Sputtering Deposition Time Research Articles

Effect of deposition parameters on optical and electrical properties of ZnO–In2O3–SnO2 thin films

A combinatorial study was carried out using a magnetron sputtering system to determine suitable ternary compositions of ZnO–In2O3–SnO2 (ZITO) thin films for optoelectronic applications. Samples were obtained on glass substrates via the co-sputtering of high purity oxide targets. Parameters such as the sputtering gas pressure, deposition time and substrate temperature were studied as the process variables and their effects on the composition, optical, and electrical properties of the thin films were examined in detail. The results have revealed that the samples deposited under a sputtering gas pressure of 10 mTorr and deposition time of 45 min in the Zn-rich region presented the best optical properties (max. 84%), whereas In-rich compositions exhibited better electrical properties (min. 14 Ω/□). More specifically, 61.7 at.% Zn, 31.4 at.% In, and 6.9 at.% Sn was determined as the most suitable ZITO composition for various optoelectronic applications. In addition, the increase in deposition temperature enhanced the optoelectronic properties of the thin film samples as well as their crystal quality.

Microstructure and Magnetic Properties Dependence on the Sputtering Power and Deposition Time of TbDyFe Thin Films Integrated on Single-Crystal Diamond Substrate

As giant magnetostrictive material, TbDyFe is regarded as a promising choice for magnetic sensing due to its excellent sensitivity to changes in magnetic fields. To satisfy the requirements of high sensitivity and the stability of magnetic sensors, TbDyFe thin films were successfully deposited on single-crystal diamond (SCD) substrate with a Young’s modulus over 1000 GPa and an ultra-stable performance by radio-frequency magnetron sputtering at room temperature. The sputtering power and deposition time effects of TbDyFe thin films on phase composition, microstructure, and magnetic properties were investigated. Amorphous TbDyFe thin films were achieved under various conditions of sputtering power and deposition time. TbDyFe films appeared as an obvious boundary to SCD substrate as sputtering power exceeded 100 W and deposition time exceeded 2 h, and the thickness of the films was basically linear with the sputtering power and deposition time based on a scanning electron microscope (SEM). The film roughness ranged from 0.15 nm to 0.35 nm, which was measured by an atomic force microscope (AFM). The TbDyFe film prepared under a sputtering power of 100 W and a deposition time of 3 h possessed the coercivity of 48 Oe and a remanence ratio of 0.53, with a giant magnetostriction and Young’s modulus effect, suggesting attractive magnetic sensitivity. The realization of TbDyFe/SCD magnetic material demonstrates a foreseeable potential in the application of high-performance sensors.

X-ray Photoelectron Spectroscopy (XPS) Analysis of Ultrafine Au Nanoparticles Supported over Reactively Sputtered TiO2 Films.

The impact of a titania (TiO2) support film surface on the catalytic activity of gold nanoparticles (Au NP) was investigated. Using the reactive dc-magnetron sputtering technique, TiO2 films with an amorphous, anatase, and nitrogen-doped anatase crystal structure were produced for a subsequent role as a support material for Au NP. Raman spectra of these TiO2 films revealed that both vacuum and NH3 annealing treatments promoted amorphous to anatase phase transformation through the presence of a peak in the 513–519 cm−1 spectral regime. Furthermore, annealing under NH3 flux had an associated blue shift and broadening of the Raman active mode at 1430 cm−1, characteristic of an increase in the oxygen vacancies (VO). For a 3 to 15 s sputter deposition time, the Au NP over TiO2 support films were in the 6.7–17.1 nm size range. From X-ray photoelectron spectroscope (XPS) analysis, the absence of any shift in the Au 4f core level peak implied that there was no change in the electronic properties of Au NP. On the other hand, spontaneous hydroxyl (–OH) group adsorption to anatase TiO2 support was instantly detected, the magnitude of which was found to be enhanced upon increasing the Au NP loading. Nitrogen-doped anatase TiO2 supporting Au NP with ~21.8 nm exhibited a greater extent of molecular oxygen adsorption. The adsorption of both –OH and O2 species is believed to take place at the perimeter sites of the Au NP interfacing with the TiO2 film. XPS analyses and discussions about the tentative roles of O2 and –OH adsorbent species toward Au/TiO2 systems corroborate very well with interpretations of density functional theory simulations.

