Thin Film Deposition Parameters Research Articles

A study on the fabrication procedure for a high-D/Ti-ratio-deuterated-titanium film on the disk-type neutron generator target

This study aims to present thin film deposition and deuterium adsorption procedure to fabricate disk-type targets with high D/Ti values for a neutron generator and increase their lifespan. The neutron target consists of a titanium thin film with hydrogen loading, and a copper substrate for heat removal. We optimized the incident deuterium ion beam energy and thin film thickness using Geant4 simulations. Additionally, we calculated the expected neutron yield under the optimized conditions. The hydrogen adsorption conditions were optimized by comparing the H/Ti results as per hydrogen adsorption temperature and loading time using titanium foils of different thickness values. Hydrogen (or deuterium) adsorption ratio is strongly influenced by the surface condition and the deposition conditions of the thin film. A titanium film was deposited in various conditions of plasma DC power and substrate temperature. The quality of the thin film was evaluated through surface roughness evaluation and thin film sheet resistance for each deposition conditions. Subsequently, the hydrogen adsorption results were compared according to the quality of the thin titanium films, and the thin titanium film deposition conditions with the highest hydrogen adsorption ratio were confirmed. The selected conditions were applied to conduct deuterium adsorption. In conclusion, this study underscores the critical relationship between thin film quality and hydrogen (or deuterium) adsorption ratio, reinforcing the importance of optimizing thin film deposition parameters for the design of neutron generator disk-type targets with high quality of film and extended lifespan.

Characterization of ZnO, Ga-Doped ZnO, and Nd-Ga-Doped ZnO Thin Films Synthesized by Radiofrequency Magnetron Sputtering

Here is described the influence of deposition parameters of ZnO thin films doped with Ga and co-doped with (Ga + Nd) upon the structural, morphological, optical and electrical properties. The transparent conductive thin films were fabricated by radiofrequency (RF) magnetron sputtering using a power of 100 W and a deposition distance of 6 cm. The deposition was performed on glass substrates heated at 150 °C with a time deposition of 90 min. The influence of doping upon the structure of thin films was analyzed by x-ray diffraction (XRD). Optical transmission measurements showed an 85% transparency in the visible range for the undoped ZnO films and the transparency of these films decreased when the dopants were added. Micro-structural analysis obtained by atomic force microscopy (AFM) evidenced that the type of doping modify the microstructure of thin films. Raman and resistivity measurements emphasize the successful incorporation of dopants into the ZnO host material.

Control of Oxygen Vacancy Ordering in Brownmillerite Thin Films via Ionic Liquid Gating.

Oxygen defects and their atomic arrangements play a significant role in the physical properties of many transition metal oxides. The exemplary perovskite SrCoO3-δ (P-SCO) is metallic and ferromagnetic. However, its daughter phase, the brownmillerite SrCoO2.5 (BM-SCO), is insulating and an antiferromagnet. Moreover, BM-SCO exhibits oxygen vacancy channels (OVCs) that in thin films can be oriented either horizontally (H-SCO) or vertically (V-SCO) to the film’s surface. To date, the orientation of these OVCs has been manipulated by control of the thin film deposition parameters or by using a substrate-induced strain. Here, we present a method to electrically control the OVC ordering in thin layers via ionic liquid gating (ILG). We show that H-SCO (antiferromagnetic insulator, AFI) can be converted to P-SCO (ferromagnetic metal, FM) and subsequently to V-SCO (AFI) by the insertion and subtraction of oxygen throughout thick films via ILG. Moreover, these processes are independent of substrate-induced strain which favors formation of H-SCO in the as-deposited film. The electric-field control of the OVC channels is a path toward the creation of oxitronic devices.

Thin Film Barrier Layers with Increased Performance and Reduced Long-Term Degradation in SOFCs

