Search Results (81)

The development of organic light-emitting diodes (OLEDs) for high-resolution, large-area displays relies on effective encapsulation technology. Accordingly, this study proposes a novel multilayer structure utilizing a cyclo-olefin polymer-based film. This solution significantly reduces process time and cost while achieving remarkable barrier performance. Optimization involved presenting various models and enhancing substrate–film adhesion via ultraviolet or plasma treatment, consequently improving water vapor transmission rate. Furthermore, the optimized structure’s feasibility as an OLED encapsulation layer was confirmed. These results promise to enhance core technological capabilities, improving production yield and minimizing costs—key factors for next-generation displays. Full article

Accumulative rolling bonding (ARB) Cu/Nb nanolaminates have been widely observed to exhibit unique and large numbers of interface-based plasticity mechanisms, and these have been associated with the many extraordinary properties of the material system, especially resistances in extreme engineering environments (mechanical/pressure, thermal, irradiation, etc.) and ability to self-heal defects (microstructural, as well as radiation-induced). Recently, anisotropy in the interface shearing mechanisms in the material system has been observed and much discussed. The Cu/Nb nanolaminates appear to shear on the interface planes to a much larger extent in the transverse direction (TD) than in the rolling direction (RD). Related to that, in this present study we observe interface rotation in Cu/Nb ARB nanolaminates under constrained and unconstrained loading conditions. Although the primary driving force for interface shearing was expected only in the RD, additional shearing in the TD was observed. This is significant as it represents an interface rotation, while there was no external rotational driving force. First, we observed interface rotation in in situ rectangular micropillar compression experiments, where the interface is simply sheared in one particular direction only, i.e., in the RD. This is rather unexpected as, in rectangular micropillar compression, there is no possibility of extra shearing or driving force in the perpendicular direction due to the loading conditions. This motivated us to subsequently perform in situ microbeam bending experiments (microbeam with a pre-made notch) to verify if similar interface rotation could also be observed in other loading modes. In the beam bending mode, the notch area was primarily under tensile stress in the direction of the beam longitudinal axis, with interfacial shear also in the same direction. Hence, we expect interface shearing only in that direction. We then found that interface rotation was also evident and repeatable under certain circumstances, such as under an offset loading. As this behaviour was consistently observed under two distinct loading modes, we propose that it is an intrinsic characteristic of Cu/Nb interfaces (or FCC/BCC interfaces with specific orientation relationships). This interface rotation represents another interface-based or interface-mediated plasticity mechanism at the nanoscale with important potential implications especially for design of metallic thin films with extreme stretchability and other emerging applications. Full article

Metallic nanolaminates generally show ultra-high strength but low ductility due to their vulnerability to shear instability during deformation. Herein, we report the simultaneous enhancement in hardness (by 11.9%) and suppression of shear instability in a 10 nm Cu/Zr nanolaminate, achieved by introducing a nanoscale Cu₆₃Zr₃₇ amorphous interfacial layer (AIL) between the crystalline Cu and Zr layers via magnetron sputtering. The effect of AIL and its thickness (h) (h = 2, 5, and 10 nm) on the hardness and shear instability behavior was explored using nano- and micro-indentation tests. An abnormal increase in hardness occurs at h = 2 nm when h is decreased from 10 to 2 nm, deviating from the prediction of the rule of mixtures. This abnormal strengthening is attributed to thinner AIL, which induces an increased density of crystalline/amorphous interfaces, thereby generating a pronounced interface strengthening effect. The micro-indentation results show that shear banding was suppressed in the nanolaminate with AIL, as evidenced by fewer shear bands as compared to its homogeneous counterpart. This enhanced resistance to shear instability may originate from the crystalline/amorphous interface that provides more sites for dislocation nucleation, emission, and annihilation. Furthermore, two distinct shear banding modes were observed in the nanolaminate with AIL; i.e., a cutting-like shear banding emerged at h = 10 nm, whereas a kinking-like shear banding occurred at h = 2 nm. The potential mechanism of the AIL-thickness-dependent shear banding was analyzed based on the crack propagation model of the Griffith criterion. This study provides a comprehensive insight into the strengthening and tunable shear instability of super-nano metallic laminates by AIL. Full article

