Sputtering Of Films Research Articles

Magnetic anisotropy and electrical property of CoZrTaB thin films deposited by oblique sputtering

Soft magnetic materials have been studied extensively in recent years due to their applications in micro-transformers, micro-inductors, spin dependent memories etc. Achieving high uniaxial anisotropy is one of the most important properties for these materials. Oblique angle sputtering without the presence of the magnetic field enables the ease thus lower cost of the adoption of magnetic materials in applications. With a highly soft magnetic material, one can operate the devices made out of these films at giga hertz regions without significant loss of efficiency thus desirable for applications such as power conversion and radio frequency (RF) devices. This work focuses on analyzing different growth conditions of thin films of CoZrTaB and the resulting magnetic and electrical properties of the films. Thin films are grown by oblique-angle sputtering, where the sputtering gun forms an angle with respect to the sample substrate normal, ranging from 0 to 75 degrees. External magnetic field normally applied in order to form magnetic anisotropy is not used during film sputtering process. Using vibrating sample magnetometer, it was observed that films resulting from small oblique angles have no clear magnetic anisotropy developed; whereas in samples deposited at large angles close to 60°, there is clear magnetic anisotropy observed. Scanning electron microscopy imaging of the cross-section of film suggests the formation of tilted columns, which is likely to be the reason for magnetic anisotropy. Resistivity of the films was measured systematically and found to increase as the magnitude of oblique angle during sputtering increased.

Preferential sputtering of metal oxide mixture thin films

Metal oxide mixture materials enable the production of dielectric multilayer coatings for highest power laser applications. During thin film deposition, when using sputtering techniques in combination with composite target materials, preferential sputtering occurs on the target surface. The quantitative analysis of the mixture thin film composition, usually performed by ion beam based depth profiling methods, is also affected by preferential sputtering. To gain a deeper understanding, the atomic composition variation of sputtered mixture material surfaces is calculated applying the Monte Carlo simulation program tridyn. The simulation results are compared to the atomic composition gradient measured via depth profiling x-ray photoelectron spectroscopy for mixture thin films composed of HfO2, Sc2O3, Al2O3, and SiO2. The deviations between the experimental and simulated data are discussed with respect to the different mixture material combinations.

Effect of ion bombardment on the properties of Nb2O5 films deposited in large coating chamber

Niobium pentoxide (Nb2O5) films were deposited with dual ion assisted deposition (DIAD) on silicon and corning 7980 substrates, to investigate the effects of ion bombardment on the properties of the films deposited in large coating chamber. In this paper, comparative studies of the optical and structural properties, surface topography and absorption have been conducted. Samples deposited without DIAD had large transmittance loss, low packing density and high absorption. All the Nb2O5 films showed amorphous structures which in line with the sputtering films. The SEM analysis suggested that the films deposited via DIAD possessed densely packed columnar microstructures. The XPS analysis indicates that the vast majority of Nb on these surfaces (deposited with DIAD) is in an oxidized state. The films fabricated with anode voltage of 260 V and anode current of 7.0 A of the two ion sources showed the lowest impurity content as well as the lowest surface roughness and absorption in our experiments.

Effects of RF Magnetron Sputtering Deposition Power on Crystallinity and Thermoelectric Properties of Antimony Telluride and Bismuth Telluride Thin Films on Flexible Substrates

