Magnetron Co-sputtering Method Research Articles

Bactericidal efficiency of nanostructured Al–O/Ti–O composite thin films prepared by dual magnetron reactive co-sputtering technique

Mixed oxide Al–O/Ti–O composite nanostructured thin films were prepared at Ar:O2 gas ratio of 70:30 (7:3 in sccm) by reactive magnetron co-sputtering method. The effect of Al in the films on the antibacterial efficiency has been studied. In situ optical emission spectra (OES) were recorded in order to study the plasma chemistry as well as nucleation and growth process during deposition. The films were characterised by X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), field emission scanning electron microscope (FESEM), optical contact angle (OCA) and UV–visible transmission spectra (UV–vis). The qualitative and quantitative bactericidal efficiency was studied through SEM image of the treated E. coli cells (Escherichia coli NCIM 2809) and optical density (OD) measurement using UV–vis spectrometer, respectively. The better bactericidal efficiency was observed in the film with more Al content. The crystallinity, surface chemical composition, band gap in context of Al present in the films were discussed and correlated to bactericidal efficiency in the light of in situ investigation of plasma from OES.

Enhanced thermoelectric properties and layered structure of Sb2Te3 films induced by special (0 0 l) crystal plane

In this Letter, special (00l) crystal plane and uniquely alternate stress field can favorably influence the carrier and phonon transport properties of layered films. The oriented p-Sb2Te3 layered films have been successfully fabricated by the simple magnetron co-sputtering method. The measurement results show that the layered Sb2Te3 films with each layer ∼40nm are (00l)-preferential orientation. The highly (00l)-oriented Sb2Te3 layered film with a thermoelectric dimensionless figure-of-merit ZT=1.22 was obtained at room temperature. Introduction of such preferential (00l) crystal plane and uniquely alternate stress field into TE films is therefore a very promising approach.

Thermal effect on the structure and optical properties of Ge–Te–In thin films

Amorphous thin films with composition of Ge61.44Te31.39In7.17 were prepared by magnetron co-sputtering method on chemically cleaned glass substrates. The effect of thermal treatment on structure and optical properties had been investigated. As-deposited and annealed thin films were investigated by X-ray diffraction (XRD), Scanning electron microscope (SEM), Visible/near-infrared transmission spectroscopy and Raman spectra. XRD and SEM results show that an amorphous-to-crystalline phase transition occurs after annealing and the crystalline degree increases with increasing annealing temperature, which in turn, lead to the change in the optical constant. According to the classic Tauc equation, it can be found that the optical band gap of the thin films rises with increasing annealing temperature up to 150°C and then drastically decreases with temperature beyond 200°C. This behavior is interpreted on the basis of the change in the structure of the thin films, from amorphous to crystalline state, with increasing the annealing temperature. Raman spectra studies reveal that the formation of c-GeTe is mainly responsible for the macroscopic phase transition during the crystallization process.

The surface topography, structural and mechanical properties of Ge1 − xCx films prepared by magnetron co-sputtering

Non-hydrogenated germanium carbide (Ge1−xCx) films were prepared by magnetron co-sputtering method in a discharge of Ar. The surface topography, chemical bonding configurations and hardness were characterized by means of atomic force microscopy, X-ray photoelectron spectroscopy (XPS) and nanoindentation technique. The substrate temperature (Ts) exhibited important influence on the film surface topography. With the increase of Ts, the films became smoother owing to stronger diffusion. The film mass density varied between 4.40g/cm3 and 4.47g/cm3 depending on Ts. A progressive densification of the film microstructure occurred with Ts increasing. The XPS results showed that both the content of the GeGe bond and the content of the CGe bond in the films increased as Ts increased. The relationship between the chemical bonding and the mechanical properties of the Ge1−xCx films was also explored. It showed that the hardness of the films increases from 7.47GPa to 11.48GPa as Ts increases from 200°C to 700°C. Therefore, increasing the substrate temperature led to a more dense and hard Ge1−xCx film.

