RF Magnetron Co-sputtering Research Articles

Chromium nano-segregation and intermediate band formation in heavily-doped ZnS:Cr films

X-ray absorption spectroscopy, X-ray diffraction, and UV–Vis spectroscopy were employed to investigate heavily-doped ZnS:Cr films prepared by RF magnetron co-sputtering. EDS indicates ca. 5 at. % Cr incorporation as well as slight S-deficiency. XAS in the Zn K- and Cr K-edges revealed Zn-by-Cr substitution and segregation of Cr nanoclusters which lead to significant lattice distortion. XRD indicates a 44 % increase in the strain, an increase in the lattice parameter, and a decrease in the crystallite size upon Cr incorporation. The presence of Cr nanoclusters contributed to changes in the band gap, a large Urbach tail parameter of 565 meV, and the formation of an intermediate band arising from the Cr 3d spin-up states. The results suggest ZnS:Cr films in the heavily doping regime could lead to applications in photovoltaics and spintronics.

Analysis of optical, structural, and morphological properties of a Ti-doped α-Fe2O3 thin film produced through RF and DC magnetron Co-sputtering

In this study, a Titanium (Ti) doped α-Fe2O3 (hematite) thin layer was synthesized onto a glass substrate, employing the simultaneous DC and RF magnetron sputtering method. The investigation focused on examining specific physical properties of the film. The optical, structural, morphological, and elemental features of the resulting Ti-doped α-Fe2O3 thin film were characterized using different characterization techniques. The XRD studies indicated a rhombohedral crystal structure in the studied thin film. The calculation of the Eg value for the thin film, based on absorption measurements, resulted in a value of 2.19 eV. Raman peaks were identified within the range of 218 cm−1 to 1300 cm−1. According to SEM images, the thin film exhibited a uniform surface morphology across the substrate. AFM images revealed a low root mean square (RMS) roughness value, indicating a smooth Ti:Fe2O3 thin film surface.

Grown Silicon Iron Oxide by DC- RF Magnetron Co-Sputtering Technique

In this study, the structure of silicon iron oxide (Si:Fe2O3) was grown using co-sputtering. The Si:Fe2O3 film was grown on glass substrates at a pressure of 8.5 mTorr and a temperature of 450°C for 35 minutes. Optical measurements have revealed that the band gap of the structure ranges from 2.54 to 2.73 eV. The roughness values of the films in AFM images are Ra 3.08 nm and Sa 2.7 nm for Si:Fe2O3, and Ra 1.88 nm and Sa 2.09 nm for Fe2O3, respectively. As can be seen from the XPS figures, the change in binding energy is attributed to electron exchange among silicon, iron, and oxygen. In the iron-silicon oxide structure, the energy increases slightly as a result of the chemical environment. XRD measurements indicate that the size of crystal grains decreases gradually with an increase in silicon content. The Si4+ ion has a strong tendency to distribute itself within the tetrahedral region of spinel-like structures. The behavior of the structure is influenced by the stoichiometry of oxygen. The consistent results from both XRD and SEM images indicate that the crystal grain sizes gradually decrease as the silicon content increases.

Zirconium doped indium oxide thin films as transparent electrodes for photovoltaic applications

In this work we report on ultra-thin Zirconium doped In2O3 transparent conductive films grown at room temperature via RF-Magnetron co-sputtering. Samples from 15 nm to 90 nm thick, and low Zr atomic concentration (0.6–0.9 at.%), were annealed at T = 200 °C after the deposition. The phase-transition from amorphous to crystalline, confirmed by XRD measurements, leads to an improvement of both electrical and optical properties. The thinnest film (15 nm) shows electrical resistivity as low as 5 × 10−4 Ωcm, with carrier mobility of 20 cm2V−1s−1, and optical transmittance up to 80 % in visible and near-infrared range. IZrO electrode performances were tested through external quantum efficiency (EQE) measurements on a semi-finite Silicon Heterojunction bi-facial solar cell. The EQE values for 90 nm thick film are comparable to that of standard ITO when IZrO films are implemented as front electrodes. These results suggest that ultra-thin IZrO films may be successfully used to reduce costs and the amount of Indium used in Indium-based transparent conductive oxide layers for solar cells.

