Radio Frequency Magnetron Sputtering Method Research Articles

Effect of substrate-tilting angle-dependent grain growth and columnar growth in ZnO film deposited using radio frequency (RF) magnetron sputtering method

Effect of substrate-tilting angle-dependent grain growth and columnar growth in ZnO film deposited using radio frequency (RF) magnetron sputtering method

Fabrication of GaN nanocrystalline thin films Schottky metal-semiconductor-metal ultraviolet photodetectors

Gallium nitride nanocrystalline thin films (GaN NCTH) were prepared on Si substrates using the radio frequency magnetron sputtering (RF) method. XRD patterns with narrow peaks intensity and field emission scanning electron microscopy (FESEM) images exhibits of the GaN nanoparticles have covered surfaces of the substrate with a regular distribution smooth and an average particles size proximately between are 10–20 nm. AFM indicates a smooth surface and RMS is 1.38 nm of GaN NCTH and the optical band gap was calculated to be 3.38 eV. The current-voltage characteristic of metal-semiconductor-metal (M-S-M) GaN ultraviolet photodetectors (UV-PD) in the dark and irradiated with 370 nm light and intensity was (1.4) mW/cm2 evaluated under bias voltages of −1 to 5 V. The average rise time speed of the photodetector is about 22 ms when current increases from 10 % to 90 % of its value of saturation, while the average fall time is 17 ms when current decreases from 90 % to 10 % of its value of saturation. UV-PD displays 19–261 sensitivity at a different voltage bias; internal photodetector gain between the low value is 1.19 at 8 V and 1.59 at 2 V.

Development of the ZnO:Ga nanorod arrays as an alpha particle scintillation screen for the associated particle neutron generator

The development of associated alpha particle scintillation screen that takes into account high spatial resolution, ultrafast temporal resolution, and high signal-to-noise ratio is the key to promote the “fingerprint” technology in the field of explosive detection—the deuterium–tritium (D–T) reaction associated particle neutron generator (APNG). Herein, the highly uniform and densely packed ZnO:Ga nanorod arrays, as designed alpha particle scintillation screen for the APNG, is proposed and prepared on a ZnO-seeded substrate by a radio frequency magnetron sputtering and hydrothermal method. The simulation results show that the theoretical cutoff thickness is 7.6 μm for 3.5 MeV alpha particles, and the increase in array spacing is conducive to suppress transverse light output and improve its light output efficiency and spatial resolution simultaneously. Through hydrogen annealing treatment, the slow decay component is completely suppressed and the integrated intensity of the fast decay component with a rising edge response of 1 ns is significantly enhanced by nine times.

Optimization of optoelectronic performance of ITO/AG/ITO electrodes by using taguchi method and spectroscopic ellipsometry technique

In this study, a sandwich-structured electrode composed of indium tin oxide (ITO)/metal silver layer/ITO was prepared by the radio frequency magnetron sputtering method. We used the Taguchi method and spectroscopic ellipsometry (SE) analysis to optimize the geometrical structures of the electrodes and the sputtering power for the silver layer. While the Taguchi method allows us to rapidly optimize the manufacturing parameters, SE analysis enables us to precisely evaluate the thickness of each layer of the electrodes, so that the whole optimization process is more precise and effective. When the silver layers of different samples are sputtered under the same conditions, the difference in their thickness is often [Formula: see text] nm. Thus, it is difficult to understand the influences of the manufacturing parameters on the optoelectronic performance of the electrodes. Experimental results show that the thickness of the silver layer was the main factor affecting the transmittance and sheet resistance of the electrodes. However, the decisive factors for the Haacke index in the visible light range were the thickness of the bottom ITO film. Nonetheless, the signal-to-noise (S/N) ratios of some factors are quite close. Thus, further analyses are needed to understand this phenomenon. After optimization, the Haacke index is [Formula: see text], which is better than the 19.45 of the best sample, suggesting that this experiment has improved the optoelectronic properties of the electrode.