Gadolinium-doped ceria (CGO) is placed between yttrium-stabilized zirconia (YSZ) electrolyte and strontium-based electrode as a barrier layer to avoid the formation of SrZrO3 insulating phase during solid oxide fuel cell operation. This phase is observed in as-fabricated state-of-the-art cells, which evidences cation inter-diffusion during the sintering process [1]. The impact of this element to the degradation of cells is still under study, in part due to the high complexity of long-term tests necessary for the appropriate understanding of the involved phenomena. Among the efforts for improving barrier layers, the use of vacuum techniques such as sputtering and Large Area Pulsed Laser Deposition (LA-PLD) have been explored, allowing the implementation of dense layers at lower processing temperature compared with traditional deposition techniques (i. e. screen printing). CGO barrier layer thin film deposition and annealing parameters were previously optimized in a leading to an important increase of power density compared to a state-of-the-art button cell at 750ºC using a dense layer of 2 µm. Remarkable results were also obtained when the PLD barrier layer was up-scaled to large area cells of 80 cm2 and tested in short-stack configuration for long-term operation [2].Here we present a thorough investigation of post mortem cells operated in short-stacks under realistic conditions during 15000h, comparing cells produced with state-of-the-art techniques with those produced by LA-PLD. At the light of the results, we provide tools for the improvement of the fabricated thin film layers, by finding the optimal combination between the protective role of the diffusion barrier layer, a good performance and the reduction of the PLD deposition time. Button cells with PLD barrier layer of 800 nm, 400 nm and 200 nm were fabricated and tested in SOFC mode at 750ºC. It is shown that the barrier layer thickness has no impact on the electrochemical performance and the durability which allows the use of thinner layers and a drastic reduction of the deposition time of the CGO barrier layer made by PLD.Summed to the increased performance, the durability of the layers is evaluated, subjecting the cell with the thinnest film to an aging process for 3,500 h. Post-mortem characterization of the barrier layers and interfaces was conducted by Scanning-electronic microscope and Electron Probe Micro Analysis with Wavelength Dispersive X-Ray (EPMA-WDX) to observe any microstructural changes as well as any changes in composition due to cation inter-diffusion.[1] Morales et al., Journal of Power Sources 344 (2017) 141-151.[2] Morales et al. ACS Applied Energy Materials 1 (2018) 1955-1964.

Growth of LixLaySrzMnO3 thin films by pulsed laser deposition: complex relation between thin film composition and deposition parameters

LixLaySrzMnO3 thin films of various compositions (x,y,z) have been grown using pulsed laser deposition. The compositions of the films have been studied as a function of deposition temperature, target-to-substrate distance and deposition pressure with respect to different cation ratios of the targets by inductively coupled plasma mass spectrometry. When growing multi-elemental oxide thin films containing lithium (with its large mass difference to other elements), lithium loss is most probably inevitable. But the desired thin film composition can be achieved by selecting specific growth conditions and different target compositions. The experiments also elucidate some of the mechanisms behind the incongruent lithium transfer from the targets to thin films.

Stable magnesium zinc oxide by reactive Co-Sputtering for CdTe-based solar cells

Magnesium zinc oxide (MZO) is a promising front contact material for CdTe solar cells. Due to its higher band gap than traditional CdS, MZO can reduce parasitic absorption to significantly increase short-circuit current density while also providing a benefit of conduction band offset tuning through Mg:Zn ratio optimization. MZO has been successfully implemented into CdTe devices, however its stability has been of concern. The MZO stability issue has been attributed to the presence of oxygen in the CdTe device processing ambient, leading to double-diode behavior (S-kink) in the current density-voltage curves. Here we report on MZO thin films deposited by reactive co-sputtering. The reactively co-sputtered MZO thin films have encouraging stability, show no significant variation in work function of the surface over a period of 6 months, as measured by Kelvin probe. Energy conversion efficiencies of around 16% have been achieved both with and without presence of oxygen in device processing ambients across multiple research facilities. These efficiencies should be possible to increase further by tuning of the thin film deposition and device processing parameters, especially through optimization of the back contact.

Determination and Improvement of Deposition Parameters of TiO2 Thin Films via ALD

Determination and Improvement of Deposition Parameters of TiO2 Thin Films via ALD

Optimization of the deposition parameters of Ni-20Cr thin films on thermally sprayed Al2O3 for sensor application

Ni-Cr (80–20 at.-%) thin films were synthesized by means of DC magnetron sputtering on thermally sprayed Al2O3 insolating coatings. In view of the application as a thin-film thermocouple, the ceramic layer provides an electrical as well a thermal insulation. The thin film must feature a good adhesion as well as a good electrical conductivity to be suitable as a thin-film thermocouple. Design of Experiments was utilized to determine if deposition parameters including the bias-voltage, heating power, and chamber pressure have a significant influence regarding critical scratch load, hardness to Young's modulus ratio, and electrical resistance. It was found out that the bias-voltage is the most important influencing factor. In order to extract the significant parameters, the morphology and topography were analyzed by means of SEM. The structural properties were obtained by means of XRD on an atomic level, using synchrotron radiation. Mechanical properties, such as the hardness and Young's modulus, as well the scratch load were evaluated using nanoindentation and a scratch-tester. To verify the findings, an optimized thin film was deposited, which showed an increased layer adhesion and a significantly lower electrical resistance.

