RF Sputtering Process Research Articles

Enhanced grain orientation in Sb2Se3 thin films deposited on Mo/BSG substrates via RF-sputtering and selenization

The alignment of the Sb2Se3 absorber grains along the c-axis, resulting from their quasi-1D ribbon-like growth, has been found to enhance current density, thereby enabling high power conversion efficiencies in Sb2Se3-based thin film solar cells. This study presents a controllable method for depositing Sb2Se3 thin films with highly oriented grains and a compact morphology, making them suitable for large-scale solar cell applications. A combination of magnetron sputtering and post-deposition isothermal selenization techniques was used. This process involved sputtering antimony onto Mo-coated Borosilicate glass (BSG) substrates, followed by selenizing the films at different temperatures in argon-gas filled quartz ampoules. The influence of several partial Ar-gas pressures and selenization temperatures on the grain growth was studied to achieve enhanced preferred grain orientations and compact morphology of the Sb2Se3 thin films. Selenization at 380 °C resulted in dominant vertical grain orientations with respect to the substrate surface of the Sb2Se3, as confirmed by scanning electron microscopy and X-ray diffraction analysis, without compromising surface compactness. Although occasional micro-voids remain in the films, further optimization could eliminate these imperfections. The developed sequential method, where Sb layer was deposited by RF-sputtering process, followed by an annealing at elevated temperature in the presence of Se and argon gas pressure, holds potential for large-scale production and the fabrication of other quasi-1D chalcogenide thin films.

High Sensitivity CH4 and CO2 Gas Sensor Using Fiber Bragg Grating Coated with Single Layer Graphene

This article outlines the development of a Fiber Bragg Grating (FBG) intended for use as a sensor for CH4 and CO2 gases. Following fabrication, the FBG was effectively treated with a layer of Graphene Material through a modified RF Sputtering process. This coating procedure involved introducing argon gas into the chamber and subjecting the FBG, securely held by two vacuum stages, to a temperature range of 27°C to 600°C by adjusting the power supplied to the cathode and anode, ranging from 0 to 125 Watts. Subsequently, the FBG was employed as a key sensing element within an experimental setup aimed at measuring gas concentrations within a confined space. The assessment involved analyzing the reflected signal of the FBG using an Optical Interrogator System, which demonstrated a shift in the Bragg wavelength of the reflected signal corresponding to varying gas concentrations. This study indicates promising outcomes for the Graphene-coated FBG as a gas sensor. The sensor’s sensitivity was evaluated based on the Bragg wavelength shift resulting from gas presence within the chamber. The Graphene-coated FBG exhibited sensitivities of 3.3 ppm for CH4 and 3.7 ppm for CO2, surpassing those reported in prior research efforts.

Fast response fabricated MoS2-photodiode based thin film

In this study, we present the fabrication and characterization of a thin film based on 1 T-MoS2 pn photodiode for the purpose of quick response photodetection application. The photodiode was fabricated using RF-sputtering process. The scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) techniques were employed to investigate the surface topology and structural characteristics of the nanostructured MoS2 thin film. The electrical properties of the photodiode that was produced were examined by conducting measurements of its current–voltage (I-V) characteristics across a range of bias voltages spanning from − 2 to + 2 V. The external quantum efficiency (EQE) of the pn photodiode that was produced was determined to be as high as 9.8%. Additionally, the internal quantum efficiency (IQE) was found to be as high as 10.5%. Furthermore, a time response of 1.748 ms was observed. The findings of this study illustrate the capability of MoS2 photodiodes in facilitating rapid response photodetection applications.

Thickness-dependent resistive switching memory characteristics of NiO nanodisks fabricated by AAO nanotemplate

Forming and set/reset operating voltages are critical issues encountered with a decrease in resistive random-access memory (RRAM) sizes. This study investigated the thickness-dependent resistive switching properties of NiO nanodisks. The NiO RRAM nanodisks, with a diameter of 100 nm and varying thicknesses, were fabricated on Pt/Ta/SiO2/Si substrates using anodic aluminum oxide templates through the RF sputtering process. In the electroforming process, the forming voltage of the NiO nanodisk effectively reduced with a decrease in the thickness. The electric field enhancement in localized regions appeared to contribute to the reduction in the forming voltage. In addition, the set/reset operating voltage of the NiO nanodisk RRAM decreased with a decrease in the thickness. We conclude that the use of the C-AFM tip strengthened the local electric field in NiO nanodisk RRAM cells, leading to the reduction of the set/reset voltage with a decrease in the thickness.

