Effect Of Substrate Temperature Research Articles

The Microstructures and Characteristics of NiO Films: Effects of Substrate Temperature.

The influence of the substrate temperature on the structural, surface morphological, optical and nanomechanical properties of NiO films deposited on glass substrates using radio-frequency magnetron sputtering was examined by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible spectroscopy and nanoindentation, respectively. The results indicate that the substrate temperature exhibits significant influences on both the grain texturing orientation and surface morphology of the films. Namely, the dominant crystallographic orientation of the films switches from (111) to (200) accompanied by progressively roughening of the surface when the substrate temperature is increased from 300 °C to 500 °C. The average transmittance of the NiO films was also found to vary in the range of 60-85% in the visible wavelength region, depending on the substrate temperature and wavelength. In addition, the optical band gap calculated from the Tauc plot showed an increasing trend from 3.18 eV to 3.56 eV with increasing substrate temperature. Both the hardness and Young's modulus of NiO films were obtained by means of the nanoindentation continuous contact stiffness measurements mode. Moreover, the contact angle between the water droplet and film surface also indicated an intimate correlation between the surface energy, hence the wettability, of the film and substrate temperature.

Overcoming metal-rich surface chemistry limitations of ScAlN for high electrical performance heterostructures

While metal-rich ScAlN epitaxy has traditionally led to mixed phase films by controlling the surface chemistry with transient metal doses utilizing a pulsed method of molecular beam epitaxy, phase-pure, metal-rich epitaxy of ScAlN was demonstrated, showing improved structural and electrical characteristics. The effects of substrate temperature and III/V ratio were studied, and an x-ray diffraction figure of merit and surface roughness as low as 225 arcsec and 0.68 nm, respectively, were demonstrated. A significant catalytic effect is observed with the use of Sc in metal-rich conditions, resulting in varied growth rates with substrate temperature and Sc surface coverage. This catalytic effect results in complications when selecting synthesis conditions and for in situ monitoring and can be accounted for improved phase purity. The variation of growth rates with Sc surface coverage introduces non-linearities to the transient initiation stage of growth but also introduces a feedback stabilization of the surface chemistry. Accounting for these complexities, a Sc0.2Al0.8N high electron mobility transistor (HEMT) heterostructure is demonstrated with a sheet resistance of 152 Ω/□, a mobility of 700 cm2/Vs, and a sheet charge of 5.9 × 1013 cm−2.

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films.

This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that TS below 500 °C favors the growth of V2O5 phase, whereas higher TS (≥500 °C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (Tt), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at TS lower than 650 °C presents significant challenges.

Effects of solution-shearing process parameters on charge carrier mobility in green solvent-processed organic field-effect transistors

In this work, we explored the effect of solution-shearing processing parameters, coating speed and substrate temperature, on the electrical properties of solution-processed organic field-effect transistors (OFETs) based on 2-decyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C10) when green solvents are used. Organic semiconductor thin films were solution-sheared with various coating speeds and substrate temperatures and film morphologies/microstructures were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis. Our data demonstrate that crystal growth of Ph-BTBT-C10 molecule is highly affected by the two solution shearing processing parameters and, especially, the OFET devices fabricated with cyclohexanone as green solvent exhibited the charge carrier mobility as high as 5.1 cm2/Vs with optimized processing condition. This work could further provide a guideline for process optimization for fabricating high-performance green solvent-processed OFETs.

Effect of substrate temperature on the growth of Nb3Sn film on Nb by multilayer sputtering

We report on the fabrication of niobium tin (Nb3Sn) films by multilayer sequential sputtering on niobium at substrate temperatures ranging from room temperature to 250 °C. The multilayers were then annealed inside a separate vacuum furnace at 950 °C for 3 h. The material properties of the films were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and transmission electron microscopy. The superconducting properties of the films were studied by four-point probe resistivity measurements from room temperature to below the superconducting critical temperature Tc. The highest film Tc was 17.76 K, obtained when the multilayers were deposited at room temperature. When the deposition temperature was raised to 250 °C, a significant reduction in voids was achieved while the film's Tc was 17.58 K.