The incorporation of MAX phase interface layers into silicon carbide (SiC) composites has been shown to significantly enhance mechanical properties, particularly under irradiation conditions. However, conventional Ti-based MAX phases suffer from thermal instability and tend to decompose at high temperatures. In this work, an Sc₂SnC coating was successfully synthesized onto the surface of SiC fibers (SiC_f) via an in situ reaction between metals and pyrolytic carbon (PyC) in a molten salt environment. The PyC layer, pre-deposited by chemical vapor deposition (CVD), served as both a carbon source and a structural template. Characterization by SEM, XRD, and Raman spectroscopy confirmed the formation of Sc₂SnC coatings with a distinctive hexagonal flake-like morphology, accompanied by an internal ScC_x intermediate layer. By turning the Sc-to-Sn ratio in the molten salt, coatings with varied morphologies were achieved. ScC_x was identified as a critical intermediate phase in the synthesis process. The formation of numerous defects during the reaction enhanced element diffusion, resulting in preferential growth orientations and diverse grain structures in the Sc₂SnC coating. Full article

In this research, we mainly increase the adhesion of PMMA substrate and film, which is reflected in the environmental test. This study used plasma-enhanced atomic layer deposition (PEALD) to find the relationship between the intensity of XRD reflection peak and the root-mean-square surface roughness (σ_RMS) of hafnium dioxide (HfO₂) at different thicknesses by reducing the plasma power at different process temperatures. In this experiment, HfO₂ was found to have the highest intensity of XRD at its maximum thickness. According to the different intensities of XRD of HfO₂ at different thicknesses, aluminum oxide (Al₂O₃) was inserted as crystallization cutoff layers, and the two materials were combined into nanolaminates. The corresponding σ_RMS value also changed from 1.25 to 0.434 nm after treatment under the fourth experimental design. This study improved this mismatch between interfaces by adjusting the yield strength and ductility using Al₂O₃ layers and by creating an inhibition layer. In addition, through the processing of inserted Al₂O₃ layers, the degree of crystallization was changed so that the material and substrate could maintain their normal surfaces without cracking after the environmental tests. After inserting five 1 nm thick Al₂O₃ layers, the environmental test results were improved. The test time was increased from the original 56 h to 352 h. Full article

In this study, an inorganic multilayer barrier film was fabricated on the polyethylene naphthalate (PEN) substrate, which was composed of a SiO₂ layer prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and a Al₂O₃/ZnO nanolaminate produced by plasma-enhanced atomic layer deposition (PEALD). The multilayer composite film with a structure of 50 nm SiO₂ + (4.5 nm Al₂O₃/6 nm ZnO) × 4 has excellent optical transmittance (88.1%) and extremely low water vapor permeability (3.3 × 10⁻⁵ g/m²/day, 38 °C, 90% RH), indicating the cooperation of the two advanced film growth methods. The results suggest that the defects of the SiO₂ layer prepared by ICP-CVD were effectively repaired by the PEALD layer, which has excellent defect coverage. And Al₂O₃/ZnO nanolaminates have advantages over single-layer Al₂O₃ due to their complex diffusion pathways. The multilayer barrier film offers potential for encapsulating organic electronic devices that require a longer lifespan. Full article

Polycrystalline SnO₂-HfO₂ nanolaminated thin films were grown by atomic layer deposition (ALD) on SiO₂/Si(100) and TiN substrates at 300 °C. The samples, when evaluated electrically, exhibited bipolar resistive switching. The sample object with a stacked oxide layer structure of SnO₂ | HfO₂ | SnO₂ | HfO₂ additionally exhibited bidirectional threshold resistive switching properties. The sample with an oxide layer structure of HfO₂ | SnO₂ | HfO₂ displayed bipolar resistive switching with a ratio of high and low resistance states of three orders of magnitude. Endurance tests revealed distinguishable differences between low and high resistance states after 2500 switching cycles. Full article

