Reactive RF Magnetron Co-sputtering Research Articles

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.

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.

Structural, optical and electrical properties of indium doped Cu2ZnSn(S,Se)4 thin films synthesized by the DC and RF reactive magnetron cosputtering

Element doping into the Cu2ZnSn(S,Se)4 (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu2InxZn1-xSn(S,Se)4 (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu2ZnSnS4 (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (PIn). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In3+ into the main lattice of CZTSSe. The partial Zn2+ cations were substituted by In3+ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the PIn was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as PIn increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at PIn = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm2V−1s−1, which is a potential material as the absorption layer of high-performance solar cells.

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.

Ba-acceptor doping in ZnSnN2 by reactive RF magnetron sputtering: (002) faceted Ba–ZnSnN2 films

Zn-IV-N2 semiconductors display outstanding optoelectronic behavior and hence developed as an effective thin film absorber materials in photovoltaic devices. However, alkaline-earth metallic dopants can improve the performance of Zn-IV-N2 semiconductors. In view of this, Barium (Ba) acceptor was successfully doped into ZnSnN2 crystal lattice with various dopant concentrations (∼0–7%) by reactive RF magnetron co-sputtering at 450 °C. The orthorhombic structured Ba doped ZnSnN2 (Ba:ZTN) films with preferential orientation along (002) plane were obtained. Hall measurement studies revealed that the type of conduction is changed from the conventional n-type to p-type via Ba doping. The deposited Ba:ZTN films exhibited high hole concentration in the range of 1018-1019 cm−3 with low resistivity of ∼10−1 Ω cm and a reasonable mobility of ∼0.5–5 cm2 V−1 s−1. The doping of Ba at either Zn or Sn site would be responsible for the p-type conductivity in Ba:ZTN films. The variations in the surface properties such as morphology and topography of ZnSnN2 on Ba doping were described by FE-SEM and AFM analysis. Further analysis by UV–Vis–NIR and X-ray photoelectron spectroscopies were also performed in order to reveal the optical performance and chemical bonding, composition of Ba:ZTN thin films. The existence of Ba2+ ions in Ba:ZTN was confirmed by the obtained binding energies from XPS analysis. From the collective results, it is suggested that Ba:ZTN could be employed as effective p-type layer in thin film solar cells.

Fast response of CO2 room temperature gas sensor based on Mixed-Valence Phases in Molybdenum and Tungsten Oxide nanostructured thin films

Molybdenum - tungsten oxide (Mo1-xWxO3, x = 1, 0.8, and 0.6) nanostructured thin films-based room temperture (RT) gas sensors are prepared by means of reactive RF magnetron co-sputtering at 400 °C. The structural, morphology, topography, optical, and electrical characterizations of the prepared sensors are carried out by XRD Rietveld structure refinement analyses, SEM, AFM, UV-VIS spectrophotometer, and source meter. By controlling the deposition temperture of 400 °C, a co-existing phase of MoO3 and MoO2 in WO3 matrix is presented with high oxygen vacancies concentration as calculated from the XRD Rietveld Refinement analyses. By increasing the Mo content, the calculated oxygen vacancies concentration increases by factor of 1.36. The optical characterization of Mo0.2W0.8O3 thin film shows a high transparent of 99.6% at 500 nm. The prepared thin films have successfully tested to detect carbon dioxide (CO2) at RT (20 °C) with high selectivity and repeatability. The Mo0.4W0.6O3 sensor film shows an electrical Schottky contact with fast response and recovery times towards CO2 under UV light activation. Mo0.4W0.6O3 thin film under dark and UV conditions were able to detect low CO2 concentration of 2 and 0.5 sccm CO2 at RT, respectively. Under UV illumination, Mo0.4W0.6O3 film shows a fast response and recovery time of 6.53 and 8.05 s at 0.5 sccm with sensitivity of 29.19%. Under UV photonic activation, higher electron concentration is presented in the oxide surface, which leads to high probability for reaction with CO2 molecules, and consequently enhanced the chemisorption of CO2. The enhanced CO2 gas sensitivity and fast response may refer to the high oxygen vacancies concentration and the active role of the grain boundaries in MoO2, MoO3 and WO3 mixed-valence nanostructured under UV activation.