Study on CoAl intermetallic compound films for advanced interconnect applications: Experimental and DFT investigations

This paper reports the results of a materials study on co-sputtered CoAl thin films for interconnect applications based on both experiments and computations. We modulate the composition and microstructure of the CoAl films by controlling the deposition conditions (sputtering power, substrate temperature, and deposition time). The morphology and microstructure of the films are investigated using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The measurement of the film resistivity reveals a strong stoichiometry effect: the lowest (∼30 μΩ∙cm) for the stoichiometric film. It also discloses a typical trend of size dependence: the resistivity increases rapidly with the thickness decreasing (from 38 μΩ∙cm for 43 nm to 72 μΩ∙cm for 13 nm). We also compute the resistivity dependence on the film thickness by solving the Boltzmann transport equation with inputs of the electronic and phononic structures from the first-principles density functional theory and the electron-phonon relaxation time modified according to the film thickness. Furthermore, we devised a simple model considering the effects of grain sizes and scattering at grain boundaries on the resistivity to describe the transport behavior in CoAl. Our calculated results were found consistent with our experimentally observed ones.

Time‐Resolved Grazing Incidence X‐Ray Absorption Spectroscopy for the In Situ Investigation of the Initial Stages of Sputter‐Deposited Copper Thin Films

The sputter deposition and the growth of thin copper films on float glass substrates are in situ studied using grazing incidence, reflection mode X‐ray absorption fine structure spectroscopy with subsecond time resolution. The experimental data are compared with model calculations, assuming the presence of crystalline, face‐centered cubic metallic Cu nanostructures. From a detailed analysis of the measured spectra, the film thickness as well as the surface roughness is determined, leading to a detailed understanding of the films growth as a function of the sputter deposition time. In particular, different stages of film growth can clearly be distinguished from the fits of the experimental data. The results suggest the formation of isolated, approximately nm‐sized copper clusters in the initial phase of the film deposition for the first few seconds, a coalescence phase with a nominal thickness of ≈1.5−2.8 nm, constant roughness of about 1.4 nm for the subsequent ≈5 s, and finally 3D growth of the Cu crystallites in the film for later stages of film growth. Further prospects of the methodology are given.

Microstructure and optical properties of PbSe nanocrystalline films prepared by magnetron sputtering

PbSe nanocrystalline films were prepared using magnetron sputtering with different sputtering powers and deposition times. The obtained samples were characterized by X-ray diffractometry (XRD), field-emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), confocal Raman spectroscopy, UV–Vis–NIR spectroscopy, and spectrofluorophotometry. The XRD and XPS results show that the crystallization quality improves and the Pb/Se atomic ratio tends toward 1:1 with increasing sputtering power and deposition time. The morphology of PbSe particles varies from near-spherical to rod-like or cotton-like and then to triangular with increasing deposition time, consistent with the changed main growth orientation. The optical band gap of PbSe films decreases with increasing film thickness and grain size. A visible photoluminescence peak is observed at 655 nm, and its intensity strongly depends on the crystallization quality and morphology of PbSe particles, which is well consistent with the XRD and SEM results. Therefore, PbSe films with good luminescence performance can be obtained by adjusting sputtering power and deposition time.

Effect of RF Sputtering Power and Deposition Time on Optical and Electrical Properties of Indium Tin Oxide Thin Film

Indium tin oxide (ITO) films are widely used as transparent conducting electrodes in solar cells, gas sensors, and car windows because of their high electrical conductivity and good optical transparency in the visible region. In this work, ITO thin films were prepared by cathodic radio‐frequency (RF) sputtering using an ITO target with 90% In2O3 and 10% SnO2. The structural properties were studied by X‐ray diffraction (XRD), scanning electronic microscopy (SEM), and X‐ray reflectometry (XRR). Electrical measurements were performed by applying the four‐point method and studying the Hall Effect. Finally, optical properties were taken by the UV‐Vis‐NIR spectrophotometry. The effect of the RF power and deposition time on optical and electrical properties was investigated. It is shown that by using a RF power of 110–80 W, one can prepare crystalline samples with low resistivity, which is an aimed property for TCO semiconductors. Electrical measurements revealed that the resistivity decreases by increasing the RF power and/or the deposition time.

