Reactive RF Magnetron Sputtering Technique Research Articles

Doping and thickness variation influence on the structural and sensing properties of NiO film prepared by RF-magnetron sputtering

The NiO and NiO–Cu doped films with various Cu contents of 5.68, 10.34, and 14.64 at%. Were deposited on a glass substrate with various thickness 50, 100, and 150 nm by RF-reactive magnetron sputtering technique. The effect of the thickness and the doping on the structural, electrical, and sensory properties of the films was mainly investigated. The X-ray diffraction studies revealed that all the deposited films were of single crystalline nature and exhibited cubic structure with preferential growth along 200 and only NiO peaks appear in the NiO–Cu films and when the thickness increased from 50 to 150 nm, the grain size increases from 24.38 to 25.036 nm. Compositional analysis indicated that Cu content increased in the film as the bonded chips increase in the target surface. The electrical resistivity of the NiO film showed a high electrical resistivity 280 K Ω detected by a four point probe measurement and when the Cu content in the films is 5.68 at%. The ρ value is reduced significantly to 45.9 K Ω as Cu content is increased to 10.34 at%, and it further decreases to 25.3 K Ω when the Cu content further increases to 14.64 at% the resistivity value decrease to 10.45 K Ω. The Hall measurement for all NiO and Cu-doped NiO films shows p-type conduction and reduction in the mobility of charge carrier from 9.67 × 102 to 8.46 × 10 cm2/V s, when the concentrations of the charge carriers increase from 4.30 × 1010 to 4.23 × 1013 cm−3. The sensory measurements for NiO and Cu-doped NiO films, show that the 50 nm thickness has the highest sensitivity and response time for the NO2 gas at the operating temperature 150 °C.

Growth of TiO<SUB>2</SUB> Films by RF Magnetron Sputtering for MOS Gate Dielectrics: Influence of Substrate Temperature

Titanium dioxide thin films were deposited by RF reactive magnetron sputtering technique on p-type silicon(100) substrates held at temperatures in the range 303-673 K. The influence of substrate temperature on the core level binding energies, chemical bonding configuration, crystallographic structure and dielectric properties was investigated. X-ray photoelectron spectroscopy studies and Fourier transform infrared transmittance data confirmed the formation of stoichiometric films with anatase phase at a substrate temperature of 673 K. The films formed at 303 K were nanocrystalline with amorphous matrix while those deposited at 673 K were transformed in to crystalline phase and growth of grains in pyramidal like structure as confirmed by X-ray diffraction and atomic force microscopy respectively. Metal-oxide-semiconductor capacitors were fabricated with the configuration of Al/TiO2/Si structures. The current voltage, capacitance voltage and conductance voltage characteristics were studied to understand the electrical conduction and dielectric properties of the MOS devices. The leakage current density (at gate voltage of 2 V) decreased from 2.2 x 10(-6) to 1.7 x 10(-7) A/cm(2), the interface trap density decreased from 1.2 x 10(13) to 2.1 x 10(12) cm(-2) eV(-1) and the dielectric constant increased from 14 to 36 with increase of substrate temperature from 303 to 673 K.

Microstructural evolution of sputtered ZnO thin films with rapid thermal annealing

Zinc oxide thin films were deposited on silicon substrates by reactive RF magnetron sputtering technique. Post-deposition rapid thermal annealing of the sputtered thin films was carried out by varying temperatures, annealing duration and oxygen flow rate. The films, annealed at 1000 °C for 150 s in air ambient, have shown highest degree of crystallinity. The surface of the ZnO films, annealed for longer period, was greatly modulated with the evolution of porous surface. The films annealed in oxygen ambient have shown smoother morphology with the reduction in surface roughness. The characteristic absorption band of Zn–O became prominent due to the increase in Zn–O bond density during rapid thermal annealing process. A significant reduction of the deep level emission in the photoluminescence spectra was observed for annealed samples, whereas the near band edge ultraviolet emission was suppressed for the films annealed in oxygen ambient due to the oxygen adsorption at the film surface.