The effects of Ar + N2 plasma power-based attachment of metal nanoparticles on the electron field emission properties of carbon nanotubes

An ideal vacuum-based electron emitter requires a low turn-on field and quick emission processes. Carbon nanotubes (CNTs) have great potential for emission applications, but have some limitations that affect their performance. Consequently, they can benefit from the alteration of their surface morphology upon decoration with plasma-based metal nanoparticles. In this work, we have attached iron nanoparticles on the CNTs surface via a radio frequency (rf) sputtering process using Ar + N2 gas with various plasma power in steps of 50 W. Field emission scanning electron microscopy (FESEM) micrographs have confirmed the attachment of the iron nanoparticles and etching of the nanotubes surface at high plasma power. The Raman spectra strongly confirm the formation of defects in the carbon sheet of the nanotubes. In the plasma treatment process, the increase in the Dband intensity enhanced the degree of disorder and may be beneficial for enhanced emission properties. The field electron emission properties are significantly enhanced after the Fe nanoparticles attached with plasma incorporated in terms of the reduction in Eto (1.64 from 2.02 V/μm) &Eth (1.98 from 2.64 V/μm), and increase in J (391.11–1179.24 μA/cm2) and β (1419–2900), respectively. The field emission parameters of the field emitters are modified due to incorporation of nitrogen species, attached Fe nanoparticles, and reduction in the nanotube density. The as-prepared field emitters also qualified the orthodox field emission hypothesis test by exhibiting fextr values in an acceptable range. Therefore, we can use the Ar + N2 plasma-based Fe nanoparticles decorated CNT field emitters in vacuum electronic device applications.

Investigation of the RF Sputtering Process and the Properties of Deposited Silicon Oxynitride Layers under Varying Reactive Gas Conditions.

In a single process run, an amorphous silicon oxynitride layer was grown, which includes the entire transition from oxide to nitride. The variation of the optical properties and the thickness of the layer was characterized by Spectroscopic Ellipsometry (SE) measurements, while the elemental composition was investigated by Energy Dispersive Spectroscopy (EDS). It was revealed that the refractive index of the layer at 632.8 nm is tunable in the 1.48–1.89 range by varying the oxygen partial pressure in the chamber. From the data of the composition of the layer, the typical physical parameters of the process were determined by applying the Berg model valid for reactive sputtering. In our modelling, a new approach was introduced, where the metallic Si target sputtered with a uniform nitrogen and variable oxygen gas flow was considered as an oxygen gas-sputtered SiN target. The layer growth method used in the present work and the revealed correlations between sputtering parameters, layer composition and refractive index, enable both the achievement of the desired optical properties of silicon oxynitride layers and the production of thin films with gradient refractive index for technology applications.

