Direct Current Magnetron Sputtering Research Articles

Correlation between physical properties and electrochromic performances of DC magnetron sputtered a-WOx thin films

Tungsten oxide thin films were grown on different substrates by the conventional process of direct current magnetron sputtering. A series of amorphous WOx (a-WOx) films, with variable stoichiometry and porosity, were achieved with different total pressure (Pt) induced by oxygen flow rate (Q(O2)) variation. The objective of this study is to determine the couple (Q(O2); Pt) necessary to achieve optimal electrochromic performances of WOx and also study the correlation between physical properties and electrochromic performances. The WOx films optical transmittance evolved from opaque to transparent with the increase of Q(O2). A degradation of films refractive index and the increase of their porosity, both mainly due to the increase of Pt, were observed. The Raman spectroscopy indicated the presence of different W valence states in the as deposited a-WOx films. They all contain W4+, but W6+ were found only into transparent or semi-transparent films. A weak peak of W5+ was observed into the semi-transparent film. Electrical properties studied by Metal-Oxide-Semiconductor structures showed a decrease of the oxide capacitance when Q(O2) and Pt increase. The WOx transparent and optically reversible films, deposited with lower values of (Q(O2); Pt), i.e., Q(O2) = 4.5 sccm and 6 sccm, and Pt = 1.13 Pa and 1.37 Pa, respectively, exhibited the highest values of WOx/Si interface traps average density and positive ions density (Nss). The positive Nss reflects the oxygen deficiency amount in the films. These films were resistive to the discoloration process but showed the highest coloration efficiency CE632nm = 44.4 cm2/C and 42.2, respectively. Their coloration times were tc = 19 s and 22 s, and their discoloration times were td = 180 s and 75 s, respectively. They exhibited the highest optical modulation close to Δ T632nm = 76 %.

Investigate the heat conduction between film and substrate during sputtering process by multi-layer structure NiCr/NiSi film thermocouples

The three layers of structure NiCr/NiSi film thermocouples (TFTCs) were deposited onto the glass substrate by the direct current pulsed magnetron sputtering technique. The hot junctions of three TFTCs were overlapped. Between the hot junctions, SiO2 insulation films were deposited. Then, the heat conduction between TiO2 film and substrate was investigated. The results showed that at the initial stage of TiO2 film growth, the electromotive force (EMF) of top TFTC was higher than that of middle TFTC. EMF difference between top and middle TFTCs increased with time. Meanwhile, EMF of bottom TFTC was also higher than that of middle TFTC. EMF difference between bottom and middle TFTCs increased with time. Until the critical time, the middle TFTC received the heat conduction from TiO2 film and substrate. At the critical time, EMF difference between top and middle TFTCs, as well as between bottom and middle TFTCs, reached the maximum, which meant the heat conduction equilibrium state between top, middle, and bottom TFTCs. Then, because of the heat conduction from hot junction to pads of TFTCs, EMF difference between top and middle TFTCs, as well as between bottom and middle TFTCs, both decreased with time.

Structural and Mechanical Properties of CrN Thin Films Deposited on Si Substrate by Using Magnetron Techniques

Chromium nitride thin films are known for their good mechanical properties. We present the characteristics of ultrathin chromium nitride films under 400 nm thickness deposited on silicon substrates by direct current and high-power impulse magnetron sputtering techniques. The methods of investigation of the CrN films were scanning electron microscopy, atomic force microscopy, and nanoindentation. Qualitative and quantitative analyses were performed using AFM and SEM images by fractal dimension, surface roughness and gray-level co-occurrence matrix methods. Our results show that using magnetron techniques, ultrathin CrN films with excellent mechanical properties were obtained, characterized by values of Young’s modulus between 140 GPa and 250 GPa for the samples obtained using high-power impulse magneton sputtering (HiPIMS) and between 240 GPa and 370 GPa for the samples obtained using direct current sputtering (DC). Stiffness measurements also reveal the excellent mechanical properties of the investigated samples, where the samples obtained using HiPIMS sputtering had stiffness values between 125 N/m and 132 N/m and the samples obtained using DC sputtering had stiffness values between 110 N/m and 119 N/m.

