Reactive Magnetron Sputtering Method Research Articles

Effect of abnormally oriented grains on the ferroelectric properties of Al0.65Sc0.35N thin films

The wide bandgap wurtzite Al1-xScxN ferroelectric material is compatible with semiconductor processes and offers advantages such as high remanent polarization (Pr) and high-temperature stability. To clear the relationship between the structure zone model (SZM), abnormally oriented grains (AOGs) and the ferroelectric properties, the Al0.65Sc0.35N films were prepared at various sputtering pressures (0.32–0.90 Pa) and substrate temperatures (200–500 ℃) on low resistance n+-(111) Si substrate by the radio frequency dual-source reactive magnetron sputtering method using Al and Sc targets under pure N2 gas. The introduction of AOGs facilitates compressive stress reduction and promotes ferroelectric switching. However, excessive AOGs will damage the (002) orientation, leading to loss of ferroelectricity. The Al0.65Sc0.35N films synthesized under a sputtering pressure of 0.52 Pa and a substrate temperature of 400 ℃ exhibited a lower leakage current at high electric field, with a Pr value of 154.3 μC/cm2 and a negative coercive field (Ec-) of 3.1 MV/cm at a testing frequency of 1 kHz. The outstanding comprehensive properties support the large potential of Al1-xScxN ferroelectric material for high-performance FeRAM devices.

Thermochromic properties and surface chemical states of reactive magnetron sputtered vanadium oxide thin films at various deposition pressures

Vanadium oxide thin films were prepared using reactive magnetron sputtering method, varying the deposition pressures from 4 to 10 mTorr while maintaining the other sputtering parameters constant. Our investigations revealed sensitive dependence of deposition pressure, chemical states of the V and O atoms, crystal phases, and thermochromic (TC) optical modulation. Specifically, the film deposited at 8 mTorr displayed distinct TC characteristics with a prevalent monoclinic m-VO2 phase according to X-ray diffraction (XRD), supported by X-ray photoelectron spectroscopy (XPS). Optical transmittance modulation and electrical property measurements revealed a metal–insulator transition (MIT), confirming the intimate connection between TC characteristics and presence of the m-VO2 phase. Films deposited at pressures lower or higher than 8 mTorr exhibited typical semiconductor behavior without TC characteristics, further supported by in situ XRD, where (110) plane shifted to lower angle upon heating above τC. Chemical state analysis by XPS revealed a clear correlation between V−O peaks and the presence of a VO2 phase, with the film deposited at 8 mTorr displaying relatively large peak fitted area indicative of the VO2 phase. These findings highlight the critical and sensitive dependence of the deposition conditions in tailoring the properties of vanadium oxide thin films and provide valuable insights for potential applications in chromogenic films.

Effect of N2 reactive gas flow rate on the structural, optical and wettability properties of silicon carbon oxynitride thin films

In the current research, the silicon carbon oxynitride (SiCON) thin film was deposited on the silicon (Si) substrate by radio frequency (RF) reactive magnetron sputtering method. To comprehensively assess the impact of nitrogen flux rate on thin film characteristics, a suite of advanced analytical methods was utilized. The GIXRD analysis confirmed that the SiCON thin film is amorphous in structure. Additionally, Raman spectroscopy detected no graphite nanocrystals within the film. Ellipsometry measurements further showed that the refractive index of the thin films rises with increased nitrogen flux in the reactive gas, indicating a direct correlation between nitrogen concentration during deposition and optical properties. Based on the designs made with McLeod's software, the amount of reflection can be reduced up to 5.7 % at the wavelength of 4 μm and up to 8.5 % in the wavelength range of 3–5 μm for an optimal thickness thin film. The atomic force microscopy (AFM) examination revealed that the surface roughness of the thin films decreases as the nitrogen flux in the reactive gas mixture increases. Additionally, measurements of the water contact angle (WCA) indicated that the SiCON thin films exhibit a hydrophilic state.