One step sputtered MoS2 field-effect transistor

In this study, variable thickness MoS2 which is one of the most important 2D materials, was grown in a single step radio frequency magnetron sputtering (RFMS) method from a MoS2 target. Successful large area, continuous and homogeneous formation of MoS2 thin film have been shown by Raman mapping measurements. Structural, morphological, elemental composition of MoS2 films grown at different thicknesses was performed using SEM and XPS. Dozens of MoS2-based FET was fabricated with a single lithography step on the same substrate.MoS2 based FETs showed a mobility value of 0.07- 0.16 cm2/Vs increasing with MoS2 film thickness and a current on/off ratio of about 103-104. It has been demonstrated that the FETs show ambipolar characteristics.

A-axis oriented Zn0.72Mg0.28O epitaxial thin films with large second-order nonlinear susceptibility

Large nonlinear susceptibility that originates from strong electronic polarization enables ultrafast nonlinear optical devices. This work discovers that Mg incorporation has important contribution for enhancing second-order nonlinear susceptibility (χ (2)) and laser-induced surface-damage threshold of wurtzite ZnO epitaxial thin films deposited by radio-frequency magnetron sputtering method. Second-harmonic generation measurements derive that as-deposited Zn0.72Mg0.28O shows a gain of 48%, 77% and 33% in χ 33, χ 31 and χ 15 with respect to as-deposited ZnO. Specially, the annealed Zn0.72Mg0.28O has a χ 33 value of −57.0 ± 1.8 pm V−1, which gets comparable to that of LiNbO3 crystals. Triple-axis x-ray diffraction measurements conclude that the Mg incorporation should increase the χ (2) under optical frequency electric field by strengthening electronic polarization rather than increasing the residual strain in the film. Furthermore, the annealed Zn0.72Mg0.28O exhibits an increase of 48% in laser-induced surface-damage threshold relative to [11–20] ZnO crystals. These findings open the way of the Zn0.72Mg0.28O thin films to ultrafast nonlinear optical devices.

The effect of nitrogen-doped titanium dioxide-modified stainless steel brackets on Streptococcus mutans.

To evaluate the effect of nitrogen (N)-doped titanium dioxide (TiO2) coated stainless steel brackets activated with natural visible light and dental operating lights on Streptococcus mutans concentration in the plaque of orthodontic patients at 30 and 60 days. A total of 30 patients were recruited for this split-mouth study; 60 upper lateral incisor brackets constituted the study sample. A total of 30 brackets (15 right and 15 left) were coated with N-doped TiO2 using the (radio frequency) magnetron sputtering method. Plaque samples were collected at 30 days and 60 days after appliance placement. S mutans concentration was evaluated using real-time polymerase chain reaction. At both time intervals, the concentration of S mutans in the control group was greater than that in the study group (P = .005). In both the study and the control groups, the S mutans concentrations significantly increased from 30 to 60 days (P = .005). N-doped TiO2, on exposure to natural visible light and dental operating light, was effective in reducing the plaque concentration of S mutans in orthodontic patients. The efficacy was better at 30 days than at 60 days after placing the orthodontic appliances.

Effect of SiO2 buffer layer on thermoelectric response of In2O3/ITO thin film thermocouples

Thin film thermocouples can be applied in in-situ temperature measurement. Herein, the flexible In2O3/ITO thin film thermocouples accompanying with the excellent thermoelectric response were prepared by using radio-frequency magnetron sputtering method. A SiO2 buffer layer was accreted between the flexible polyimide substrate and the thermocouples. The effects of the SiO2 buffer layer on morphology, optical transmission, resistances and thermoelectric response of thin film thermocouples were systematically studied. The results show that the resistances of In2O3/ITO thin film thermocouples with SiO2 buffer layer exhibited a consistent trend with the increasing of bending cycles. Under the bending strain of 0.13%, an average Seebeck coefficient was 171.7 μV/°C for the thin film with the SiO2 layer, which was 2.8 times than the film without SiO2 layer. This work presents a great potential for achieving high thermoelectric response of thin film thermocouples, and it also provides an interesting insight of flexibility and bending strain through buffer layer accretion.