Cu/TiO2 thin films prepared by reactive RF magnetron sputtering

Cu/TiO2 thin films were deposited on glass substrates by reactive RF magnetron sputtering technique. Crystalline structure, surface morphology and electronic structure were studied using X-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy (XPS). Transmittance and absorptance of these films were characterized by UV–Vis spectroscopy. XRD patterns demonstrate that TiO2 films deposited on glass substrate at 300 °C are observed to be in pure anatase phase, whereas Cu/TiO2 films are amorphous in nature at 300 °C substrate temperature. The crystallinity of Cu/TiO2 thin films decreases with increasing the dopant concentrations of Cu in TiO2 films. XPS studies show that Cu is in +2 oxidation state in all films. The optical band gap of Cu/TiO2 films decreases from ~3.3 to ~2.0 eV with the increase in the copper concentration. Further, antimicrobial studies of Cu/TiO2 films with ~3.9 at.% Cu exhibit high transmittance and best antimicrobial activity against E. coli and S. aureus compared to other doped films.

Effect of thermal annealing on structural, optical and electrical properties of RF reactive magnetron sputtered CdO thin films

Recently, there has been a lot of interest on transparent conducting oxide (TCO) materials which have common application in solar cells and some optoelectronic devices. In this work, cadmium oxide (CdO) thin films have been deposited on glass substrates by RF reactive magnetron sputtering technique and subsequently annealed in air from 200 °C to 500 °C. The effect of annealing temperature on the structural, morphological, optical and electrical properties of CdO films is systematically investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, UV-visible spectrophotometer and Hall effect measurements. X-ray diffraction (XRD) studies showed that the films are polycrystalline in nature with a preferential orientation along (2 0 0) plane. Atomic force microscopy studies showed that these films are very smooth with maximum root mean square roughness of 3.13 nm. The CdO films formed at annealing temperature of 400 °C exhibited optical transmittance of 84%, electrical resistivity of 1.9 × 10 −3 Ω cm and figure of merit of 1.8 × 10 −3 Ω −1 .

Evaluation of transverse piezoelectric coefficient of ZnO thin films deposited on different flexible substrates: a comparative study on the vibration sensing performance.

We report on the systematic comparative study of highly c-axis oriented and crystalline piezoelectric ZnO thin films deposited on four different flexible substrates for vibration sensing application. The flexible substrates employed for present experimental study were namely a metal alloy (Phynox), metal (aluminum), polyimide (Kapton), and polyester (Mylar). ZnO thin films were deposited by an RF reactive magnetron sputtering technique. ZnO thin films of similar thicknesses of 700 ± 30 nm were deposited on four different flexible substrates to have proper comparative studies. The crystallinity, surface morphology, chemical composition, and roughness of ZnO thin films were evaluated by respective material characterization techniques. The transverse piezoelectric coefficient (d31) value for assessing the piezoelectric property of ZnO thin films on different flexible substrates was measured by a four-point bending method. ZnO thin films deposited on Phynox alloy substrate showed relatively better material characterization results and a higher piezoelectric d31 coefficient value as compared to ZnO films on metal and polymer substrates. In order to experimentally verify the above observations, vibration sensing studies were performed. As expected, the ZnO thin film deposited on Phynox alloy substrate showed better vibration sensing performance. It has generated the highest peak to peak output voltage amplitude of 256 mV as compared to that of aluminum (224 mV), Kapton (144 mV), and Mylar (46 mV). Therefore, metal alloy flexible substrate proves to be a more suitable, advantageous, and versatile choice for integrating ZnO thin films as compared to metal and polymer flexible substrates for vibration sensing applications. The present experimental study is extremely important and helpful for the selection of a suitable flexible substrate for various applications in the field of sensor and actuator technology.

High‐density remote plasma sputtering of high‐dielectric‐constant amorphous hafnium oxide films

Abstractmagnified imageHafnium oxide (HfOx) is a high dielectric constant (k) oxide which has been identified as being suitable for use as the gate dielectric in thin film transistors (TFTs). Amorphous materials are preferred for a gate dielectric, but it has been an ongoing challenge to produce amorphous HfOx while maintaining a high dielectric constant. A technique called high target utilization sputtering (HiTUS) is demonstrated to be capable of depositing high‐k amorphous HfOx thin films at room temperature. The plasma is generated in a remote chamber, allowing higher rate deposition of films with minimal ion damage. Compared to a conventional sputtering system, the HiTUS technique allows finer control of the thin film microstructure. Using a conventional reactive rf magnetron sputtering technique, monoclinic nanocrystalline HfOx thin films have been deposited at a rate of ∼1.6 nm min−1 at room temperature, with a resistivity of 1013 Ω cm, a breakdown strength of 3.5 MV cm−1 and a dielectric constant of ∼18.2. By comparison, using the HiTUS process, amorphous HfOx (x = 2.1) thin films which appear to have a cubic‐like short‐range order have been deposited at a high deposition rate of ∼25 nm min−1 with a high resistivity of 1014 Ω cm, a breakdown strength of 3 MV cm−1 and a high dielectric constant of ∼30. Two key conditions must be satisfied in the HiTUS system for high‐k HfOx to be produced. Firstly, the correct oxygen flow rate is required for a given sputtering rate from the metallic target. Secondly, there must be an absence of energetic oxygen ion bombardment to maintain an amorphous microstructure and a high flux of medium energy species emitted from the metallic sputtering target to induce a cubic‐like short range order. This HfOx is very attractive as a dielectric material for large‐area electronic applications on flexible substrates.