Optical and electrophysical properties of nitride TiAlSiN and carbonitride TiAlSiCN coatings: influence of reactive magnetron deposition regimes

The development of thin-film thermal control coatings for small spacecraft is relevant. Coatings based on titanium nitride are capable of functioning in unfavorable conditions of near and deep space, due to their high resistance to the irradiation by high-energy particles. Using the reactive magnetron sputtering method, the nanostructured TiAlSiN and TiAlSiCN coatings were formed on the substrates of silicon oxide (SiO2), glass-ceramic CT-1 and single-crystalline silicon (Si(100)). A study of the electrophysical and optical properties of the formed coatings was carried out. The deposited coatings demonstrate a good reflectivity in the infrared range of spectrum (700–2000 nm), what is important for reducing the overheating of the spacecraft (SC) under the influence of the direct sunlight. In the visible range of spectrum (400–700 nm), a low level of total Rtotal reflection is observed. This is promising for satellites designed to observe the Earth’s surface. The values of solar absorption coefficients αs, emissivity coefficients ε0, ratios αs/ε0, as well as the equilibrium temperature Tр for the samples under study were obtained. The values of resistivity ρ and surface resistance R□, electron concentration N and electron mobility μ were determined. It has been discovered that TiAlSiN, TiAlSiCN films are electrically conductive: ρTiAlSiN = (92÷4260) ∙ 10–7 Ω ∙ m, ρTiAlSiCN = (51÷2360) ∙ 10–7 Ω ∙ m. It has been found that adding carbon to the coating composition reduces the resistance. The obtained nanostructured coatings of TiAlSiN nitride and TiAlSiCN carbonitride can be used as temperature control coatings for small spacecrafts.

Impact of blocking layers based on TiO2 and ZnO prepared via direct current reactive magnetron sputtering on DSSC solar cells

The optimization of dye-sensitized solar cells (DSSCs) technology towards suppressing charge recombination between the contact and the electron transport layer is a key factor in achieving high conversion efficiency and the successful commercialization of this type of product. An important aspect of the DSSC structure is the front blocking layer (BL): optimizing this component may increase the efficiency of photoelectron transfer from the dye to the semiconductor by reduction charge recombination at the TiO2/electrolyte and FTO/electrolyte interfaces. In this paper, a series of blocking layer variants, based on TiO2 and ZnO:TiO2, were obtained using the reactive magnetron sputtering method. Material composition, structure and layer thickness were referred to each process parameters. Complete DSSCs with structure FTO/BL/m-TiO2@N719/ EL-HSE/Pt/FTO were obtained on such bases. In the final results, verification of opto-electrical parameters of these cells were tested and used for the conclusions on the optimal blocking layer composition. As the conclusion, application of blocking layer consists of neat TiO2 resulted in improvement of device efficiency. It should be noted that for TiO2:ZnO/CuxO and TiO2/CuxO cells, higher efficiencies were also achieved when pure TiO2 was used as window layer. Additionally it was proven that the admixture of ZnO phase inspires Voc and FF growth, but is overall unfavorable compared to pristine TiO2 blocking layer and the reference cell, according to the final cell efficiency.

Optimization of TiN/TiOxNy Laminated Electrode Films for High-Performance Gene Sequencing Chip

With continuous advancement of the fourth generation nanopore gene sequencing technology, the requirements for performance of the electrode films in gene sequencing chips are increasing. This study utilized the high vacuum reactive magnetron sputtering method to examine the impact of working pressure on the electrical, electrochemical, crystal structure, chemical composition, and surface morphology of TiOxNy thin films in detail. The findings revealed that the TiN thin film deposited at 0.4 Pa exhibited the lowest resistivity of 391.9 μΩ·cm. Additionally, the TiOxNy thin film deposited at 1.6 Pa demonstrated the highest volumetric specific capacitance of 35.37 mF·cm−2·μm−1 at 5 mV·s−1. Utilizing the optimal parameters, TiOxNy laminated electrode thin films were in situ grown. Through measurements and analysis, it was found that the TiOxNy electrode thin film effectively achieves a 29.35% improvement in specific capacitance compared to the single layer TiOxNy electrode thin film. The integration of a TiN current collector with low resistivity effectively reduced the internal resistance of the electrode system and decreased the response time to 0.038 s. The features of low impedance and high specific capacitance of TiOxNy laminated thin films offer promising prospects for the preparation of gene sequencing chip with high throughput.