No‐Heating Deposition of 1‐μm‐Thick Y‐Doped HfO2 Ferroelectric Films with Good Ferroelectric and Piezoelectric Properties by Radio Frequency Magnetron Sputtering Method

Y‐doped HfO2 ferroelectric films of ≈1 μm thick are deposited without heating by a radio frequency magnetron sputtering method. {100}‐oriented epitaxial films with orthorhombic phase are grown on (100)ITO//(100)YSZ substrates without heating. Their crystal structure is almost unchanged after postheat treatment at 800 °C. Ferroelectricity is confirmed for the no‐heating‐deposited films by polarization−electric field (P−E) curves, and their remanent polarization (Pr) and coercive fields are 12 μC cm−2 and 1.5 MV cm−1, respectively. These values are also almost unchanged after the postheat treatment. However, the postheat‐treated films show a lower breakdown electric field compared to the as‐deposited films without heat treatment. Approximately 1 μm‐thick films are also prepared without heating on (111)ITO/(111)Pt/TiOx/SiO2/(100)Si and (111)Pt/TiOx/SiO2/(100)Si substrates. Almost pure orthorhombic/tetragonal phase is deposited on both substrates without heating. The Pr value of the film on the (111)ITO/(111)Pt/TiOx/SiO2/(100)Si substrate is about 1.5 times larger than that on the (111)Pt/TiOx/SiO2/(100)Si substrate due to the better crystallinity of the film lattice‐matched with the underlying ITO layer. The effective piezoelectric constant (d33,f) of the film deposited on the (111)ITO/(111)Pt/TiOx/SiO2/(100)Si substrate without heating is estimated to be 4 pm V−1. The present low process temperature leads us to expect novel applications, especially for low‐heat‐resistance applications.

Development of Sapphire Optical Temperature Sensing System Used in Harsh Environment Sensing

A sapphire optical fiber blackbody radiation sensor based on the high temperature multilayer structure of wolfram and aluminum oxide has been developed. Through the analysis of Planck’s law, the linear relationship between the temperature and the square root of the voltage is theoretically deduced. Radio frequency magnetron sputtering method is used to sputter and deposit high-temperature wolfram metal film and aluminum oxide film on sapphire fiber. In order to meet the needs of real-time temperature measurement, an online acquisition system of optical signals is designed to complete the demodulation and storage of signals. The high-temperature experiment results show that the temperature response sensitivity is 0.00113V1/2/℃ between 300℃ and 1750℃, and it can work stably for more than 10 hours. The sensor is calibrated in the metrology institute where a maximum quoted error of 0.84% within a range between 900 ℃ and 1600℃ is proved. Compared with the traditional high temperature measurement method, the sensor has the advantages of compact structure, anti-electromagnetic interference, large measuring range, and good linearity, which can be widely used in the sensing and measurement of extreme high temperature environments such as aero-engine tail injection temperature monitoring, combustion chamber temperature monitoring of aero-engine simulation test benches.

Bandgap tunable Al1-In N films for ultraviolet–visible photodetectors with wide spectral response

Al 1- x In x N films allow the bandgap to be adjusted in a wide range, which is fascinating for optoelectronic applications, especially in ultraviolet–visible and wavelength-selective photodetection. Herein, the single-phase Al 1- x In x N films with tunable bandgap are synthesized via a well-designed radio-frequency (RF) magnetron sputtering method. By means of placing an In sheet on the Al target, we can control the Al and In composition in Al 1- x In x N films via only changing the RF power on the target. With increasing the RF power from 100 to 300 W, the In composition ( x value) in Al 1- x In x N films can be adjusted from 0.94 to 0.34. Accordingly, the bandgaps are adjusted from 2.20 to 2.95 eV. Importantly, the photoresponse wavelengths of Al 1- x In x N films are broadened from UV to visible light with raising the x value. The photoresponsivity of the Al 1- x In x N film photodetectors is 0.0124 mA/W ( x = 0.34), 0.118 mA/W ( x = 0.52), and 0.126 mA/W ( x = 0.67) under 365 nm, 532 nm, and 650 nm illumination, respectively. The corresponding response times are as fast as 2.37 s, 1.98 s, and 1.39 s, respectively. Our synthesis strategy of Al 1- x In x N films proposed in this work will open exciting opportunities for semiconductor bandgap adjustment and wavelength-selective detection of optoelectronic devices.

