Showing papers on "Sputter deposition published in 2019"

Hybrid chemical vapor deposition enables scalable and stable Cs-FA mixed cation perovskite solar modules with a designated area of 91.8 cm2 approaching 10% efficiency

Abstract: The development of scalable deposition methods for stable perovskite layers is a prerequisite for the development and future commercialization of perovskite solar modules. However, there are two major challenges, i.e., scalability and stability. In sharp contrast to a previous report, here we develop a fully vapor based scalable hybrid chemical vapor deposition (HCVD) process for depositing Cs-formamidinium (FA) mixed cation perovskite films, which alleviates the problem encountered when using conventional solution coating of mainly methylammonium lead iodide (MAPbI3). Using our HCVD method, we fabricate perovskite films of Cs0.1FA0.9PbI2.9Br0.1 with enhanced thermal and phase stabilities, by the intimate incorporation of Cs into FA based perovskite films. In addition, the SnO2 electron transport layer (ETL) (prepared by sputter deposition) is found to be damaged during the HCVD process. In combination with precise interface engineering of the SnO2 ETL, we demonstrate relatively large area solar modules with efficiency approaching 10% and with a designated area of 91.8 cm2 fabricated on 10 cm × 10 cm substrates (14 cells in series). On the basis of our preliminary operational stability tests on encapsulated perovskite solar modules, we extrapolated that the T80 lifetime is approximately 500 h (under the light illumination of 1 sun and 25 °C).

The effect of post annealing temperature on grain size of indium-tin-oxide for optical and electrical properties improvement

Abstract: Background (Problem) Indium tin oxide (ITO) is a transparent conductive oxide (TCO) thin film used as a transparent electrode. Given its high demand for the manufacture of transparent electrodes (high visible light transmittance, low resistance) in applications such as liquid crystal displays, touch screens, light emitting devices and solar cells, ITO thin films have attracted immense research interest. Objectives This study determines the effect of grain size on the optical and electrical properties of the ITO thin films under different annealing temperatures. Materials and methods ITO thin film was deposited at room temperature by a high frequency magnetron sputtering method using a target composed of In2O3 and SnO2. The structural, optical and electrical properties of the thin films annealed at 250 °C, 350 °C, 450 °C and 550 °C for 1 h were then analyzed. Results The research shows the grain size of indium-tin oxide thin films is strongly related to annealing conditions. The grain size was found to increase with increasing annealing temperature, although the crystal structure did not change for all the samples. It was observed that the lowest resistivity (500 × 10−4 Ω-cm) and highest optical transmittances (90–98%) of ITO films were obtained at annealing temperature of 450 °C. At low annealing temperatures, the measured resistivity is dependent on the effect of grain size, where it decreases with increasing grain size. Conclusion This work showed that the grain size of ITO thin films is strongly influenced by post annealing technique and conditions applied, thus providing a tool for enhancing the optical and electrical properties of the film.

Paradigm shift in thin-film growth by magnetron sputtering: From gas-ion to metal-ion irradiation of the growing film

