Search Results (704)

This study provides a comprehensive investigation into the growth behavior of boron nitride (BN) buffer layers on Silicon carbide (SiC) substrates and their influence on interfacial band alignment. BN layers were deposited on semi-insulating SiC by RF magnetron sputtering with deposition times of 2.5, 5, and 7.5 min (these deposition times are specific experimental parameters to adjust the thickness of the amorphous BN layer, not intrinsic material properties of BN). Atomic force microscopy revealed that the surface roughness of the BN layers initially decreased and then increased with thickness, indicating an evolution from nucleation to continuous film formation, followed by surface coarsening. Transmission electron microscopy confirmed the BN thicknesses of approximately 3.25, 4.91, and 7.57 nm, showing that the layers gradually became uniform and compact, thereby improving the structural integrity of the BN/SiC interface. Band alignment was analyzed using the Kraut method, yielding a valence band offset of ~0.36 eV and a conduction band offset of ~2.34 eV for the BN/SiC heterojunction. This alignment indicates that the BN buffer layer introduces a pronounced electron barrier, effectively suppressing leakage, while the relatively small VBO facilitates hole transport across the interface. These findings demonstrate that the BN buffer layer enhances interfacial bonding, reduces defect states, and enables band structure engineering, offering a promising strategy for improving the performance of wide-bandgap semiconductor devices. Full article

This paper presents the growth and in situ optical characterization of silicon nanowires (Si NWs) on Al₂O₃(0001) substrates that are thermally faceted using the atomic low angle shadowing technique (ATLAS) method. Annealing Al₂O₃ substrates in air before surface faceting was used for the first time, as identified by atomic force microscopy (AFM). Planar Si NW arrays were subsequently deposited and characterized in real-time by reflectance anisotropy spectroscopy (RAS). RAS measurements detected irreversible spectral changes during growth, e.g., red-shift in peak energy for marking amorphous Si NW formation. Blue-shifts in RAS spectra following annealing post-growth at varied temperatures were found to be associated with structural nanowire development. AFM analysis following annealing detected dramatic changes in morphology, e.g., quantifiable differences in NW height and thickness and complete disappearance of nanowire structures at high temperatures. These results confirm the validity of in situ RAS as a monitoring tool for nanowire growth and illustrate Si NW morphology’s sensitivity to thermal processing. Full article

To evaluate the effect of nitrogen and hydrogen on the corrosion resistance of diamond-like carbon (DLC) coatings, potentiodynamic tests were carried out on DLC coatings deposited under various reactive atmosphere compositions on martensitically hardened 34CrAlNi steel. In order to replicate actual operating conditions of steel components, the tests were conducted both in a reference 3.5% NaCl solution and in natural mine waters, which are in direct contact with mining gearbox mechanisms. Although it is generally assumed that the addition of other elements tends to deteriorate the corrosion resistance of amorphous carbon coatings, such doping simultaneously improves adhesion to metallic substrates, and enhanced adhesion in turn contributes to improved corrosion resistance. Variation in the proportions of the doping elements altered the damage morphology on the sample surface, as well as the corrosion current density, corrosion potential, and polarization resistance. Improvements in corrosion resistance parameters correlated with the quality of the coating–substrate adhesion, evaluated in accordance with the VDI3918 standard. The most favorable properties were obtained for coatings deposited under a gas composition of N₂:CH₄:H₂ with a ratio of 3:4:2. Full article