Investigation of nitrogen doped ZnO thin films: Effects on their structural and optical properties

Un-doped and nitrogen-doped ZnO thin films were grown by using radio frequency (RF) magnetron sputtering method changing the nitrogen flow rate between 0% −12.5% and the thickness dependence of films was determined. The effect of nitrogen doping concentration on the structural, morphological, and optical properties of zinc oxide thin films was studied. X-ray diffraction (XRD) analysis confirmed that the nitrogen-doped ZnO films belong to the hexagonal crystal structure. The optical properties of the grown samples were examined by optical spectrophotometer and spectroscopic ellipsometer. Transmittance spectra were obtained by spectrophotometer measurements and the effect of nitrogen ratio was investigated. It has been observed that as the nitrogen ratio increases, the transmittance decreases up to ∼500 nm and then increases. By using the transmittance curve, the energy band gap was calculated. Further detailed optical analysis was made by the spectroscopic ellipsometry technique. Fitting was performed to ensure the agreement between the experimentally obtained Ψ values and theoretically determined Ψ values using the Cauchy model. As a result, the refractive index was found for each film and it was observed that the refractive index decreased as the nitrogen ratio increased. The scanning electron microscopy (SEM) measurements showed that the surface morphology of the films changes with N doping. Nitrogen was observed in Fourier transform infrared spectra analysis. 5% nitrogen-doped ZnO films were grown on the glass substrate using RF magnetron sputtering at room temperature. Samples are prepared by varying thicknesses during the deposition process. XRD and SEM measurements of the samples show the variation in the crystal structure and surface morphology of the film with varying thicknesses. All the samples are tested for the transmittance and band gap. The increase of film thickness increases the grain size. The transmittance is influenced by the film thickness. • Un-doped and nitrogen doped ZnO thin films were grown by using RF magnetron sputtering method. • The band gap values were changed by changing N doping. • The refractive index values of ZnO films decrease with the introduction of nitrogen into the structure. • The band gaps decreased from 3.25 eV to 3.20 eV as the thickness increased. • Zn–N bonds were attributed at ∼1380 and ∼1502 cm −1 .

Enhanced sensitivity of low-cost fabricated fluorine doped ZnO metal semiconductor metal photodetector

The literature mostly reports on thin-film fluorine-doped zinc oxide (FZnO) and has yet to fabricate metal semiconductor metal (MSM) photodetectors (PDs) based on FZnO nanostructures for the enhancement of photoresponse parameters despite their huge potential. In this work, ZnO film of 32 nm-thick was deposited and used as a seed layer on silicon (Si) substrates with the aid of the radio frequency (RF) magnetron sputtering method. Vertically well-aligned FZnO nanorods (NRs) were later grown on the seeded substrates via a hydrothermal method and annealed for 1 h at 400 °C. The formation of well-aligned hexagonal NRs at low fluorine doping was revealed by field emission scanning microscopy (FESEM), and energy-dispersive X-ray (EDX) analysis confirmed the presence of fluorine doping. X-ray diffraction (XRD) investigation confirmed the growth of good crystal quality hexagonal wurtzite F–ZnO NRs along the (002) direction, and bandgaps were estimated using UV–Vis–NIR spectroscopy. Photoluminescence (PL) measurement has revealed the main emission peak for ultraviolet (UV) is centered at 375 nm and a red-shifted emission with fluorine doping has been identified. An F2 UV MSM PD device is fabricated. Upon exposure to UV light (395 nm) at 4 V, it displayed a high sensitivity of 1.1 × 105%, responsivity of 0.66 A/W, detectivity of 1.30 × 1010 Jones, a response time of 90 ms, and recovery time of 110 ms.

Development of a High-Resolution Acoustic Sensor Based on ZnO Film Deposited by the RF Magnetron Sputtering Method.