Influence of Ar:O2 Mixing Ratio on Characteristics of Tio2 Nanostructured Thin Films Deposited by DC Reactive Magnetron Sputtering Method

Abstract: In this paper, titanium dioxide nanostructured thin films TiO2 were deposited on unheated glass substrates by applying the DC reactive magnetron sputtering method. Three TiO2 films were deposited using argon sputtering gas with different oxygen ratios: 10%, 25%, and 50%. The resulting films had thicknesses of 200, 184, and 140 nm, respectively. The structural, morphological, optical, and electrical properties of deposited thin films were studied. X-ray diffraction (XRD) data showed that the samples exhibited an amorphous phase. It was found from atomic force microscopy (AFM) that the deposited thin films had a nanostructure, and the heights of their nanograins were 16, 24, and 30 nm, respectively. It was observed from the root-mean-square height RMS values that the films had low roughness. The UV-Vis-NIR spectroscopy showed that the films become more transparent with the increase in oxygen content. The direct band gap ranged between 3.68 and 3.88 eV, while the indirect band gap ranged from 3.3 to 3.66 eV. The highest intensity photoluminescence emission was obtained for the film deposited at 50% O2. In addition, the impedance spectroscopy showed that the films’ resistance did not change with changing oxygen content. Keywords: Magnetron sputtering, Titanium dioxide, X-ray diffraction, Absorption spectra, Atomic Force Microscopy, Photoluminescence, Impedance.

Band alignment engineering at ultra-wide bandgap GeO2/SiO2 heterointerfaces

Owing to the tremendous contribution for the carrier transport across the interface, the band alignment engineering in oxide semiconductor heterojunctions (OSHs) is of vital importance for developing oxide semiconductor optoelectronic devices. Here, we have deposited a series of ultra-wide bandgap GeO2 thin films on quartz substrates by the direct-current reactive magnetron sputtering method to construct the OSHs and described the effect of the flow rate ratios of O2 and Ar (O2:Ar) and substrate temperatures on the bandgap energies of GeO2 films and band alignments at the interface of OSHs. Based on the energy loss spectra of O 1 s peaks, the tunable bandgap energies ranging from 4.37 to 5.37 eV have been achieved for GeO2 films. An obvious variation of band alignments has been found in the OSHs, suggesting the dramatically influence of deposition conditions. The valence band offsets are determined to be ranging from 1.85 to 1.96 eV (from 1.88 to 1.95 eV) and the conduction band offsets are calculated to be ranging from 1.88 to 2.78 eV (from 1.74 to 2.19 eV) for the GeO2 films grown at different O2:Ar (substrate temperatures), respectively, due to the nonlocalization of the oxygen vacancies in valence band and the formation of single hexagonal phase in the GeO2 film. Our findings on the band alignment engineering in the GeO2/SiO2 heterointerfaces will open the way for developing GeO2-based optoelectronic devices.

The Influence of Nitrogen Flow on the Stoichiometric Composition, Structure, Mechanical, and Microtribological Properties of TiN Coatings.

Utilizing reactive DC magnetron sputtering method, TiN coatings were deposited on the silicon substrates at different nitrogen flows and powers. A study of the X-ray phase composition of the coatings was carried out. The stoichiometric composition of the coatings was determined using energy dispersive x-ray spectroscopy. The structure of the surface, cross-section, and thickness of the coatings were determined using scanning electron (SEM) and atomic force microscopy (AFM). A significant change in the surface structure of TiN coatings was established with changes in deposition power and nitrogen flow. SEM images of cross-sections of all coated samples showed that the formation of coatings occurs in the form of a columnar structure with a perpendicular orientation relative to the silicon substrate. The mechanical properties (elastic modulus E and microhardness H) of TiN coatings of the first group demonstrate a maximum at a nitrogen flow of 3 sccm and are 184 ± 11 GPa and 15.7 ± 1.3 GPa, respectively. In the second group, the values of E and H increase due to a decrease in the size of the structural elements of the coating (grains and crystallites). In the third group, E and H decrease. Microtribological tests were carried out in 4 stages: at a constant load, multi-cycle for 10 and 100 cycles, and with increasing load. The coefficient of friction (CoF) and specific volumetric wear ω depend on the roughness, topology, and mechanical properties of the resulting coatings. Fracture toughness was determined using nanoscratch and depends on the mechanical properties of TiN coatings. Within each group, coatings with the best mechanical and microtribological properties were described: in the first group-TiN coating at 3 sccm (with (29.6 ± 0.1) at.% N), in the second group-TiN coating at 2 sccm (with (40.8 ± 0.2) at.% N), and in the third group-TiN coating at 1 sccm (c (37.3 ± 0.2) at.% N).