Structural, optical and mechanical properties of Ti-doped Ta2O5 films for PV glass covers

Ti doped Ta2O5 thin films (TTO) with uniform thickness were prepared on photovoltaic glass substrates by DC and RF magnetron co-sputtering with different target powers. The surface morphology and microstructure of the films were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). The composition of the films was analyzed by X-ray photoelectron spectroscopy. The optical parameters of the films were measured by UV–visible spectrophotometer. The hardness and Young 's modulus of the coating were tested by nanoindentation. XPS analysis shows that the main components of TTO films are TiO2 and Ta2O5. SEM and AFM results show that the surface of the TTO film is smooth and flat, with uniform elemental distribution and nanometer roughness. The SEM cross-sectional morphology shows that the TTO film presents a dense columnar structure growth. The TEM results show that the TTO films do not show bright diffraction rings and mainly exhibit an amorphous phase structure dominated by Ta2O5. The optical test results show that the maximum transmittance of TTO film can reach 94.59 %. The transmittance of TTO films shows a decreasing trend with increasing sputtering power of the target, while the opposite is true for reflectance and refractive index. The optical band gap of the TTO films is between 4.12 eV and 4.42 eV. The mechanical test results show that the hardness of the TTO film can reach up to 9.53 Gpa. The hardness of TTO film increases with the increase of target power. The H/E and H3/E2 values indicate that Ti doped Ta2O5 films are favourable for improving the resistance to plastic deformation of the films. Comprehensive analyses show that Ti doped Ta2O5 films can have both excellent optical and mechanical properties. TTO films can provide a valuable reference for the study of PV glass protective layer.

Effects of deposition temperature on the mechanical and structural properties of amorphous Al–Si–O thin films prepared by radio frequency magnetron sputtering

Aluminosilicate (Al–Si–O) thin films containing up to 31 at.% Al and 23 at.% Si were prepared by reactive RF magnetron co-sputtering. Mechanical and structural properties were measured by indentation and specular reflectance infrared spectroscopy at varying Si sputtering target power and substrate temperature in the range 100 to 500 °C. It was found that an increased substrate temperature and Al/Si ratio give denser structure and consequently higher hardness (7.4 to 9.5 GPa) and higher reduced elastic modulus (85 to 93 GPa) while at the same time lower crack resistance (2.6 to 0.9 N). The intensity of the infrared Si-O-Si/Al asymmetric stretching vibrations shows a linear dependence with respect to Al concentration. The Al–O–Al vibrational band (at 1050 cm−1) shifts towards higher wavenumbers with increasing Al concentration which indicates a decrease of the bond length, evidencing denser structure and higher residual stress, which is supported by the increased hardness. The same Al–O–Al vibrational band (at 1050 cm−1) shifts towards lower wavenumber with increasing substrate temperature indicating an increase in the average coordination number of Al.

Micro-scale tribological study of a Ni-Cr-Fe-Ti-Al-V high entropy alloy thin film by magnetron co-sputtering of Inconel-718 and Ti-6Al-4V

In this study, we fabricated high entropy alloy (HEA) thin films by RF magnetron co-sputtering of Inconel 718 and Ti-6Al-4V targets. Their coefficient of friction (CoF) and specific wear rate (K0) were investigated to evaluate their potential as a material for MEMS moving parts. By placing different number of Ti-6Al-4V pellets (samples abbreviated as IT2, IT4, IT6) on an Inconel 718 target (abbreviated as IT0), Ni-Cr-Fe-Ti-Al-V HEA thin films with configurational entropy of mixing (∆Sconf) >1.5R were successfully deposited. Electron microscopy and diffraction confirms that IT0 possessed a mixed nanocrysalline/amorphous structure, while the Ti-added IT2, IT4 and IT6 films were amorphous. They also have a significantly reduced root-mean-square roughness. In order to evaluate their micro-scale wear behavior, various tribological studies including indentation, scratch test and scanning wear test were conducted. From IT0 to IT6, film hardness H increases while reduced modulus Er remains similar. Plastic criterion Rw is also reduced, showing that the films IT2, IT4 and IT6 are more prone to elastic deformation. Scratch test also reveals that IT6 can afford the highest normal load before the transition of wear mode occurs. Lastly, a scanning wear test was conducted to evaluate the specific wear rate (K0) of each HEA film. It was found that IT6 had the lowest value of K0 = 2.26 × 10−4 mm3 N−1 m−1, which was also a lot lower than Si-to-Si (K0 = 0.0183 mm3 N−1 m−1) wear in other studies. The excellence of IT6 can be attributed to the fact that alloying of Ti effectively reduced the average interatomic distance in the HEA films, resulting in a densely packed, very elastic microstructure. Therefore, IT6 is expected to have longer service life than silicon if it were made into MEMS moving parts.