Evolution of the Shadow Effect with Film Thickness and Substrate Conductivity on a Hemispherical Workpiece during Magnetron Sputtering

When depositing films on a complex workpiece surface by magnetron sputtering, the shadow effect occurs and causes the columnar structure to tilt toward the substrate owing to the oblique incident angle of the plasma flux, affecting the microstructure and properties of the films. Improving the surface diffusion could alleviate the shadow effect, whereas changing the energy of the deposited particles could improve surface diffusion. Different substrate conductivities could affect the energy of the deposited particles when they reach the substrate. In this study, Si (semiconductor) and SiO2 (insulator) sheets are mounted on the inner surface of a hemispherical workpiece, and Ti films with different thicknesses (adjusted by the deposition time) are deposited on the inner surface of the hemispherical workpiece by direct current magnetron sputtering. The results show that there is a threshold thickness and incident angle before the films are affected by the shadow effect. The threshold could be affected by the film thickness, the incident angle, and the conductivity of the substrate. The threshold would decrease as the film thickness or incidence angle increased or the conductivity of the substrate decreased. When the film thickness or incident angle does not reach the threshold, the film would not be affected by the shadow effect. In addition, the film deposited later would tilt the vertical columnar structure of the film deposited earlier. Owing to the different conductivities, the shadow effect manifest earlier for Ti films deposited on the insulator SiO2 than for films deposited on the semiconductor Si when the film thickness is >500 nm.

Preparation and Structural Investigation of Ultra-Uniform Mo Films on a Si/SiO2 Wafer by the Direct-Current Magnetron Sputtering Method

As a kind of important strategic resource, molybdenum (Mo) and its alloys are widely applied in solar cells and 5G radio frequency filters. In order to improve the yield of industrial production, it is important to reduce the nonuniformity of thin-film thickness. We prepared Mo films on CMOS compatible Si/SiO2 wafers through a magnetron sputtering method and systematically investigated the effect of tuning of several process parameters on film thickness nonuniformity and other structural properties, including crystallite size (D), microstrain (ε), and dislocation density (δ). At optimized sputtering power (80 W), chamber pressure (0.4 Pa), argon flow rate (90 sccm), substrate temperature (350 °C), and target–substrate distance (9 cm), the deposited 200 nm-thick Mo films show a unified <110> preferred orientation, and the film thickness nonuniformity reaches an excellent value of 0.46%, with a surface roughness of 0.83 nm and the full width at half maximum (FWHM) of X-ray diffraction (XRD) (110) rocking curve as low as 0.47°. Our results provide efficient reference for the preparation of uniform metal films, which have potential for improving the quality and yield in filter device manufacturing.

Effect of Microstructure of TiN /TiCN Layer on the Structural, Mechanical and Tribological Properties of the Ti/TiN/TiCN Films

A direct current magnetron sputtering (DCMS) system at room temperature was applied to deposit the Ti/TiN/TiCN films. In order to research the effect of the microstructure of the TiN/TiCN layer on the Ti/TiN/TiCN films, the deposition time ratio of the TiN/TiCN layer ranged from 28.57 to 200%, and the whole deposition time of the films and the deposition time of Ti layer were constant. In this work, the relationship between structure and mechanical properties of films were investigated. The research results showed that the composition and structure of the films only slightly changed, while the crystalline orientation of the TiCN layer was of significant variation with the deposition time of the TiN layer. It is shown that the adhesion strength and internal stresses were 18.6 ± 1.5 N and 140 MPa when the deposition time ratio was 50%. By adjusting the deposition time ratio, the films displayed significant improvement in tribological behaviors. The coefficients of friction (COF) for the films deposited under deposition time ratio of 50% were about only 0.139 when the value of COF was stabilized. This work can provide a good wear-resisting film prepared approach at room temperature.