Isothermal and non-isothermal spreading of a viscous droplet on a solid surface in total wetting condition

We study the isothermal and non-isothermal spreading of viscous silicone oil droplets on a glass surface in total wetting condition. In particular, the effects of viscosity, impact velocity, and substrate temperature on the spreading dynamics are reported. We employ high-speed photography to record time-varying droplet shapes from the side. An infrared camera maps the temperature distribution on the liquid–gas interface. In the isothermal inertial-capillary or early regime, the initial spreading is driven by inertial forces, and kinetic energy converts into surface energy and gets dissipated by bulk viscosity. The later stage is governed by the balance of surface energy and viscosity dissipation, i.e., capillary–viscous or late regime. The characteristics timescales of the two regimes are obtained using scaling arguments. The measured crossover time from early to late spreading regimes for different cases of impact velocity and viscosity corroborates with a scaling analysis developed in the present work. Measurements confirm the value of exponents of established power-law spreading with time in early and late regimes r∼tn. At a larger substrate temperature, the spreading magnitude is larger for droplets with larger viscosity and is explained by the reduction of viscous dissipation by heating the droplet. However, in the case of non-isothermal spreading of a low viscosity droplet, recoiling after the early spreading reduces the spreading magnitude compared to the isothermal case. We explain the recoiling and spreading rates obtained in different cases. We analyze unsteady heat transfer between the droplet and substrate by combining measurements and a numerical model.

Heating influence on hierarchical structures fabricated by direct laser interference patterning

The combination of direct laser interference patterning (DLIP) with laser-induced periodic surface structures (LIPSS) enables the fabrication of functional surfaces reported for a wide spectrum of materials. The process throughput is usually increased by applying higher average laser powers. However, this causes heat accumulation impacting the roughness and shape of produced surface patterns. Consequently, the effect of substrate temperature on the topography of fabricated features requires detailed investigations. In this study, steel surfaces were structured with line-like patterns by ps-DLIP at 532 nm. To investigate the influence of substrate temperature on the resulting topography, a heating plate was used to adjust the temperature. Heating to 250 ^{circ }C led to a significant reduction of the produced structure depths, from 2.33 to 1.06 µm. The reduction is associated with the appearance of a different LIPSS type, depending on the grain orientation of the substrates and laser-induced superficial oxidation. This study revealed a strong effect of substrate temperature, which is also to be expected when heat accumulation effects arise from processing surfaces at high average laser power.

Effects of substrate temperature on the growth of CuO nano/micro rods by ion beam sputter deposition

CuO nano/micro rods were deposited on Si substrates by ion beam sputter deposition at substrate temperatures 300 °C, 350 °C, 400 °C and 450 °C. The effects of changing substrate temperature on the structural properties and surface morphology of the deposited CuO nano/micro rods were studied. Field Emission Scanning Electron Microscopy micrographs showed that at substrate temperature of 300 °C and 350 °C, tiny nanoparticles were observed on the surface of CuO thin films and at substrate temperature of 400 °C and 450 °C, CuO nano/micro rods of lengths (100 nm to 1 μm) and diameters (25 nm to 30 nm) observed in a periodic arrangement. X-Ray Diffraction (XRD) analysis showed that all the diffraction peaks of the samples were single-crystalline CuO corresponded to () orientation. From the crystallographic analysis using XRD data, crystallite sizes of the samples increased (18 to 32 nm) with the increase of substrate temperature. The Micro-Raman spectroscopy investigation shows that all the Raman peaks observed were phonon modes of CuO and as the substrate temperature increased, the intensities of the Rama peaks increased. Hence, by changing substrate temperatures, it is possible to deposit high quality CuO nano/micro thin films with tunable structures, morphologies and sizes for different optoelectronic applications through ion beam sputter deposition.

Growth of (SmxGa1−x)2O3 by molecular beam epitaxy

The (SmxGa1−x)2O3 alloy system is a potential new dielectric for compound semiconductors such as GaAs. Using molecular beam epitaxy under metal-modulated growth conditions, we grew the binary oxide, Sm2O3, at two substrate temperatures (100 and 500 °C) and optimized the structural, morphological, and electrical properties of the films. Decreasing the Sm cell temperature suppressed the formation of the monoclinic phase and promoted the growth of the cubic phase. Next, the ternary oxide, (SmxGa1−x)2O3, was deposited to investigate the effects of Ga incorporation. Optimization experiments were used to determine the effects of substrate temperature and samarium cell temperature (i.e., growth rate) on film stoichiometry, phase distribution, and microstructure in these films. Films grown at 500 °C showed significant surface roughness and the presence of multiple crystalline phases. Since all of the Sm-based oxides (i.e., samarium oxide with and without gallium) were found to have unbonded Sm metal, annealing experiments were carried out in oxygen and forming gas to determine the effects of annealing on film stoichiometry. The motivation behind annealing in forming gas was to see whether this commonly used technique for reducing interface densities could improve the film quality. GaAs metal-oxide-semiconductor diodes with (SmxGa1−x)2O3 showed breakdown fields at 1 mA/cm2 of 4.35 MV/cm, which decreased with increasing Sm unbonded metal content in the films.