Enhancement on the hardness and oxidation resistance property of TiN/Ag composite films for high temperature applications by addition of Si

Titanium nitride and silver (TiN/Ag) composite films exhibited the excellent self-lubricating properties in a wide temperature range due to the formation of the Ag rich tribolayer in the contact. However, Ag addition usually reduces the hardness and oxidation resistance properties of the films. In this paper, TiN/Ag/Si3N4 composite films were deposited using RF magnetron co-sputtering system to improve the mechanical and oxidation resistance properties of the TiN/Ag film. XRD and TEM analysis revealed that three-phases could be identified on the TiN/Ag/Si3N4 films: face-centered cubic (fcc) TiN, fcc-Ag and amorphous Si3N4 phases. The hardness of the TiN/Ag film increased from ∼16 GPa to ∼24 GPa for TiN/Ag/Si3N4 with 15.3 at.% of Si due to the formation of the nanocomposite structure. The addition of Si allowed a significant improvement on the oxidation resistance temperature, and effectively avoiding of Ag diffusion, and thereby contributing the stability of the hardness of the film after annealing treatment.

Bandgap tunability and local structure of MgxZn1–xO (0 ≤ x ≤ 1) thin films grown by RF magnetron co-sputtering

Bandgap tunability and local structure of MgxZn1–xO (0 ≤ x ≤ 1) thin films grown by RF magnetron co-sputtering

Annealing temperature effect on the surface properties and antimicrobial activity of SnSe thin films

In this study, tin selenide thin films with various atomic ratios were fabricated using the RF magnetron co-sputtering method and annealed at different temperatures. In order to observe the structural and chemical properties of the thin films, various characterization tools and methods such as atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy, Kelvin probe, and antimicrobial test against Escherichia coli were performed. SEM and AFM images showed that the surface morphology of the thin films changed at 573 K. Additionally, the phase changed from amorphous to orthorhombic SnO2 at high temperature, which was confirmed by XRD results. XPS results confirmed SnSe thin films was oxidized and Se evaporated as the annealing temperature increased. The work function of thin films with higher contents of Sn than Se were increased from 5.23 to 5.68 eV as the annealing temperature increased. On the other hand, the work function of thin films with higher Se content than Sn decreased from 5.86 to 5.44 eV. Antimicrobial testing revealed that the SnSe thin films exhibit a stronger effect compared to pure Sn and Se thin films.

Mobility Enhancement in P-Type SnO Thin-Film Transistors via Ni Incorporation by Co-Sputtering

Oxide semiconductors have been considered one of the most promising candidates for flexible electronics applications owing to their low process temperatures and good reliability. However, the low mobility of p-type oxide semiconductors limits the performance of flexible oxide-TFT-based CMOS technology. In this study, p-type SnO_<i>x</i>:Ni thin films were deposited by reactive rf magnetron co-sputtering, a technique compatible with the current industrial semiconductor manufacturing technology, from Sn and Ni targets. As the Ni-gun power increased, the distribution of Ni in the SnO_<i>x</i>:Ni thin film changed from a more uniform dispersion to nanoclusters, resulting in the crystalline phase transition of SnO_<i>x</i>:Ni from <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-SnO (110)-dominant polycrystalline to amorphous and then to <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-SnO (101)-dominant polycrystalline. A high-mobility inverted-staggered p-type SnO_<i>x</i>:Ni TFT was then fabricated on a glass substrate with a maximum process temperature of 225&#x00B0;C, which is compatible with flexible polymeric substrates. The TFT fabricated at an optimal Ni-gun power of 42 W exhibited an impressive field-effect mobility of 11 cm²V^&#x2212;1s^&#x2212;1 and on current of <inline-formula> <tex-math notation="LaTeX">$35.2 ~\mu \text{A}$ </tex-math></inline-formula> per channel width-to-length ratio; these values are comparable to those of a typical n-type oxide TFT. These results should contribute toward flexible oxide-TFT-based CMOS technology.

Enhanced Electrochromic Performance of All-Solid-State Electrochromic Device Based on W-Doped NiO Films

Electrochromic materials have attracted much attention due to their promising applications in smart windows and thermal control. However, NiO is a weak point for a complementary ECD and needs to be improved due to its low optical modulation and charge density. In this work, the W-doped NiO films are designed and prepared by RF magnetron co-sputtering to improve the performance of the NiO. The results shows that the optical modulation of the W-NiO (52.7%) is significantly improved compared with pure NiO (33.8%), which can be assigned to the increase in lattice boundaries due to the W doping. The response time of W-NiO is 8.8 s for coloring and 7.2 s for bleaching, which is similar to that of NiO film. The all-solid-state electrochromic devices (ECDs) that employed W-NiO as a complementary layer are prepared and exhibit a high-transmittance modulation of 48.5% in wavelengths of 450–850 nm and an emittance modulation of 0.28 in 2.5–25 μm, showing great application potential in the field of smart windows and spacecraft thermal control devices. The strategy of preparing NiO doped by W indicates an innovative direction to obtain ECDs with high performance.