Thermoelectric materials carry significant promise for self-powering future generations of unattended microdevices and wearable devices. The current increased interest in such devices highlights the need for research to provide understanding of the basic material properties of thermoelectric materials, specifically in thin-film form, deposited on flexible polymer substrates. In this study, the surface topography, crystalline structure, and electrical properties of sputtered thin films of two of the most common thermoelectric materials, i.e., antimony telluride (Sb2Te3) and bismuth telluride (Bi2Te3), supported on silicon and polymer substrates were investigated. The study focuses on determining the effect of the sputtering power and underlying substrate on the crystal structure formation as well as grain size of the resulting thin film. Radiofrequency (RF) magnetron sputtering with power levels from 50 W to 200 W was used to deposit these layers on several test structures. The results demonstrate that increasing the RF sputtering power resulted in (i) an increase in the crystalline size (from 0.48 nm to 29.66 nm for Sb2Te3 and from 10.60 nm to 20.29 nm for Bi2Te3), (ii) a significant increase in the content of tellurium (Te) in the Sb2Te3 and Bi2Te3 thin films, (iii) an order-of-magnitude increase in the electrical conductivity of the Bi2Te3 thin film fabricated on silicon wafer, and (iv) a 150% increase in the Seebeck coefficient for both Bi2Te3 and Sb2Te3 samples. Furthermore, surface roughness analysis showed that deposition on polyimide substrate modestly increased the surface roughness (Ra), from 6.59 nm to 9.91 nm for Bi2Te3 and from 12.46 nm to 15.41 nm for Sb2Te3. The electrical resistivity of Bi2Te3 thin films on polyimide was found to be 2.72 × 10−3 Ω m, compared with 1.58 × 10−3 Ω m on silicon substrate, while for Sb2Te3,, the electrical resistivity on polyimide substrate increased to 580 × 10−3 Ω m as compared with 145 × 10−3 Ω m on silicon substrate. Taken together, the results of this work demonstrate that the use of high deposition power during RF sputtering of Sb2Te3 and Bi2Te3 thin films results in significant improvements in their crystallinity, conductivity, and Seebeck coefficient, which are key material properties of great importance for thermoelectric materials.

Synergy of experiment and model for reactive HiPIMS: effect of discharge parameters on WOx composition and deposition rate

Reactive high-power impulse magnetron sputtering of tungsten oxide films using metallic tungsten target (72 mm in diameter) in argon-oxygen atmosphere (total pressure of 0.75 Pa) was carried out. The effect of various discharge parameters on the deposition rate and film oxygen concentration was investigated. Moreover, a model combining a reactive high-power impulse magnetron sputtering model and a discharge plasma model for the ionization region was successfully used for deeper insight into the effect of particular discharge parameters such as voltage pulse length (from 100 –800 µs), oxygen partial pressure (from 0.25–0.50 Pa) or the value of pulse-averaged target power density (from 2.5–500 W cm−2). The results of the presented model, most notably trends in the target- and substrate oxide fraction, composition of particle fluxes onto the substrate, degree of W atom ionization or degree of O2 molecule dissociation are discussed and put into context with experimentally measured quantities.

一种高性能氧化钒热敏薄膜的制备和应用

A method for preparing high performance vanadium oxide thermosensitive thin films and its application were reported. Using reactive magnetron sputtering film deposition technology, the preparation process of vanadium oxide thin films was optimized by changing the sputtering power during the deposition of vanadium oxide thermosensitive thin films, the deposition rate of vanadium atoms was adjusted when they touched the surface of the substrate after being sputtered. At the same time, the equipment was modified and upgraded, that is, a control power supply outside the vanadium sputtering chamber was added to accurately control the sputtering voltage and oxygen partial pressure and other parameters to accurately control the current density in the reaction process. A vanadium oxide film with a sheet resistance of 500 kΩ/□ and a temperature coefficient of resistance (TCR) of −2.7% K−1 was prepared. The experimental results show that the noise equivalent temperature difference (NETD) performance of uncooled infrared focal plane detector made of high-performance vanadium oxide thermal sensitive film is reduced by 30% and the noise is reduced by 28%. The overall performance of the uncooled focal plane detector has been improved significantly.

Effect of Voltage Pulse Width and Synchronized Substrate Bias in High-Power Impulse Magnetron Sputtering of Zirconium Films

The Zr film microstructure is highly influenced by the energy of the plasma species during the deposition process. The influences of the discharge pulse width, which is the key factor affecting ionization of sputtered species in the high-power impulse magnetron sputtering (HiPIMS) process, on the obtained microstructure of films is investigated in this research. The films deposited at different argon pressure and substrate biasing are compared. With keeping the same average HiPIMS power and duty cycle, the film growth rate of the Zr film decreases with increasing argon pressure and enhancing substrate biasing. In addition, the film growth rate decreases with the elongating HiPIMS pulse width. For the deposition at 1.2 Pa argon, extending the pulse width not only intensifies the ion flux toward the substrate but also increases the fraction of highly charged ions, which alter the microstructure of films from individual hexagonal prism columns into a tightly connected irregular column. Increasing film density leads to higher hardness. Sufficient synchronized negative substrate biasing and longer pulse width, which supports higher mobility of adatoms, causes the preferred orientation of hexagonal α-phase Zr films from (0 0 0 2) to (1 0 1¯ 1). Unlike the deposition at 1.2 Pa, highly charged ions are also found during the short HiPIMS pulse width at 0.8 Pa argon.