Tailoring optoelectronic properties of earth abundant ZnSnN2 by combinatorial RF magnetron sputtering

Zn-IV-N2 semiconductors are often considered as imminent materials alternative to InGaN and requisite thin film photovoltaic absorber materials for light harvesting due to its direct band gap, steep absorption onset and disorder-driven band gap tenability. In view of this, ZnSnN2 thin films were successfully prepared by reactive RF magnetron co-sputtering with different Sn concentrations at 450 °C substrate temperature. The films grown at 450 °C with different Sn target power were found to be orthorhombic crystal structure which has higher grain size (13–28 nm), low carrier density (−4.99 × 1018 to −7.01 × 1017 cm−3) and the maximum mobility (11.1 to 15.5 cm2 V−1 s−1). The phase purity and chemical bonding states of ZnSnN2 were investigated by XPS analysis. Vibrational modes of ZnSnN2 confirmed the presence of N-bonding with Zn and Sn. The optical band gap decreased from 1.96 to 1.77 eV as the Sn power increased. Hence, it is suggested that ZnSnN2 thin film grown under this technique could be utilized as efficient absorber layer in thin film solar cells due to the astonishing optical and electrical properties.

Role of copper/vanadium on the optoelectronic properties of reactive RF magnetron sputtered NiO thin films

In this study, pristine nickel oxide (NiO), copper-doped NiO (Cu–NiO) and vanadium-doped NiO (V–NiO) thin films were deposited using reactive RF magnetron co-sputtering as a function of dopant sputtering power. Cu (0–8 at%) and V (0–1 at%) were doped into the NiO lattice by varying the sputtering power of Cu and V in the range of 5–15 W. The effect of dopant concentration on optoelectronic behavior is investigated by UV–Vis–NIR spectrophotometer and Hall measurements. XRD analysis showed that the preferred orientation of the cubic phase for undoped NiO changes from (200) to (111) plane when the sputtering parameters are varied. The observed changes in the lattice parameters and bonding states of the doped NiO indicate the substitution of Ni ions by monovalent Cu and trivalent V ions. The optical bandgap of pristine NiO, Cu–NiO, and V–NiO was found to be 3.6, 3.45, and 3.05 eV, respectively, with decreased transmittance and resistivity. Further analysis using SEM and AFM described the morphological behavior of doped NiO thin films and Raman spectroscopy indicated the structural changes on doping. These findings would be helpful in fabricating solid-state solar cells using doped NiO as efficient hole transporting material.

Structural and mechanical evolution of TiAlSiN nanocomposite coating under influence of Si3N4 power

Abstract In this study, we have reported the microstructural and mechanical properties of nanocrystalline Titanium Aluminum Nitride (TiAlN) embedded in amorphous Silicon Nitride (Si 3 N 4 ) nanocomposite films. The films were deposited on Si substrate by using DC\RF reactive magnetron co-sputtering of TiAl and Si 3 N 4 targets by varying power to the Si 3 N 4 target. The films were investigated using grazing incident X-ray diffraction (GIXRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), stylus profiler and nanoindentation. GIXRD shows the formation of crystalline cubic Ti 3 AlN phase in the films. With the increase in Si 3 N 4 power, crystal growth of TiAlN diminishes. FESEM micrographs showed the uniformly distributed, well developed, sharp-edged, irregular shaped grains on the surface of the films. The silicon-rich region was observed at inter-grain boundary region and the micrographs visualize the presence of amorphous Si 3 N 4 on the edge of crystal grains. The amorphous content increases with Si 3 N 4 power. EDS confirms the presence of all elements in the films. The optimum mechanical properties were observed at 70 W Si 3 N 4 target power. Hardness, elastic modulus, elastic recovery and resistance to plastic deformation of film rises from 40 W to 70 W target power and then reduces at 90 W.

Lattice extension in Cu3NMgx thin films and the induced effect

Foreign atoms occupying extrinsic positions other than lattice sites of the original matrix can effectively bring out new material properties. Ternary Cu3NMgx thin films with x up to x = 0.32 were synthesized on silicon and quartz substrates by RF reactive magnetron cosputtering of copper and magnesium targets, in which the Mg atoms occupy the previously empty centers of unit cells of the cubic Cu3N lattice. The upper limit was determined by the deteriorated crystallinity of the deposits due to weakened overall bonding strength and lattice expansion. With increasing amount of Mg dopant atoms, the Cu3NMgx compounds exhibit a steadily narrowed band gap that the room temperature electrical resistivity drops by four orders of magnitude, yet all the deposits remain n-type semiconductor. The factors contributing to the reduced electrical resistivity in Cu3NMgx compounds with larger x values are discussed. These results may inspire more efforts towards material design via lattice extension for new and largely adjustable material properties.