Magneto-optical effect in GdN epitaxial thin film

We report the cooperative phenomena of magneto-optical effect in AlN/GdN/AlN heterostructure grown by reactive rf magnetron sputtering technique performed under a base pressure less than 5×10−6 Pa. The ultra-high vacuum conditions during growth of GdN enable to curtail the oxophilicity character. The temperature dependent optical absorbance measurements have been carried out to evaluate the direct optical band gaps at the X point through the Tauc plots for the heterostructure. We observed for the first time that the optical absorbance studies demonstrate an exceptional splitting in valance and conduction bands in GdN below the critical temperature. The splitting energy is slightly increased with increase of temperature range of 30–55 K and the difference is merely ΔE=28 meV. Furthermore, the splitting energy drastically increases from 30 K to 3 K and the difference is ΔE=102 meV. This startling increase convincing that there is rapid increase of magnetic moments caused by long range correlation of spins.

Synthesis and biological characterization of zirconium oxynitride thin film growth by radio-frequency sputtering

Thin films of zirconium oxynitride were grown on common glass, silicon substrates (100) and on stainless steel 316L using the reactive RF magnetron sputtering technique. The films were analyzed through structural, morphological, and biocompatibility studies. The structural analysis was carried out using X-ray diffraction (XRD), and the morphological analysis was carried out using scanning electron microscopy (SEM) and atomic force microscopy (AFM). These studies were done as a function of growth parameters, such as power applied to the target, substrate temperature, and flow ratios. The studies of biocompatibility were carried out on zirconium oxynitride films deposited on stainless steel 316L through proliferation and cellular adhesion. The XRD analysis showed that films deposited at 623K, with a flow ratio ΦN2/ΦO2 of 1.25 and a total deposit time of 30min grew preferentially oriented along the (111) plane of the zirconium oxynitride monoclinic phase. The SEM analyses showed that the films grew homogeneously, and the AFM studies indicated that the average rugosity of the film was 5.9nm and the average particle size was 150nm. Finally, through the analysis of the biocompatibility, we established that the films have a better surface than the substrate (stainless steel 316L) in terms of adhesion and proliferation of bone cells.

Atomic scale observation of phase separation and formation of silicon clusters in Hf higk-κ silicates

Hafnium silicate films were fabricated by RF reactive magnetron sputtering technique. Fine microstructural analyses of the films were performed by means of high-resolution transmission electron microscopy and atom probe tomography. A thermal treatment of as-grown homogeneous films leads to a phase separation process. The formation of SiO2 and HfO2 phases as well as pure Si one was revealed. This latter was found to be amorphous Si nanoclusters, distributed uniformly in the film volume. Their mean diameter and density were estimated to be about 2.8 nm and (2.9 ± 0.4) × 1017 Si-ncs/cm3, respectively. The mechanism of the decomposition process was proposed. The obtained results pave the way for future microelectronic and photonic applications of Hf-based high-κ dielectrics with embedded Si nanoclusters.

Study on mixed vanadium oxide thin film deposited by RF magnetron sputtering and its application

Vanadium oxide (VOx) thin films were deposited on fused quartz using a pure metal vanadium target by RF reactive magnetron sputtering technique. Film microstructure, valence state, optical transmittance properties were studied. The mixed valence VOx thin films deposited with different thickness were found to be amorphous. And the optical transmittance curves are flatness in certain wavelength region. These films can be used to control the relative light intensity of the rubidium light beam between the rubidium lamp and the vapor cell, in order to optimize the working parameters of the rubidium frequency standard (RAFS).