Growth mechanism and field emission of B doped AlN films

This paper highlights the effect of boron dopant on the field emission and growth mechanism of AlN films. The films have been grown by reactive RF magnetron sputtering method. For undoped films, columnar AlN structure was obtained. In the case of boron doped AlN films, the structure growth proceeded gradually through four layers of different thicknesses and structures. It was found that boron favors the formation of an amorphous layer within which oxygen and boron based precipitates develops, retarding the growth of columnar morphology. Depth profiling X-ray photoelectron spectroscopy analyses confirm the presence of B-O, B-N, Al-B and Al-O groups.The study on the field emission (FE) properties of undoped and B doped AlN films on Si substrates indicates that the addition of boron allow to improve FE properties with low turn on field of 2.6 V/μm and low threshold filed of 3.07 V/μm. Such good field emission properties can be attributed to the formation of densely nanograined surface and the appearance of boron based groups.

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.

Epitaxial growth of nano-texturized NiO films on MgO (001) substrates by a reactive magnetron sputtering method

Epitaxial films with nanostructures are of great significance for some special applications. In this work, nano-texturized NiO films are epitaxially grown on MgO (001) substrates by a reactive magnetron sputtering method. The evolution in morphology is studied as a function of deposition time, and the influences of substrate temperature, oxygen partial pressure, and the substrate treatment before deposition of NiO on the formation of nano-texturized NiO films are explored. It is found that the non-symmetrically epitaxial growth of nano-texturized NiO films can be linked with the surface damages of MgO (001) substrate, which leads to the coalescence of adjacent NiO grains preferentially occurs along the direction of 〈100〉 and 〈010〉, but they do not coalesce simultaneously following the other directions. In addition, the optical property of nano-texturized NiO films is studied using the Cauchy model.

The structure and micromechanical properties of TiAlSiN, TiAlSiCN coatings formed by the method of reactive magnetron sputtering

Nanostructured nitride TiAlSiN and carbonitride TiAlSiCN coatings are herein formed by reactive magnetron sputtering on various types of substrates: single-crystal silicon (100) and Titanium Grade2. To control and manage the coating process, the developed modular gas flow control complex (MGFCC) is used. The elemental composition is studied byenergy dispersive X-ray spectroscopy (EDX), the structure by X-ray diffraction (XRD), the morphology by scanning electron microscopy (SEM), whereas the micromechanical properties by nanoindentation. It is discovered that the formed coatings over the entire range of parameters α = 0.421–0.605 have a single-phase structure (Ti,Al)N, which is a disordered solid solution with a face-centered cubic (fcc) lattice. The average crystallite size of the (Ti,Al)N phase varies in the range (20–30) ± 5 nm. It is found that a decrease in the degree of reactivity α from α = 0.605 to α = 0.421 leads to an increase in the rate of deposition of nitride TiAlSiN and carbonitride TiAlSiСN coatings on silicon substrates by 200–300 %. The hardness of the formed coatings varies in the range H = 28.74–48.99 GPa, Young’s modulus E = 324.97–506.12 GPa. TiAlSiN, TiAlSiCN coatings demonstrate high values of impact strength indices H/E* = 0.07–0.12 and plastic deformation resistance indices H3/E*2 = 0.13–0.72. It is detected that the degree of reactivity α has a significant effect on the micromechanical properties of the formed coatings. The structure and micromechanical properties of the formed nanostructured nitride and carbonitride TiAlSiN, TiAlSiCN coatings are suitable for use in space technology applications.