Semiconducting p-type MgNiO:Li epitaxial films fabricated by cosputtering method

Li-doped ternary MgxNi1−xO thin films were deposited on (0001) Al2O3 substrates by a radio frequency (RF) magnetron cosputtering method with MgO and NiO:Li targets. The Mg mole fraction and Li content were relatively controlled by changing RF power for the MgO target over a range of 0–300 W, while the NiO:Li target was kept at 150 W. As a result, all films were epitaxially grown on (0001) Al2O3 substrates with the relationship of [1¯1¯0]NiO||[111¯0]Al2O3, [1¯12¯]NiO||[21¯1¯0]Al2O3 (in-plane), and [1¯11]NiO||[0001¯]Al2O3 (out-of-plane), and showed p-type semiconducting properties. Furthermore, from x-ray diffraction patterns, the authors found that MgO was effectively mixed with NiO:Li without structural deformation due to low lattice mismatch (0.8%) between NiO and MgO. However, the excess Li contents degraded the crystallinity of the MgNiO films. The band-gap of films was continuously shifted from 3.66 eV (339 nm) to 4.15 eV (299 nm) by the RF power of the MgO target. A visible transmittance of more than 80% was exhibited at RF powers higher than 200 W. Ultimately, the electrical resistivity of p-type MgNiO films was improved from 7.5 to 673.5 Ωcm, indicating that the Li-doped MgNiO films are good candidates for transparent p-type semiconductors.

Crystallization phase transition in the precursors of CIGS films by Ar-ion plasma etching process

Mixed alloy Cu–In–Ga precursors were deposited from Cu–Ga alloy and Indium targets by the DC magnetron co-sputtering method. There were four crystallization phases, In, CuIn2, Cu11In9 and Cu3Ga, identified in the precursor after deposition. A large grain-size CIGS film was achieved by controlling the annealing period for selenization and utilizing a two-stage selenization process for secondary crystallization during rapid thermal annealing process. As the annealing temperature increased, the phase transitions moved toward the Cu-rich inter-metallic phases. In addition, the phase transition, stoichiometric ratio and surface-morphology were modified by Ar-ion plasma etching process of the precursors. The results show that after the ion etching process, the precursors can be transferred into a single Cu11In9 crystallization phase and the number of crevices increased due to the soft texture of indium on the surface of the precursors. Finally, CIGS films with good crystalline properties were achieved after a suitable selenization process of only 1-stage.

Codeposited Zn–Mg coating with improved mechanical and anticorrosion properties

A Zn–Mg coating was prepared by magnetron co-sputtering method on carbon steel with Zn layer pre-deposited using an alkaline non-cyanide zinc bath. The morphologies, chemical compositions, mechanical properties and anticorrosion properties of specimens were investigated. The microhardness of the Zn–Mg coating increased from 244HV25 of the electroplated Zn coating to 323HV25. The electrochemical test in NaCl solution showed that the Zn–Mg coating had a passive region around the potential of 300mV. Salt water immersion test in 3.5wt.% NaCl solution also showed corrosion property improvement. The red rust generation time of Zn–Mg coating was doubled compared with the Zn coating. The possible mechanism of the improvement of corrosion resistance of Zn–Mg coating is proposed.

Study on preparation and characteristics of Fe- and Mn-doped AlN thin films

Fe- and Mn-doped AlN thin films were prepared on Si substrates by direct current (DC) magnetron co-sputtering method in the atmospher of Ar and N2 mixture. The influences of sputtering currents and the target to substrate distance on the structure of the films were investigated by X-ray diffraction and Raman spectroscopy, respectively. Surface morphology and composition were studied by scanning electron microscope (SEM) with an energy dispersive X-ray spectroscopy (EDS) attachment. The magnetism of Mn- and Fe-doped AlN films was measured by vibrating sample magnetometer (VSM) at room temperature (RT). Processing of the Mn-doped AlN films produces Mn clusters in the samples. Due to the presence of the antiferromagnetism Mn clusters, ferromagnetism is either suppressed or disappears. The Fe-doped AlN films show ferromagnetism at RT, which should arise from the AlFeN ternary alloy. With the increase of the Fe target sputtering current, the Fe concentration is increased from 6.81 at.% to 16.17at.%; the saturation magnetization Ms is reduced from 0.27 emu·cm-3 to 0.20 emu·cm-3, and the coercive force Hc is increased from 57 Oe to 115 Oe, this is because the separation of Fe ions get shorter and the antiferromagnetic coupling is enhanced.