Effect of Yb-doping on structural and electrical properties of BiFeO3 thin films

In this paper, the incorporation of ytterbium into the BiFeO3 thin film was fabricated on the Pt/Ti/SiO2/Si substrates by using both dc and rf magnetron co-sputtering method at room temperature. The impact of ytterbium content on structural properties and electrical characteristics of the BiFeO3 thin films was investigated. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy techniques were applied to examine the crystal structures, elemental compositions, microstructures, and film morphologies of these thin films, respectively. The Yb-doped BiFeO3 thin film fabricated at the 11 W condition exhibited the lowest leakage current and the highest remnant polarization among these conditions. This result is attributed to the formation of a stronger BiFeO3 (202) component leading to the decrease in oxygen vacancies.

Mathematical model depicting the deposition kinetics process into rf-magnetron co-sputtering of strontium barium titanate thin films

"Thin films deposition kinetics of BaXSr1-XTiO3 (BST)/nichrome is modeled by the stoichiometric rate of a perovskite-type material such as ABO3, where cations A, B, and the anion oxygen should ideally have a 1:1:3 rate, respectively. The experimental stoichiometry data measured by EDS on films of 240 nm, and the Ba/Sr, (Ba+Sr)/Ti rates considered in percentages starting from arithmetic and the sigmoidal relationship between Ba and Sr. They show relationships in sigmoidal, exponential, and parabolic mathematical functions that together describe the BST thin films deposition kinetics by means of RFMagnetron Co-Sputtering (RFMCS). The proposed mathematical model is fundamental to optimize, explain and use the deposition process working conditions, such as the working pressure, the Ar/O2 rate in percentage, and sccm. The controlled applied power on each BaTiO3 (BTO) and SrTiO3 (STO) targets achieve more accurate stoichiometry in thin films deposition for solid solutions on quaternary materials."

Effect of Al Concentration on Microstructure and Properties of AlNbTiZr Medium-Entropy Alloy Coatings.

The AlNbTiZr medium-entropy alloy (MEA) coatings with different Al contents were prepared on N36 zirconium alloy substrates by RF magnetron co-sputtering. The morphology, microstructure, mechanical properties, surface wettability and corrosion resistance of the AlNbTiZr MEA coatings were studied to evaluate the surface protection behavior of zirconium alloy cladding under operation conditions of a pressurized water reactor. The results showed that all the coatings were composite structures with amorphous and bcc-structured nanocrystals. With the increase of Al content, both the elastic modulus and hardness decreased first and then increased. The hydrophobicity of the coatings was enhanced compared with that of the substrate. The 10.2 at.% Al AlNbTiZr coating had the best corrosion resistance and the minimum oxygen penetration depth, which originated from the formation of a denser oxide layer consisting of Nb2Zr6O17 and ZrO2. This study provides an improved idea for the design and development of Al-containing MEA coating materials for accident tolerant fuel.

Corrosion and Wear performances analysis of PVD CrMoN/Cr Coatings

Tools coated CrN based alloys are currently used in several industries for machining and manufacturing, but present severe wear, limiting their service life. Seeking an alternative, three CrMoN monolayers (~1µm in thickness) coatings with varying in the Mo percentage content were elaborated using the RF magnetron co-sputtering method. These coatings were evaluated and compared with the alloy currently used (CrN) by electrochemical tests in NaCl solution (stationary and no stationary method) and sliding wear tests (ball-on-disc configuration) performed at room temperature. The results indicate that the samples coated with CrMoN presented better performance against wear and corrosion than the uncoated sample. Among the coatings, the labeled C1 (27 % Mo) showed the best corrosion resistance as it presents a positive corrosion potential Ecorr. However, the best wear resistance (lowest coefficient of friction) was shown by coating labeled C4 (33 % Mo). All of the tested specimens underwent abrasive wear in addition to adhesive wear.