High-temperature oxidation resistance of CrAlN thin films prepared by DC reactive magnetron sputtering

CrAlN thin films were prepared by using the reactive DC unbalanced magnetron sputtering method from the single alloy target on a silicon substrate. The effect of annealing temperature in the air which ranges from 500℃ to 900℃ for 1 h on phase structure, film composition, surface morphology, microstructure, and hardness was investigated by XRD, EDS, FE-SEM, and Nanoindentation techniques, respectively. The high-temperature (up to 900℃) oxidation resistance of the thin film was also evaluated. The result shows that solid solutions of (Cr,Al)N with (111), (200), and (220) planes for the as-deposited film and no oxide phase were found after annealing with different temperatures. The O content slightly increases with an increase in the annealing temperature with various Cr, Al, and N contents found by the EDS. From the FE-SEM result, as increased annealing temperature, the evolution of cross-sectional morphology from dense to compact columnar structure was exhibited but the oxides layer was not detected. These results concluded that the as-deposited thin film showed good oxidation resistance when annealed in air at an elevated temperature reaching 900℃. Moreover, the film’s hardness decreased from 61.19 GPa to 50.11 GPa with increasing the annealing temperature observed by the Nanoindentation technique.

(Digital Presentation) P-n Heterostructured Mos for NOx Gas Sensing

The significant air pollution caused mainly by exhaust and factory emissions has become a considerable hazard to human survival and development [1]. Nitrogen oxides (NOx) are a family of poisonous and highly reactive gases which forming at fuel high temperatures burn [2]. As an industrial source, such as power plants, industrial boilers, cement kilns, and turbines, NOx pollution is emitted by automobiles, trucks and various non-road vehicles (e.g., construction equipment, boats, etc.) [3]. Hazardous compounds such as NOx with negative environmental and human health consequences, must be controlled to avoid ecological disasters [4]. Metal-oxide-semiconductors (MOSs) as a class of chemoresistive sensors have attracted great attention in environmental monitoring, automotive emission monitoring and food safety testing, due to their low production cost, high sensitivity, simplicity of use and their ability to detect various gases [5].Due to its inherent advantages in charge carrier mobility, chemical activity, and redox potential, TiO2 (n-type) is a widely used and extensively researched MOSs. At the same time, CuO is also known to be an active transition-metal based semiconductor (p-type) having a lower electrical resistance value as well as a narrow band gap. A promising strategy for improving the gas sensitivity at room temperature (RT) is to apply p-n heterostructures to modulate resistance more strongly. The active surface area and nanoarchitecture affect the gas sensors' sensitivity. The provision of porous MOSs nanostructures to improve the diffusion channel and increase the adsorption of target gas molecules is the most promising means of achieving enhanced sensitivity [6-7]. The mentioned structures may be created using the glancing angle deposition (GLAD) reactive magnetron sputtering method. The TiO2/CuO heterostructure gas sensors were synthesized by reactive magnetron sputtering using the GLAD. The application CuO layer improves the gas sensor device's sensitivity due to electron-hole pair recombination and a reduction in the concentration of charge carriers in the TiO2 and CuO layers. The identical circumstances of 10 ppm and RT were used for each gas selectivity test. It demonstrates the potential of using heterostructured CuO/TiO2 nanorods as N2O gas sensors. Dynamic gas response analysis shows that the response time is only 47s, whereas the recovery time is 80s. The dynamic gas sensing measurements at various N2O gas concentrations exhibit excellent linearity at 50 ppb to 5 ppm range. The sensor's gas response was 2% at a very low N2O concentration (50 ppb) and 9.8% at 5 ppm. Thus, the research findings indicate that the p-n heterostructured CuO/TiO2 nanorods synthesized by reactive magnetron sputtering using the glancing angle deposition show fast response and recovery times in ultra-low N2O gas concentration in RT. It can be used as excellent N2O gas sensors for quickly monitoring air pollution. Acknowledgements. This research has been funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP13067814) and Nazarbayev University under the Collaborative Research Program (Grant No. 021220CRP0122). References Zhu, L., Zeng, W. Room-temperature gas sensing of ZnO-based gas sensor: A review // Sensors and Actuators A: Physical. – 2017. №267. –P. 242-261. https://doi.org/10.1016/j.sna.2017.10.021.Bhati, V., Hojamberdiev, M., & Kumar, M. The enhanced sensing performance of ZnO nanostructures-based gas sensors: A review // Energy Reports – 2019. №6. P. – 46-62. https://doi.org/10.1016/j.egyr.2019.08.070.Daryakenari, A., Apostoluk, A., & Delaunay, J. Effect of Pt decoration on the gas response of ZnO nanoparticles // Physica Status Solidi (C). – 2012. №10(10). P. – 1297-1300. https://doi.org/10.1002/pssc.201200937H.B. Kim, S.P. Eckel, J.H. Kim, F.D. Gilliland, Exhaled NO: determinants and clinical application in children with allergic airway disease Allergy Asthma Immunol Res, 8 (2016), pp. 12-21Dae-Sik Lee, Jun-Woo Lim, Sang-Mun Lee, Jeung-Soo Huh, Duk-Dong Lee, Fabrication and characterization of micro-gas sensor for nitrogen oxides gas detection, Sensors and Actuators B: Chemical, Volume 64, Issues 1–3, 10 June 2000, Pages 31-36M. Chen, Z. Wang, D. Han, F. Gu, G. Guo, Porous ZnO Polygonal Nanoflakes: Synthesis, Use in High-Sensitivity NO 2 Gas Sensor, and Proposed Mechanism of Gas Sensing, J. Phys. Chem. C. 115 (2011) 12763–12773. https://doi.org/10.1021/jp201816d.L. Van Duy, N. Van Duy, C.M. Hung, N.D. Hoa, N.Q. Dich, Urea mediated synthesis and acetone-sensing properties of ultrathin porous ZnO nanoplates, Mater. Today Commun. 25 (2020) 101445. https://doi.org/10.1016/j.mtcomm.2020.101445.