Abstract: Ion irradiation is a key tool for controlling the nanostructure, phase content, and physical properties of refractory ceramic thin films grown at low temperatures by magnetron sputtering. However, in contrast to gas-ion bombardment, the effects of metal-ion irradiation on properties of refractory ceramic thin films have not been extensively studied due to (i) low metal-ion concentrations (a few percents) during standard direct-current magnetron sputtering (DCMS) and (ii) difficulties in separating metal-ion from gas-ion fluxes. Recently, the situation has changed dramatically, thanks to the development of high-power impulse magnetron sputtering (HiPIMS), which provides highly-ionized metal-ion plasmas. In addition, careful choice of sputtering conditions allows exploitation of gas-rarefaction effects such that the charge state, energy, and momentum of metal ions incident at the growing film surface can be tuned. This is possible via the use of pulsed substrate bias, synchronized to the metal-ion-rich portion of each HiPIMS pulse. In this review, the authors begin by summarizing the results of time-resolved mass spectrometry analyses performed at the substrate position during HiPIMS and HiPIMS/DCMS cosputtering of transition-metal (TM) targets in Ar and Ar/N2 atmospheres. Knowledge of the temporal evolution of metal- and gas-ion fluxes is essential for precise control of the incident metal-ion energy and for minimizing the role of gas-ion irradiation. Next, the authors review results on the growth of binary, pseudobinary, and pseudoternary TM nitride alloys by metal-ion-synchronized HiPIMS. In contrast to gas ions, a fraction of which are trapped at interstitial sites, metal ions are primarily incorporated at lattice sites resulting in much lower compressive stresses. In addition, the closer mass match with the film-forming species results in more efficient momentum transfer and provides the recoil density and energy necessary to eliminate film porosity at low deposition temperatures. Several novel film-growth pathways have been demonstrated: (i) nanostructured N-doped bcc-CrN0.05 films combining properties typically associated with both metals and ceramics, (ii) fully-dense, hard, and stress-free Ti0.39Al0.61N, (iii) single-phase cubic Ti1−xSixN with the highest reported SiN concentrations, (iv) unprecedented AlN supersaturation in single-phase NaCl-structure V1−xAlxN, and (v) a dramatic increase in the hardness, due to selective heavy-metal ion bombardment during growth, of dense Ti0.92Ta0.08N films deposited with no external heating.Ion irradiation is a key tool for controlling the nanostructure, phase content, and physical properties of refractory ceramic thin films grown at low temperatures by magnetron sputtering. However, in contrast to gas-ion bombardment, the effects of metal-ion irradiation on properties of refractory ceramic thin films have not been extensively studied due to (i) low metal-ion concentrations (a few percents) during standard direct-current magnetron sputtering (DCMS) and (ii) difficulties in separating metal-ion from gas-ion fluxes. Recently, the situation has changed dramatically, thanks to the development of high-power impulse magnetron sputtering (HiPIMS), which provides highly-ionized metal-ion plasmas. In addition, careful choice of sputtering conditions allows exploitation of gas-rarefaction effects such that the charge state, energy, and momentum of metal ions incident at the growing film surface can be tuned. This is possible via the use of pulsed substrate bias, synchronized to the metal-ion-rich port...

A nanoscale p-n junction photoelectrode consisting of an NiOx layer on a TiO2/CdS nanorod core-shell structure for highly efficient solar water splitting

Abstract: The TiO2/CdS system has attracted great attention in solar water-splitting applications owing to its desirable electronic and optical properties. With the aim of enhancing its photoelectrochemical water splitting efficiency, an efficient strategy is proposed via nanostructuring and linking it in a p–n junction configuration with NiOx. The deposition of TiO2 nanorods (NRs) and CdS was achieved using a hydrothermal synthesis route in the sequence, after which NiOx was deposited via RF magnetron sputtering. Characterisation revealed the uniform deposition of CdS onto the TiO2 NRs, forming a core-shell morphology, and the deposition of NiOx on top of the TiO2-NR/CdS resulted in a nanostructured p–n junction. X-ray photoelectron spectroscopy was used to resolve the valence band edge, and impedance studies confirmed the formation of a p–n junction; accordingly, the probable band edge positions of the photoelectrode were identified. The optimised TiO2-NR/CdS-NiOx p–n junction electrode exhibited a remarkable photocurrent of ˜30 mA cm−2 (at 1 V vs. Ag/AgCl) under AM 1.5 G simulated sunlight and an incident photon-to-current efficiency of ˜97% at 500 nm. Furthermore, during illumination, the production of H2 gas occurred with a faradaic efficiency of 95%. The results of the study demonstrate the advantage of utilizing the TiO2-NR/CdS-NiOx system in a p-n junction configuration to greatly enhancethe charge generation, separation and suppression of the charge recombination, which boosts its photoelectrochemical water-splitting performance.

Fabrication of ZnO@Ag3PO4 Core-Shell Nanocomposite Arrays as Photoanodes and Their Photoelectric Properties.