In the study, an acoustic sensor for a high-resolution acoustic microscope was fabricated using zinc oxide (ZnO) piezoelectric ceramics. The c-cut sapphire was processed into a lens shape to deposit a ZnO film using radio frequency (RF) magnetron sputtering, and an upper and a lower electrode were deposited using E-beam evaporation. The electrode was a Au thin film, and a Ti thin film was used as an adhesion layer. The surface microstructure of the ZnO film was observed using a scanning electron microscope (SEM), the thickness of the film was measured using a focused ion beam (FIB) for piezoelectric ceramics deposited on the sapphire wafer, and the thickness of ZnO was measured to be 4.87 μm. As a result of analyzing the crystal growth plane using X-ray diffraction (XRD) analysis, it was confirmed that the piezoelectric characteristics were grown to the (0002) plane. The sensor fabricated in this study had a center frequency of 352 MHz. The bandwidth indicates the range of upper (375 MHz) and lower (328 MHz) frequencies at the −6 dB level of the center frequency. As a result of image analysis using the resolution chart, the resolution was about 1 μm.

Improvement of transparent conductive indium tin oxide based multilayer films on p-silicon through the inclusion of thin copper-aluminium metals interlayer

The distinguished transparent conductive indium tin oxide (ITO) based multilayer films with thin copper-aluminium (Cu-Al) metals interlayer (ITO/Cu-Al/ITO) were prepared on p-type silicon (Si) by radio frequency and direct current magnetron sputtering methods. The ITO/Cu-Al/ITO (ICAI) films structural, topological, optical and electrical properties coupled with electronic properties of ICAI/p-type Si interface were investigated at different post annealing temperature up to 600 °C. Despite the inclusion of Cu-Al metals interlayer, structural analysis results yielded an amorphous structure for the as-deposited films. The films become polycrystalline with a cubic bixbyite structure after post annealing treatment. Dominant In2O3 (222) and Cu (111) peaks intensities were observed at 500 °C and 600 °C indicating substantial enhancement in the films crystallinity at high moderate temperatures. The ICAI films reveal a smooth surface roughness with improved growth in grain size after post annealing treatment as examined by microscopic equipment.The films optical transmittance promptly increased from 73.2% (for as deposited film) to 88.7% (for annealed film at 600 °C) at 470 nm in the visible region with increasing post annealing temperature. The film annealed at 600 °C exhibits excellent electrical characteristics with a very low electrical resistivity of 2.44 × 10−5 Ω cm and sheet resistance of 3.26 Ω/sq. The ICAI films optoelectronic properties as calculated by figure of merit (FOM) show outstanding performance at 600 °C with a high FOM of 92.47 × 10−3 Ω−1 in spite of the reduced ITO films thickness. In addition, admirable ICAI/p-type Si interface quality was observed after post annealing treatment (at 600 °C) as indicated by current-voltage characteristics results. These improved ICAI multilayer films can be favourable for silicon heterojunction solar cells and other low resistance optoelectronic applications.

A prototypical near-infrared light-emitting diode from CdS/Si heterojunctions based on the defect emissions in the interface

Optimizing and tuning the interface to enhance the performance of heterojunctions is an important research topic in the optoelectronic fields. In the present work, a CdS layer of ∼5.0 nm in the thickness, which is prepared by the radio frequency magnetron sputtering method, has been incorporated in the interface of CdS/Si heterojunctions which is constructed through depositing nano CdS films on porous polysilicon by using the chemical bath deposition method. Through the annealed treatment at 500 oC in the Ar atmosphere, the CdS/Si heterojunctions show typical rectification characteristics with the improved turn-on voltage from ∼2.10 V to ∼0.83 V. At the forward voltage of ∼6.0 V, a green band can be observed. With increasing the applied voltage, the near-infrared emission band can be obtained, which is ascribed to the transition from the sulfur vacancies in the surface CdS layers to the cadmium interstitials in the interface. It is believed that understanding of near-infrared emission from CdS/Si heterojunction is crucial to the field of optoelectronic devices.

In-vitro Comparative Assessment of Antibacterial and Anti-adherent Effect of Two Types of Surface Modificants on Stainless Steel Orthodontic Brackets Against Streptococcus mutans