Study Results for Intensity of Sputtering of Thin Carbon Films by Uranium Fission Fragments

Study Results for Intensity of Sputtering of Thin Carbon Films by Uranium Fission Fragments

Anodic titania nanotubes decorated with gold nanoparticles produced by laser-induced dewetting of thin metallic films

Herein, we combine titania layers with gold species in a laser-supported process and report a substantial change of properties of the resulting heterostructures depending on the major processing parameters. Electrodes were fabricated via an anodisation process complemented with calcination to ensure a crystalline phase, and followed by magnetron sputtering of metallic films. The obtained TiO2 nanotubes with deposited thin (5, 10 nm) Au films were treated with a UV laser (355 nm) to form Au nanoparticles on top of the nanotubes. It was proven that selected laser working parameters ensure not only the formation of Au nanoparticles, but also simultaneously provide preservation of the initial tubular architecture, while above-threshold laser fluences result in partial destruction (melting) of the top layer of the nanotubes. For almost all of the samples, the crystalline phase of the nanotubes observed in Raman spectra was maintained independently of the laser processing parameters. Enhanced photoresponse up to ca 6 mA/cm2 was demonstrated by photoelectrochemical measurements on samples obtained by laser annealing of the 10 nm Au coating on a titania support. Moreover, a Mott–Schottky analysis indicated the dramatically increased (two orders of magnitude) concentration of donor density in the case of a laser-treated Au–TiO2 heterojunction compared to reference electrodes.

Ion-plasma sputtering of Co and Mo nanometer thin films near the sputtering threshold

In this work, we present results of a study of low-energy (Е i < 200 eV) sputtering of Co and Mo nanometer thin films in high-density argon plasma of a low-pressure radio-frequency inductive discharge with a controlled incident ion energy and ion current density onto the sample. The average ion energy was determined by the negative self-bias potential, which arises when the RF bias power is applied to the substrate. The ion current density was determined from the ratio of the increments in the RF bias power and the self-bias potential. The sputtering rate was determined in situ by a refractometric method from a sharp change in the intensity of a reflected laser beam signal at the moment of a removal of a metal film. Precise control of sputtering made it possible to detect a formation of nanoscale structures at a stage near the end of sputtering of metal films. The experimentally determined sputtering yields of Co and Mo were in agreement with the results of semiempirical calculations. We demonstrate that for ion-plasma sputtering, removal of Co and Mo atoms occurs at ion energy lower than the sputtering threshold.

Deposition Rate and Electrochromic Properties of Ni Oxide Thin Films Deposited By Sputtering Using Water Vapor As a Reactive Gas