The use of molybdenum-based alloys as materials for components operating under high temperatures and significant mechanical loads is widely recognized due to their excellent mechanical properties. However, their low high-temperature resistance remains a critical limitation, which can be effectively mitigated by applying protective coatings. In this study, we investigate the influence of a two-step coating process on the properties and performance of the TZM molybdenum alloy. In the first step, pack cementation was performed. Simultaneous surface saturation with aluminum and silicon, a process known as aluminosiliconizing, was conducted at 1000 °C for 6 h. The saturating mixture comprised powders of aluminum, silicon, aluminum oxide, and ammonium chloride. The second step involved the application of a pre-ceramic coating based on polyhydrosiloxane modified with silicon and boron. This treatment effectively eliminated pores and cracks within the coating. Thermodynamic calculations were carried out to evaluate the likelihood of aluminizing and siliconizing reactions under the applied conditions. Aluminosiliconizing of the TZM alloy resulted in the formation of a protective layer 20–30 µm thick. The multiphase structure of this layer included intermetallics (Al₆₃Mo₃₇, MoAl₃), nitrides (Mo₂N, AlN, Si₃N₄), oxide (Al₂O₃), and a solid solution α-Mo(Al). Subsequent treatment with silicon- and boron-modified polyhydrosiloxane led to the development of a thicker surface layer, 130–160 µm in thickness, composed of crystalline Si, amorphous SiO₂, and likely amorphous boron. A transitional oxide layer ((Al,Si)₂O₃) 5–7 µm thick was also observed. The resulting coating demonstrated excellent structural integrity and chemical inertness in an argon atmosphere at temperatures up to 1100 °C. High-temperature stability at 800 °C was observed for both coating types: aluminosiliconizing, and aluminosiliconizing followed by the pre-ceramic coating. Moreover, additional oxide layers of SiO₂ and B₂O₃ formed on the two-step coated TZM alloy during heating at 800 °C for 24 h. These layers acted as an effective barrier, preventing the evaporation of the substrate material. Full article

In this study, high-conductivity W-doped Ga₂O₃ thin films were successfully fabricated by directly depositing a composition of Ga₂O₃ with 10.7 at% WO₃ (W:Ga = 12:100) using electron beam evaporation. The resulting thin films were found to be amorphous. Due to the ohmic contact behavior observed between the W-doped Ga₂O₃ film and platinum (Pt), Pt was used as the contact electrode. Current-voltage (J-V) measurements of the W-doped Ga₂O₃ thin films demonstrated that the samples exhibited significant current density even without any post-deposition annealing treatment. To further validate the excellent charge transport characteristics, Hall effect measurements were conducted. Compared to undoped Ga₂O₃ thin films, which showed non-conductive characteristics, the W-doped thin films showed an increased carrier concentration and enhanced electron mobility, along with a substantial decrease in resistivity. The measured Hall coefficient of the W-doped Ga₂O₃ thin films was negative, indicating that these thin films were n-type semiconductors. Energy-Dispersive X-ray Spectroscopy was employed to verify the elemental ratios of Ga, O, and W in the W-doped Ga₂O₃ thin films, while X-ray photoelectron spectroscopy analysis further confirmed these ratios and demonstrated their variation with the depth of the deposited thin films. Furthermore, the W-doped Ga₂O₃ thin films were deposited onto both p-type and heavily doped p⁺-type silicon (Si) substrates to fabricate heterojunction diodes. All resulting devices exhibited good rectifying behavior, highlighting the promising potential of W-doped Ga₂O₃ thin films for use in rectifying electronic components. Full article

To improve the applicability of tetragonal zirconia (TZP) in the high-vacuum friction drive field, a strategy combining Cr ion implantation-modified layer and hydrogen-containing amorphous carbon coating was proposed in this study. The designed coating (WC/a-C:H) consists of a Cr bonding layer, a WC-rich load-bearing layer and an a-C:H target layer. The effects of implantation voltage on the adhesion strength of WC/a-C:H coatings were investigated. The tribological behaviors of WC/a-C:H against TZP and TZP self-mated pairs at various loads in high vacuum were comparatively explored. The results indicated that when the TZP substrate was modified by a Cr ion implantation layer, the WC/a-C:H coating showed obviously better adhesion strength. Therein, at the implantation voltage of 30 kV, the coating exhibited the optimal adhesion of 88 N, which was 112% higher than that of the coating on original TZP. Surprisingly, the WC/a-C:H coating featuring maximum adhesion strength also achieved a high friction coefficient (>0.22) and exceptional wear resistance across a wide load range of 0.5~15 N in high vacuum. Compared with the TZP self-mated wear pairs, the wear rates of both the WC/a-C:H coating and its counterparts decreased by 1~2 orders of magnitude. Unlike the severe abrasive wear and plastic deformation of the TZP self-mated pairs, even at 15 N, the WC/a-C:H coating exhibited mild abrasive wear and adhesive wear mechanisms. Full article