Ion Beam Analysis, structure and corrosion studies of nc-TiN/a-Si3N4 nanocomposite coatings deposited by sputtering on AISI 316L

In this work, nanocomposite coatings of nc-TiN/a-Si3N4, were deposited on AISI 316L stainless steel substrate by a DC and RF reactive magnetron co-sputtering technique using an Ar–N2 plasma. The structure of the coatings was characterized by means of XRD (X-ray Diffraction). The substrate and coating corrosion resistance were evaluated by potentiodynamic polarization using a Ringer solution as electrolyte. Corrosion tests were conducted with the purpose to evaluate the potential of this coating to be used on biomedical alloys. IBA (Ion Beam Analysis) techniques were applied to measure the elemental composition profiles of the films and, XPS (X-ray Photoelectron Spectroscopy) were used as a complementary technique to obtain information about the compounds present in the films.The nanocomposite coatings of nc-TiN/a-Si3N4 show crystalline (TiN) and amorphous (Si3N4) phases which confer a better protection against the corrosion effects compared with that of the AISI 316L.

Transparent conducting Ga-doped ZnO thin films grown by reactive co-sputtering of Zn and GaAs

Transparent conducting Ga-doped ZnO films have been deposited by rf reactive magnetron co-sputtering of Zn and GaAs in Ar–O2 mixture at a total flow rate of 30sccm. Ga-doped ZnO films deposited with 1% GaAs target area coverage exhibit high transparency and low electrical resistivity in a narrow operational window of substrate temperature in the range of 350–400°C and 3–4% O2 in the sputtering gas mixture. The film deposited under optimized conditions contains low arsenic impurity (~0.1at.%) and exhibits ~80% or higher average transmittance in the visible region and electrical resistivity of ~9×10−6Ω-m, which corresponds to sheet resistance of 12–15Ω/sq. The film exhibits carrier concentration ~7×1026m−3 and Hall mobility ~10−3m2V−1s−1. The high carrier concentration of the film results in the appearance of plasma resonance at ~1400nm followed by high reflectance at longer wavelengths and widening of the band gap to ~3.7eV due to heavy doping effects.

TiSiN Films by Reactive RF Magnetron Co-Sputtering for Ultra-Low-Current Phase Change Memory

Our simulation reveals that the programming current of phase change memory (PCM) is expected to dramatically reduce to tens of μA with the help of a heating layer. TiSiN films by reactive RF magnetron co-sputtering are investigated for application to the heating layer of the ultra-low-current PCM. The resistivity of TiSiN films is well controlled from around to with increasing N2partial flow rate to 10%. The effect of annealing on the TiSiN films exhibits the relative stability of the resistivity of the films. This implies that these TiSiN films can be used as a universal heating layer for the intensively researched phase change materials.

Enhanced Current Transportation in Siliconriched Nitride (SRN)/Silicon-riched Oxide (SRO) Multilayer Nanostructure

Abstract A novel structure of silicon-riched nitride (SRN)/silicon-riched oxide (SRO) is proposed and prepared using RF reactive magnetron co-sputtering. High temperature annealing of SRN/SRO multilayers leads to formation of Si nanocrystals (NC) from isolating SRN and SRO layers simultaneously, which efficiently improves carrier transport ability compared to conventional SRN/Si3N4 counterpart. Micro-Raman scattering analysis reveals that SRN layer has dominating number of denser and smaller Si NCs, while SRO layer has relatively less, sparser and bigger Si NCs, as confirmed by high resolution transmission electron microscopy observation. The substitute SRO layers for Si3N4 counterparts significantly increase the amount of Si NCs as well as crystallization ratio in SRN layers; while the average Si NC size can be well controlled by the thickness of SRN layers and the content of N, and hence an obvious stronger absorption in UV region for the novel structure can be observed in absorption spectra. The I–V characteristics show that the current of hybrid SRN/SRO system increases up to 2 orders of magnitude at 1 V and even 5 orders of magnitude at 4 V compared to that of SRN/Si3N4 structure. Si NCs in SiOy layers provide a transport pathway for adjacent Si NCs in SiNx layers. The obvious advantage in carrier transportation suggests that SRN/SRO hybrid system could be a promising structure and platform to build Si nanostructured solar cells.