Ni oxide is well known electrochromic (EC) materials. And nickel hydroxide (Ni (OH)2) and oxyhydroxide (NiOOH) are considered to be electrochemically more active than nickel oxide (NiO). Reactive sputtering is one of the most commonly used techniques for obtaining compound thin films, however, deposition rate of compound thin film is low. We have reported that the deposition rate of sputtered nickel oxide thin film increased remarkably by substrate cooling using a liquid nitrogen and injection of water vapor (H2O) onto the target surface in argon (Ar) atmosphere [1]. In this study, we studied the effect of the direction of water vapor injection and the substrate temperature on deposition rate, composition and EC characteristics of the Ni oxide thin films.Ni oxide thin films were prepared by an RF magnetron sputtering system at substrate temperatures (Ts) of -80 °C and -170 °C. Ar and H2O were used as sputtering gas, and the flow rates of Ar and H2O were kept constant at 2.5 cc/min. H2O was injected onto the substrate or target surface. RF power and sputtering gas pressure were constant at 50 W and 50 mTorr, respectively. Film thickness was measured using a stylus profiler, and deposition rate was calculated using the film thickness and sputtering time. Crystal structure and chemical bonding state of the films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. Optical and electrical properties of the films were studied by UV-Vis spectroscopy and four probe method. EC properties of the films were evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) in a 1 M KOH aqueous electrolyte.Figure 1 shows the deposition rate of Ni oxide thin films deposited at Ts=-80 °C and -170 °C with the H2O injection onto the substrate or target surface. At Ts=-80 °C, high deposition rates of 30-35 nm/min were obtained regardless of the direction of H2O injection. The deposition rates are much higher than that obtained by conventional reactive sputtering at room temperature (4nm/min) [1]. In contrast, the deposition rate varied from 21 nm/min for H2O injection to substrate 38 nm/min (the highest deposition rate) for H2O injection to target at Ts=-170 °C. Highly transparent films with a transmittance above 80% were obtained regardless of the direction of H2O injection at Ts=-80 °C, however, the transmittances of the films deposited at Ts=-170 °C were low. From the four probe method measurement, the thin film deposited at Ts=-170 °C with H2O injection to substrate was found to be a mixed film of metal Ni and Ni oxide with a resistivity of 3.3×10-4Ωcm. The films deposited at Ts=-80 °C with H2O injection to substrate or target and the film deposited at -170 °C with H2O injection to target were considered to be NiO or Ni(OH)2. CV and CA measurements showed that the film deposited at Ts=-80 °C with H2O injection to target had good cycle stability and large transmittance change of 58% at a wavelength of 600nm.In summary, the deposition rate, chemical composition, and EC properties of the Ni oxide films were found to be strongly dependent on the substrate temperature and the direction of H2O injection. The films deposited with H2O injection to target at Ts=-170 °C showed the highest deposition rate and that deposited at Ts=-80°C with H2O injection to target showed the largest transmittance change.REFERENCES[1] Y. Yokoiwa et al, Jpn. J. Appl. Phys. 58 (2019) 055504. Figure 1

Residual stress determination in thin films by X-ray diffraction and the widespread analytical practice applying a biaxial stress model: An outdated oversimplification?

Compressive stresses are commonly desired in thin films and the stress state in layers and coatings is in general evaluated assuming a biaxial nature of stress. But how thin is thick enough, or how many atom layers are necessary until this model assumption fails and a hydrostatic term joins in? In order to provide an answer molybdenum has been magnetron sputtered on display glass in layer thicknesses from 100 nm up to 2000 nm and afterwards investigated by X-ray diffraction to determine the residual stress state in the [110] fiber-textured sputtered films. It will be demonstrated that the use of a biaxial stress model might only be justified for thin layers if at all.

Surface Modification of Pb1 – xSnxSe Films during Plasma Treatment Near the Sputtering Threshold

The processes of the plasma sputtering of epitaxial lead-tin selenide films near the sputtering threshold are studied. Pb1 – xSnxSe films (x = 0.03, 0.07) with a thickness of 0.5–2 microns are grown by molecular-beam epitaxy on CaF2/Si(111) substrates. The films are plasma treated with radio-frequency high-density low-pressure inductively coupled argon plasma with an ion energy of 20–25 eV at typical process times of 60–360 s. As a result of plasma treatment for a prolonged period, the formation of hollow metal particles of nano- and submicron sizes is observed on the surface. Using scanning electron microscopy methods, it is shown that the lateral dimensions of the obtained structures, their shape and surface density vary over wide ranges and significantly depend on the time of plasma sputtering. The features of plasma sputtering for the studied films and films of a binary compound of lead selenide are compared.

Experimental Investigation on the DLC Film Coating Technology in Scroll Compressors of Automobile Air Conditioning