Oxygen Reduction Reaction Activity of Nanocolumnar Pt Thin Film Electrocatalyst Deposited on Carbon Support By High Pressure Sputtering

Proton-exchange membrane fuel cell (PEMFC) is one of the most important sources of clean energy especially for automotive applications, which currently utilizes platinum nanoparticles dispersed on carbon (Pt/C) as a catalyst. However, the catalyst activity and durability need to be improved and the cost of the fuel cell need to be reduced for successful commercialization. Extensive research has been done to improve the catalyst activity and durability, reduce the amount of platinum used and reduce its manufacturing cost. Continuous thin film layer approach is a promising candidate for non-conventional catalysts to address these challenges. For this purpose, nanocolumnar Pt thin film (Pt-TF) layers supported on carbon was fabricated by high pressure sputtering (HIPS) and investigated as oxygen reduction reaction (ORR) electrocatalysts for PEMFCs. HIPS is a simple physical vapor deposition method that is scalable and easily applicable to industrial sputter deposition systems, in which atoms come to the substrate surface with oblique angles and form columnar structures. Different Pt-TF/C weight ratios ranging from 5% to 20% and Pt:Ni (1:3) TF/C were studied. Weight loading was controlled by changing the sputter deposition time. X-ray diffraction analysis revealed the existence of Pt and formation of the Pt:Ni alloy on carbon support. Electrochemical characterization of the carbon-supported Pt-TF samples was conducted by cyclic voltammetry and rotating disk electrode measurements in an aqueous perchloric acid electrolyte. The electrochemically active surface area, mass activity and specific activity of the Pt-TF/C samples were found to be increasing as the Pt-TF/C ratio was increased.

Microstructural Evolution and ORR Activity of Nanocolumnar Platinum Thin Films with Different Mass Loadings Grown by High Pressure Sputtering

Nanocolumnar platinum thin films (Pt-TFs) with different Pt mass loadings were grown by high pressure sputtering (HIPS) and investigated as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte membrane fuel cell applications. Mass loading was controlled by changing the sputter deposition time. A cauliflower-like columnar microstructure was achieved by depositing the Pt-TFs onto a microporous layer (MPL)-like surface composed of carbon particles in order to mimic catalyst-coated gas diffusion electrodes. Microstructural evolution of HIPS Pt-TFs and their ORR activity were investigated. Electrochemical characterization of the nanocolumnar Pt-TFs was performed by cyclic voltammetry and rotating disk electrode measurements on Pt-TF/MPL-like-layer/glassy-carbon samples in an aqueous perchloric acid electrolyte. The electrochemically active surface area increased from 18 to 39 m2 g−1 as the Pt mass loading was decreased. Specific activity of the films was similar (∼600 μA cm−2) for all Pt mass loadings, due to the similar nanoparticle sizes of ∼5 nm as observed by transmission electron microscopy and X-ray diffraction. Mass activity of the films increased from 0.11 to 0.26 A mg−1 as the Pt mass loading was decreased, which is an indication of the effective Pt utilization and better access through the catalyst layer at lower Pt mass loadings.