(Invited) Molecular Beam Epitaxy and Dislocation Dynamics of Metamorphic Inassb for Long-Wavelength Infrared Applications

Long-wavelength infrared (IR) III-V based devices have long been of interest for potential applications such as chemical sensing and large format IR imaging. Within the III-V family, only the InAs1-xSbx bulk alloy in composition range 0.45 ≤ x ≤ 0.8, offers the required bandgap energy (Eg ) from 100 to 125 meV at an operating temperature of 80K and below [1]. Over this composition range however, the InAs1-xSbx lattice constant varies from 6.24 to 6.39 Å, where a lack of conventional substrates has restricted progress on the growth and study of this material system. To bridge this lattice-constant gap while maintaining relatively low defect densities, we employed a metamorphic step-graded InAs1-xSbx buffer on GaSb, enabling the study of low-Eg InAs1-xSbx as a function of growth conditions. Using this method, we investigated the effect of substrate temperature (Tsub ) and group V to group III flux ratio (beam equivalent pressure, V/III) on Sb incorporation of the lowest-Eg cap layer [2]. We also used x-ray reciprocal space mapping (RSM) to examine the effect of growth conditions on strain and dislocation dynamics. Following these growth studies, we employed the metamorphic InAs1-xSbx in an InAs/InAsSb superlattice designed with a cutoff wavelength of 9 µm which leads to improved absorption compared with the lattice-matched counterpart.We first grew, via molecular beam epitaxy, several InAs1-xSbx step-graded structures in which the Sb/(As+Sb) flux ratio was varied from 0.05 to 0.50 in 0.05 increments (see figure), under various Tsub and V/III. Nomarski imaging revealed smoother surfaces under a V/III=10, the highest ratio we attempted. At this higher V/III, we observed the cross-hatch morphology expected for metamorphic materials and found that the cross-hatch spacing changes, implying a change in dislocation dynamics, with Tsub . We then used photoluminescence (PL) to measure the Sb-content in the cap layer as well as compare intensities between samples. We found the highest Sb-incorporation to occur when Tsub =415 C and V/III=10, while the most intense samples used Tsub =415-430 C and V/III=10 [2].Using RSM along [110] with (004) and (115) reflections, we identified the Sb composition in each layer. This allowed comparison of Sb-content as a function of Sb/(As+Sb) for various Tsub and V/III. The results suggest that V/III has little effect on Sb incorporation, in direct conflict with our previous PL results [2]. To understand the discrepancy between PL and RSM, we measured (004) RSM of the same three samples with the x-ray beam incident along [1-10], revealing extremely different strain relaxation compared to the [110] case (see figure). Asymmetric strain relaxation has been observed in other III-V graded buffer systems and has been explained by different dislocation formation energies and glide velocities along each direction resulting from the core structure of the dislocation being terminated with either a group-III or a group-V element [3]. Transmission electron microscopy is ongoing to further understand the dislocation dynamics in these samples.Taking this all together allowed us to investigate the effect of substrate lattice-constant on strain-balanced InAs/InAsSb superlattices designed for 9 µm cutoff wavelength [4]. Theoretically, by using a larger substrate lattice-constant the superlattice design results in larger electron-hole wavefunction overlap, ultimately increasing photon absorption. Our experimental results confirm this theory, even in the presence of increased threading dislocations inherent to the required lattice-mismatch.[1] I. Vurgaftman et al. JAP 89, 5815-5875 (2001).[2] Tomasulo et al. J. Vac. Sci. and Technol. B 36, 02D108 (2018).[3] France et al. J. Appl. Phys. 107, 103530 (2010); Gelczuk et al., J. Cryst. Growth 310, 3014 (2008).[4] Affouda, Tomasulo et al., Appl. Phys. Lett. 110, 181107 (2017). Figure 1