The friction of the orbiting scroll leads to large power consumption and low energy efficiency of the scroll compressor. The common methods to solve this problem are high cost and a complex process. Considering special structures and operating principles to apply the coating technology on the scroll compressor is a new subject. Given the material of the orbiting scroll being aluminum alloy, the unbalanced magnetron sputtering technology for the orbiting scroll of the scroll compressor was chosen and the Cr transition layer was coated to enhance the bonding strength. Moreover, we innovatively performed an experiment to verify the feasibility of unbalanced magnetron sputtering film coating technology for the diamond-like carbon film coated in the scroll compressor. This article elaborates the parameter test methods of the film properties before and after experiments and the experimental system components. The results showed that the diamond-like carbon film has low coefficient and high bonding strength, which renders it a good wear-reducing effect and an excellent self-lubricating property. Due to the thin film layer and high operating temperature, the thickness should be increased to raise the abrasion resistance. The refrigeration system with the scroll compressor coated with the diamond-like carbon film can satisfy the national standard conditions with low Vickers hardness. Its performance was improved at low speed. Therefore, the unbalanced magnetron sputtering with increased Cr bond layer is a feasible and appropriate technology for coating diamond-like carbon film.

Reactive sputtering of CSx thin solid films using CS2 as precursor

We deposit CSx thin solid films by reactive direct current magnetron sputtering of a C target in an argon plasma, using carbon disulfide (CS2) as a precursor to film growth. We investigate the influence of the partial pressure of the CS2 vapor introduced into the plasma on the composition, the chemical bonding structure, the structural, and the mechanical properties as determined by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), and nanoindentation for films deposited at 150 and 300 °C. The Raman and the XPS results indicate that S atoms are incorporated in mostly sp2 bonded C network. These results agree with previous ab-initio theoretical findings obtained by modeling of the CSx compound by the Synthetic Growth Concept. The microstructure of the films as well as the results of their Raman characterization and the nanomechanical testing results all point out that with the increasing S content some sp3 bonding is admixed in the predominantly sp2 bonded CSx network, leading to typical amorphous structure with short and interlocked graphene-like planes for S contents between 2% and 8%. We conclude that CSx thin solid films deposited by using CS2 as a precursor would be CSx films deposited at low temperature of ~150 °C and with an S content in the region of 6 at.% may be interesting candidates for applications as hard/elastic protective coatings.

A High‐Performing Asymmetric Supercapacitor of Molybdenum Nitride and Vanadium Nitride Thin Films as Binder‐Free Electrode Grown through Reactive Sputtering

Transition‐metal nitride (TMN) thin‐film‐based electrodes are recognized for high‐performance, stable, flexible, and smart supercapacitors (SCs), as they exhibit extensive voltage range, good sustainability, and high electrical conductivity. Herein, using reactive DC magnetron sputtering, molybdenum nitride (Mo2N) and vanadium nitride (VN) thin films are deposited on 304 stainless steel substrate at 200 °C for asymmetric SC (ASC) applications. ASC is constructed using VN@SS as negative electrode and γ‐Mo2N@SS as positive electrode and examines the electrochemical behavior in aqueous solutions of 1 m Na2SO4 at several scan rates and current densities. To scrutinize the crystallographic details and electronic configuration of as‐deposited thin‐film electrodes, X‐ray diffraction and X‐ray photoelectron spectroscopy are used. To visualize the surface morphology, film thickness, and elemental composition, field‐emission scanning electron microscopy and energy dispersive X‐ray analysis is used. The results imply that TMN thin‐film‐based electrodes bestow super‐hydrophilic nature and give enhanced capacitance value along with excellent rate performance. This work demonstrates VN@SS and γ‐Mo2N@SS thin‐film‐based electrode for ASC, which show a high capacitance of ≈85.50 Fg−1 and a high specific power of ≈23.3 Wh kg−1 with a broadened voltage window of ≈1.4 V, and this is a potential candidate for energy storage devices.

Alumina film sputter deposition on mold steel by large-area electron beam irradiation

During the large-area EB irradiation, plasma generation is confirmed by collision of electrons with vaporized workpiece materials above the substrate surface due to its high energy density. This phenomenon would cause the sputtering of target material when it is set near the substrate surface. Thus, there is a possibility for coating a target material on the substrate surface by the large-area EB irradiation. The simultaneous sputter deposition of target material with melting and resolidification of workpiece surface by the large-area EB would improve the adhesion strength between the coated film and the workpiece surface. In this study, a new ceramics coating method with sputtering of target tube by large-area EB irradiation is proposed. Ceramic target tube made of alumina is put on the substrate surface of mold steel, and the large-area EB is irradiated to the substrate surface. The alumina film with thickness of several micro meter can be formed on the substrate surface. Moreover, the film formation mechanism is discussed by changing material property of a jig supporting the alumina target tube. The spectrum of plasma generated on the substrate surface during the EB irradiation is also analyzed. It is made clear that the magnetic property of jig greatly influences on the film formation. Furthermore, main components of plasma generated on workpiece surface during the process are components of steel in the case of low number of EB irradiation, while much more alumina component as a film is detected in the case of high number of EB irradiation.