Thickness dependent optical, structural, morphological, photocatalytic and catalytic properties of radio frequency magnetron sputtered nanostructured Cu2O–CuO thin films

Nanostructured thin films of Cu2O–CuO with improved photocatalytic and catalytic activities were developed by RF magnetron sputtering. Thickness-dependent optical, structural, morphological, photocatalytic and catalytic performance of the Cu2O–CuO films were investigated using field emission scanning electron microscopy (FESEM), XRD, AFM, RBS, UV–Vis absorption, PL and X-ray photoelectron spectroscopy. FESEM analyses showed nanoparticles which increased in size from 7 to 13 nm with increase in sputter deposition time and were confirmed to be of Cu2O–CuO from Raman and XPS studies. Increase in thickness of Cu2O–CuO thin film from 7 to 50 nm led to increase in surface roughness, decrease in band gap and reduction in PL intensity. Cu2O–CuO thin films showed thickness-dependent enhanced photocatalytic and catalytic activities towards degradation of methylene blue, methyl orange and 4-nitrophenol from water. The enhanced light utilization capability, suppressed charge recombination and small crystallite size of the developed nanostructured Cu2O–CuO thin films are the key factors responsible for their enhanced photocatalytic and catalytic performance.

UV laser induced gold nanoparticle fabrication dependent on initial film properties

The laser parameters, energy density and number of pulses, influence the UV laser-induced formation of gold nanoparticles on glass substrates. But also the deposition rate and the thickness of the gold layers used are important criteria for nanoparticle production. This is due to the fact that the resulting microstructures and the optical properties of the gold layers change by variation of sputtering power and deposition time based on different growth conditions of the films. The laser power of the KrF excimer laser used was varied from 50 to 500 mJ/cm2, the pulse number from 1 to 10 pulses and the film thickness from 20 nm to 60 nm as well. Low deposition rates produce layers with higher transparency for the same film thickness. The significant [111] texture of the films with grain sizes from 11 nm to 25 nm in dependent on the deposition rate, evaluated by x-ray diffraction and electron backscatter diffraction, changes after laser exposure. Particle size distributions were evaluated by scanning electron microscopy. Uni- or bi-modal distributions were observed dependent on deposition rate and laser parameters. The position and the width of nanoparticle plasmon resonances vary accordingly.

Synthesis and optimization of photocatalytic performance of WO3-loaded TiO2 nanotube array layers

TiO2 nanotube arrays were grown by anodic oxidation of the surface of Ti metal foils in an electrochemical cell with organic electrolyte containing fluorine, using constant bias voltage, 30 V. The average typical diameter and length of the as-prepared tubes were 87 nm and 3.8 μm, respectively. The titania nanotube arrays surface was subsequently loaded with WO3 non-contiguous thin layers by plasma-assisted RF sputtering. The addition of WO3 on the nanotube surface resulted in the formation of semiconductor heterojunctions, which lead to supplementary spatial separation of electron–hole pairs and reduced the recombination rate. Macroscopically, this is certified by increased lifetime of the photocatalytic activation and associated increase of surface wettability. In the current experiments, four sample sets with increasing WO3 coverage were prepared by increasing the sputter-deposition time of the WO3 material. Nanotube array morphology, structure and elemental composition were investigated by high-resolution scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and energy-dispersive x-ray spectroscopy. A comparison was made between the characteristics of the WO3-loaded nanotube layers and a reference bare TiO2 nanotube arrays layer. Annealing the samples at 420 °C led to the development of predominant anatase. The effects of UV irradiation and the presence of dopant fluorine species were further investigated and discussed as means to modifying the generation of hydroxyl radicals. Optimal conditions for the best photocatalytic performance of titania nanotube arrays were established via monitoring the degradation of methylene blue pollutant.

WS2 Nano-petals and Nano-bristles Supported on Carbon Nanotubes for Electron Emission Applications

Atomically thin WS2 nano-petals and nano-bristles were synthesized on vertically aligned carbon nanotubes (CNT) via magnetron sputtering at room temperature. The formation of the nano-petal morphology requires reaching a critical threshold in sputter deposition time, below which an amorphous film of WO3 is obtained instead. Increasing the deposition time past a second threshold results in a change to the nano-bristle morphology. Both WS2 nano-petals and nano-bristles were able to significantly enhance the electron emission of properties. The lowest turn-on voltage measured was to be 295 V and 355 V for the nano-petals and nano-bristles respectively, versus 425 V for pristine CNTs. The variation in the turn-on voltage is due to the electrical contacts at the interface between the different WS2 structures, which induces current saturation at high emission currents. These results demonstrate that 2D WS2 layers can be synthesized without the need for chemical routes and high growth temperatures if an appropriate template is employed.