Analysis of MEMS cantilever sensor for sensing volatile organic compounds

Increased concentration of Volatile Organic Compound (VOC) in environment can cause severe health issues and create the ozone layer at ground level. The increased concentration of ozone at the ground level creates the smog which will affect the biodiversity of mother earth, environment and human health in many ways. Many researchers have persuaded the continuous research on miniaturized sensors to detect the VOC with high sensitivity and selectivity. This paper presents the design and fabrication of MEMS cantilever sensor to sense VOCs viz., acetone (C3H6O) and Isopropyl alcohol (C3H8O). Here, the metal oxide films of Poly-vinyl-pyrrolidone (PVP) and Amino-propyl-tri-ethoxy-silane (3-APTES) having 600 nm thickness is deposited on oxidized p-type Si surface by RF sputtering process. The cantilever structure of 128 μm length, 80 μm width and thickness 600 nm is designed having a sensor area of 10,240 μm 2 . With this design specification the sensor is simulated in COMSOL Multiphysics software. Then, the sensor is fabricated using surface micromachining technique. The detection of VOCs is carried out by omnicant instrument. Here, the detection sensitivity of PVP and 3-APTES towards Acetone and Isopropyl alcohol are analyzed. The experimental results show that, PVP coated sensor performs 39% increase in sensitivity as compared to 3-APTES coated sensor to detect acetone, and 3-APTES coating sensor exhibit 7.5% increase in sensitivity to detect Isopropyl alcohol as compared to PVP coated sensor. • The cantilever sensor is designed in COMSOL Multiphysics and fabricated using surface micromachine technique. Then the fabricated sensor is tested in the omnicant instrument. By this experimentation following results and conclusions are drawn. • The coating material PVP and 3 APTES is tested against acetone and Isopropyl alcohol. The sensitivity of PVP with acetone is found 39% greater than sensitivity of 3-APTES with acetone. The sensitivity of PVP with isopropyl alcohol is 7.5% greater than 3PATES with Isopropyl alcohol. • The sensitivity of cantilever sensor is directly proportional to length and inversely proportional to the thickness of the cantilever beam. • The sensitivity is directly proportional to thickness of coated material on the sensor surface. The metal oxide film PVP is the preferable coating material to detect VOC Acetone. 3-APTES is preferable coating material to detect the Iso propyl alcohol.

Three-Dimensionally Architected Solid Oxide Fuel Cells for Low-Temperature Operation

Recently, while eco-friendly energy storage/conversion technologies have been attracting attention, researches have been reported to improve performance and provide multiple functions by applying three-dimensional nano-/micro-structures to energy devices. In general energy devices, the electrolyte and electrodes located on both sides have been designed to have a flat interface, but in the end, developed structures in consideration of three-dimensional efficiency should be required. Among them, in solid oxide fuel cells (SOFCs), which have advantages such as high efficiency and fuel flexibility, studies on the use of advanced cell structures were conducted to lower the operating temperature. Although micro-SOFC using etching or laser processing has been reported, there are limitations in practical operation due to poor material/structural stability and low pattern resolution. In this paper, we developed a novel ceramic micropatterning process by imprinting a pyramid-shaped polymer mold made by soft lithography on the anode support. Furthermore, we have implemented a three-dimensional SOFC with record-high cell performance through the combination of thin film process and large-area cell manufacturing technology. For microscale patterning of the anode, polymer-ceramic anode films with low elastic modulus was prepared by the tape casting process, and the anode support with pyramidal patterns was fabricated through the subsequent imprinting process. The imprinted pattern was maintained after the sintering process. Then, through RF sputtering and pulsed laser deposition (PLD) process, the nanoscale anode functional layer (nAFL), Y2O3-stabilized ZrO2 (YSZ), Gd0.1Ce0.9O1.95 (CGO) and La0.6Sr0.4CoO3- δ (LSC) layer were deposited to fabricate a full cell. To analyze the electrochemical effect of three-dimensional electrode/electrolyte interface, 3DA-cell with ceramic micropatterning process and Planar-cell with flat interface were compared. Interestingly, 3DA-cell showed higher performance than Planar-cell at all operating temperatures, and resulted in 55 % enhanced maximum power density (PDmax) and 19 %, 52 % decreased polarization, ohmic resistance at 500 °C, respectively. Notably, the CGO-based 3DA-cell using CGO as the main electrolyte material recorded a high PDmax of 0.931 W/cm2 at 500 °C. Therefore, to find the factors that improve the electrochemical performance, the microstructures of two different cells were analyzed by scanning electron microscope (SEM), transmission electron microscopy (TEM) and 3D reconstruction method. From the 3D reconstruction result, the nAFL/YSZ interface area, CGO/LSC interface area, and active TPB length of AFL of 3DA-cell increased by about 33 %. 23 %, and 64 % compared to Planar-cell, whereas pore volume ratio of AFL did not change. Therefore, it was confirmed that the increase of the electrode/electrolyte interface area by ceramic micropatterning had a direct effect on the improvement of cell performance, and the internal structure of AFL was not affected by the imprinting process. Furthermore, to demonstrate the versatility of ceramic micropatterning process, a 5 cm x 5 cm large-area three-dimensional thin film SOFC was fabricated and its performance was evaluated. As a result, we set a new milestone in SOFC technology by reporting a power of ~ 13 W at 500 °C, and confirmed the consistency of our process through a cell reproducibility test. Additionally, the stability of the three-dimensional structure was verified through the operation without notable degradation for 500 hours under the condition of 5 A and 8 A current load. This work exhibits an outstanding breakthrough to accomplish high-performance, high-stable large-area SOFCs, and can accelerate commercialization to the portable and transportation devices.

