Radio Frequency Magnetron Sputtering Research Articles

Optical and electronic properties of BCN films deposited by magnetron sputtering.

Boron carbonitride (BCN) films containing hybridized bonds involving B, C, and N over wide compositional ranges enable an abundant variety of new materials, properties, and applications; however, their electronic performance is still limited by the presence of structural and electronic defects, yielding sluggish mobility and electrical conductivity. This work reports on mechanically stable BCN films and their corresponding optical and electronic properties. The ternary BCN films consisting of hybridized B-C-N bonds have been achieved by varying N2 flow by the radio frequency magnetron sputtering method. The BCN films show a bandgap value ranging from 3.32 to 3.82eV. Hall effect measurements reveal an n-type conductivity with an improved hall mobility of 226cm2/V s at room temperature for the optimal film. The n-BCN/p-Si heterojunctions exhibit a nonlinear rectifying characteristic, where the tunneling behavior dominates the injection regimes due to the density of defects, i.e., structural disorder and impurities. Our work demonstrates the tunable electrical properties of BCN/Si p-n diodes and, thus, is beneficial for the potential application in the fields of optics, optoelectronics, and electrics.

Fabrication of thin-film batteries composed of LiCoO2, Li3PO4, and Li layers

AbstractThis paper reports the fabrication of thin-film batteries which are composed of three stacking layers: LiCoO2, Li3PO4, and Li. First, a LiCoO2 layer is constructed on an electron-conductive substrate by pulsed laser deposition as a cathode. The crystallinity of the LiCoO2 layer is mainly controlled by the cationic ratio of Li and Co. Subsequently, an amorphous Li3PO4 layer with a high ionic conductivity is further deposited on the cathode LiCoO2 layer by radio frequency magnetron sputtering as a solid electrolyte. To avoid any possible damage which causes the formation of resistive species between LiCoO2 and Li3PO4, bias control of the substrate during Li3PO4 deposition is essential. Finally, a Li metal layer is deposited as an anode/current collector on the Li3PO4/LiCoO2 bilayer by resistive heating evaporation in a vacuum at an elevated temperature for the formation of a low resistive interface. The fabricated three-layer thin-film battery shows a high-rate capability when the LiCoO2 layer is a (104)-oriented epitaxial film.

The Impact of Temperature and Power Variation on the Optical, Wettability, and Anti-Icing Characteristics of AZO Coatings

The structural, wettability, and optical characteristics of aluminum-doped zinc oxide (AZO) thin films were studied with the objective of understanding the impact of deposition power and deposition temperature. Thin films were deposited using a radio frequency (RF) magnetron sputtering technique. The power output of the RF was augmented from 200 to 260 W, and the temperature was increased from 50 to 200 °C, which led to the development of a (002) peak for zinc oxide. The study of film thickness was carried out using the Swanepoel envelope method from data obtained through the UV-Vis spectrum. An increase in surface roughness value was shown to be connected with fluctuations in temperature as well as increases in deposition power. The findings revealed that as deposition power and temperature increased, the value of optical transmittance decreased, ranging from 70% to 90% based on the deposition parameters within the range of wavelengths that extend from 300 to 800 nm. The wettability properties of the samples were studied, and the maximum contact angle achieved was 110°. A Peltier apparatus was utilised in order to investigate the anti-icing capabilities, which revealed that the icing process was slowed down 3.38-fold. This work extends the understanding of the hydrophobicity and anti-icing capabilities of AZO thin films, specifically increasing both attributes which provide feasible options for purposes requiring resistance to ice.

High-temperature growth of ZnSnN2 layer via radiofrequency magnetron sputter epitaxy

Abstract ZnSnN2 layers were grown directly on Al2O3 (0001) substrates via radiofrequency magnetron sputter epitaxy at various substrate temperatures using N2 gas and a ZnSn alloy target. The crystalline quality and surface morphology of the ZnSnN2 layers were examined. X-ray diffraction patterns indicated that ZnSnN2 layers grown at substrate temperatures of 600 and 700 °C had wurtzite-type structures. The gross full width at half maximum (FWHM) value of the X-ray rocking curve (XRC) for the (0002) plane of the ZnSnN2 layer grown at 700 °C was 324 arcsec. The XRC for the (0002) plane contained two components, and the FWHM values of these components were 206 and 1520 arcsec for the highly c-axis-oriented columnar domains and disordered structure inside the ZnSnN2 layer, respectively. Metallic Sn was detected in a ZnSnN2 layer grown at 800 °C.