Structural, optical and electrical properties of Cd-doped SnO2 thin films grown by RF reactive magnetron co-sputtering

Transparent conducting SnO2:Cd thin films were prepared by RF reactive magnetron co-sputtering on glass slides at a substrate temperature of 500°C using CdO as cadmium source. The films were deposited under a mixed argon/oxygen atmosphere. The structural, optical and electrical properties were analyzed as a function of the Cd amount in the target. The X-ray diffraction shows that polycrystalline films were grown with both the tetragonal and orthorhombic phases of SnO2. The obtained films have high transmittance and conductivity. The figure of merit of SnO2:Cd films are in the order of 10−3Ω−1, which suggests that these films can be considered as candidates for transparent electrodes.

Effects of silicon content on the structure and mechanical properties of (AlCrTaTiZr)–Six–N coatings by reactive RF magnetron sputtering

Multi-component (AlCrTaTiZr)–Six–N films were deposited on silicon wafers by reactive RF magnetron co-sputtering. The effect of silicon content on the structure, morphology and mechanical properties of the nitride films was investigated. Nitride films with lower silicon content remained as a simple NaCl-type face-centred cubic (FCC) structure. As the silicon content reached 7.9 at%, thermodynamically driven phase separation occurred, leading to a nanocomposite structure consisting of an FCC solid-solution nitride and an amorphous SiNx phase. These nitride films exhibited a high hardness of 34 GPa and remained at a constant level up to 7.9 at% Si. The reduced hardness at a silicon content of 10.2 at% was attributed to the appreciable amounts of softer amorphous segregation. The silicon incorporation significantly improved the oxidation resistance of (AlCrTaTiZr)N films. The film containing 7.9 at% Si annealed at 1000 °C for 2 h in air only had a 330 nm-thick oxide layer. The optimum Si content is 7.9 at% since it gives the best combination of hardness and oxidation resistance.

Superhydrophilic stability enhancement of RF co-sputtered Ti xSi 1− xO 2 thin films in dark

Ti x Si 1− x O 2 compound thin-film systems were deposited by reactive RF magnetron co-sputtering technique. The effect of Ti concentration on the hydrophilicity of Ti x Si 1− x O 2 compound thin films was studied and it was shown that the films with Ti 0.6Si 0.4O 2 composition possess the best hydrophilic property among all the grown samples. Surface ratio and average roughness of the thin films were measured by atomic force microscopy (AFM). Surface chemical states and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). In addition, XPS revealed that the amount of Ti–O–Si bonds in nanometer depth from the surface of the Ti 0.6Si 0.4O 2 films was the maximum, which resulted in the most stable superhydrophilic property. According to XRD data analysis for the pure TiO 2 films, the polycrystalline anatase phase was formed with an average grain size of about 15 nm. Moreover, amorphous phase was also formed for the Ti x Si 1− x O 2 compound systems due to presence of silicon in the films. Finally, optical properties of the films such as transmission, reflection and band gap energy were investigated using UV–vis spectrophotometry. It was found that the transmittance of the films was decreased with increasing Ti concentration in the films.

Structure and optical properties of Zr1−xSixN thin films on sapphire

A series of zirconium silicon nitride (Zr1−xSixN) thin films were grown on r-plane sapphire substrates using reactive RF magnetron co-sputtering of Zr and Si targets in a N2/Ar plasma. X-ray diffraction pole figure analysis, X-ray reflectivity, X-ray photoelectron spectroscopy (XPS), optical microscopy, and optical absorption spectroscopy were used to characterize the film stoichiometries and structures after growth at 200°C and post-deposition annealing up to 1000°C in ultra-high vacuum. The atomically clean r-plane sapphire substrates induce high quality (100) heteroepitaxy of ZrN films rather than the (111) orientation observed on steel and silicon substrates, but the addition of Si yields amorphous films at the 200°C growth temperature. After the annealing treatment, films with Si content x<0.15 have compressive stress and crystallize into a polycrystalline structure with (100) fiber texture. For x>0.15, the films are amorphous and remain so even after ultra-high vacuum annealing at 1000°C. XPS spectra indicate that the bonding changes from covalent to more ionic in character as Si―N bonds form instead of Zr―N bonds. X-ray reflectivity, atomic force microscopy (AFM) and optical microscopy data reveal that after post-deposition annealing the 100nm thick films have an average roughness <2nm, except for Si content near x=0.15 corresponding to where the film becomes amorphous rather than being polycrystalline. At this stoichiometry, evidence was found for regions of film delamination and hillock formation, which is presumably driven by strain at the interface between the film and sapphire substrate. UV–visible absorption spectra also were found to depend on the film stoichiometry. For the amorphous Si-rich films (x>0.15), the optical band gap increases with Si content, whereas for Zr-rich films (x<0.15), there is no band gap and the films are highly conductive.

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO 2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO 2 thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H 2 atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.