CuO/ZnO Heterojunction Nanostructured Sensor Prepared on MEMS Device for Enhanced H2S Gas Detection

Gas sensing properties of pure ZnO and CuO layered ZnO nanostructures prepared on Micro Electro Mechanical system (MEMS) devices has been investigated. ZnO nanostructure is prepared using hydrothermal process and the structure deposited has rough surface with number of pores. CuO films (25 nm and 50 nm) are deposited on the ZnO nanostructure using RF sputtering process and the total thickness of 25 nm CuO layered ZnO is recorded about 3.30 μm. For the sake of gas sensing working conditions, MEMS microheater thermal properties are also studied. CuO coated ZnO MEMS device is tested for H2S gas at 200 °C temperature. Gas sensing properties of 25 nm thickness CuO on ZnO MEMS device sensor shown 42.5% of enhanced sensing response at 1 ppm when compared to pure ZnO sensor which only showed 23.2% response. The enhanced sensing response is due to the formation of CuO and ZnO heterojunctions. The sensor exhibited good sensitivity towards H2S gas than other gases (SO2, CO, NH3 and ethanol) at the operating temperature of 200 °C. A random repeatability test at 800 ppb H2S gas concentration is done with 25 nm CuO layered ZnO which showed good repeating sensing results.

Electrical and Optical Studies of Reactively Sputtered Indium Oxide Thin Films

Electrical and optical properties of transparent conducting Indium Oxide (In2O3) thin films were studied. These films were deposited by reactive RF sputtering process using Indium target in the presence of oxygen as reactive gas with argon. The pressure and the oxygen gas flow ratios during sputtering were varied to investigate their effect on the resistivity, optical transmission, refractive index, and optical bandgap of In2O3 thin films. The lowest reported resistivity in this study is 2 × 10−3 Ω-cm. The optical transmission was more than 80% in the wavelength range of 400 nm to 800 nm. The optical study revealed the wide optical bandgap of 3.712 eV and 3.875 eV of the deposited In2O3 films. The films showed refractive indices in the range of 1.99 to 2.22. The elemental composition of In2O3 films has been studied through X-ray Photoelectron Spectroscopy (XPS).

Innovative Infrared-pulsed laser assisted RF sputtered β-Ga2O3 thin film at low temperature process

Innovative new method for the pulsed laser assisted radio-frequency sputtering at low temperature process was successfully applied for the β phase Ga2O3 thin film as wide band gap materials. Thin film of wide bandgap material, β-Ga2O3, was successfully deposited on SiO2/Si and quartz substrates by employing radio-frequency sputtering system with assisting process of ytterbium-laser irradiation. Both sputtering system and infrared pulsed laser irradiation process were employed at the same time to increase the acquired energy densities for the adatoms on the thin film growth process. X-ray diffraction patterns (XRD) showed the prominent peaks of unique crystalline properties of Ga2O3 thin films in β phase. The optical energy bandgap of Ga2O3 thin films derived from spectral transmittance was measured in the range of 4.90–5.06 eV for a variation of laser power. High resolution X-ray photon spectroscopy (XPS) analysis showed that O 1s and Ga 3d position in core level. We confirm that infrared optical energy was effectively added to fabricate β-Ga2O3 thin film by employing the Yb-laser-assisted RF sputtering process.