Origin of Ferromagnetism in Zn1−xCoxO Thin Films: Evidences Provided by Hard and Soft X-Ray Absorption Spectroscopy

Although dilute magnetic semiconductors have promising potentials in spintronics applications, the mechanism of their ferromagnetism remains ambiguous. The extensive theoretical models and exotic experimental evidences provide self-consistent but usually contradictory explanations on its either intrinsic or extrinsic origins. We find room temperature ferromagnetism in a series of Zn1−xCoxO (0.03 ≤ x ≤ 0.10) thin films prepared using magnetron co-sputtering method and treated with post-annealing at temperatures 350°C and 500°C. The origin of the ferromagnetism is investigated in terms of electronic structure combining hard x-ray absorption spectroscopy (XAS) at Zn and Co K-edge, and soft x-ray XAS at O K-edge and Co L2,3-edge. The full multiple scattering theory is employed to reinforce the interpretation of the XAS spectra, which concludes that full substitution of zinc by cobalt is responsible for the room temperature ferromagnetism due to the d states of cobalt within the framework of bound magnetic polaron. Moreover, the evidence of cobalt nanoclusters is detected at highly doped and annealed samples. The first principles calculation confirms the electronic structural evidences via the formation energy.

Fabrication and characterization of the gapless half-Heusler YPtSb thin films

Half-Heusler YPtSb thin films were fabricated by magnetron co-sputtering method on MgO-buffered SiO2/Si(001) substrates. X-ray diffraction pattern and Energy dispersive X-ray spectroscopy confirmed the high-quality growth and stoichiometry. The temperature dependence of the resistivity shows a semiconducting-type behavior down to low temperature. The Hall mobility was determined to be 450 cm2/Vs at 300K, which is much higher than the bulk value (300 cm2/Vs). In-plane magnetoresistance (MR) measurements with fields applied along and perpendicular to the current direction show opposite MR signs, which suggests the possible existence of the topological surface states.

The activation process through a bimodal transmittance state for improving electrochromic performance of nickel oxide thin film

In this study, we investigated the potential of using nickel oxide (NiO)-lithium phosphorous oxynitride (LiPON) composite as an anode electrode in electrochromic devices and evaluated the effect of Li+ insertion (or extraction) kinetics and diffusion of Li+. NiO–LiPON composite thin films were fabricated using the RF magnetron co-sputtering method. Here, we observed, for the first time, the bimodal colored states of the NiO–LiPON composite. This was caused by reacting both Ni metal and LiO under extremely cathodic condition, which enhanced the electrochromic properties – electrochromic response time and optical modulations – of the device. We also found that the NiO–LiPON composite thin films displayed long term stability.

Investigation of co-sputtered LiZnSnO thin film transistors

We proposed the fabrication of Li–Zn–Sn–O (LZTO) thin film transistors (TFTs) using a magnetron co-sputtering method. To analyze the effects of Li incorporation on the amorphous LZTO TFTs, Hall measurement and X-ray photoelectron spectroscopy were performed. It was found that the increased addition of Li to the ZTO system caused the suppression of carrier creation. At an optimized condition (~12at.% Li) for LZTO TFTs, we achieved a saturation mobility of ~10.4cm2/Vs, a subthreshold voltage of 0.25V/decade, a threshold voltage (Vth) of 3.9V, and an Ion/off ratio of 2×108. Furthermore, the optimized device exhibited much better photo-bias stability (ΔVth=−3.3V) than the reference ZTO device (ΔVth=−10.8V) under the negative bias illumination stress condition.