Strong nonlinear-polarization in ZnMgO epitaxial thin-films with Li incorporation

Abstract The second-order nonlinear-polarization originated from the interaction between thin-film material with second-order nonlinear susceptibility (χ(2) ) and high-power laser is essential for integrated optics and photonics. In this work, strong second-order nonlinear-polarization was found in a-axis oriented Zn1-xMgxO (ZnMgO) epitaxial thin-films with Li incorporation, which were deposited by radio-frequency magnetron sputtering. Mg incorporation (x>0.3) causes a sharp fall in the matrix element χ33 of χ(2) tensor, although it widens optical bandgap (Eopt ). In contrast, moderate Li incorporation significantly improves χ33 and resistance to high-power laser pulses with a little influence on Eopt . In particular, a Zn0.67Mg0.33O:Li [Li/(Zn+Mg+Li)=0.07] thin-film shows a |χ33 | of 36.1 pm/V under a peak power density (Ep ) of 81.2 GW/cm2, a resistance to laser pulses with Ep of up to 124.9 GW/cm2, and an Eopt of 3.95 eV. Compared to that of ZnO, these parameters increase by 37.8%, 53.4%, and 18.6%, respectively. Specially, the Zn0.67Mg0.33O:Li shows higher radiation resistance than a Mg-doped LiNbO3 crystal with a comparable Eopt . First-principle calculations reveal the Li occupation at octahedral interstitial sites of wurtzite ZnO enhances radiation resistance by improving structural stability. X-ray photoelectron spectroscopy characterizations suggest moderate Li incorporation increases χ33 via enhancing electronic polarization. These findings uncover the close relationship between the octahedra interstitial defects in wurtzite ZnMgO and its nonlinear-polarization behavior under the optical frequency electric field of high-power laser.

The ferroelectric and piezoelectric properties of (Hf1-x Ce x )O2 films on indium tin oxide/Pt/TiO x /SiO2/(100)Si substrates obtained using a no-heating radio-frequency magnetron sputtering deposition method

Abstract The effect of composition and film thickness on the ferroelectric and piezoelectric properties of (Hf1-x Ce x )O2 films deposited without substrate heating was investigated. (Hf1-x Ce x )O2 films with various x values (x=0.07–0.27) and thickness (150–880 nm) were deposited via radio-frequency (RF) magnetron sputtering on indium tin oxide (ITO)/Pt/TiO x /SiO2/(100)Si substrates. The crystalline phases of the films were observed by X-ray diffraction. The measurements of electrical properties revealed ferroelectric phases in the x range of 0.11–0.21. The film with x=0.16 exhibited the maximum remanent polarization (P r) of 15 µC/cm2, as well as the highest effective piezoelectric coefficient. In addition, the ferroelectric and structural properties remained almost unchanged with increasing film thickness. Therefore, the no-heating deposition of ferroelectric (Hf1-x Ce x )O2 films and their phase stability with respect to thickness were demonstrated for the first time. This work provides a pathway for the deposition of ferroelectric (Hf1-x Ce x )O2 films on flexible, wearable sensors.

Controllable physicochemical properties of WOx thin films grown under glancing angle.

In this work, various physicochemical properties are investigated in nanostructured WOx thin films prepared by radio-frequency magnetron sputtering for optoelectronic applications. A glancing angle of 87° is employed to grow films of different thicknesses, which are then exposed to post-growth annealing. Detailed local probe analyses in terms of morphology and work function of WOx films are carried out to investigate thickness-dependent property modulations of the as-deposited and annealed films. The analyses show a reasonably good correlation with photoelectron spectroscopic measurements on the films and the bulk I-V characteristics acquired on a series of WOx/p-Si heterojunction diodes. The presence of a critical WOx thickness is identified to regulate the rectification ratio values at the WOx/p-Si heterostructures and increase in series resistance within the bulk of the films. The present study provides valuable insights to correlate optical, electrical, and structural properties of WOx thin films, which will be beneficial for fabricating WOx-based optoelectronic devices, including photovoltaic cells.