Argon pressure dependent optoelectronic characteristics of amorphous tin oxide thin films obtained by non-reactive RF sputtering process

In this work, amorphous tin oxide thin films were deposited by non-reactive radio frequency magnetron sputtering. A ceramic $${\text{SnO}}_2$$ target was used, while different working pressures were employed. The target to substrate distance was fixed to 17 cm, and the substrate was not intentionally heated. The properties of $${\text{SnO}}_2$$ (thickness, refractive index dispersion, optical band gap, resistivity, free carriers concentration, carriers mobility, carriers majority type and their scattering time) have been inferred from spectroscopic ellipsometry, conventional UV-Vis spectroscopy and specific Hall electrical measurements. Thickness and refractive index are slightly dependent on the deposition conditions, while the optical band gap, free carriers concentration and their mobilities are changing from sample to sample. The evolution of the optical band gap and carriers concentration is correlated to the active defects concentration. Amorphous $${\text{SnO}}_2$$ films grown at 0.4 Pa have the lowest resistivity of $$0.86\,\Omega \, \hbox {cm}$$ , a carrier concentration of $$1.05 \times 10^{18}\,\hbox {cm}^{-3}$$ , and a Hall mobility of $$6.8\,\hbox {cm}^{2}$$ / Vs. The average optical transmittance in visible spectrum is 76%.

Structural and electrical properties of Al/BiFeO3/ZrO2/n-Si structure for non-volatile memory application

In this communication, the structural and electrical properties of metal–ferroelectric–insulator–silicon (MFIS) capacitor structure have been reported for non-volatile memory applications. Sol–gel with spin coating and rf sputtering process have been used for depositing BiFeO3 (BFO) and ZrO2 films, respectively. It has been observed that BFO film shows pure ferroelectric phase, uniform grain size and maximum refractive index at annealing temperature of 500 °C. Thermo-gravimetric analyzer and differential scanning calorimetry analysis indicate good agreement with X-ray diffraction of BFO film. In ZrO2 thin film, it has been observed that ZrO2 is in amorphous state at all annealing temperatures and the maximum refractive index has been found at annealing temperature of 400 °C. Al/ZrO2/n-Si (MIS), Al/BiFeO3/n-Si (MFS) and Al/BiFeO3/ZrO2/n-Si (MFIS) structures have been fabricated to investigate the electrical characteristics. The memory window has been observed by capacitance–voltage (C–V) characteristics and it improves from 1.9 V in MFS structure to 5.4 V in MFIS structure with 8 nm dielectric layer. Leakage current density has been observed by current density–gate voltage (J–V) characteristics and it is order of 10−5 A/cm2 in MF150 nmI8 nmS structure. No charge value degrades up to 1012 iteration cycles in MF150 nmI8 nmS structure.

Annealing Effect on Microstructure and ElectricalCharacteristics of n-ZnO/p-Si HetrojunctionDiode Fabricated by RF Sputtering Process

This article reports fabrication and microstructural characterization ofn-ZnO/p-Si heterojunction diode. Nanostructured Zinc Oxide (ZnO) thinfilm was deposited on p-type silicon (Si) and glass substrates using RFsputtering process for fabricating n-ZnO/p-Si heterojunction diode. Theeffect of annealing temperature on the structural and morphologicalproperties of ZnO thin films has been observed. After deposition,these films are annealed. Structural properties, surface morphologyand quality of thin film have been studied using XRD, AFM, FE-SEMand Energy Dispersive X-ray Spectroscope (EDX) measurements. XRDresults confirms the formation of ZnO. The crystallite size of ZnO filmswas increased by annealing it at 523 K. The average crystallite size ofas deposited nanostructured ZnO thin film was found to be 28 nm.The junction properties of n-ZnO/p-Si heterojunction diodes wereinvestigated using current–voltage measurements. The current wereanalyzed by sweeping the voltage from -6V to +6V and and the kneevoltage was found to be around 1.9V.