Electrochemical mechanical polishing is a critical technology for improving the surface quality of silicon carbide (SiC) substrates. However, the fundamental electrochemical corrosion mechanism of the SiC substrate remains incompletely understood. In this study, the electrochemical corrosion behavior of the SiC substrate is explored through comprehensive experiments and molecular dynamics simulations. Key findings demonstrated that the 4H-0° SiC exhibited the highest corrosion rate in a 0.6 mol/L NaCl electrolyte. The corrosion rate increased as the voltage rose within the range of 2 to 20 V. When the voltage was between 20 and 25 V, the system entered the stable passivation region, while when the voltage was 25 to 30 V, partial dissolution of the surface oxide layer occurred. Molecular dynamics simulations further revealed that both amorphization degree and reaction depth on the SiC surface showed a decreasing trend at elevated voltages, suggesting a corresponding reduction in the corrosion rate when the voltage exceeded the optimal range. OH⁻, O²⁻, and •OH generated by the electrolysis of water during electrochemical corrosion would rapidly react with the surface of the SiC anode, and subsequently form a SiO₂ modified layer. Moreover, these atomistic insights establish a scientific foundation for achieving superior surface integrity in large-diameter SiC substrates through optimized electrochemical mechanical polishing processes. Full article

Due to the exceptional corrosion resistance, chemical stability, and dense microstructure, carbon-based thin films are extensively employed in hydrogen energy systems. This study employed magnetron sputtering to fabricate amorphous carbon (a-C) films on SS316L substrates, aiming to improve the corrosion resistance of bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs). Using a Taguchi design, the effects of working pressure, sputtering power, substrate bias, and deposition time on film properties were systematically examined and optimized. Films were examined via field emission scanning electron microscopy (FE-SEM), contact angle measurements, and electrochemical tests. Comprehensive evaluation by the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method identified optimal conditions of 1.5 Pa pressure, 150 W radio frequency (RF) power, −250 V bias voltage, and 60 min deposition, yielding dense, uniform films with a corrosion current density of 1.61 × 10⁻⁶ A·cm⁻² and a contact angle of 106.36°, indicative of lotus leaf-like hydrophobicity. This work enriches the theoretical understanding of a-C film process optimization, offering a practical approach for modifying fuel cell bipolar plates to support hydrogen energy applications. Full article

Material surfaces are of primary importance in biomaterial development, significantly influencing implant lifespan and clinical success. Consequently, coating technologies are frequently employed to modify surface properties and functionality. Plasma-based amorphous carbon coatings have been widely applied to all classes of substrates to improve their tribology, corrosion resistance, hardness, and even biological properties. Plasma technology is widely recognized to be effective, not only for the deposition of amorphous carbon coatings but also for substrate pre-treatment, in which it may play a key role in activating surfaces and enhancing interfacial adhesion. Amorphous carbon coatings can be classified into two major categories: diamond-like carbon (DLC) and polymer-like carbon (PLC), according to their mechanical properties. Regardless of their nature, the adhesion of both types of amorphous carbon coatings to the substrate has always represented a major challenge. Several strategies have been reported to enhance the adhesion of DLC coatings to silicon wafers, metals, and glass substrates. However, few studies report strategies aimed at controlling the adhesion of (both types of) amorphous carbon coatings to polymeric substrates, polymeric implants, and polymeric devices. Therefore, this work aims to provide a state-of-the-art review on the adhesion of amorphous carbon coatings to polymeric substrates for biomedical applications. Furthermore, this review presents the main techniques used to assess adhesion and the strategies available to improve adhesion between coatings and polymeric substrates. Full article