Optimization of Electrical and Morphological Properties of MCrAlY thin films deposited by DC magnetron sputtering using Taguchi method

The objective of the research work was to optimize and standardize sputtering parameters based on physical parameters and electrical properties of the coatings. The experimental and statistical investigation was conducted for optimizing the sputtering parameters. The sputtering parameters were selected as sputtering power, working gas pressure, substrate temperature and deposition time. For coating of MCrAlY thin film on a borofloat glass substrate, the electrolytic MCrAlY target was used based on a design of experiment layout. The thin film coatings were characterized for film thickness and surface roughness. The optimum conditions for maximum thickness and minimum surface roughness are sputtering power (17.57 W), working gas pressure (5x10-3mbar), substrate temperature (100˚C) and deposition time (32 min). The ANOVA results for film thickness showed the contribution of deposition time (93.92) followed by working pressure (3.26 %), substrate temperature (2.052 %) and power (0.646%)

DC reactively sputtered TiNx thin films for capacitor electrodes

Being used as typical electrode layers in the state-of-the-art microelectronic devices, titanium nitride (TiNx) thin films have to meet the critical requirements for high conductivity, low surface roughness and thickness. In this work, TiNx thin films were deposited by direct current (DC) reactive sputtering in a nitrogen and argon ambient using a titanium target. Upon systematically adjusting the sputtering current, target-substrate distance and deposition time, the evolution of film properties were investigated in detail in terms of the composition, crystalline structure, resistivity, thickness and surface roughness. At finally optimized deposition conditions, ultra-thin (∼ 10 nm) TiNx thin films with a low resistivity of 125 µΩ cm and small surface roughness of 0.297 nm can be obtained. These superior performances together with low-running cost suggest great promise for the TiNx thin films to be used as electrodes in microelectronic devices.

Controlled Ag-TiO2 heterojunction obtained by combining physical vapor deposition and bifunctional surface modifiers

A controlled physical method without any solvent was used to grow Ag nanoparticles on TiO2 by use of mercaptoacetic acid as a bifunctional surface modifier. The fabricated Ag-TiO2 tight heterojunction was proposed as an innovative photocatalytic material. The particle size, chemical nature, morphology, and chemical bonding between mercaptoacetic acid, Ag, and TiO2 were characterized by UV–vis absorption spectroscopy, powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The photocatalytic activity of TiO2 combined with the excellent electron acceptor abilities and visible light absorption of small spherical Ag nanoparticles resulted in efficient photoinduced degradation of a cationic organic pollutant (methylene blue) under UV–vis light. The nanocatalyst material obtained with a sputter time of 30 s under simulated sunlight results in almost complete degradation (97%) of methylene blue after 120 min. The particle size, tight attachment to TiO2, and distribution of Ag nanoparticles were controlled for the first time through a physical method by use of controlled chemical bonding to bifunctional surface modifiers and an appropriate sputter deposition time.

3D nano-architected metallic glass: Size effect suppresses catastrophic failure

We investigate the mechanical behavior of 3D periodically architected metallic glass nanolattices, constructed from hollow beams of sputtered Zr-Ni-Al metallic glass. Nanolattices composed of beams with different wall thicknesses are fabricated by varying the sputter deposition time, resulting in nanolattices with median wall thicknesses of ∼88 nm, ∼57 nm, ∼38 nm, ∼30 nm, ∼20 nm, and ∼10 nm. Uniaxial compression experiments conducted inside a scanning electron microscope reveal a transition from brittle, catastrophic failure in thicker-walled nanolattices (median wall thicknesses of ∼88 and ∼57 nm) to deformable, gradual, layer-by-layer collapse in thinner-walled nanolattices (median wall thicknesses of ∼38 nm and less). As the nanolattice wall thickness is varied, large differences in deformability are manifested through the severity of strain bursts, nanolattice recovery after compression, and in-situ images obtained during compression experiments. We explain the brittle-to-deformable transition that occurs as the nanolattice wall thickness decreases in terms of the “smaller is more deformable” material size effect that arises in nano-sized metallic glasses. This work demonstrates that the nano-induced failure-suppression size effect that emerges in small-scale metallic glasses can be proliferated to larger-scale materials by the virtue of architecting.