Molecular Beam Epitaxy of in2Se3 Thin Films

In2Se3 is a polymorphous metal-chalcogenide system1 where each phase exhibits dramatically different functional properties. α-In2Se3 is a two-dimensional, ferroelectric semiconductor2,3 and has shown promise in low-power, neuromorphic electronic devices4,5. β-In2Se3 is a two-dimensional, centrosymmetric semiconductor and has shown promise in photodetectors6. γ-In2Se3 is a three-dimensional, defect- wurtzite wide bandgap semiconductor that has shown promise as a precursor layer for CuInSe2 solar cells7. Considered together, the bandgaps of these materials range from 1.3eV to 2.5eV8. Understanding how to synthesize phase-pure thin-films of In2Se3 is of interest to harness the properties of these materials for applications in electronic devices.α-In2Se3 is thermodynamically stable below 200 oC and transitions to the 2D, centrosymmetric β-In2Se3 phase upon heating above 200 oC1. While the β to α-In2Se3 phase transition is achievable in bulk synthesis via slow cooling2, the β to α-In2Se3 phase transition does not occur as readily in thin-films. Recent studies on thin-film synthesis of In2Se3 have demonstrated β- and/or γ-In2Se3 films at temperatures above the thermodynamic stability range of α-In2Se3 (200 oC). Two reports from the last two years demonstrate large-area synthesis of β-In2Se3 thin-films metal-organic chemical vapor deposition and molecular beam epitaxy (MBE) on sapphire at temperatures greater than 300 oC6,9. Another study reported MBE synthesis of metastable, strained, mixed phase β/γ-In2Se3 films on Si(111) substrates at 180 oC10. One study from 2018 claims deposition of large-area α-In2Se3 thin-films on graphene at a substrate temperature of 250 oC via molecular beam epitaxy; however, it is difficult to distinguish the α from β phase by the Raman spectra and TEM micrograph along the c-axis.In this study we demonstrate thin-film synthesis of In2Se3 over a wide array of synthesis conditions via molecular beam epitaxy. We systematically investigate the effects of substrate temperature, cooling rate after deposition, substrate surface, Se/In flux ratio, and precursor type on the structure and properties of In2Se3 films. We characterize the crystalline phase, stoichiometry, and crystal morphology via Raman Spectroscopy, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy, respectively.(1) Okamoto, H. In-Se ( Indium-Selenium ). J. Phase Equilibria 2004, 25 (2).(2) Küpers, M.; Konze, P. M.; Meledin, A.; Mayer, J.; Englert, U.; Wuttig, M.; Dronskowski, R. Controlled Crystal Growth of Indium Selenide, In2Se3, and the Crystal Structures of α-In2Se3. Inorg. Chem. 2018, 57, 11775–11781.(3) Xiao, J.; Zhu, H.; Wang, Y.; Feng, W.; Hu, Y.; Dasgupta, A.; Han, Y.; Wang, Y.; Muller, D. A.; Martin, L. W.; et al. Intrinsic Two-Dimensional Ferroelectricity with Dipole Locking. Phys. Rev. Lett. 2018, 120 (22), 227601.(4) Tang, B.; Tang, B.; Hussain, S.; Xu, R.; Cheng, Z.; Liao, J.; Chen, Q. Novel Type of Synaptic Transistors Based on a Ferroelectric Semiconductor Channel. ACS Appl. Mater. Interfaces 2020, 12 (22), 24920–24928.(5) Wang, L.; Liao, W.; Wong, S. L.; Yu, Z. G.; Li, S.; Lim, Y. F.; Feng, X.; Tan, W. C.; Huang, X.; Chen, L.; et al. Artificial Synapses Based on Multiterminal Memtransistors for Neuromorphic Application. Adv. Funct. Mater. 2019, 29 (25), 1–10.(6) Claro, M. S.; Grzonka, J.; Nicoara, N.; Ferreira, P. J.; Sadewasser, S. Wafer-Scale Fabrication of 2D β-In2Se3 Photodetectors. Adv. Opt. Mater. 2020, 2001034, 1–9.(7) Ashok, A.; Regmi, G.; Velumani, S. Growth of In2Se3 Thin Films Prepared by the Pneumatic Spray Pyrolysis Method for Thin Film Solar Cells Applications. 2020 17th Int. Conf. Electr. Eng. Comput. Sci. Autom. Control. CCE 2020 2020, 2–7.(8) Li, J.; Li, H.; Niu, X.; Wang, Z. Low-Dimensional In2Se3 Compounds: From Material Preparations to Device Applications. ACS Nano 2021, 15 (12), 18683–18707.(9) Zhang, X.; Lee, S.; Bansal, A.; Zhang, F.; Terrones, M.; Jackson, T. N.; Redwing, J. M. Epitaxial Growth of Few-Layer β-In2Se3 Thin Films by Metalorganic Chemical Vapor Deposition. J. Cryst. Growth 2020, 533 (December 2019), 125471.(10) Shen, Y. F.; Yin, X. B.; Xu, C. F.; He, J.; Li, J. Y.; Li, H. D.; Zhu, X. H.; Niu, X. Bin. Growth and Structural Characteristics of Metastable β-In2Se3 Thin Films on H-Terminated Si(111) Substrates by Molecular Beam Epitaxy. Chinese Phys. B 2020, 29 (5).