The study aimed to form thin Bi₂S₃ films simultaneously on various textile materials using the environmentally friendly, low-cost successive ionic layer adsorption and reaction (SILAR) method at ambient temperature, and to evaluate the influence of the textile’s composition on the resulting composites’ surface phase composition, morphology, and optical properties. The deposited films were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, and ultraviolet–visible (UV-Vis) diffuse reflectance spectroscopy. This paper discusses how the structure and composition of the textiles affect the phase and elemental composition, crystallinity, morphology and optical properties of the formed films. The properties of the films are then compared. Depending on the textiles used, the formed films can be amorphous or polycrystalline, and can be rich in sulphur or near stoichiometric. Accordingly, the normalised atomic percentages of Bi in the films range from 3.62% to 33.87%, and those of S range from 96.38% to 66.13%. The optical energy gap value of the composites also varies depending on the textile substrate, ranging from E_g = 1.58 eV to E_g = 1.8 eV. These properties directly impact the films’ applications. We have obtained a rather low value of the optical energy gap in a simpler way. Full article

The efficacy of indoor residual spray (IRS) products is affected by various factors, such as the substrate on which they are sprayed and the surface concentration and bioavailability of the insecticide. This study investigated the potential of bespoke silica particles (hereafter referred to as ‘X-tec silica’) as a unique carrier for insecticides to reduce the insecticide content in an IRS formulation by improving pickup by mosquitoes and optimising the physical state of the insecticide while maintaining its residual biological activity on a surface. Molecular computer modelling was used to define the critical crystallisation size of clothianidin, and silica particles were manufactured with pore diameters smaller than this length to maintain the insecticide in an amorphous state. Silica carriers were then formulated to incorporate clothianidin inside their pores, and a full material characterisation was conducted to assess the clothianidin coating position on/in the silica particles, their concentration, and their physical form. The clothianidin-formulated silica (10%) was sprayed at three different application rates (30, 60, and 90 mg active ingredient (a.i.)/m²) onto two surfaces: glazed and unglazed tiles. The tiles were tested for bioefficacy against the insecticide-susceptible Anopheles gambiae s.s. Kisumu mosquito strain at 1 week and 8 months post-spray application. At 1 week post-spray application, at 60 and 90 mg a.i./m² application rates, 100% mortality was observed on both surfaces within 48 h. For the lowest concentration (30 mg a.i./m²), 100% mortality was reached within 72 h on glazed tiles; however, for unglazed tiles, due to the surface irregularity and porosity, it remained below 60%. At 8 months post-spray application, on glazed tiles, 100% mortality was reached within 24 h at 60 and 90 mg a.i./m² application rates and within 48 h at 30 mg a.i./m². On unglazed tiles, 96 h mortality was not measured; however, 100% mortality was reached within 72 h (90 mg a.i./m²) and 120 h (60 mg a.i./m²) at higher concentrations. At the lowest concentration (30 mg a.i./m²) at 120 h, mortality only reached 25%. The lowest application rate tested (30 mg a.i./m²) is ten times lower than that of current products on the market and demonstrates the potential of this approach. Preliminary findings from this study suggest that X-tec silica particles may enhance the effectiveness of IRS using clothianidin. However, further extensive research is needed to confirm this. Full article

Laser cladding with ultrafast cooling rates enables effective fabrication of metallic glass matrix composite (MGMC) coatings, significantly enhancing the hardness, corrosion resistance, and mechanical properties of metallic substrates. In this study, a multi-layer Zr₆₅Al_7.5Ni₁₀Cu_17.5 (at. %) MGMC coating was successfully fabricated by laser cladding technology. The effects of the region-dependent microstructural evolution on micro-mechanical properties and corrosion resistance were systematically investigated. The results indicated that the high impurity content of the powder feedstock promoted the crystallization of the coating during laser cladding. Moreover, coarse columnar crystals in the bottom region of the coating nucleated epitaxially at the coating/substrate interface and propagated along the thermal gradient parallel to the building direction, while dendritic crystals dominated the middle region under moderate thermal gradients. In the top region, fine dendritic and equiaxed crystals deposited in the amorphous matrix, due to the lowest thermal gradient and the highest cooling rate. Correspondingly, nanoindentation results revealed that the top region exhibited peak hardness (H), maximum elastic modulus (E), and optimal H/E ratio, exceeding values in both the bottom region and substrate. Simultaneously, the metallic glass matrix composite coating demonstrated significantly better corrosion resistance than the substrate due to its amorphous phase and protective passive film formation. This work advances amorphous solidification theory while expanding applications of metallic glasses in surface engineering. Full article

