength, UV-blocking a-SiN:H thin films were deposited at different H2 flow rates ranging from 2 to 8 sccm. The average transmittance of 460 nm thick Al-Si-N thin films was measured to be greater than 80% in the visible spectral range, and the maximum hardness of 31 GPa was obtained at 24 at% Si content. The UV transmittance of 140 nm thick a-SiN:H thin films was found to be less than 3% at wavelengths shorter than 300 nm. The double-layer structure of Al-Si-N (460 nm)/a-SiN:H (140 nm) showed a hardness of 29 GPa and an average transmittance of 78% for visible light along with a UV transmittance of less than 3%. In this study, the protective coating layer deposition for PC glazing applications was developed and characterized.

Industrial-scale deposition of highly uniform and precise optical interference filters by the use of an improved cylindrical magnetron sputtering system

The manufacture of precision optical interference coatings requires a process with sufficient accuracy, precision, uniformity, and stability to produce economic quantities of coatings with acceptable yield. This paper compares the capabilities of the plasma assisted reactive magnetron sputtering (PARMS) process with the compound-assisted reactive sputtering process (CARS). Compared with PARMS, CARS exhibited superior process accuracy, stability and uniformity by being less sensitive to equipment and process temperatures, and to cathode and machine conditioning. A uniformity deviation of less than ±0.15% is demonstrated for different optical multilayer filters over substrates of 200mm diameter. The CARS process stability and precision are also demonstrated using many coating runs of a sensitive, broadband antireflective coating without the need for optical monitoring. Thus, it is shown that CARS combines the advantages of the Metamode (high stability) and the PARMS process (low optical absorption).

Phase stability, mechanical properties and thermal stability of Y alloyed Ti–Al–N coatings

The increasing demand for Ti1−xAlxN protective coatings, especially when applied on cutting and milling tools, trigger further studies to enhance their wear performance at high-temperature conditions. To obtain requirements such as high oxidation and corrosion resistance and simultaneously high hardness and elasticity, the formation of quaternary alloys with 4d–transition metals such as yttrium (Y) is a promising approach. In order to study the impact of varying Al and Y content on the industrially preferred cubic structure of Ti1−xAlxN, several Ti1−x−yAlxYyN coatings were deposited using a plasma-assisted reactive magnetron sputtering process. Decreasing Y and Al content favour the formation of the single phase cubic structure. The thermal stability of coatings with single-phase cubic structure was carried out by annealing experiments in vacuum and ambient atmosphere. An increase in hardness of about 10% can be assigned to age-hardening effects which result in its hardness maximum of ≈32.4GPa for Ta=1200°C for Ti0.51Al0.47Y0.02N. The formation of wurtzite structured AlN can be observed for annealing at temperatures above 1100°C. Oxidation experiments (20h at ≈850°C) result in the formation of the typically layered oxide scale (Al2O3 and Ti-rich oxides) on top of the Ti1−x−yAlxYyN coating. For Ti0.51Al0.47Y0.02N, the consumed nitride layer thickness is with ≈20% of the ~3.5-μm film thickness, the minimum of the coatings investigated. In contrast to this, Y free coatings are fully oxidised after 20h annealing in ambient atmosphere at ≈850°C.

유도결합 플라즈마 스퍼터링 장치에서 MgO의 반응성 증착 시 공정 진단

Process analysis was carried out during deposition of MgO by inductively coupled plasma assisted reactive magnetron sputtering in Ar and <TEX>$O_2$</TEX> ambient. At the initiation of Mg sputtering with bipolar pulsed dc power in Ar ambient, total pressure showed sharp increase and then slow fall. To analyse partial pressure change, QMS was used in downstream region, where the total pressure was maintained as low as <TEX>$10^{-5}$</TEX> Torr during plasma processing, good for ion source and quadrupole operation. At base pressure, the major impurity was <TEX>$H_2O$</TEX> and the second major impurity was <TEX>$CO/N_2$</TEX> about 10%. During sputtering of Mg in Ar, <TEX>$H_2$</TEX> soared up to 10.7% of Ar and remained as the major impurity during all the later process time. When <TEX>$O_2$</TEX> was mixed with Ar, the partial pressure of Ar decreased in proportion to <TEX>$O_2$</TEX> flow rate and that of <TEX>$H_2$</TEX> dropped down to 2%. It was understood as Mg target surface was oxidized to stop <TEX>$H_2$</TEX> emission by Ar ion sputtering. With ICP turned on, the major impurity <TEX>$H_2$</TEX> was converted into <TEX>$H_2O$</TEX> consuming <TEX>$O_2$</TEX> and C was also oxidized to evolve CO and <TEX>$CO_2$</TEX>.

Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications

Thin films of aluminum oxide (Al2O3), tantalum pentoxide (Ta2O5), titanium oxide (TiO2), yttrium oxide (Y2O3) and zirconium oxide (ZrO2) were deposited by plasma assisted reactive dual magnetron sputtering to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The effect of deposition parameters such as cathode, plasma power and oxygen gas flows were studied and the operational working points were determined. Both power and lambda control were used to optimize the optical quality of each material. By using lambda control feedback system, the magnetron power fluctuates to sustain a fixed oxygen flow in the target area reducing the compound layer growth on the material and maintaining a healthy deposition rate. The optical properties, structure and crystalline phase of each film were found to be dependent on the process parameters. X-ray diffraction (XRD) analysis revealed that the thin films varied from amorphous to highly crystalline depending on the deposition conditions. X-ray photoelectron spectroscopy (XPS) was utilized for surface compositional analysis revealing that films had varying stoichiometric ratios which are controlled for each material by the deposition parameters chosen. The waveguide loss for the thin film layers was investigated and Ta2O5 was shown to have a slab waveguide loss of ~1dB/cm at both visible and infra-red wavelengths making it ideal for planar waveguide and laser applications. TiO2, Y2O3 and ZrO2 were found to deposit in a highly crystalline phase. Waveguiding in the TiO2 layers was not possible at 633nm or in the infrared region. The Y2O3 samples gave low loss (2–4dB/cm) at the 1.3 and 1.5μm wavelengths but no waveguiding at 633nm or 833nm was possible. Atomic force microscopy showed rough surface topography for TiO2, Y2O3 and ZrO2 akin to their crystalline growth with the SEM images confirming the regular crystalline columnar structure for the case of Y2O3 and ZrO2.