Effect of substrate temperature and RF power on the structural and optical properties of sputtered ZnO thin films

ZnO thin films have been deposited on glass substrates by radio frequency (RF) magnetron sputtering from a zinc oxide target in order to investigate the effect of RF power and substrate temperature on the properties of the deposited films. The structural and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis transmission spectra and photoluminescence (PL). All ZnO thin films exhibited diffraction peak of (002) corresponding to c-axis orientation and the film deposited at 450°C exhibited the larger grain size as a result of stress relaxation. It is observed that the increase in substrate temperature or sputtering power can facilitate the growth of ZnO in (100) and (101) direction. PL emission was obtained at UV and visible region for the excitation wavelengths of 280 nm and 390 nm respectively. PL study indicated that both the crystal quality and stoichiometry can influence the UV PL emission in ZnO thin films. Dependence of temperature and power on transmission spectra was studied and the optical band gap was calculated.

Synthesis and characterization of spray deposited nanostructured WO3 thin films for ammonia sensing applications

• This paper presents the effect of substrate temperature on chemically sprayed WO 3 thin films to detect ammonia vapours at room temperature. • Prepared nanostructured thin films at different substrate temperatures of 350–450 °C have been characterised for structural, morphological, optical and gas sensing properties. • The WO 3 film deposited at a substrate temperature of 400 °C has shown better structural, morphological properties and excellent ammonia sensing features at room temperature. • This film has shown good sensitivity with a quick response and recovery times with the least detection limit of 1 ppm. Nanostructured tungsten oxide (WO 3 ) thin films are prepared on glass substrates at different substrate temperatures (350–450 °C) using the chemical spray pyrolysis technique. The effects of substrate temperature on structural, morphological and optical properties of the WO 3 films are systematically studied using X-ray diffraction (XRD), UV–visible photo spectroscopy, Raman spectroscopy and atomic force microscopy (AFM). The XRD analysis of the synthesised WO 3 films have shown crystalline nature and preferred orientation along with (0 1 2) direction. The optical bandgap of the thin films is determined using the absorption spectra obtained with UV–visible spectroscopy. The surface features of the deposited thin films are investigated using AFM with contact mode. The gas-sensing performance of the prepared thin films is investigated using a static method towards various ammonia concentrations at an operating temperature of 27 °C. The WO 3 film deposited at a substrate temperature of 400 °C has shown the best response towards ammonia vapours with a response and recovery times of 61 s and 34 s with the least detection limit of 1 ppm.

Effect of substrate temperature on structural, optical, and photoelectrochemical properties of Tl2S thin films fabricated using AACVD technique