SiO2: A Novel Electrolyte for High-Performance All-Solid-State Electrochromic Devices

For the practical application of electrochromic devices (ECDs), the development and preparation of high-performance electrolyte materials is one of the urgent problems to be solved. In this work, an all-solid-state ECD with the integrated structure of glass/ITO/WO3/Li/SiO2/NiO/ITO has been prepared by the magnetron sputtering method. The amorphous SiO2 film prepared by pulsed direct current reactive magnetron sputtering was used as the electrolyte layer in the ECD for the first time and shows promising potential due to its ultrahigh transparency, good intrinsic electronic insulation, and loose structure for fast ion conduction. The ECD exhibits low leakage current density (8.5 μA cm–2 for bleaching and 43.4 μA cm–2 for coloring), high optical modulation (ΔT = 71.9% at 707 nm), fast response speed (1.1 s for the bleaching process and 8.5 s for the coloring process), excellent cycle stability, and high coloration efficiency (126.4 cm2 C–1). This work not only indicates that SiO2 as a dielectric material can be used as the electrolyte layer in all-solid-state ECDs but also provides new avenues in the selection of electrolyte materials for the preparation of high-performance ECDs.

A-phase tantalum film deposition using bipolar high-power impulse magnetron sputtering technique

In this study, a method for forming a highly adhesive and ductile α-phase tantalum film on 304 stainless steel using the bipolar high-power impulse magnetron sputtering (bipolar HiPIMS) technique was investigated. The growth of brittle β-phase tantalum, which is commonly formed when using conventional direct current magnetron sputtering methods (DCMS) at room temperature, was prevented by the high-energy ions directed toward the growing films. The results showed the formation of an extremely thin (<70 nm) α-phase tantalum film without any additional processes, such as substrate biasing or heating. In addition, a high adhesion strength exceeding 45 MPa, broadened intermixed layer, and nanocrystalline microstructure were achieved by the effect of positive voltage. These results indicate that the bipolar HiPIMS technique is a facile deposition method for modifying the substrate surface and forming high-quality crystalline films. Our tantalum films are optimized to protect substrates against corrosion in severely harsh mechanical, chemical, and thermal environments. To confirm the superiority of the bipolar HiPIMS technique over HiPIMS and DCMS, the properties of the films formed using the three methods were analyzed via X-ray diffraction, Auger electron spectroscopy, atomic force microscopy, scanning electron microscopy, and pull-off adhesion testing.

Effect of substrate bias on the microstructure and mechanical and tribological properties of ZrNbTiMo refractory high entropy alloy film

ZrNbTiMo refractory high entropy alloy (RHEA) films were deposited via direct current magnetron sputtering under different substrate biases (0 to −200 V). The phase structure, microstructure, surface roughness, mechanical, and tribological properties of the ZrNbTiMo RHEA films were investigated. Results show that the ZrNbTiMo RHEA films exhibit a single body-centered-cubic structure. As the substrate bias increases, the preferred orientation of the ZrNbTiMo RHEA films changes from (110) to (200). The surface roughness of the films decreases from 3.9 nm to 2.0 nm then increases to 4.1 nm. The growth mechanism can be understood as the result of the interaction of ion incident direction, ion bombardment effect, and atom diffusion ability which are controlled by the substrate biases. The hardness of the films increases from 6.8 GPa (0 V) to 21.3 GPa (−200 V). The maximum fracture toughness (0.968 MPa × m1/2) is obtained under −200 V. The wear resistance does not exhibit a monotonically increasing trend with the increase of substrate bias. The films deposited under −50 and − 100 V have lower values of H/E and H3/E2, but these films still possess better wear resistance. The wear mechanism of the ZrNbTiMo RHEA films is investigated in detail from the microstructure perspective.