Mechanical and fatigue properties of electro-less Ni-P coating on brass substrates by plasma-etched pretreatment

The pretreatment of brass substrates traditionally involves roughening and then activation, before electro-less coating with a Ni–P alloy. The Taguchi method is used to determine the effect of the parameters for electro-less Ni–P coating on the microstructure, mechanical properties and fatigue life. An orthogonal array (L9 33) and a signal-to-noise ratio and analysis of variance are used to determine the effect of the deposition parameters. In the confirmation runs, using optimal Ni–P thin film deposition parameters (pH 4, plating temperature 70 °C, plating time 60 min), the improvement in the fatigue life is 8.10% and in the hardness is 3.61%. Energy dispersive spectrometer (EDS) measurements show that the concentration of phosphorus (P) gradually decreases from 17.07 to 16.83 at.%, which gives the Ni–P films greater hardness and fatigue life. This study replaces traditional roughening and activation pretreatments with oxygen plasma etching. Traditional roughening and then activation produces more micro cracks or micro pores in the coating than the oxygen plasma-etched coating. The intensity of the Ni (2 0 0) and (1 1 1) diffraction peak, increases for oxygen plasma pretreatments. A comparison of the substrate pretreatment using oxygen plasma etching with traditional roughening then activation shows that the fatigue life is increased from 40 times to 60 times and the film’s hardness is increased from 549.3 Hv to 617.3 Hv.

Optimization of exchange bias in Co/CoO magnetic nanocaps by tuning deposition parameters

In the present work, we report exchange bias tuning by varying thin film deposition parameters such as synthesis method and underlying layer patterning. The patterned substrates for this study were prepared by self-assembly of polystyrene (PS) latex spheres (~530nm) on Si (100) substrate. The desired magnetic nanocaps composed of CoO/Co bilayer film on these patterned substrates were prepared by molecular beam epitaxy technique under ultra-high vacuum conditions. For this, a Co layer of ~10nm thickness was deposited on the substrates and then oxidized in-situ to form CoO/Co/PS in-situ oxidized film or ex-situ in ambiance which also gives CoO/Co/PS naturally oxidized film. Simultaneously, reference thin films of Co (~10nm) were also prepared on plane Si substrate and similar oxidation treatments were performed on them respectively. The magnetic properties studied using SQUID technique revealed higher exchange bias (~1736Oe) in the in-situ oxidized Co/PS film as compared to that in naturally oxidized Co/PS film (~1544Oe) and also compared to the reference film. The observed variations in the magnetic properties are explained in terms of surface patterning induced structural changes of the deposited films and different oxidation methods.

2D and 3D Analyses of Metal Oxide Thin Films Examined by Atomic Force Microscope

Atomic force microscope (AFM) is a useful tool to capture the two- and three-dimensional image of height and size of nanostructured thin film. It operate by measuring the forces between a sharp tip and surface of the measured sample. In addition, AFM is equipped with powerful software for image processing to interpret experimental results in detail. For example, by using the height and scanning length parameters of measured sample, average roughness and root mean square roughness can be evaluated. In the present works, the effect of image flattening process toward the surface roughness and surface fluctuations of metal oxide thin films will be presented. Set of samples were prepared by magnetron sputtering deposition and sol-gel coating techniques. In gas sensor industries using metal oxide thin film, surface roughness of metal oxide thin films are very important in order to improve the sensitivity and respond time of gas sensor. Therefore, optimization of thin film deposition and characterization are very important. The correlation between the three-dimensional image and thin film deposition and image processing parameters will also be presented.

Optimization of zinc sulfide thin film coating process using response surface methodology

Zinc sulfide (ZnS) thin films have been deposited on glass substrates at room temperature using chemical bath deposition method. Application of response surface methodology and central composite design for optimizing the ZnS films deposition parameters and understanding the significance and interaction of the factors affecting the film quality was discussed in this work. pH, stirring speed and deposition time were investigated as variables and band gap was selected as response in this study. The samples were characterized using X-Ray diffraction, scanning electron microscope and ultraviolet–visible spectroscopy measurements. The optimal conditions for the deposition parameters of the ZnS thin films have been found to be: pH of 10.1, stirring speed of 163 rpm and deposition time of 31 h. Under these conditions, the experimental band gap of ZnS was 3.95 eV, which is well in close agreement with value (3.97 eV) predicted by the model.