Underlayer effect on the soft magnetic, high frequency, and magnetostrictive properties of FeGa thin films

The soft magnetic, microstructural, and magnetostrictive properties of Fe81Ga19 (FeGa) film sputter deposited onto 2.5-nm Ta, Cu, and Ni80Fe20 (NiFe) underlayers were investigated. The films deposited with an underlayer showed increased in-plane uniaxial anisotropy and a decrease in in-plane coercivity. The smallest coercivity was observed in FeGa deposited with a NiFe underlayer at 15 Oe, compared to 84 Oe for films deposited directly on Si. In addition, an effective Gilbert damping coefficient (αeff) as low as 0.044 was achieved for a 100-nm FeGa film with a NiFe underlayer. The coercivity and αeff were shown to decrease further as a function of FeGa film thickness. The FeGa films were also able to retain or increase their saturation magnetostriction when deposited on an underlayer. This enhancement is attributable to the impact of the underlayer to promote an increased (110) film texture and smaller grain size, which is correlated to the lattice match of the underlayer of the sputtered FeGa film. Among the underlayers studied, NiFe promoted the best enhancement in the soft magnetic properties for FeGa thin films, making it an attractive material for both strain-mediated magnetoelectric and microwave device applications.

Impact of HfO2 buffer layer on the electrical characteristics of ferroelectric/high-k gate stack for nonvolatile memory applications

For the proposed work, the electrical properties of metal–ferroelectric–insulator–silicon (MFeIS) capacitors with Sr0.8Bi2.2Ta2O9 (SBT) ferroelectric film deposited on HfO2/Si substrate have been investigated. The SBT film was deposited by RF sputtering and HfO2 film by plasma-enhanced atomic layer deposition (PEALD). The structural characteristic of the deposited ferroelectric and dielectric films was obtained using X-ray diffraction and multiple angle ellipsometric analysis. XRD results indicate the polycrystalline and perovskite structure of the SBT film and amorphous structure of the HfO2 film annealed at different temperatures. SBT film deposited on the silicon substrate and annealed at 500 °C shows the maximum refractive index of 3.46 with the maximum grain size of 32 nm. Metal/ferroelectric/silicon (MFeS), metal/ferroelectric/metal (MFeM), metal/insulator/silicon (MIS) and metal/ferroelectric/insulator/silicon (MFeIS) structures were fabricated to obtain the electrical and ferroelectric properties. MFeIS structure with 10 nm buffer layer shows the improved memory window of 5 V as compared to the 3.07 V in the MFeS structures. MFeI(10 nm)S structure even shows endurance higher than 1012 read/write cycles and data retention for more than 8 h.

Measurement of thin film magnetostriction using field-dependent atomic force microscopy

Measurement of thin film magnetostriction is a challenging task, as magnetostrictive material deformations in parts per million, in conjunction with materials at small dimensions, require high precision, often with dedicated set-ups, for reproducible results. We have developed a novel approach employing a commercial atomic force microscope (AFM) with attached electromagnets. Magnetostriction measurements are demonstrated on 50–500 nm thick Fe81Al19 films sputter deposited directly on high aspect ratio commercial AFM micro-cantilevers. A magnetostrictive deflection of the cantilever bimorph translates into a deflection force acting in a contact mode measurement, which is interpreted and recorded as a change in height. For determination of the magnetostriction coefficient λs, we have developed a modified version of the equation for the magnetostrictive deflection of a cantilever bimorph by Guerrero and Wetherhold, taking into account long-range attractive forces acting during contact mode AFM measurements in air. The sub-atomic precision of the AFM, combined with the widespread availability of all components and the simple set-up, makes the measurement of magnetostriction on films of just a few tens of nanometers thickness easily accessible.