One-step sputtering of MoSSe metastable phase as thin film and predicted thermodynamic stability by computational methods

We present the fabrication of a MoS2−xSex thin film from a co-sputtering process using MoS2 and MoSe2 commercial targets with 99.9% purity. The sputtering of the MoS2 and MoSe2 was carried out using a straight and low-cost magnetron radio frequency sputtering recipe to achieve a MoS2−xSex phase with x = 1 and sharp interface formation as confirmed by Raman spectroscopy, time-of-flight secondary ion mass spectroscopy, and cross-sectional scanning electron microscopy. The sulfur and selenium atoms prefer to distribute randomly at the octahedral geometry of molybdenum inside the MoS2−xSex thin film, indicated by a blue shift in the A1g and E1g vibrational modes at 355 cm−1 and 255 cm−1, respectively. This work is complemented by computing the thermodynamic stability of a MoS2−xSex phase whereby density functional theory up to a maximum selenium concentration of 33.33 at.% in both a Janus-like and random distribution. Although the Janus-like and the random structures are in the same metastable state, the Janus-like structure is hindered by an energy barrier below selenium concentrations of 8 at.%. This research highlights the potential of transition metal dichalcogenides in mixed phases and the need for further exploration employing low-energy, large-scale methods to improve the materials’ fabrication and target latent applications of such structures.

Monolithic Use of Inert Gas for Highly Transparent and Conductive Indium Tin Oxide Thin Films.

Due to its excellent electrical conductivity, high transparency in the visible spectrum, and exceptional chemical stability, indium tin oxide (ITO) has become a crucial material in the fields of optoelectronics and nanotechnology. This article provides a thorough analysis of growing ITO thin films with various thicknesses to study the impact of thickness on their electrical, optical, and physical properties for solar-cell applications. ITO was prepared through radio frequency (RF) magnetron sputtering using argon gas with no alteration in temperature or changes in substrate heating, followed with annealing in a tube furnace under inert conditions. An investigation of the influence of thickness on the optical, electrical, and physical properties of the films was conducted. We found that the best thickness for ITO thin films was 100 nm in terms of optical, electrical, and physical properties. To gain full comprehension of the impact on electrical properties, the different samples were characterized using a four-point probe and, interestingly, we found a high conductivity in the range of 1.8-2 × 106 S/m, good resistivity that did not exceed 1-2 × 10-6 Ωm, and a sheet resistance lower than 16 Ω sq-1. The transparency values found using a spectrophotometer reached values beyond 85%, which indicates the high purity of the thin films. Atomic force microscopy indicated a smooth morphology with low roughness values for the films, indicating an adequate transitioning of the charges on the surface. Scanning electron microscopy was used to study the actual thicknesses and the morphology, through which we found no cracks or fractures, which implied excellent deposition and annealing. The X-ray diffraction microscopy results showed a high purity of the crystals, as the peaks (222), (400), (440), and (622) of the crystallographic plane reflections were dominant, which confirmed the existence of the faced-center cubic lattice of ITO. This work allowed us to design a method for producing excellent ITO thin films for solar-cell applications.

Electrochemical catalysis of aluminum diboride thin film fabricated by radio-frequency magnetron sputtering

This study explores a novel ambient-condition method as a potential alternative to the Haber-Bosch process for ammonia synthesis. Aluminum diborides thin films were deposited using sputtering and calcination techniques to investigate the relationship between crystallinity and various properties including electrochemical catalysis, electrical conductivity, surface morphology, and bonding states. The results indicate that the calcined films reduce the electrical resistivity and exhibit enhanced crystallinity, and catalytic activity, particularly for ammonia synthesis. The findings highlight the significant impact of crystallinity on electrocatalysis in this context.