Abstract: In this study, we combine the methods of magnetron sputtering, hydrothermal growth, and stepwise deposition to prepare novel ZnO@Ag3PO4 core-shell nanocomposite arrays structure. Through scanning electron microscope (SEM) topography test, energy dispersive spectrometer (EDS) element test and X-ray diffractometry (XRD) component test, we characterize the morphology, element distribution and structural characteristics of ZnO@Ag3PO4 core-shell nanocomposite arrays structure. At the same time, we test the samples for light reflectance, hydrophilicity and photoelectric performance. We find that after deposition of Ag3PO4 on ZnO nanorods, light reflectance decreases. As the time of depositions increases, light reflectance gradually decreases. After the deposition of Ag3PO4, the surface of the sample shows super hydrophilicity, which is beneficial for the photoelectric performance test. Through the optical transient response test, we find that the photo-generated current reaches a maximum when a small amount of Ag3PO4 is deposited. As the time of depositions of Ag3PO4 increases, the photogenerated current gradually decreases. Finally, we conducted an alternating current (AC) impedance test and also verified the correctness of the photocurrent test. Therefore, the structure is expected to be prepared into a photoanode for use in fields such as solar cells.

Black carbon-doped TiO2 films: Synthesis, characterization and photocatalysis

Abstract: Black colour TiO2 films were synthesized on amorphous fused silica substrates by DC magnetron sputtering technique with carbon powders placed at the working magnetron surface. Comprehensive sample analysis by X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy showed that the rutile/anatase heterostructure TiO2 films were successfully formed. Moreover, observation of O Ti C bonds confirmed that TiO2 phase was doped by carbon additives. Scanning electron microscopy, atomic force microscopy and X-ray diffraction were used to identify the effect of deposition time and TiO2 film thickness on the surface morphology, roughness and crystallite size. Results of electron spin resonance showed that oxygen vacancies were generated on the surface with trapped unpaired electrons. Optical analysis by UV–vis light spectrophotometer showed that TiO2 films with carbon additives improve its capability to absorb visible light. Accordingly, methylene blue bleaching experiments under UV A and visible light irradiation showed that black colour TiO2 films are capable to decompose methylene blue solution at both UV A and visible light irradiation.

Highly Transparent and Broadband Electromagnetic Interference Shielding Based on Ultrathin Doped Ag and Conducting Oxides Hybrid Film Structures.

Abstract: Reducing electromagnetic interference (EMI) across a broad radio frequency band is crucial to eliminate adverse effects of increasingly complex electromagnetic environment. Current shielding materials or methods suffer from trade-offs between optical transmittance and EMI shielding capability. Moreover, poor mechanical flexibility and fabrication complexity significantly limit their further applications in flexible electronics. In this work, an ultrathin (8 nm) and continuous doped silver (Ag) film was obtained by introducing a small amount of copper during the sputtering deposition of Ag and investigated as transparent EMI shielding components. The electromagnetic Ag shielding (EMAGS) film was realized in the form of conductive dielectric-metal-dielectric design to relieve the electro-optical trade-offs, which transmits 96.5% visible light relative to the substrate and shows an excellent average EMI shielding effectiveness (SE) of ∼26 dB, over a broad bandwidth of 32 GHz, covering the entire X, Ku, Ka, and K bands. EMI SE >30 dB was obtained by simply stacking two layers of EMAGS films together and can be further improved up to 50 dB by separating two layers with a quarter-wavelength space. The flexible EMAGS film shows a stable EMI shielding performance under repeated mechanical bending. In addition, large-area EMAGS films were demonstrated by a roll-to-roll sputtering system, proving the feasibility for mass production. The high-performance EMAGS film holds great potential for various applications in wearable electronics, healthcare devices, and electronic safety areas.