Tribological properties of metal doped a-C film by RF magnetron sputtering method

We deposited various metal doped amorphous carbon (a-C:Me) films by radio frequency (RF) magnetron co-sputtering method. Tungsten (W), molybdenum (Mo), and chromium (Cr) were used as the doping metals in a-C film. The applied power on carbon and metal (W, Mo, and Cr) target were 150W and 40W, respectively. a-C:Me films exhibited smooth and uniform surface roughness and the hardness over 15GPa. Specially, a-C:W film showed the maximum hardness of 18.5GPa. The coefficient of friction of a-C:W film is relatively lower than that of other films and the critical load value of a-C:W film is higher. These results are related to the concentration of metal in the carbon matrix by the difference of sputtering yield and the change of the structure by the metal bonding. Consequently, W metal is good candidate as the doping metal for the improvement of tribological characteristics.

Synthesis of titanium oxide thin films containing antibacterial silver nanoparticles by a reactive magnetron co-sputtering system for application in biomedical implants

Titanium oxide thin films containing silver (Ag) nanoparticles were synthesized on commercially pure titanium (cp-Ti) substrates using a reactive magnetron co-sputtering method. The goal was to maximize bactericidal activity along with sustained biocompatibility. Furthermore, this study examined the correlation between Ag nanoparticle dispersion in the films and the antibacterial efficacy of the Ag ions released from the films. The results showed that there might be two factors affecting the inhibition of bacterial attachment to the surface of the specimens: surface morphology and Ag ion release. MTT assay results demonstrated that there was no cytotoxicity on fibroblast cells in any group. Overall, the magnetron sputtered Ag nanoparticle-containing titanium oxide coatings in this study can be used as an efficient antibacterial layer with sustained biocompatibility.

Middle-ultraviolet-enhanced photodetectors based on Mg0.4Zn0.6O/ZnO homojunction with a high selectivity for 300 nm around light

High-quality Mg0.4Zn0.6O film with a ZnO buffer layer was prepared on glass by the reactive magnetron cosputtering method, and the MgZnO/ZnO homojunctions were fabricated into metal–semiconductor–metal middle ultraviolet (UV) photodetectors (PDs). The MgZnO-based PD with a ZnO buffer layer showed a high selectivity for 300 nm around middle UV light and its responsivity was larger than that of the PD without a buffer layer. Its peak responsivity was 0.45 A W−1 at 300 nm under −5 V bias, which was comparable to the highest value ever reported in MgZnO-based PDs. Also, we observed that the PDs with a smaller spacing of the finger electrodes showed a larger responsivity, indicating that the PD with a small spacing shows a large internal gain. The results may provide a simple route to gain low-cost and high-performance middle UV PDs.

Preferential growth of Bi2Te3 films with a nanolayer structure: enhancement of thermoelectric properties induced by nanocrystal boundaries

Preferential growth of different crystal planes in layered Bi2Te3 thin films with each layer <40 nm has been achieved by a simple magnetron co-sputtering method. The preferential growth of (015) plane or (001) was achieved at special depositing conditions due to the more sufficient growth along the in-plane direction induced by the enhanced diffusion of atoms and lower deposition rate. The Bi2Te3 film with preferential growth of (001) plane possesses about two times higher electrical conductivity and Seebeck coefficient as compared to the film with preferential growth of (015) plane, due to the greatly enhanced carrier mobility. Furthermore, the thermal conductivity has been suppressed due to more phonon scattering at grain boundaries, compared with ordinary Bi2Te3 alloys and films.