Abstract Thin films of thallium sulphide (Tl2S) were grown on the FTO surface at three different temperatures (500°C, 550°C, and 600°C) using the aerosol-assisted chemical vapor deposition approach. A thallium diethyldithiocarbamate (Tl[CNS2(C2H5)3]) complex was used as a single-source precursor in tetrahydrofuran (THF) solvent under an inert atmosphere of argon in all deposition experiments. The impact of deposition temperature on structural, morphological, and optical properties of Tl2S thin films was explored using different experimental techniques such as X-ray diffraction (XRD), field-emission scanning electron (FESEM) microscopy, and UV-visible spectrophotometry. XRD analysis specifies that crystallite size varies from 120 to 90 nm with the increase in temperature from 500°C to 600°C. FESEM results revealed that Tl2S films were grown as hexagonal, petals, and marigold flower-like particles at 500°C, 550°C, and 600°C, respectively. UV-visible spectrophotometric analysis shows a decrease in band gap energies with temperature: 1.92 eV at 500°C, 1.72 eV at 550°C, and 1.42 eV at 600°C. The photoelectrochemical measurement in terms of linear sweep voltammetry confirms that the temperature variation has a significant effect on the photoconversion efficiency of Tl2S thin films, and photocurrent density increases from 0.56 to 0.76 mA·cm−2 when the temperature is increased from 500°C to 600°C.

Spreading and shrinking behaviors of oil films with different viscosities on a cold immiscible liquid substrate

The spreading behavior of an oil film on an immiscible liquid substrate plays an important role in practical phenomena such as oil spills and thermal spraying. Especially in extremely cold regions such as the Arctic regions, the spreading behavior and balanced state of the spilled oil may be significantly affected due to the varying oil physical properties caused by the low temperature. The effect of low-temperature conditions on the spreading behavior remains poorly understood. The spreading experiments of silicone oils with viscosities of 50, 100, 350, and 1000 cs were carried out on cold substrates by controlling the liquid substrate temperature in the range of − 20 °C to 20 °C through a circulating bath. The effects of substrate temperature on the spreading morphology, equilibrium thickness, spreading rate and other parameters of the oil film were investigated. When the temperature was greater than 10 °C, silicone oils spread continuously, whereas when the temperature was less than 0 °C, some of them first exhibited a short period of shrinking behavior before spreading. The surface tensions at three interfaces, namely oil–air, oil–substrate, and substrate–air, were analyzed comprehensively. A novel equilibrium equation of the gravity-surface tension based on Neumann’s triangle rule was derived to calculate the stable thickness of the oil film, in which the contact angle at the three-phase junction was measured experimentally, and the quantitative relationship between the surface tension and temperature was considered. The calculated results were in excellent agreement with the experimental results. A modified prediction model was fitted to accurately describe the spreading velocity of the silicone oil by considering the effect of temperature on the viscosity and density. Finally, the variations in the temperature inside the oil film were discussed to explain the shrinking phenomenon. The study provides theoretical support for the creation of oil spill clean-up methods for low-temperature waters.

Effect of substrate temperature on the surface and interface properties of NiTi atmospheric plasma sprayed coating

Atmospheric plasma spraying (APS) is one of the most preferred coating processes, which comes under thermal spraying technology. It has a wide range of applications due to its versatility in surface modifications. By the APS technique, different high-temperature application materials like cermets, and ceramics, can be coated on a substrate whose surface properties have to be modified in an extreme environment. Ni50Ti50 (at.%) alloy became more focus of interest for researchers and industrialists due to their two extraordinary smart properties such as shape memory effect (SME), and superelasticity (SE) which can protect any structural materials from catastrophic failure. Compared to various deposition routes, APS is an economical process to apply NiTi on mild steel. NiTi smart alloy also exhibits good wear resistance, corrosion resistance, damping behaviour, and high load-bearing capacity. In terms of mechanical properties, it has high strength and hardness at high temperatures. Owing to these properties, NiTi alloy can be used to protect structural materials such as mild steel from catastrophic failure. In this study, mild steel was coated at 100 °C, 200 °C, 300 °C and 400 °C preheating temperatures by APS techniques using an equiatomic NiTi alloy. The surface and interface characterization were performed using an optical microscope, SEM, XRD, Hardness test and 3D optical profilometer. It was found that along with the desired NiTi phase, some of the intermetallic and oxide phases are responsible for the mechanical strength. The surface and interface morphologies show that NiTi splat formation by APS results in better surface bonding and dense coating. With increase in the substrate temperature, the hardness of a coating interface increases with decrease in the number of pores at coating interface.

Effect of substrate temperature on the properties of spray deposited Ga2O3 thin films, for solar blind UV detector applications

In this work, Ga2O3 thin films were deposited on glass substrates by chemical spray pyrolysis technique at three different substrate temperatures 350 °C, 400 °C, and 450 °C. The structural, optical, morphological and electrical characteristics of the deposited sample thin films were investigated. From the studies, it is understood that by tuning substrate temperature, we can extensively change the properties of the film. Optimum temperature for coating Ga2O3 thin films was understood and the work was extended to demonstrate a simple deep UV detector, working in photoconductive mode. The fabricated device exhibit medium response to UV light at 254 nm. The present work report the fabrication of solar blind UV detector based on Ga2O3 thin film, grown using low cost, easily scalable spray deposition technique.