Structural, Electrical and Optical Studies of ZnO/TiO2Thin Films Fabricated by RF Sputtering Process for UV application

Structural, Electrical and Optical Studies of ZnO/TiO2Thin Films Fabricated by RF Sputtering Process for UV application

Magnetron configurations dependent surface properties of SnO2 thin films deposited by sputtering process

The effect of balanced magnetron (BM) and unbalanced magnetron (UBM) configurations, in RF sputtering process, on the surface properties of SnO2 thin films has been investigated. X-ray photoelectron spectroscopy (XPS) Sn3d and O1s core spectra reveal that the films deposited at RF power of 250 W under BM configuration consist of Sn4+ oxidation states, while those deposited under UBM configuration consist of Sn4+ and Sn2+ oxidation states. This has been attributed to the migration of oxygen atoms from SnO2, resulting in the formation of Sn interstitial and oxygen vacancies. The contact angle (θ) recordings reveal that the UBM configuration results in more hydrophobic surface (140.6°) of SnO2 thin films than that under BM configuration (129.6°). Further, Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) results indicate that the SnO2 thin films deposited under UBM configuration have better density with granular grains in comparison to that under BM configuration. The present studies establish the fact that magnetron configurations in sputtering process have significant impact on the surface properties of SnO2 thin films.

Design and Development of Humidity Sensor Based on Alumina and Zirconium Dioxide

Humidity calculation is one of the most significant issues in different applications such as automated system, irrigation, instrumentation, climatology and GPS. The design and fabrication of Humidity sensor are mostly used for industries and laboratory applications. This work highlights the fabrication of humidity sensor based on alumina (Al2O3) used as substrate and Zirconium Dioxide (ZrO2) as active or sensing material to detect both moisture and air temperature in the environment. The objective was to fabricate a humidity sensor of compact size with better sensitivity and spatial resolution at low cost. In this project, AUTOCAD software was used for designing and was developed a miniaturized thin film sensor over a ceramic substrate and deposition of active sensing material was done through RF sputtering process. The fabricated humidity sensor has been characterized under different humidity conditions and the results showed a faster response.

Effect of Sr and La co-doping on structural and electrical properties of RF sputtered PZT thin films

Doping in lead-zirconate-titanate (PZT) thin films is on the rise for next generation micro-electro-mechanical systems (MEMS) and energy harvesting applications, owing to their improved ferroelectric and piezoelectric properties. Strontium, lanthanum and neodymium like elements are the most exploited for such applications. This paper reports realization of a PZT thin film with strontium and lanthanum co-doping in tandem, Pb1−x−3y/2SrxLay(Zr0.56Ti0.44)O3 x = 0.06, y = 0.03 (PSLZT), by RF sputtering process. Different process conditions like substrate temperature from 250 °C–350 °C and annealing temperature from 650 °C–750 °C are studied to achieve pyrochlore free PSLZT thin film. The structure, surface morphology, surface topography and ferroelectric characteristics are investigated using x-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM) and P-E analyser, respectively. Nanoscale polarization switching processes and the local surface displacements are studied to ascertain that the PSLZT thin film exhibits the ferroelectric and piezoelectric properties. Experimental results reveal that the present PSLZT thin film has a polarization of 5.5 μC cm−2, leakage current density of 10−5 A cm−2 and piezoelectric charge coefficient, d33, of 87 pm V−1, which are suitable for realization of various new piezoelectric MEMS sensors.

Structural and Optical Properties of ZnS Thin Films Fabricated by Using RF Sputtering and Rapid Thermal Annealing Process for Buffer Layer in Thin Film Solar Cells

Structural and Optical Properties of ZnS Thin Films Fabricated by Using RF Sputtering and Rapid Thermal Annealing Process for Buffer Layer in Thin Film Solar Cells

Developing an empirical relationship for optimizing surface roughness of TiC thin film grown by magnetron sputtering using Taguchi analysis

The surface roughness of thin films coating is an important factor that affects the performance capability of material in industrial and scientific application. Surface roughness influences properties such has nanohardness, wear, friction and corrosion. This research focuses on the influence of RF magnetron process parameters on the surface roughness of TiC thin film grown on Ti6Al4V substrate. Taguchi optimization method was used to determine the contribution ratio of the RF sputtering process parameters and mathematical predictive models were developed for optimization of TiC thin film surface roughness. The structural characterization of the TiC thin film was examined using Grazing incidence X-ray diffractometer. The optimization analysis revealed that the RF power contributed the most to the behaviour of the TiC thin film surface roughness with a contribution rate of 87.97%. The percentage error from the predictive models developed are very meagre and shows good agreement with the acceptable limit. From the GIXRD analysis, the (200) orientation plane was noticed to be the preferential peak in all the coatings.