Effects of power on ion behaviors in radio-frequency magnetron sputtering of indium tin oxide (ITO)

Abstract This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide (ITO) target. The positive ion energies exhibit an upward trajectory with increasing RF power, attributed to heightened plasma potential and initial emergent energy. Simultaneously, the positive ion flux escalates owing to amplified sputtering rates and electron density. Conversely, negative ions exhibit broad ion energy distribution functions (IEDFs) characterized by multiple peaks. These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential, alongside ion transport time. This elucidation finds validation in a one-dimensional model encompassing the initial ion energy. At higher RF power, negative ions surpassing 100 eV escalate in both flux and energy, posing a potential risk of sputtering damages to ITO layers.

Effect of Deposition Working Power on Physical Properties of RF-Sputtered CdTe Thin Films for Photovoltaic Applications.

The main objective of this study was to determine the variation in the properties of cadmium telluride (CdTe) thin films deposited on a p-type Si substrate by the radio frequency magnetron sputtering technique at four different working powers (70 W, 80 W, 90 W, and 100 W). The substrate temperature, working pressure, and deposition time during the deposition process were kept constant at 220 °C, 0.46 Pa, and 30 min, respectively. To study the structural, morphological, and optical properties of the CdTe films grown under the mentioned experimental conditions, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical spectroscopy were used. For a better analysis of the films' structural and optical properties, a group of films were deposited onto optical glass substrates under similar deposition conditions. The electrical characterisation of Ag/CdTe/Al "sandwich" structures was also performed using current-voltage characteristics in the dark at different temperatures. The electrical measurements allowed the identification of charge transport mechanisms through the structure. New relevant information released by the present study points towards 90 W RF power as the optimum for obtaining a high crystallinity of ~1 μm nanostructured thin films deposited onto p-Si and optical glass substrates with optical and electrical properties that are suitable for use as absorber layers. The obtained high-quality CdTe nanostructured thin films are perfectly suitable for use as absorbers in CdTe thin-film photovoltaic cells.

Etching and Compositional Ratio Effect on the Surface Properties of Bismuth Telluride Thin Films

Bismuth telluride has garnered considerable attention owing to its versatile properties applicable in thermoelectric and antibacterial domains, as well as its intriguing topological insulating properties. In this work, our group fabricated bismuth telluride thin films with various ratios using radio frequency magnetron sputtering. The surface properties of these thin films were thoroughly analyzed by employing a diverse array of analytical techniques, including X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), four-point probe and contact angle (CA) measurements. Specifically, our XPS findings indicated that Bi is more susceptible to oxidation than Te following Ar+-ion etching. Pure Te thin films exhibited the highest Rq value of 31.2 nm based on AFM and SEM results due to their larger grain sizes. The XRD patterns revealed a peak at 27.75° for thin films with 20% Te, attributed to its rhombohedral structure. Moreover, thin films with 30% Te yielded the highest weighted average work function with a value of 4.95 eV after etching. Additionally, pristine Bi and Te thin films demonstrated the most robust hydrophobic properties compared to intermediate-composition thin films, as determined by CA measurements.

Highly sensitive self-powered solar-blind ultraviolet photodetectors based on n-Zn1-xFexO/p-Si heterojunctions