Preparing CuO, Cu2O thin films at various argon gas by using reactive dc magnetron sputtering method

Copper oxide (Cu2O, CuO) has been formed by dc reactive magnetron sputtering method of glass substrates, whereas pure target of the solid copper was sputtered with a mixture of plasma for argon gas and oxygen gas which are used form these films. Under vacuum chamber pressure on 1.2×10-5 Pa, Ar was varying from 5 to 15 sccm while other deposition parameters were fixed. X-ray photoelectron spectroscopy, XRD diffractions system, Atomic Force Microscopy (AFM), hall effect measurement system, and UV–VIS spectrophotometer were used to calculate the characteristic of the deposited thin films. Thin film at 5 sccm has investigated n-type of CuO thin film with direct band gap of 1.8eV and p-type of Cu2O at 15 sccm with direct band gap of 2.7eV. The influence of changing the Ar on the electrical and the optical properties was investigated in this study, furthermore in this study approved that the reactive dc magnetron sputtering method is suitable to prepare two type of semiconductors by change only one condition.

DC sputtered ZrO2/Zn(1−x)Sn(x)O thin-film transistors and their property evaluation

A bottom gate staggered 30 nm Zn(1−x)Sn(x)O (x = 0.14) (TZO)-based thin-film transistors (TFTs) were fabricated using DC magnetron reactive sputtering method. Highly transparent 120 nm dc sputtered ZrO2 was used as a gate dielectric. The oxygen flow rate was varied from 20 to 24% during channel layer (TZO) coating and its effect on structural, morphological, optical, chemical, and electrical parameters were systematically studied. A nano scale roughness was noticed by atomic force microscopy (AFM), and ultra-smooth nature in root mean square roughness (RMS) was observed with an increment in the oxygen flow ratio. The increase in the oxygen-related defects with increase in the oxygen flow ratio in channel layer was evident from X-ray photoelectron spectroscopy (XPS). The electrical characterization of gate dielectric was carried out for Al–ZrO2–Al structure. The high capacitance density ~ 121.9 nF/cm2 for 120 nm ZrO2 was obtained from the capacitance–voltage (C–V) measurement. The fabricated TFTs operated in n-channel depletion mode and indicated pinch-off region at lower source–drain voltages. In addition, the transfer characteristics of TFTs confirmed Ion/Ioff ratio of 105, with a field effect mobility of 23 cm2/V.s. This low temperature processed TFT unlocks the possibility of use in the next generation foldable display technology.