Transition-metal oxides (TMOs) possess pronounced optoelectronic properties and are widely exploited in photovoltaics and photocatalysis. Here, we introduce a hot wire oxidation sublimation deposition (HWOSD) that directly converts elemental Mo and W into amorphous MoO_x and WO_x films on various substrates. Scanning electron microscopy and atomic force microscopy reveal uniform thickness and conformal coverage over textured and planar surfaces. X-ray photoelectron spectroscopy indicates high oxygen contents with stoichiometric ratios of 2.94 (MoO_x) and 2.91 (WO_x). Optical measurements show transmittances > 94% across 400–1200 nm, yielding optical band gaps of 1.86 eV (MoO_x) and 2.67 eV (WO_x). The conductivities of MoO_x and WO_x were 2.58 × 10⁻⁶ S cm⁻¹ and 5.14 × 10⁻⁷ S cm⁻¹ at room temperature, and the TMO/Si surface potential differences are 200 mV and 114 mV, respectively. Minority-carrier-lifetime measurements indicate that MoO_x films confer an additional passivation benefit to the i a-Si:H/c-Si/i a-Si:H stack. Annealing of MoO_x and WO_x realized their phase transition from an amorphous state to a polycrystalline state, with changes in their optical transmittance in the visible light region. Investigation of the photovoltaic performances of MoO_x and WO_x as HTLs deposited by HWOSD demonstrates their excellent electronic functionality in optoelectronics. These results establish HWOSD as a scalable, low-temperature method to fabricate high-quality TMO films and expand their potential in advanced optoelectronic devices. Full article

Aluminum nitride (AlN) is a material of wide interest in the optoelectronics and high-power electronics industry. The deposition of AlN thin films at elevated temperatures is a well-established process, but its implementation on flexible substrates with conductive oxides, such as ITO-glass or ITO-PET, poses challenges due to the thermal degradation of these materials. In this work, the deposition and characterization of AlN thin films by reactive sputtering at a low temperature (RT and 100 °C) on ITO-glass and ITO-PET substrates are presented. The structural, optical, and electrical properties of the samples have been analysed as a function of the sputtering power and the deposition temperature. XRD analysis revealed the absence of peaks of crystalline AlN, indicative of the formation of an amorphous phase. EDX measurements performed on the ITO-glass substrate with a radiofrequency power applied to the Al target of 175 W confirmed the presence of Al and N, corroborating the deposition of AlN. SEM analyses showed the formation of homogeneous and compact layers, and transmission optical measurements revealed a bandgap of around 5.82 eV, depending on the deposition conditions. Electrical resistivity measurements indicated an insulating character. Overall, these findings confirm the potential of amorphous AlN for applications in flexible optoelectronic devices. Full article

Organic light-emitting diodes (OLEDs) have emerged as a critical battleground in display technology due to their self-emissive and foldable properties. However, the adoption of polyimide (PI) as a flexible substrate material introduces technical challenges, particularly image sticking. This study proposes an interfacial polarization mechanism to explain this phenomenon, confirmed through dielectric and ferroelectric spectroscopy. The results show that introducing an amorphous silicon (α-Si) interlayer significantly improves interface compatibility, increasing the polarization response frequency from 74 Hz to 116 Hz and reducing residual polarization strength from 2.81 nC/cm² to 1.00 nC/cm². Practical tests on OLED devices demonstrate that the optimized structure (PI/α-Si/SiO₂) lowers the image sticking score from 3.46 to 1.67, validating the proposed mechanism. This research provides both theoretical insights and practical solutions for mitigating image sticking in flexible OLED displays. Full article