Morphological, optical, catalytic and photocatalytic properties of RF magnetron sputtered Au-Cu2O-CuO nanocomposite thin films

Plasmonic nanocomposite thin films represent an important set of materials which has gained huge attention for photocatalytic and catalytic applications. We report on fabrication of thin films of Au-Cu2O-CuO nanocomposites by RF magnetron co-sputtering which were thoroughly analyzed by atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis-DRS, UV-vis absorption and photoluminescence spectroscopy (PL). AFM and FESEM analyses revealed nanoparticle growth with increase in Au content of the nanocomposite. XPS analysis revealed the existence of Au, Cu2O and CuO in the obtained films. The prepared nanocomposite thin film demonstrated excellent sunlight driven photocatalytic performance for the degradation of organic pollutants and significant catalytic activity for the transformation of 4-nitrophenol (4-NP). Au-Cu2O-CuO nanocomposite thin film removed 73.1% of methyl orange (MO) and 86.2% of methylene blue (MB) in only 28 min of solar exposure. Improved visible light absorption together with better charge separation and improved transport of charge carriers due to Au nanoparticles embedded in Cu2O-CuO thin film significantly improved the catalytic and photocatalytic features of the nanocomposite. The reusability and role of radicals in the photocatalysis for Au-Cu2O-CuO nanocomposite thin film are also highlighted.

Compositional ratio effect on the physicochemical properties of SnSe thin films

In this study, tin selenide thin films with different atomic ratio combinations were fabricated utilizing the RF magnetron co-sputtering method. In order to analyze the innate physicochemical properties of the thin films, various characterization tools such as scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and contact angle measurements were used. SEM and AFM images revealed that incorporating higher amounts of Se increases the resulting grain size and surface roughness. Additionally, Se incorporated thin films were amorphous in nature, which was confirmed by XRD results. From the XPS spectra, the Sn 3d5/2 peak was deconvoluted into three peaks: (Sn4+, 487 ± 0.3 eV), (Sn2+, 486.3 ± 0.3 eV), (Sn0, 484.9 ± 0.3 eV) and the Sn4+ species only existed in pure Sn thin films potentially due to inevitable surface oxidation. UPS and Kelvin probe (KP) measurements were conducted to calculate work function values. Based on UPS results, the work function values increased from 4.29 eV to 6.01 eV with increasing Se content. Similarly, the work function values from KP measurements increased from 4.84 eV to 5.71 eV with increasing Se content. Using data from contact angle measurements, it was deduced that pure Sn thin films are hydrophobic but become more hydrophilic with increasing Se content.

Preparation and tunable optical properties of amorphous AlSiO thin films

Thin films in the aluminosilicate (AlSiO) system containing up to 31 at. % Al and 23 at. % Si were prepared by reactive RF magnetron co-sputtering in order to investigate the dependence of film formation and optical properties on substrate temperature and Si and Al contents. The obtained films were amorphous with smooth microstructure. The growth rate at different substrate temperatures ranged from 1.2 to 3.3 nm/min and increase with increasing the Si target power. The roughness decreases and thickness increases with increasing Si content. The thickness of the films grown at a deposition temperature of 100 °C is found to be higher than the films deposited at 300 and 500 °C. The AlSiO-coated glasses have a higher transmission in the visible region than the uncoated glass. The spectroscopic ellipsometry analysis reveals that the refractive index value decreased with decreasing the Al content, having extinction coefficient values of zero in the measured spectral region and band gap values ≥ 3.4 eV. The obtained thin films have over 90% transmittance in the visible range and no systematic variation of transmittance was observed with substrate temperature. The results suggest that glass substrate coated with AlSiO thin films have improved optical properties.

Impact of Cu addition on the optoelectronic properties of Zn3N2 thin films: n to p-type transitions

Copper-doped Zinc Nitride (Cu:Zn3N2) films are grown on glass and Si substrates at various concentration of Cu (2.7, 4.9 and 5.7 at.%) by reactive RF magnetron co-sputtering. The impact of Cu atomic concentration on the structural and optoelectronic properties of Zn3N2 films is discussed in detail. Incorporation of Cu ions into Zn3N2 host lattice is confirmed by EDAX analysis. Hall Effect results indicate that the fabricated film exhibited p-type conductivity with high hole concentration of 1.78–1.36 × 1018 cm−3, resistivity of 0.48–0.56 Ω cm, and high hole mobility of ~8 cm2 V−1 s−1. The transmittance of Cu:Zn3N2 films are found to be in the range of 11–18% at the wavelength of 500 nm and hence the band gap decreases from 1.80 to 1.61 eV when Cu doping content is increased. These findings would assist Cu:Zn3N2 as a potential candidate for p-type layer in thin film solar cells.