Tribological properties of a-C:W film deposited by radio frequency magnetron Co-sputtering method

We deposited the tungsten doped amorphous carbon (a-C :W) film on silicon (Si) substrate by radio frequency (RF) magnetron co-sputtering method. Tungsten (W) was used as the doping metal of a-C film. Carbon and metal components were deposited simultaneously on the Si substrate by co-sputtering method, and the applied RF power on the graphite (C) was 150W and it on tungsten (W) metal target was from 20W to 50W, respectively. In this work, the influence of RF power in W target on the structural, physical, and tribologcal properties of the a-C:W films was experimentally investigated. The hardness increased with increasing RF power in W target and exhibited the maximum hardness value about 18.5GPa at the condition of RF power in W target, and the adhesion and surface roughness properties improved with increasing RF power in W target. However the friction property is declined with increasing RF power. Consequently, the improvement of physical properties in a-C:W films is associated with the enhancement of energetic ions bombardment and the increase of W contents in amorphous matrix by increasing RF power in W target.

Effect of annealing on microstructure and dielectric properties of Zn2Ti3O8 thin films by reactive co-sputtering

Microstructure and dielectric properties of Zn2Ti3O8 films deposited on Pt/Cr/SiO2/Si via a DC reactive magnetron co-sputtering method using zinc and titanium metal targets in O2/Ar atmosphere are investigated. The as-deposited Zn–Ti–O film has an amorphous microstructure. A single Zn2Ti3O8 phase appeared when the films were annealed at 500°C and 600°C for 1h. As the temperature further increased to 700 and 800°C, it was found that Zn2Ti3O8 and ZnTiO3 phases coexisted. A phase transformation from cubic Zn2Ti3O8 and rhombohedral ZnTiO3 to cubic Zn2TiO4 and rutile TiO2 was observed while a further increase in temperature up to 900°C. The heat treatment also induces a change in the surface morphology of the thin films observed by scanning electron microscopy. Transmission electron microscopy examination indicated that the film annealed at 700°C was composed of Zn2Ti3O8 and ZnTiO3 with fine and large grains in microstructure, respectively. The study also reveals that the dielectric constant of the films depends on the annealing temperature. When annealing at 600°C, the Zn2Ti3O8 films has the following properties at 1MHz: dielectric constant=32.9, tan δ=0.022.

Cluster organization in co-sputtered platinum-carbon films as revealed by grazing incidence X-ray scattering

Nanostructured platinum-carbon thin films were prepared by magnetron co-sputtering method for designing efficient catalytic thin films, like fuel cells electrodes. The in-depth morphology of composite films was studied using surface sensitive X-ray techniques (grazing incidence small-angle scattering and reflectivity), consolidated by electron microscopy investigations. This study elucidates the growth mode of co-sputtered platinum-carbon thin film: 2-nm-sized platinum clusters are growing in surrounding simultaneously growing carbon columns (20-nm diameter range). In particular, the platinum cluster growth and distribution in the plane of the substrate surface are driven by surface diffusion and coalescence phenomena. Finally, this anisotropic distribution of platinum clusters correlated to the textured morphology of carbon matrix leads to a catalytic thin film morphology very suitable for electrochemical processes in fuel cell electrodes.

Optical and electrical properties of nonstoichiometric a-Ge1−xCx films prepared by magnetron co-sputtering

Amorphous non-hydrogenated germanium carbide (a-Ge1−xCx) films have been prepared by magnetron co-sputtering method in a discharge of Ar. The dependence of structural and chemical bonding properties on the Ge/C ratio (R) has been investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The relationship between the chemical bonding and the optical and electrical properties of the a-Ge1−xCx films has also been explored. It has been shown that the refractive index of the films increases from 2.9 to 4.4 and the optical gap decreases from 1.55 to 1.05eV as R increases from 1.22 to 5.67. Moreover, the conductivity σ increases clearly and the activation energy Ea decreases with the increasing R owing to the reduction of sp3 CGe bonds. The a-Ge1−xCx films exhibit refractive index and optical gap values changing with x in a wide range, which may make a-Ge1−xCx films good candidates in the fields of protection coatings for IR windows and electronic devices.