DC PLANAR MAGNETRON SPUTTER DEPOSITION OF BORON THIN FILMS AND THEIR PROPERTIES

In this study, boron thin films were deposited on metal substrates using planar direct current (DC) magnetron sputtering with a pure boron target. Boron has high electrical resistance, severely impeding its application in a magnetron discharge; however, it is a semiconductor and its resistance decreases as the temperature increases. We used a planar magnetron with a boron target that was heated in a DC discharge current up to 50 mA in argon and nitrogen at a pressure of 2-3 mTorr. For these discharge parameters, at a distance of 5 cm from the target the boron deposition rate was about 150 nm/h. Thin boron films with thickness up to 1 &amp;mu;m were obtained and their surface morphology was studied. The deposition technique and the properties of the films are discussed.

Tungsten oxide thin film for room temperature nitrogen dioxide gas sensing

Tungsten oxide (WO3) thin films for gas sensing have been successfully deposited using reactive direct current (DC) magnetron sputtering at different deposition temperatures (300 °C, 400 °C and 500 °C). The structural, morphological properties, thickness and composition have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering spectrometry (RBS) techniques. To investigate the effect of deposition temperature on the gas sensing properties of deposited thin films on alumina substrates, was conducted using the Kenosistec gas sensing unit. WO3 thin film deposited at 500 °C exhibited a higher response when sensing Nitrogen dioxide (NO2) at room temperature as compared to the thin films prepared at 300 °C and 400 °C, respectively. However, as deposited WO3 thin films exhibited low sensitivity when sensing reducing gases such as hydrogen (H2) and ammonia (NH3), which was an indication of good selectivity properties of WO3 related sensors.

High performance inorganic all-solid-state electrochromic devices based on Si3N4 ion conducting layer

In electrochromic devices (ECDs), ion conducting layer has the vital function of conducting ions and blocking electrons. However, the limited electron blocking ability and preparation technology of conventional ion conducting materials hinder the commercial application of all-solid-state ECDs. In this work, a novel ion conducting material Si 3 N 4 film was deposited by pulsed direct current (p-DC) reactive magnetron sputtering with a Si target, and shows promising potential due to its ultrahigh transparency, anti-reflection effect and remarkable electron blocking ability. An ECD with the structure of glass/ITO/WO 3 /Li/Si 3 N 4 /NiO/ITO has been fabricated by magnetron sputtering, in which Si 3 N 4 film was used as ion conducting layer for the first time. The ECD presents much less leakage current density (<35 μA cm −2 ), large optical transmittance modulation (72.3% at 625 nm), fast response (1.3 s for bleaching and 13.1 s for coloring), high coloration efficiency (94.46 cm 2 C −1 ) and excellent cycle stability (91.4% retention of the maximum optical modulation after 10,000 cycles). This work not only demonstrates the great prospect of Si 3 N 4 film as an ion conducting layer in ECDs, but also provides a new idea in the selection of ion conducting materials for developing high-performance inorganic all-solid-state ECDs. • The Si 3 N 4 film is used as an ion conducting layer in ECDs for the first time. • Si 3 N 4 film was prepared by pulsed DC reactive magnetron sputtering. • The Si 3 N 4 film exhibits ultrahigh transparency and anti-reflection effect. • The Si 3 N 4 -based all-solid-state ECD shows large optical modulation 72.3% at 625 nm. • The ECD displays superior cycle stability over 10,000 cycles.

Diblock copolymer pattern protection by silver cluster reinforcement.

Pattern fabrication by self-assembly of diblock copolymers is of significant interest due to the simplicity in fabricating complex structures. In particular, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) is a fascinating base material as it forms an ordered micellar structure on silicon surfaces. In this work, silver (Ag) is applied using direct current magnetron sputter deposition and high-power impulse magnetron sputter deposition on an ordered micellar PS-b-P4VP layer. The fabricated hybrid materials are structurally analyzed by field emission scanning electron microscopy, atomic force microscopy, and grazing incidence small angle X-ray scattering. When applying simple aqueous posttreatment, the pattern is stable and reinforced by Ag clusters, making micellar PS-b-P4VP ordered layers ideal candidates for lithography.