Preparation of Orthorhombic WO3 Thin Films and Their Crystal Quality-Dependent Dye Photodegradation Ability

Abstract: Direct current (DC) magnetron sputtering deposited WO3 films with different crystalline qualities were synthesized by postannealing at various temperatures. The in-situ DC sputtering deposited WO3 thin film at 375 °C exhibited an amorphous structure. The as-grown WO3 films were crystallized after annealing at temperatures of 400–600 °C in ambient air. Structural analyses revealed that the crystalline WO3 films have an orthorhombic structure. Moreover, the crystallite size of the WO3 film exhibited an explosive coarsening behavior at an annealing temperature above 600 °C. The density of oxygen vacancy of the WO3 films was substantially lowered through a high temperature annealing procedure. The optical bandgap values of the WO3 films are highly associated with the degree of crystalline quality. The annealing-induced variation of microstructures, crystallinity, and bandgap of the amorphous WO3 thin films explained the various photoactivated properties of the films in this study.

Electronic Effects Determine the Selectivity of Planar Au–Cu Bimetallic Thin Films for Electrochemical CO2 Reduction

Abstract: Au–Cu bimetallic thin films with controlled composition were fabricated by magnetron sputtering co-deposition, and their performance for the electrocatalytic reduction of CO2 was investigated. The ...

Engineering of Al/CuO Reactive Multilayer Thin Films for Tunable Initiation and Actuation

Abstract: Sputter-deposited Al/CuO multilayers represent the state-of-the-art of energetic nanomaterials. As such, they offer an opportunity for tunable ignition and actuation because their theoretical energy densities are significantly higher than most conventional secondary explosives while being less sensitive to undesired initiation. Both the sensitivity and combustion properties (temperature, rate and products released) can be manipulated via the layering, reactant spacing and stoichiometry of the multilayer and, to a lesser extent, via interface engineering. In this article, we first describe the technology of deposition of Al/CuO multilayers focusing on direct current sputter deposition followed by a comprehensive review of the materials structural characteristics. Next, experimental and theoretical works performed on these reactive multilayered materials to date is presented in terms of methods used, the results acquired on ignition and combustion properties, and conclusions drawn. Emphasis is placed on several studies elucidating the fundamental processes that underlie propagating combustion reactions. We examine the influence of the « ceiling » temperature that traduces the multilayer disintegration when reaching high temperatures (e.g., vaporization temperatures). This paper provides a good support for engineers to safely propose Al/CuO multilayers structure to regulate the energy release rates and ignition threshold in order to manufacture high performance and tunable initiator devices.

Comparative Study on Performance of IGZO Transistors With Sputtered and Atomic Layer Deposited Channel Layer

Abstract: The structural, chemical, and electrical properties of amorphous indium gallium zinc oxide (a-IGZO) films by magnetron sputtering and atomic layer deposition (ALD) were investigated where both a-IGZO films had a comparable cation composition. The ALD-derived a-IGZO film exhibited the higher atomic packing density, the effective suppression of trap-like oxygen vacancy defect (VO), and the enhancement in the hybridization of the sp orbital of In, Ga, and Zn cations compared to those of the sputtered a-IGZO film. Hence, a significant improvement in terms of the field-effect mobility was observed for the thin-film transistors with an In0.50Ga0.34Zn0.16O channel by ALD (36.6 cm $^{\textsf {2}}/\text{V}\cdot \text{s}$ ) compared to that of the sputtered In0.48Ga0.38Zn0.14O transistor (20.1 cm $^{\textsf {2}}/\text{V}\cdot \text{s}$ ); the ${I}_{\text {ON/OFF}}$ ratios for both were ~107. Simultaneously, the gate bias stress stability and photobias stress stability were also improved for the IGZO transistors with an ALD-derived channel, which can be explained by its reduced trap-like VO density.