The pristine and iron-doped ZnO thin films were fabricated on p-type silicon and glass substrates using the radio-frequency magnetron sputter deposition technique. The structural, morphological, and electrical properties of the deposited thin films were analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and I-V characteristics. XRD analysis revealed the preferential growth of ZnO along the c-axis, with lattice parameter (c) values of 5.216, 5.234, and 5.241 Å for the pristine ZnO, Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films, respectively. The crystallite sizes were measured to be 13.2 nm, 16.2 nm, and 18.3 nm for the respective films. The elemental analysis of the deposited films was done under X-ray photoelectron spectroscopy (XPS), which revealed the concentrations of iron Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films were 2.93 at% and 5.14 at%, respectively. Raman spectroscopy confirmed the presence of the hexagonal wurtzite structural form in the deposited films. The I-V characteristics of the deposited films confirmed the formation of a heterojunction between the film and the silicon substrate. Furthermore, the constructed heterojunction devices were evaluated for their ability to detect ultraviolet (UV) radiations of wavelengths 365 nm and 254 nm. The devices exhibited response and recovery times of less than 1 s. The detectivity values were found to be 0.321 ×1011, 1.051 ×1011, and 2.992 ×1011 Jones for the ZnO/p-Si, Zn0.97Fe0.03O/p-Si, and Zn0.95Fe0.05O/p-Si devices, respectively, under a fixed illumination intensity of 0.812 mW/cm2 for a UVA source with a wavelength of 365 nm. These results confirm the excellent photodetection ability of the constructed devices. The mechanism of UV radiation detection by the devices has also been extensively discussed.

Effect of Traps on the UV Sensitivity of Gallium Oxide-Based Structures

Resistive metal/β-Ga2O3/metal structures with different interelectrode distances and electrode topologies were investigated. The oxide films were deposited by radio-frequency magnetron sputtering of a Ga2O3 (99.999%) target onto an unheated sapphire c-plane substrate (0001) in an Ar/O2 gas mixture. The films are sensitive to ultraviolet radiation with wavelength λ = 254. Structures with interdigital electrode topology have pronounced persistent conductivity. It is shown that the magnitude of responsivity, response time τr, and recovery time τd are determined by the concentration of free holes p involved in recombination processes. For the first time, it is proposed to consider hole trapping both by surface states Nts at the metal/Ga2O3 interface and by traps in the bulk of the film.

Near infrared detection based on sputter-deposited Mn-Co-Ni-O films with a MSM structure

This work explores high-quality infrared detectors based on Mn-Co-Ni-O (MCNO) films, which were deposited by radio frequency magnetron sputtering at different temperatures ranging from 200 to 600 °C. Increasing the growth temperature was beneficial for forming smoother surfaces, higher crystallinity, and higher concentrations of Mn3+ and Mn4+ ions. However, it also resulted in a decrease in the thermal activation energy and temperature coefficient of resistance (TCR). MCNO-based metal–semiconductor-metal (MSM) structured detectors are highly sensitive to 885 nm infrared light, with the detector grown at 200 °C exhibiting the greater on/off ratio of 13.15, the largest responsivity of 0.23 A/W@-15 V, and the highest specific detectivity of 3.74 × 108 Jones and a rapid response/recovery time of 31.2/20.4 ms. This was attributed to due to its largest TCR value of −6.42 %/K, nano-pyrometric cone crystal grains on the surface, the largest Ov concentration, the lowest activation energy of Ov and electron-hole recombination efficiency, relatively high concentrations of Mn3+ and Mn4+ ions and lower resistance at 293 K. This research demonstrated that optimizing growth temperature is an effective method for significantly improving the properties of MCNO-based MSM structured detectors.

Fabrication and characterization of smart titanium alloy bolt based on high-frequency piezoelectric thin-film.

We reported here on the fabrication and characterization of a smart titanium alloy bolt based on a high-frequency piezoelectric thin-film sensor. The thin-film sensor was directly deposited on a titanium alloy bolt head with radio frequency magnetron sputtering and characterized by a scanning electron microscope and an atomic force microscope. The ultrasonic characteristics of the smart bolt, which include a pure and broad frequency spectrum peaked at 14.81MHz, high measurement accuracy below 3%, and high repeatability free from some interference from bolt detection position change, were fully characterized. No obvious frequency shift was observed with the increase in axial preload. Based on the mono-wave method [TOF (time of flight) of longitudinal mode wave], TOF change increased linearly with preload force in the range of 0-20kN. With the increase in temperature from 22 to 150°C, the TOF linearly increases while the longitudinal wave velocity linearly decreases. The results indicate the prepared smart titanium alloy bolt is suitable as a smart aviation and automotive fastener.