Effect of pH-11 Buffer as Agent Reaction Moderator in the Growth and Characterization of CdS Thin Films by CBD Technique

The effect of deposition parameters of CdS thin films developed by Chemical Bath Deposition (CBD) technique was investigated in this paper. We studied the influence of pH control of the reaction solution on the structural and optical properties of chemically deposited CdS films. Different films thicknesses of CdS were deposited onto a glass substrate. The structural surface morphology of as-deposited CdS thin films was characterized by SEM, XRD, profilometer, and ultraviolet–visible spectroscopy. The physical conditions were kept identical while growing the samples. The investigation of the effect of the synthesis method on the change the ammonium hydroxide by buffer pH-11 contributed in increases the growth kinetics, resulting in thicker films. Over the years, thin films of II-VI semiconductor compounds are most promising for utilization in solar cells, out of which the cadmium sulfide (CdS) has received intensive attention, since its band gap lie very close to the range of maximum theoretically attainable energy conversion efficiency. CdS is an inorganic compound of yellow solid color, and due to its wide band gap, photoconductivity, and high electron affinity, is known to be an excellent heterojunction partner for p-type cadmium telluride, p-type copper indium diselenide. It has been widely used as a window material in high efficiency thin film solar cells based on cadmium telluride or copper indium diselenide [1-3]. In these devices, light penetrates the CdS layer and it is absorbed in the p-type semiconductor close to the pn junction. Also, CdS is an interesting crystal material in the area of photodetectors, semiconductor lasers, and non linear integrated optical devices. The importance of wide band gap materials is related to the possibility of fabricating light emitting diodes or laser heterostructures for emission in the visible spectral range. The CdS thin films were fabricated by CBD technique on glass substrate. The diffractogram of an

Optimization of deposition conditions of CdS thin films using response surface methodology

Cadmium sulfide (CdS) thin films were prepared on glass substrates by chemical bath deposition (CBD) technique under different pH, stirring speed and deposition time. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to optimization of deposition parameters of the CdS thin films. RSM and CCD were also used to understand the significance and interaction of the factors affecting the film quality. Variables were determined as pH, stirring speed and deposition time. The band gap was chosen as response in the study. Influences of the variables on the band gap and the film quality were investigated. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition conditions parameters such as pH (10.2–11.8), stirring speed (132–468rpm) and deposition time (33–67min) on the band gap of the films. The samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet–visible spectroscopy (UV–vis) measurements. The optimal conditions for the deposition parameters of the CdS thin films have been found to be: pH 11, 361 of stirring speed and 55min of deposition time. Under the optimal conditions theoretical (predicted) band gap of CdS (2.66eV) was calculated using optimal coded values from the model and the theoretical value is good agreement with the value (2.72eV) obtained by verification experiment.

Hexagonal structured Zn(1−x)CdxO solid solution thin films: synthesis, characterization and applications in photoelectrochemical water splitting

Hexagonal nanostructured zinc–cadmium oxide [Zn(1−x)CdxO where x = 0.08, 0.15, and 0.17] solid solution thin films were deposited on FTO coated glass substrates from a common solution of zinc acetate and a newly developed polymeric cadmium precursor by an aerosol-assisted chemical vapour deposition (AACVD) technique. The polymeric cadmium precursor [Cd3(TFA)4(OAc)2(THF)4]n (1) was synthesized by the reaction of cadmium(II)acetate dihydrate with triflouroacetic acid in THF solution and characterized by melting point, microanalysis, FTIR, 1H-NMR, thermogravimetry (TG/DTG) and single crystal X-ray analysis. The deposited thin films were characterized by powder XRD, SEM, EDX and UV-visible spectrophotometry, and tested for photoelectrochemical (PEC) water splitting to hydrogen and oxygen. The effect of various thin film deposition parameters such as solvent type, temperature and electrolyte concentration on PEC properties has been investigated. The SEM analysis illustrated that the morphology of the films changes significantly with the change of the solvent. The films deposited from THF solution have a needle-like appearance scattered vertically on the FTO-coated glass substrate. An optical band gap of 2.40 eV has been estimated by UV-visible spectrophotometry. The current–voltage characterization proved that the nanocrystalline hexagonal structured Zn0.83Cd0.17O electrodes exhibit an n-type semiconducting behaviour and the photocurrent was found to be strongly dependent on the deposition solvent, deposition temperature and electrolyte concentration. The maximum photocurrent density of 0.23 mA cm−2 at 0.55 V vs. Ag/AgCl/3 M KCl (∼1.23 V vs. RHE) was obtained for the Zn0.83Cd0.17O photoelectrode deposited at 500 °C for 45 min from 0.5 M solution of (1) and Zn(CH3COO)2·2H2O in THF.