A novel nano-laminated GdB₂C₂ material was successfully synthesized using GdH₂, B₄C, and C via an in situ solid-state reaction approach for the first time. The formation process of GdB₂C₂ was revealed based on the microstructure and phase evolution investigation. Purity of 96.4 wt.% GdB₂C₂ was obtained at a low temperature of 1500 °C, while a nearly fully pure GdB₂C₂ could be obtained at a temperature over 1700 °C. The as-obtained GdB₂C₂ presented excellent thermal stability at a high temperature of 2100 °C in Ar atmosphere due to the stable framework formed by the high-covalence four-member and eight-member B-C rings in GdB₂C₂. The GdB₂C₂ material synthesized at 1500 °C demonstrated a remarkably low minimum reflection loss (RL_min) of −47.01 dB (3.44 mm) and a broad effective absorption bandwidth (EAB) of 1.76 GHz. The possible electromagnetic wave absorption (EMWA) mechanism could be ascribed to the nano-laminated structure and appropriate electrical conductivity, which facilitated good impedance matching, remarkable conduction loss, and interfacial polarization, along with the reflection and scattering of electromagnetic waves at multiple interfaces. The GdB₂C₂, with excellent EMWA performance as well as remarkable ultra-high-temperature thermal stability, could be a promising candidate for the application of EMWA materials in extreme ultra-high temperatures. Full article

Since its invention in the 1960s, one of the most significant evolutions of metal-oxide semiconductor field effect transistors (MOSFETs) would be the 3D version that makes the semiconducting channel vertically wrapped by conformal gate electrodes, also recognized as FinFET. During recent decades, the width of fin (W_fin) and the neighboring gate oxide width (t_ox) in FinFETs has shrunk from about 150 nm to a few nanometers. However, both widths seem to have been leveling off in recent years, owing to the limitation of lithography precision. Here, we show that by adapting the Penn model and Maxwell–Garnett mixing formula for a dielectric constant (κ) calculation for nanolaminate structures, FinFETs with two- and three-stage κ-graded stacked combinations of gate dielectrics with SiO₂, Si₃N₄, Al₂O₃, HfO₂, La₂O₃, and TiO₂ perform better against the same structures with their single-layer dielectrics counterparts. Based on this, FinFETs simulated with κ-graded gate oxides achieved an off-state drain current (I_OFF) reduced down to 6.45 × 10⁻¹⁵ A for the Al₂O₃: TiO₂ combination and a gate leakage current (I_G) reaching down to 2.04 × 10⁻¹¹ A for the Al₂O₃: HfO₂: La₂O₃ combination. While our findings push the individual dielectric laminates to the sub 1 nm limit, the effects of dielectric permittivity matching and κ-grading for gate oxides remain to have the potential to shed light on the next generation of nanoelectronics for higher integration and lower power consumption opportunities. Full article

Microbolometer arrays, i.e., arrays of micro-scale pixels sensing temperature via resistance changes, have proven to be an effective basis for real-time imaging instrumentation in infrared as well as terahertz frequencies. In previous work, a design of THz and IR absorbing nano-laminates of dielectric and metal layers was studied. It was shown via numerical modeling that absorption may be maximized by appropriate choices of thickness, permittivity and conductivity. In this work, an analytical approach to the problem is formulated based on the standard recursive multiple reflection formulas for multi-layered planar structures. The results fully confirm and extend previous numerical work. A previous relationship between wavelength and silicon thickness for maximum absorption, derived numerically for specific parameter combinations, is now generalized in a parametric closed form. The method can be extended to include multiple lossy dielectric layers and may serve as a tool for optimizing the absorption characteristics of more complex layered absorbing structures. This could enhance the sensitivity of the detection scheme of interest, providing benefits in terms of cost, efficiency, precision, and adjustability. Full article