Numerical Modelling and Simulation for Sliding Wear Effect with Microstructural Evolution of Sputtered Titanium Carbide Thin Film on Metallic Materials

Titanium carbide materials are introduced into manufacturing industries for the reinforcement and surface protection of base materials due to their substantial ability to withstand severe environments, which include sliding wear, corrosion, and mechanical failures. A thin film of titanium carbide (TiC) is coated onto brass and copper substrates using the radio frequency magnetron sputtering (RFMS) deposition method. The coating process is carried out at constant processing parameters, which include a sputtering power of 200 W, a temperature of 80 °C, a deposition time of 180 min, and an argon (Ar) gas flow rate at 10 standard cubic centimetres per minute (SCCM). The coating, together with the base materials, is modelled and its behaviours are simulated using ANSYS Workbench R19.2 Academic, supported by Mechanical APDL solver for nonlinear finite element analysis (FEA). The deformation, equivalent stress–strain characteristics, and elastic–plastic properties of the coating are determined at applied loads of 60 N and 25 N and coefficients of friction (CoF) of 0.25 and 0.38 for the thin film deposition on brass and copper substrates. The sliding distance and the speed of the alloy steel ball used during the sliding wear operation are found to be 3 mm and 4 mm/s, respectively. The sliding wear modelling and simulation process are, however, designed for the ball-on-flat (BoF) wear technique with a dry sliding approach. Therefore, BoF wear simulations are also performed on titanium carbide–brass (TiC-Br) and titanium carbide–copper (TiC-Cu) conjugates for the evaluation of surface engineering applications such as cutting tools and in automotive, aerospace, thermomechanical, and biomedical fields. The ball used for the FEA wear simulation is made from alloy steel material (AISI 52100) with a radius of 3.175 mm.

Influence of Pt Ultrathin Interlayers on Magnetic Anisotropy in Ni/NiO Multilayers

Perpendicular magnetic anisotropy at transition metal/oxide interfaces plays a significant role in technological applications such as magnetic storage and spintronics. In this study, we investigate the effects of thermal annealing and Pt ultrathin interlayers on the magnetic anisotropy in Ni/NiO multilayers. Ni/NiO/Pt multilayers were fabricated via radiofrequency magnetron sputtering and natural oxidation. The static magnetic properties of the samples were studied using temperature-dependent SQUID magnetometry. We focus on a sample with a Nickel thickness of 6.7 nm in each multilayer period. This multilayer in Ni/NiO form showed the maximum enhancement of perpendicular magnetic anisotropy after mild thermal annealing in past work. In this work, we study the effects of ultrathin Pt interlayers on the magnetic properties of such a Ni/NiO multilayer before and after annealing. We have observed a further increase in perpendicular magnetic anisotropy, and we study the temperature-dependent magnetic properties of this system, which combines the favorable magnetic properties of Ni/Pt and Ni/NiO multilayers.

Effects of O2/Ar Ratio on Preparation and Dielectric Properties of CaZrO3 Films by Radio Frequency (RF) Magnetron Sputtering.

CaZrO3 (CZO) thin films were deposited on Pt/Ti/SiO2/Si substrates at 450 °C by radio-frequency magnetron sputtering technology. The microstructures and dielectric properties of CZO thin films were investigated. X-ray diffraction analysis reveals that the perovskite orthogonal CZO phase would be promoted by a higher O2 partial pressure in the flow ratio of O2/Ar after thin films were annealed at 700 °C for 3 h in air. The films prepared under the flow ratio of O2/Ar (20:40, 30:40 and 40:40) show the main perovskite crystal phase of CaZrO3 with a small amount of Ca0.2Zr0.8O1.8. The main crystal phase was Ca0.2Zr0.8O1.8 when the film was deposited under an O2/Ar ratio of 40:10. The annealed film with a 40:40 O2/Ar ratio exhibits a dielectric performance with a high dielectric constant (εr) of 25 at 1 MHz, a temperature coefficient of permittivity of not more than 122.7 ppm/°C from 0 °C to 125 °C, and a low leakage current density of about 2 × 10-7 A/cm2 at 30 V with an ohmic conduction mechanism.