Structural, optical and electrical characterizations of Mg/Ti/Ni multilayer thin films deposited by DC magnetron sputtering for hydrogen storage

Magnesium (Mg) based alloys are the most promising hydrogen storage and fuel cell alloys due to their high hydrogen content. In the present work, multilayer thin films (Mg/Ti/Ni) were prepared using direct current (DC) magnetron sputtering method. Multilayered Mg/Ti/Ni thin films were investigated by analyzing the data of different characterizations such as surface, structural, optical and electrical. Uniformity of the deposited thin films was analyzed by Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive Spectrometry (EDS) confirmed the presence of elemental composition. X-ray Diffractometer (XRD) was used to analyze structural characteristics of annealed thin films before and after hydrogenation. The variation in optical absorption and band gap has been observed, with the hydrogenation of thin film and having a larger band gap (3.27 eV) as compared to annealed thin films (2.81 eV). The semiconducting behavior of films is revealed by current voltage (I–V) characteristics of the films, and conductivity reduces after annealing and hydrogenation i.e. from 6.36 to 1.41 kΩ−1cm−1. Furthermore, Hall mobility of annealed without hydrogenated and annealed with hydrogenated thin film was improved (in the order of 103) as compared with as-deposited film. Improvement certainly helps the movement of hydrogen particularly after hydrogenation, the accumulation of hydrogen, particularly at the thin film's interface, obstructs the flow of electrons, resulting in a decrease in thin film conductivity. As a result, multilayer Mg/Ti/NI thin films are the good choice in the consideration for solid state hydrogen storage purpose.

Deposition of Ga2O3 thin films by liquid metal target sputtering

This paper reports on the deposition of amorphous and crystalline thin films of Ga2O3 by reactive pulsed direct current magnetron sputtering from a liquid gallium target onto fused (f-) quartz and c plane (c-) sapphire substrates, where the temperature of the substrate is varied from room temperature (RT) to 800 °C. The deposition rate (up to 37 nm/min at RT on f-quartz and 5 nm/min at 800 °C on c-sapphire) is two to five times higher than the data given in the literature for radio frequency sputtering. Deposited onto unheated substrates, the films are X-ray amorphous. Well-defined X-ray diffraction peaks of β-Ga2O3 start to appear at a substrate temperature of 500 °C. Films grown on c-sapphire at temperatures above 600 °C are epitaxial. However, the high rocking curve full width at half maximum values of ≈2.4–2.5° are indicative of the presence of defects. A dense and void-free microstructure is observed in electron microscopy images. Composition analysis show stoichiometry close to Ga2O3 and no traces of impurities. The optical properties of low absorptance (<1%) in the visible range and an optical band gap of approximately 5 eV are consistent with the data in the literature for Ga2O3 films produced by other deposition methods.

Influence of the deposition process and substrate on microstructure, phase composition, and residual stress state on as-deposited Cr-Al-C coatings

This paper focuses on the influence of the High Power Pulsed Magnetron Sputtering (HPPMS) and Direct Current Magnetron Sputtering (DCMS) coating deposition processes, the bias voltage, deposition temperature, and substrate on various properties of the as-deposited state of Cr-Al-C thin films. Three substrates with different coefficients of thermal expansion and electrical conductivity were used. To investigate the microstructure, phase composition, residual stress state, and mechanical properties, ex-situ and in situ synchrotron experiments were conducted accompanied by electron microscopy and nanoindentation. As-deposited Cr-Al-C coatings consisted of amorphous and crystalline areas, with the ratio highly dependent on the deposition process and substrate. The crystalline phase was identified as metastable (Cr,Al)2C. The highest crystallinity was determined for DCMS coatings. Increasing temperature and decreasing bias voltage increased coating crystallinity for HPPMS coatings. The influence of the deposition process and bias voltage was highly reduced for the substrate with low electrical conductivity. In-situ investigations of the stress state of amorphous areas revealed, that those were acting as a residual stress buffer. The hardness and Young’s modulus of the coatings were found to increase with crystallinity and were slightly increased for crystalline HPPMS coatings compared to DCMS coatings.