Investigation of Oxygen Contamination in Indium Nitride Thin Film by X-Ray Absorption Fine Structure

Local structures of indium oxynitride (InON) nano-crystal prepared by reactive gas-timing RF magnetron sputtering technique are under investigation. Since the optical properties of these InON thin films depend on gas-timing ratio, the local structure analysis is needed in order to determine the relation between the gas timing ratio and its optical properties. In this work, InON thinfilm with 30:0 seconds (N2:O2) gas-timings ratio was analyzed for its local structure using X-ray absorption fine structure (XAFS) technique in conjunction with first principle calculation. The results indicate that the crystal structure of the film is wurtzite structure which is a typical structure of InN. However from the results of Auger Electron Spectroscopy (AES), there are oxygen contents in the film. Since XAFS analysis confirmed the 4-fold local structure of Indium atom, these oxygen atoms must be substituted in nitrogen sites with slightly changing the local structure of Indium atom. The best fit of XAFS data indicated that there is an oxygen atom substituted in nitrogen site of the 4-fold indium.

Graded selective coatings based on zirconium and titanium oxynitride

The aim of this study was the development and characterization of transition metal oxynitride multilayers for optical applications. The reactive RF magnetron sputtering technique in rotation mode was used for stacking of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) nanolayers. The depositions were carried out in a reactive Ar+N2+O2 atmosphere by sputtering titanium and zirconium targets. By means of different substrate rotation speeds, the bilayer period has been changed in the range 11–20 nm. A multilayer deposition rate increasing with the bilayer period decreasing has been evaluated. Structural, compositional, mechanical and optical analyses have been performed. The x-ray diffraction spectra confirmed the formation of a multilayer structure with a nitride formation prevalence. Non-abrupt interfaces between the layers and non-uniform chemical composition (chemical intermixing) have been detected by transmission electron microscope (TEM) observations. The gradient interface structure turns out to be an advantage for the improvement of the mechanical properties. Higher hardness values were calculated by the Chicot–Lesage and Jonsson–Hogmark models for TiNO/ZrNO multilayer compared with monolayer TiNO and ZrNO coatings. Also SIMS analysis has confirmed a compositional interface grading but also an increase in oxygen content with decreasing substrate rotation speed or similarly with decreasing deposition rate. Moreover, a tuning of the optical properties, going from metallic behaviour to dielectric with the decrease in the substrate rotation speed has been gained. The variation of the deposition rate allows a sort of ‘regulation’ of the oxygen incorporation with a precise tailoring of the optical properties. This result can be employed with the aim of depositing graded composition multilayer systems with a precise control of their optical selective wavelength properties. The improvement in the mechanical performance in graded oxynitride multilayer coatings would also allow an increase in the optical device lifetime.

Synthesis and Properties of Nanocrystalline Copper Indium Oxide Thin Films Deposited by Rf Magnetron Sputtering

Nanocrystalline copper indium oxide (CuInO2) thin films with particle size ranging from 25 nm to 71 nm have been synthesized from a composite target using reactive Rf magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) combined with glancing angle X-ray diffraction (GAXRD) analysis confirmed the presence of delafossite CuInO2 phase in these films. The optical absorption studies show the presence of two direct band gaps at 3.3 and 4.3 eV, respectively. The resistance versus temperature measurements show thermally activated hopping with activation energy of 0.84 eV to be the conduction mechanism.

Effects of annealing on the magnetic properties and microstructure of Fe-ZrN nanocomposite films

We have studied the influence of thermal annealing on the magnetic properties and microstructure of 0.7-μm-thick Fe-ZrN nanocomposite films obtained by a reactive RF magnetron sputtering technique on non-conductive substrates. The near-surface and bulk magnetostatic characteristics of the films were studied using magnetooptical and vibrating-sample magnetometers, respectively. The microstructure was determined by X-ray diffraction. It was established that the magnetic characteristics strongly depend on the annealing temperature. These dependences are explained by structural changes induced in the films by the thermal treatment.

Manufacture, microstructure and mechanical properties of CrWN and CrN/WN nanolayered coatings

Chromium nitride and tungsten nitride coatings were fabricated in sequence to form a CrN/WN nanolayered coating by rf reactive magnetron sputtering technique with a dual-gun system. The CrWN coating was also manufactured for comparison. The bilayer period of the nanolayered CrN/WN coating were controlled at 10 and 24 nm. Periodic feature of elemental distribution of the nanolayered coatings was revealed by the Auger electron spectroscopy depth profiling analysis. The phase identification results indicated that the composite CrWN coating was composed of CrN phase with solid-solution of W, while CrN and amorphous/nanocrystalline WN and W 2N phases was observed in the nanolayered CrN/WN coatings. The CrN/WN nanolayered microstructure was evaluated by scanning and transmission electron microscopy. Nanoindentation technique was employed to evaluate the mechanical properties, including hardness and Young's modulus. The nanolayered CrN/WN coatings exhibited a high hardness around 30 GPa, which was superior to that of the CrWN coating. The nanolayered structure with confined grains of the nitrides in the nano range was beneficial to the enhancement of the mechanical performance for the multilayer coating.