Bipolar HiPIMS for tailoring ion energies in thin film deposition

Abstract: The effects of a positive pulse following a high-power impulse magnetron sputtering (HiPIMS) pulse are studied using energy-resolved mass spectrometry. This includes exploring the influence of a 200 μs long positive voltage pulse (Urev = 10–150 V) following a typical HiPIMS pulse on the ion-energy distribution function (IEDF) of the various ions. We find that a portion of the Ti+ flux is affected and gains an energy which corresponds to the acceleration over the full potential Urev. The Ar+ IEDF on the other hand illustrates that a large fraction of the accelerated Ar+, gain energies corresponding to only a portion of Urev. The Ti+ IEDFs are consistent with the assumption that practically all the Ti+, that are accelerated during the reverse pulse, originates from a region adjacent to the target, in which the potential is uniformly increased with the applied potential Urev, while much of the Ar+ originates from a region further away from the target over which the potential drops from Urev to a lower potential consistent with the plasma potential achieved without the application of Urev. The deposition rate is only slightly affected and decreases with Urev, reaching ~90% at Urev = 150 V. Both the Ti+ IEDF and the small deposition rate change indicate that the potential increase in the region close to the target is uniform and essentially free of electric fields, with the consequence that the motion of ions inside the region is not much influenced by the application of Urev. In this situation, Ti+ will flow towards the outer boundary of the target-adjacent region, with the momentum gained during the HiPIMS discharge pulse, independently of whether the positive pulse is applied or not. The metal ions that cross the boundary in the direction towards the substrate, and do this during the positive pulse, all gain an energy corresponding to the full positive applied potential Urev.

Scalable and Ultrafast Epitaxial Growth of Single-crystal Graphene Wafers for Electrically Tunable Liquid-crystal Microlens Arrays

Abstract: The scalable growth of wafer-sized single-crystal graphene in an energy-efficient manner and compatible with wafer process is critical for the killer applications of graphene in high-performance electronics and optoelectronics. Here, ultrafast epitaxial growth of single-crystal graphene wafers is realized on single-crystal Cu90Ni10(1 1 1) thin films fabricated by a tailored two-step magnetron sputtering and recrystallization process. The minor nickel (Ni) content greatly enhances the catalytic activity of Cu, rendering the growth of a 4 in. single-crystal monolayer graphene wafer in 10 min on Cu90Ni10(1 1 1), 50 folds faster than graphene growth on Cu(1 1 1). Through the carbon isotope labeling experiments, graphene growth on Cu90Ni10(1 1 1) is proved to be exclusively surface-reaction dominated, which is ascribed to the Cu surface enrichment in the CuNi alloy, as indicated by element in-depth profile. One of the best benefits of our protocol is the compatibility with wafer process and excellent scalability. A pilot-scale chemical vapor deposition (CVD) system is designed and built for the mass production of single-crystal graphene wafers, with productivity of 25 pieces in one process cycle. Furthermore, we demonstrate the application of single-crystal graphene in electrically controlled liquid-crystal microlens arrays (LCMLA), which exhibit highly tunable focal lengths near 2 mm under small driving voltages. By integration of the graphene based LCMLA and a CMOS sensor, a prototype camera is proposed that is available for simultaneous light-field and light intensity imaging. The single-crystal graphene wafers could hold great promising for high-performance electronics and optoelectronics that are compatible with wafer process.

Bilayer Au nanoparticle-decorated WO3 porous thin films: On-chip fabrication and enhanced NO2 gas sensing performances with high selectivity

Abstract: We present the on-chip fabrication of bilayer Au NP-decorated WO3 nanoporous thin films (B-Au/WO3) via layer-by-layer stacking of a sacrificial colloidal template with periodic Au sputtering deposition. Technical analysis shows that the B-Au/WO3 film is homogeneous and consists of a hexagonally ordered bowl-like structure, whose surface is uniformly decorated with crystalline Au NPs. The B-Au/WO3 sensing film shows a sensitivity of 96.0, a response time of 9.0 s and a recovery time of 16.0 s for 1 ppm NO2 at a low operating temperature of 150 °C. This significantly exceeds performances of bare WO3 counterpart. Also, the B-Au/WO3 sensor demonstrates obviously enhanced sensing responses over operating temperature ranges of 75–225 °C and perfect selectivity to NO2 gas. We proposed a combined sensing mechanism, the surface Au NPs dominated chemical sensitization and inter-bedded Au NP-induced electronic sensitization, to explain the perfect sensing performances in sensitivity, response, and selectivity. The template-mediated approach focuses on precise single-layer control and facilitates direct integration of the sensing film onto the required sensor substrate. The addressed on-chip fabrication strategy along with Au NPs decoration technique might provide promising applications in construction of advanced chemiresistive gas sensors, photocatalysts and electrochromic smart windows.