Electronic origin of structure and mechanical properties in Y and Nb alloyed Ti–Al–N thin films

Abstract Ti1–xAlxN thin films are industrially well established protective coatings, whose beneficial mechanical properties are mainly based on the formation of a metastable microstructure and local composition during film synthesis. Alloying of a transition metal (TM) to Ti1–xAlxN is a promising approach to reach yet higher oxidation and corrosion resistance in high-temperature environments, while maintaining a high intrinsic hardness and elasticity, being essential for a good wear performance. In order to study the effect of alloying with Y and Nb on the structure and mechanical properties of the industrially preferred cubic (c) Ti1–xAlxN system, quaternary Ti1–x–zAlxYzN and Ti1–x–zAlxNbzN films were deposited by means of plasma-assisted reactive magnetron sputtering and investigated using X-ray diffraction, transmission electron microscopy and nanoindentation. It is shown that Y addition to c-Ti0.42Al0.58N changes its structure towards single phase wurtzite (w) Ti0.36Al0.55Y0.09N, with deteriorated mec...

等离子体辅助反应磁控溅射法沉积金属氧化物薄膜

等离子体辅助反应磁控溅射法沉积金属氧化物薄膜

Ion bombardment-induced enhancement of the properties of indium tin oxide films prepared by plasma-assisted reactive magnetron sputtering

Research on tin doped indium oxide (ITO) has for many years been stimulated by the need to simultaneously optimize the electrical, optical and mechanical properties, and by new challenges related to the deposition of transparent conducting oxides on flexible plastic substrates. In the present work, we investigate the growth and optical, electrical, and mechanical (hardness, elastic modulus and stress) properties of ITO films deposited by plasma assisted reactive magnetron sputtering (PARMS) from an indium-tin alloy target. PARMS achieves an effective control of bombardment by reactive species (e.g., O 2 +, O +) on the surface of the growing film by varying the bias voltage, V B, induced by a radiofrequency power applied to the substrate. Stress-free films possessing high transparency (> 80% — film on glass) and low resistivity (4 × 10 − 4 Ω cm) can be deposited by PARMS under conditions of intense ion bombardment (≤ 600 eV).

Microstructure and properties of nanocrystalline titanium monoxide films synthesized by inductively coupled plasma assisted reactive direct current magnetron sputtering

Titanium oxide films were deposited on unheated glass substrates by using inductively coupled plasma assisted reactive direct current magnetron sputtering. X-ray diffraction, X-ray photoelectron spectroscopy and field emission scanning electron microscope were used to analyze film structure, composition and morphology. Analysis results revealed the formation of titanium monoxide film rather than titanium dioxide film. Golden yellow nanocrystalline titanium monoxide film with a very high degree of crystallinity was formed under metallic mode of sputtering at lower temperature of <200 °C. Annealing of the golden yellow titanium monoxide film at 600 °C in the open air changed film structure to include rutile-type titanium dioxide.

Nanocrystalline vanadium oxide films synthesized by plasma-assisted reactive rf sputtering deposition

Plasma-assisted reactive rf magnetron sputtering deposition is used to fabricate vanadium oxide films on glass, silica and silicon substrates. The process conditions are optimized to synthesize phase-pure vanadium pentoxide (V2O5) featuring a nanocrystalline structure with the predominant (0 0 1) crystallographic orientation, surface morphology with rod-like nanosized grains and very uniform (the non-uniformity does not exceed 4%) coating thickness over large surface areas. The V2O5 films also show excellent and temperature-independent optical transmittance in a broad temperature range (20–95 °C). The results are relevant to the development of smart functional coatings with temperature-tunable properties.

Novel low-temperature photocatalytic titania films produced by plasma-assisted reactive dc magnetron sputtering

Robust, active, anatase titania films, 250 nm thick, are deposited onto glass at low temperatures, i.e., <100 °C, using plasma-assisted, reactive dc magnetron sputtering (PAR-DC-MS). The films are transparent and colourless and truly photocatalytic, exhibiting turnover numbers >2.0 for the photocatalytic mineralization of stearic acid. These films are typically 6.9 times more active than a sample of commercial self-cleaning glass, comprising a 15 nm layer of titania deposited by CVD, mainly because they are much thicker and, therefore, absorb more of the incident UV light. The most active of the films tested comprised particles of P25, but lacked any significant physical robustness. Similar results, but much more quickly obtained, were generated using a photocatalyst-sensitive ink, based on the redox dye, resazurin, Rz. All titania films tested, including those produced by magnetron sputtering exhibited photo-induced superhydrophilicity. The possible future application of PAR-DC-MS for producing very active photocatalytic films on substrates not renowned for their high temperature stabilities, such as plastics, is noted.