Synthesis and microstructural characterisation of reactive RF magnetron sputtering AlN films for surface acoustic wave filters

Wurtzite aluminium nitride (AlN) thin films were deposited by RF reactive magnetron sputtering technique on (1 0 0) silicon substrates at low temperature (400 °C). The microstructural properties of sputtered AlN films were investigated using X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and atomic force microscopy (AFM), to aim improvement of piezoelectric coupling for surface acoustic wave (SAW) devices. It was found that the AlN films deposited in the optimum experimental conditions, as revealed by XRD and selected area electron diffraction, exhibit a high (0 0 2) preferred orientation, where columnar crystals are grown in a non-epitaxial pattern and aligned almost perpendicular to silicon substrate. The ω rocking curve, shows that the standard deviation of columns of thin AlN films is less than 1°, which exhibit a high quality of these films. Furthermore, the AFM found a very low surface roughness less than 7 Å, which is very crucial to decrease a loss propagation in AlN films. The films synthesised with optimum conditions were used to perform SAW devices by developing inter-digital transducer on AlN/Si structure. Frequency characteristics show that the realised SAW devices exhibit good filtering performances and a good compromise between phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency.

DEPOSITION-AND-SUBSTRATE TUNABLE PHOTONIC BANDGAP IN OPTICAL RESPONSES OF HYDROGENATED AMORPHOUS SILICON CARBIDE THIN FILMS

Amorphous hydrogenated silicon carbide (a-SiC:H) thin films have been prepared by the RF reactive magnetron sputtering technique. The optical properties of the films have been studied by optical spectroscopy with an incoherent light source. The material is commonly regarded as a dielectric. We have discovered however that some films that were prepared under certain deposition conditions and on certain substrates may respond to external light as a metallic thin film, i.e. there are strongly enhanced reflection peaks in the optical spectrum. We have further discovered that some films may have a strong and broadened absorption peak at about 590 nm, which is an apparent photonic bandgap in the visible spectrum. The appearance of the photonic bandgap is very sensitive to two parameters: the substrate and the deposition gas. By changing the two parameters, one shifts the status of the film from with and without the photonic bandgap.

Study of the oxygen incorporation and structure in the low pressure sputtered YBCO films

Epitaxial thin films of YBa 2Cu 3O 7– δ (YBCO) have successfully been grown by reactive RF-magnetron sputtering technique at a low pressure (0.95 mTorr) with T C ( R=0)=85.3 K and J C mag (4.2 K)≈2×10 7 Å/cm 2. The incorporation of oxygen in the as-grown films has been controlled by using different ambient—oxygen, air and argon—during in situ cooling. The superconducting behavior of the resulting films was studied using resistance–temperature and low field a.c.-susceptibility measurements and correlated with their structure. All the films exhibited metallic conduction in the normal state. The oxygen- and air-cooled films were superconducting, and exhibited usual orthorhombic structure, but the argon-cooled films were non-superconducting and possessed tetragonal structure. This implied that the structure of the film during deposition is tetragonal, and transforms to either of the oxygen rich orthorhombic-I or -II phases depending upon the oxygen/air ambient. The ‘ δ’ values of 0.14, 0.32 and 0.70 and higher ‘ c’-parameters of 1.1785, 1.180 and 1.183 nm have been obtained for oxygen-, air- and argon-cooled films, respectively.

Dependency of reactive magnetron-sputtered SiC film quality on the deposition parameters

SiC thin films have been prepared by using RF reactive magnetron sputtering (RF-RMS). The deposition parameters have been varied over a wide range to optimize the quality of the films; substrate temperature from 700 to 1000°C, Ar/CH 4 composition from 80:20 to 50:50 and RF power from 100 to 200 W. The samples have been characterized by X-ray diffraction, Rutherford backscattering, profilometry, FTIR spectroscopy and ellipsometry. The results show that good quality silicon carbide films can be prepared by using the RF-RMS technique.