Ion-beam assisted sputtering of titanium nitride thin films

Titanium nitride is a material of interest for many superconducting devices such as nanowire microwave resonators and photon detectors. Thus, controlling the growth of TiN thin films with desirable properties is of high importance. This work aims to explore effects in ion beam-assisted sputtering (IBAS), were an observed increase in nominal critical temperature and upper critical fields are in tandem with previous work on Niobium nitride (NbN). We grow thin films of titanium nitride by both, the conventional method of DC reactive magnetron sputtering and the IBAS method, to compare their superconducting critical temperatures T_{c} as functions of thickness, sheet resistance, and nitrogen flow rate. We perform electrical and structural characterizations by electric transport and x-ray diffraction measurements. Compared to the conventional method of reactive sputtering, the IBAS technique has demonstrated a 10% increase in nominal critical temperature without noticeable variation in the lattice structure. Additionally, we explore the behavior of superconducting T_c in ultra-thin films. Trends in films grown at high nitrogen concentrations follow predictions of mean-field theory in disordered films and show suppression of superconducting T_c due to geometric effects, while nitride films grown at low nitrogen concentrations strongly deviate from the theoretical models.

Formation of pure anatase TiO2 using the reactive pulsed dc magnetron sputtering method for controlling the target poisoning state

AbstractThe use of pulsed dc‐sputtering sources for reactive magnetron sputtering with oxygen offers a possibility to suppress the negative effects of target poisoning (such as arcing). This results in a wide process range for the selection of a desired operating point. The control of target poisoning plays a major role in maintaining constant coating properties and affects the stoichiometry of the reactive coating, as well as the coating rate and the economic impact of the coating process. In a hysteresis, the target poisoning during the reactive sputtering of titanium under oxygen addition proceeds nonlinearly. Without the use of a suitable target poisoning control technique, the sputtering process can abruptly change to an unstable state. As a result, variations of stoichiometry can occur during the deposition process. A proven method for maintaining a stable reactive sputtering process is the control of oxygen flow with the input variable target voltage. By determining the typical oxygen hysteresis at constant target power and constant argon flow, an operating point for the control loop is derived. The desired target voltage then serves as the input variable for the control loop of the target poisoning. The controlling technique for target poisoning is a basic requirement for the production of the photolytic active anatase phase of titanium dioxide (TiO2) using reactive magnetron sputtering. The photocatalytic equipment of surfaces with a titanium dioxide coating in the anatase phase can be realized with the reactive pulsed dc magnetron sputter ion plating process (DC‐MSIP). The pulsed DC‐MSIP process facilitates coating a variety of surfaces at temperatures below 200°C in an environmentally friendly manner.

Structural and photocatalytic properties of undoped and Zn-doped CuO thin films deposited by reactive magnetron sputtering

In this research, undoped and Zn-doped CuO thin films were successfully fabricated by the reactive magnetron sputtering method. The effect of Zn dopant concentration on the enhancement of photocatalytic behavior and structural properties of CuO thin films was investigated. To obtain the optimal conditions in terms of the highest efficiency and rate in the photocatalytic degradation of methylene blue (MB), CuO films were first deposited at different oxygen partial pressures (30 %, 40 %, and 50 %). Optimal conditions, i.e., a 70 % photodegradation efficiency with a rate of 0.279 h−1 were achieved in the undoped sample deposited at a partial pressure of 40 %. Then different Zn amounts were incorporated into the CuO lattice by controlling the RF power in the range of 10–40 W. As-prepared samples were analyzed using GIXRD, XPS, PL, EIS, and UV–vis spectroscopy. The GIXRD pattern of the Zn-doped sample showed the formation of CuO without altering its monoclinic structure. XPS spectra indicated the presence of Cu2+ and Zn2+ oxidation states, which means the successful substitution of Zn2+ at Cu2+ sites in the CuO lattice. Based on EIS results, increasing the Zn cation dopant up to 0.026 led to a decrease in the charge resistance transfer compared to the undoped CuO. By increasing the amount of Zn in the cationic ratio up to 0.02, PL peak intensity reached the lowest value. Accordingly, the MB degradation efficiency increased to above 80 % in this sample. Active species involved in the photocatalytic reactions were investigated via a scavenger test. The Zn-doped CuO film showed high MB degradation efficiency even after five cycles (77 %), which made it a potential candidate for wastewater purification.