Objective: Comparative evaluation of antibacterial and anti-adherent properties of surface-modified stainless steel (SS) orthodontic brackets against Streptococcus mutans ( S. mutans). Materials and Methods: The study was conducted on 120 SS orthodontic McLaughlin, Bennett, Trevisi (MBT) 0.022″ slot by Leone, Italy. Orthodontic brackets that constituted the sample size were divided into 6 groups, consisting of 20 samples each in two control (non-surface coated) and four experimental groups. The experimental group’s surface coatings were photocatalytic zinc oxide (ZnO) and photocatalytic titanium oxide (TiO2), which were carried out by radiofrequency (RF) magnetron sputtering method for surface modification. Brackets were subjected to microbiological tests against S. mutans. For anti-adherence, weight change, pre- and postexposure, was evaluated to gauge the adherence of bacteria and colony-forming units/milliliter (CFU/mL) count measuring the survival rate of bacterial cells for antibacterial activity. Results: The TiO2-coated group showed statistically significant anti-adherence ( P-value < .05) against S. mutans than control and ZnO groups. The CFU count of TiO2 group was lower than control as well as ZnO group. Conclusion: TiO2 is superior to ZnO and should be continued to be considered for surface modification of orthodontic brackets against White Spot Lesions (WSLs) and gingivitis.

Interface analysis of SrWO4:Er3+-Yb3+/Si thin films prepared by radio frequency magnetron sputtering for upconversion emission

Upconversion (UC) emission of Er–Yb doped strontium tungstate (SrWO4:Er3+-Yb3+) thin films on silicon substrates prepared by the radio frequency (RF) magnetron sputtering method using different RF powers has been investigated and reported. The X-ray diffraction patterns showed that the tetragonal phase of SrWO4 formed with an improvement in the crystallinity of the films at higher RF power. Atomic force microscopy images demonstrated the homogeneity of the grains on the surface and an increment of grain size with an increase in RF power during deposition. Auger electron spectroscopy was used for the analysis of the interface of the thin films, the Si interdiffusion as well as the role of the thickness with an increase in the sputtering power of the RF deposition. The UC emission of the films prepared at the different RF powers excited at 980 nm was recorded. An enhancement in the intensity with an increase in the RF powers was obtained. Three different bands of UC emission were recorded, which were assigned to the 2H11/2/4S3/2 → 4I15/2 (two green bands) and the one red band (4F9/2 → 4I15/2) transitions for the Er3+ ions. The maximum intensity of UC emission was recorded at 240 W RF power due to a better crystallinity and the bigger size of the grains in the film as well as a better defined interface between the thin film and the substrate.

Morphology of hydroxyapatite and Sr coatings deposited using radio frequency-magnetron sputtering method on nanotube formed Ti-6Al-4V alloy

In this study, morphology of hydroxyapatite and Sr coatings deposited using radio frequency- magnetron sputtering method on nanotube formed Ti-6Al-4V alloy was researched. For this study, nanotube formation on the samples was performed using anodization and then the hydroxyapatite (HA) and Sr thin film was coated using a RF magnetron sputtering system. For characterization of nanotube surface, the surface was observed using various instruments.The diameter of the nanotube increased and the nanotube layer increased as the applied voltage increased. The anatase phases were well formed on the surface and significantly increased as the applied voltage increased. HA and Sr coating layer was formed thicker than that of the HA coating layer and nanotubes were covered with HA and Sr. The surface roughness of the alloy increased as the voltage increased in the order of non-coating, HA and Sr coating, and HA coating. The contact angle of the alloy surface decreased in non-coating and HA coating, whereas, contact angle of HA and Sr coating increased as the applied voltage increased.

A study for the influences of temperatures on ZnGa2O4 films and solar-blind sensing performances

In this work, ZnGa2O4 metal–semiconductor–metal solar-blind ultraviolet (UV) photodetectors were fabricated and discussed by using the radio-frequency (r.f.) magnetron sputtering method with considerations of the influences of growing and measuring temperatures on photoelectric performances in detail. With the increase of growing temperature, the grain size and optical bandgap of the films increased. Ohmic contacts were formed between the films and Ti/Au electrodes for all the samples, and the photoconductive photodetectors shown decent solar-blind photoelectric performances. At 10 V biasing voltage, the devices had fast response speed and large photo-to-dark current ratio of ∼107 at 650 °C. Moreover, we measured the dark current (I dark) and photocurrent (I photo) of these devices in the temperature range from 298 K to 598 K. With the increase of temperature, the I dark increased monotonously, while the I photo first decreased and then increased. Furthermore, this study about the effects of temperatures on the ZnGa2O4 films and photodetectors may well provide a meaningful guide for its relevant developments in the future.