Achieving 11.95% efficient Cu2ZnSnSe4 solar cells fabricated by sputtering a Cu–Zn–Sn–Se quaternary compound target with a selenization process

Abstract: In this study, earth-abundant thin film Cu2ZnSnSe4 (CZTSe) solar cells were fabricated by the magnetron sputtering of a quaternary compound target. Precursor films were deposited in a designed chemical composition followed by a selenization process under the mixed atmosphere of an active gas, H2Se, and a carrier gas, Ar. Due to the existence of the Se element within the film, a relatively low concentration of H2Se was utilized to mainly crystallize the precursors and also supplement Se. To explore the selenization process, the as-deposited CZTSe absorbers were annealed at different temperatures. The results of X-ray diffraction (XRD) and Raman scattering spectroscopy measurements showed that the CZTSe grains continuously grew after selenization. In this study, when the absorbers were annealed at 575 °C, the CZTSe solar cells were obtained with the highest efficiency of 11.95%, with the open circuit voltage (VOC) of 432.22 mV, short circuit current density (JSC) of 36.28 mA cm−2 and fill factor (FF) of 76.21%. The photoluminescence (PL) spectrum indicates that the peak center underwent a red-shift from the band gap (Eg) of 90 meV. The analyses of fluctuation modules indicate that the electrostatic potential fluctuation is dominant for the band tail. The investigations demonstrate that sputtering of the Cu–Zn–Sn–Se quaternary compound target via the selenization process can be an effective and simple method for the fabrication of high-performance CZTSe solar cells.

A new catalyst material from electrospun PVDF-HFP nanofibers by using magnetron-sputter coating for the treatment of dye-polluted waters

Abstract: In this study, polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)–based nanofibers were produced by electrospinning technique on aluminum substrate and coated with magnetron sputtering technique by using Cu2O photocatalyst target material. Resulting materials were characterized by SEM, EDX, and UV diffuse reflectance spectroscopy. Photocatalytic activity of the material was tested against methylene blue decolorization under 105 W tungsten light bulb. Methylene blue concentration was followed up by UV visible spectrophotometer at 664 nm. Kinetic modeling of the photocatalytic reaction was found suitable to the first-order kinetics. Reaction rate constants were 0.0037, 0.0044, and 0.0050 min−1 respectively with corresponding half-life times of 187, 158, and 139 min. Thanks to the genuine design of the catalyst, it allowed easy removal of the material from the solution without any residue by simple tweezers which is a promising step for getting rid of heavy and low yield of filtration processes in the separation of particulate catalysts from the treated water.

Development of Pd-Pt functionalized high performance H2 gas sensor based on silicon carbide coated porous silicon for extreme environment applications

Abstract: Present work demonstrates the hydrogen gas (H2) sensing characteristics of palladium-platinum (Pd-Pt) functionalized silicon carbide (SiC) thin film grown on porous silicon (PSi) substrate for high temperature applications. Nano-crystalline SiC thin film was deposited by RF magnetron sputtering on anodized PSi substrate. The loading of discrete ultra-thin Pd-Pt bimetallic catalytic layer was carefully controlled by varying the sputtering parameters. The proposed device architecture (Pd-Pt/SiC/PSi) revealed significant advantages, such as stable high sensing response, large tunable detection range (5–500 ppm), fast response/recovery time, excellent reproducibility, high selectivity, wide operating temperature regime (25–500 °C) and good durability. The observed high response may be ascribed to the combined effect of enhanced catalytic activity of bimetallic Pd-Pt layer and increased surface area of the proposed sensor.