Direct current reactive co-sputter deposition of CrWN films to enhance cutting tool performance

Chromium tungsten nitride (CrWN) thin films were deposited onto tungsten carbide tools substrates, by direct current (DC) reactive magnetron co-sputter at room temperature. The targets were metallic Cr and W, argon was the plasma gas and nitrogen was the reactive gas. A preliminary experiment to determine the optimal turning process parameters indicated spindle speed, feed rate, and cut depth clearly affect cutting performance. The use of a grey-based Taguchi method to determine the processing parameters of CrWN thin film deposition has been studied by considering multiple performance characteristics. Dry turning of AISI 304 stainless steel tests was carried out with these coated tools. The effect and optimization of CrWN thin film deposition parameters (DC reactive magnetron co-sputter parameters: Cr power, W power, N2/(Ar+N2) flow-rate ratios and deposition time) on the structure, roundness and flank wear in the turning operations were studied. In the confirmation runs, when using grey relational analysis, improvement of 12.64% was obtained in surface roughness, 9.09% in roundness and 25.52% in flank wear, respectively.

Hollow Bragg waveguides fabricated by controlled buckling of Si/SiO_2 multilayers

We describe integrated air-core waveguides with Bragg reflector claddings, fabricated by controlled delamination and buckling of sputtered Si/SiO2 multilayers. Thin film deposition parameters were tailored to produce a desired amount of compressive stress, and a patterned, embedded fluorocarbon layer was used to define regions of reduced adhesion. Self-assembled air channels formed either spontaneously or upon heating-induced decomposition of the patterned film. Preliminary optical experiments confirmed that light is confined to the air channels by a photonic band-gap guidance mechanism, with loss ~5 dB/cm in the 1550 nm wavelength region. The waveguides employ standard silicon processes and have potential applications in MEMS and lab-on-chip systems.

Micro-Raman characterization of Germanium thin films evaporated on various substrates

We perform an extensive micro-Raman analysis of Germanium thin films physically evaporated on several substrates including silicon, silicon oxide and glass. We investigate the dependence of crystal quality on thin film deposition parameters such as substrate temperature and growth rate. We also study the continuous transitional change of the material structure from amorphous to crystalline phases. Ge films obtained by this simple and low cost technique are a viable solution towards the realization of virtual substrates and devices.

Deposition of Functional Polymer Thin Films Using Atmospheric Pressure Plasma for Biomedical Applications – Endothelialization of Vascular Prostheses

Functionalized plasma polymer thin films were obtained in a dielectric barrier discharge at atmospheric pressure in an atmosphere of N2 and C2H4. The coatings were hydrophilic, adherent, chemically stable and presented a surface concentration of NH2 suitable for further biomolecule conjugation. Covalent grafting of a linking arm (glutaric anhydride) and subsequent conjugation of fibronectin, a protein of the extracellular matrix, were successful. Finally, endothelial cell adhesion experiments were performed directly on the functionalized thin films as well as on the conjugated coatings. Effects on cell adhesion were observed as a function of the plasma thin film deposition parameters.

Fabrication of piezoelectric AlN thin film for FBARs

This paper focuses on the fabrication of film bulk acoustic-wave resonator (FBAR) comprising an aluminum nitride (AlN) piezoelectric thin film sandwiched between two metal electrodes and located on a silicon substrate with a low-stress silicon nitride (Si3N4) support membrane for high frequency wireless applications, and analyzes the optimization of the thin AlN film deposition parameters on Mo electrodes using the reactive RF magnetron sputter system. Several critical parameters of the sputtering process such as RF power and Ar/N2 flow rate ratio were studied to clarify their effects on different electrodes characteristics of the AlN films. The experiment indicated that the process for Mo electrode was easier compared with that of the Pt/Ti or Au/Cr bi-layer electrode as it entailed only one photo resist and metal deposition step. Besides, Pt/Ti or Au/Cr electrodes reduced the resonance frequency due to their high mass density and low bulk acoustic velocity. Compared with the case of the Al bottom electrode, there is no evident amorphous layer between the Mo bottom electrode and the deposited AlN film. The characteristics of the FBAR devices depend not only upon the thickness and quality of the AlN film, but also upon the thickness of the top electrode and the materials used. The results indicate that decreasing the thickness of either the AlN film or the top electrode increases the resonance frequency. This suggests the potential of tuning the performance of the FBAR device by carefully controlling AlN film thickness. Besides, increasing either the thickness of the AlN film or higher RF power has improved a stronger c-axis orientation and tended to promote a narrower rocking curve full-width at half-maximum (FWHM), but increased both the grain size and the surface roughness. An FBAR device fabricated under optimal AlN deposition parameters has demonstrated the effective electromechanical coupling coefficient (k eff 2 ) and the quality factor (Q f x ) are about 1.5% and 332, respectively.