Formation of a Pt-Decorated Au Nanoparticle Monolayer Floating on an Ionic Liquid by the Ionic Liquid/Metal Sputtering Method and Tunable Electrocatalytic Activities of the Resulting Monolayer

A novel strategy to prepare a bimetallic Au-Pt particle film was developed through sequential sputter deposition of Au and Pt on a room temperature ionic liquid (RTIL). Au sputter deposition onto an RTIL containing hydroxyl-functionalized cations produced a monolayer of Au particles 4.2 nm in size on the liquid surface. Subsequent Pt sputtering onto the original Au particle monolayer floating on the RTIL enabled decoration of individual Au particles with Pt metals, resulting in the formation of a bimetallic Au-Pt particle monolayer with a Pt-enriched particle surface. The particle size slightly increased to 4.8 nm with Pt deposition for 120 min. The shell layer of a bimetallic particle was composed of Au-Pt alloy, the composition of which was tunable by controlling the Pt sputter deposition time. The electrochemical surface area (ECSA) was determined by cyclic voltammetry of bimetallic Au-Pt particle monolayers transferred onto HOPG electrodes by a horizontal liftoff method. The Pt surface coverage, determined by ECSAs of Au and Pt, increased from 0 to 56 mol % with elapse of the Pt sputter deposition time up to 120 min. Thus-obtained Au-Pt particle films exhibited electrocatalytic activity for methanol oxidation reaction (MOR) superior to the activities of pure Au or Pt particles. Volcano-type dependence was observed between the MOR activity and Pt surface coverage on the particles. Maximum activity was obtained for Au-Pt particles with a Pt coverage of 49 mol %, being ca. 120 times higher than that of pure Pt particles. This method enables direct decoration of metal particles with different noble metal atoms, providing a novel strategy to develop highly efficient multinary particle catalysts.

Properties of aluminum deposited chemically recycled PET fabrics

To investigate the aluminum deposition on the chemically recycled polyethylene terephthalate (CR-PET) fabrics by DC magnetron sputtering, effects of sputtering parameters (sputtering power and deposit time) on the properties of the Al deposited CR-PET fabric were examined. The variations in the properties such as wettability, optical and thermal insulation property of the CR-PET fabric sputtered under various sputtering parameters were discussed. Wettability of the Al deposited CR-PET fabrics decreased with an increase of sputtering power and deposit time, and then they leveled off above a certain condition. The light reflectance of the Al deposited CR-PET fabrics showed a maximum point with proper sputtering power and deposition time. The thermal insulation property of the Al deposited CR-PET fabrics improved with sputtering power and deposit time.

Rutherford backscattering spectroscopy and structural analysis of DC reactive magnetron sputtered titanium nitride thin films on glass substrates

Titanium nitride thin films were deposited on sodalime glass substrate using DC reactive magnetron sputtering technique with 99.99 % pure titanium target. High purity nitrogen and argon gases were used as the reactive and sputtering gases respectively. The sputtering deposition time was fixed at 10 min for all samples, while the chamber sputtering pressure was varied from 0.80 to 11.33 Pa with corresponding change in the nitrogen partial pressure. The films were characterized using Rutherford backscattering (RBS) spectroscopy, UV–visible spectrophotometry, scanning electron microscopy and optical microscopy. The RBS studies revealed disparity in film thicknesses and stoichiometry with respect to the deposition sputtering pressure. Up to 10 % oxygen concentration was observed in films deposited at relatively low sputtering pressures of 0.80 and 1.07 Pa, while no oxygen was detected in the films deposited at higher sputtering pressure. High pressure sputtered TiNx films showed distinct optical properties reminiscent of indium tin oxide with high transmission of 86.74 % maximum in the visible range and wide band gap energy of 3.78 eV.