Damage to OSG low‐k films during IPVD deposition of the Ta barrier layer

AbstractThe degradation of a porous organosilicate glass low‐k dielectric during the ionized physical vapor deposition of tantalum coating is studied. The main contribution to the damage is made by vacuum UV flux (1014–1015 s–1 cm–2) from the argon inductively coupled plasma of the ionizer, and the effect of the direct current magnetron sputter plasma is small. The damage by vacuum ultraviolet photons with an energy exceeding the band gap of the SiO2 matrix is associated not only with the removal of carbon‐containing groups (terminal CH3 and bridging CH2) but also with the breaking of Si–O bonds in the Si–O–Si matrix followed by the formation of hydrophilic Si–OH and Si–H groups. Consequently, the degree of damage can be much higher than would be expected from the depth of CH3 group depletion.

Enhancing ultraviolet response of NiO/Si heterojunction by high temperature anneal

In this work, NiO/Si heterojunction is fabricated by direct current reactive magnetron sputtering process and the effect of post anneal temperature on ultraviolet response of the heterojunction is investigated. The results indicate that the dark current is decreased and the light current is increased with annealing temperature increasing in the fabricated NiO/Si heterojucntion. When illuminated under 365 nm UV light with an intensity of 1.0 mW/cm2, the light to dark switch ratio of the fabricated NiO/Si heterojunction annealed at 800 °C is about 486.1. The corresponding ultraviolet response is enhanced by about 83.8 times compared to the heterojucntion without anneal. The switch-on and switch-off time of the 800 °C annealed NiO/Si heterojunction illuminated under 365 nm UV light are about 100 μs and 180 μs, respectively. It is expected that the NiO/Si heterojunction has enormous potential in multi-wavelength light detecting application.

Tantalum microwave resonators with ultra-high intrinsic quality factors

We acquire tantalum thin film in its α phase (α-Ta) using direct-current magnetron sputtering. According to x-ray diffraction results, 110-Ta is dominant. Quarter-wavelength coplanar waveguide resonators are fabricated with the α-Ta film and characterized at millikelvin in a dilution refrigerator. In the single photon regime, an intrinsic quality factor (Qi) up to 3×106 is obtained in these resonators. At high power, Qi rises to 6×106. Moreover, we also fabricate an array with 7 × 7 lumped element resonators using the α-Ta film. The array shows excellent uniformity. At high power, Qis of all pixels exceed 1×106. In the single photon regime, Qis of over 90% pixels exceed 1×106. Superconducting quantum computing and ultrasensitive electromagnetic wave detectors will benefit a lot from devices based on the α-Ta film.

Influence of the deposition process on the Cr2AlC phase formation during heat treatment of Cr-Al-C thin films

This paper focuses on the Cr2AlC phase formation during annealing post-treatment, with amorphous Cr-Al-C and (Cr,Al)2C as initial phases in the as-deposited state. The influence of the deposition process on the Cr2AlC formation, texture, and phase composition is investigated and an in-depth discussion of the intermediate phase is carried out. Cr-Al-C thin films were deposited by Direct Current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering with the variation of the deposition temperature. To investigate the microstructure, phase composition, and texture, in situ synchrotron and high-temperature X-ray diffraction experiments were conducted and accompanied by electron microscopy. The Cr2AlC formation can be described as a temperature and time-dependent process with one intermediate state characterized by the formation of the disordered-Cr2AlC phase. Disordered-Cr2AlC shows a similar unit cell to Cr2AlC with an increased c/a ratio. The ratio decreases during the phase formation resulting from an ordering process. Formation temperatures depend on the initial phase, with a decreased formation temperature for (Cr,Al)2C, and the deposition process. While the (002) fiber texture of (Cr,Al)2C inherited to Cr2AlC, Cr2AlC originated from amorphous Cr-Al-C showed no preferred orientation. The coatings contained Cr7C3 as an additional phase, dependent on the deposition process and initial phases.