Temperature dependence of optical and electrical properties of gamma-irradiated indium oxide thin film

In2O3 thin films were grown on glass substrates by spray pyrolysis using InCl30.4 H2O as the solute. The precursor solution of concentration 0.2 M was sprayed on substrates at two different substrate temperatures, 4000 C and 4500 C. The deposited films were exposed to different doses of gamma radiation. The optical and electrical characterisations of the irradiated layers were done to evaluate transmittance, optical bandgap, Urbach energy, resistivity and other optical and electrical parameters. Transmittance varied with irradiation and it increased with deposition temperature. Bandgap energy increased with irradiation up to a particular dose and then decreased for both higher temperature and lower temperature samples. But the critical dose for this bandgap reversal is higher for samples deposited at a higher temperature. Urbach energy shows an inverse relation with the bandgap. The refractive index is estimated using three different models and the extinction coefficient evaluated for the deposited samples. Resistivity also increased up to the same critical dose of 200 Gy for lower temperature samples and 300 Gy for higher temperature samples. The substrate temperature effect on the electrical and optical properties of gamma irradiated In2O3 thin film was studied in detail.

Superior in vitro corrosion resistance of the novel amorphous Ta/TaxOy multilayer coatings on self-expanding nitinol stents

Magnetron sputtering method is used to coat a bi-phase Ta/TaxOy multilayer on NiTi shape memory alloy as a self-expandable stent. These coatings are created to improve the properties of the surface, such as radiopacity, in-vitro corrosion resistance, and biocompatibility. Thin films are formed by simultaneously sputtering the tantalum target in an ArO2 environment, to prevent target poisoning, the ratio of the volume percentage of oxygen to the total inlet gas is 16.6 (Vol%). In addition, the effect of substrate temperature has been studied in this gas composition.Atomic force microscopy has been used to analyze surface topography and roughness. Via potentiodynamic scanning and electrochemical impedance spectroscopy, the electrochemical behavior of the uncoated and coated samples is determined in SBF solution at 37 ± 0.5 °C. Also, the amount of Ni ions released has been analyzed using inductively coupled plasma-optical emission spectrometry. As a result, the Ta/TaxOy thin films deposited at 200 °C represent excellent corrosion resistance. These practical consequences provide a possible procedure to recover the efficiency of Ta/TaxOy coatings on NiTi alloys.

MOCVD growth of ZrN thin films on GaN/Si templates and the effect of substrate temperature on growth mode, stress state, and electrical properties

Zirconium nitride (ZrN) is a candidate for contact metal and diffusion barrier in ohmic contacts for GaN-based devices due to its superior electrical conductivity and corrosion resistance. This paper reported ZrN films deposited on GaN/Si templates using metal-organic chemical vapor deposition (MOCVD) and analyzed the effect of substrate temperature (T s) on its growth mode, film stress, as well as electrical properties. Firstly, the surface morphology and film roughness of the resultant ZrN epilayers were investigated, which were found to vary dramatically with T s. Then, a temperature-dominated crystal formation process was reasonably proposed, revealing the transfer from the island to layer growth mode and the augmentation of the growth rate of ZrN with elevated T s. Stress information was obtained from the position of XRD diffraction peaks, indicating large in-plane lattice stretching in ZrN film and the presence of compressive stress in the GaN/Si template. The stress states can be related to island merger and thermal mismatch between ZrN and GaN, which proved satisfyingly advantageous in preventing the GaN layer from cracking during the subsequent preparation procedure. In addition, XPS surface and interface investigations were performed to identify the chemical state and the atomic content of the ZrN film, which also implied a relatively clear interface between the ZrN epilayer and GaN/Si template. Furthermore, Hall tests proved the resistivity of ZrN thin film can reach a minimum of 2.28 × 10−4 Ω cm, owing to the grain boundary chaining and flat film surface at high temperatures. Overall, it appears to have promising prospects for its application in the contact layer and diffusion barrier of ohmic contact in GaN-based devices.