Ultrathin encapsulation strategies show huge potential in wearable and implantable electronics. However, insightful efforts are still needed to improve the electrical and mechanical characteristics of encapsulated devices. This work introduces Al₂O₃/alucone nanolaminates using hybrid atomic/molecular layer deposition for ultrathin encapsulation structures employed in crystalline silicon nanomembrane (Si NM)-based metal-oxide-semiconductor capacitors (MOSCAPs). The comprehensive electrical and mechanical analysis focused on the encapsulated and bare MOSCAPs with three gate dielectric diameters (Ø) under planar and bending conditions, including concave bending radii of 110.5 mm and 85 mm as well as convex bending radii of 77.5 mm and 38.5 mm. Combined with the Ø-related mechanical analysis of the maximum strain in the critical layers and the practical investigations of electrical parameters, the encapsulated MOSCAPs with Ø 160 μm showed the most stable electro-mechanical performance partly due to the optimized position of the neutral mechanical plane. Comparison of the electrical changes in Al₂O₃/alucone-encapsulated MOSCAPs with Ø 160 μm, Ø 240 μm, and Ø 320 μm showed that it is beneficial to define the gate dielectric surface area of 0.02 to 0.05 mm² for Si NM-based wearable electronics. These findings are significant for leveraging the practical applications in ultrathin encapsulation strategies for reliable operations of crystalline Si NM-based integrated circuits. Full article

The exceptional strength of nanolaminates is attributed to the influence of their fine stratification on the movement of dislocations. Through atomistic simulations, the impact of interfacial structure on the dynamics of an edge dislocation, which is compelled to move within a nanoscale layer of a nanolaminate, is examined for three different nanolaminates. In this study, we model confined layer slip in three structures: nanolaminated Ag and two types of Ag/Cu nanolaminates. We find that the glide motion is jerky in the presence of incoherent interfaces characterized by distinct arrays of misfit dislocations. In addition, the glide planes exhibit varying levels of resistance to dislocation motion, where planes with intersection lines that coincide with misfit dislocation lines experience greater resistance than planes without such intersection lines. Full article

Ultrathin flexible encapsulation (UFE) using multilayered films has prospects for practical applications, such as implantable and wearable electronics. However, existing investigations of the effect of mechanical bending strains on electrical properties after the encapsulation procedure provide insufficient information for improving the electrical stability of ultrathin silicon nanomembrane (Si NM)-based metal oxide semiconductor capacitors (MOSCAPs). Here, we used atomic layer deposition and molecular layer deposition to generate 3.5 dyads of alternating 11 nm Al₂O₃ and 3.5 nm aluminum alkoxide (alucone) nanolaminates on flexible Si NM-based MOSCAPs. Moreover, we bent the MOSCAPs inwardly to radii of 85 and 110.5 mm and outwardly to radii of 77.5 and 38.5 mm. Subsequently, we tested the unbent and bent MOSCAPs to determine the effect of strain on various electrical parameters, namely the maximum capacitance, minimum capacitance, gate leakage current density, hysteresis voltage, effective oxide charge, oxide trapped charge, interface trap density, and frequency dispersion. The comparison of encapsulated and unencapsulated MOSCAPs on these critical parameters at bending strains indicated that Al₂O₃/alucone nanolaminates stabilized the electrical and interfacial characteristics of the Si NM-based MOSCAPs. These results highlight that ultrathin Al₂O₃/alucone nanolaminates are promising encapsulation materials for prolonging the operational lifetimes of flexible Si NM-based metal oxide semiconductor field-effect transistors. Full article

Ceramic–metal nanolaminates (CMNLs) are promising scratch-resistant coatings, but knowledge gaps remain regarding the interactive effects of individual layer thickness and scratch depth. This study employed molecular dynamics simulations to investigate the tribological performance of NbC/Nb CMNLs, systematically varying ceramic and metal layer thicknesses (0.5–7.5 nm) and scratch depths (3, 5 nm). Models were loaded under displacement-controlled indentation followed by scratching. Mechanical outputs like material removal, friction coefficients, normal, and friction forces quantified scratch resistance. Material removal was even below that for NbC alone, demonstrating the multilayer benefit. Thinner layers showed complete penetration by the indenter, with material rolled in front rather than piled up. Thicker layers resisted penetration, enabling pile-up and lower friction coefficients due to higher normal forces. Excessive material removal decreased normal forces and raised friction coefficients. Peak coefficient occurred around 1.5–3 nm layer thicknesses where substantial top layer volumes were removed, minimizing ceramic under the indenter. Layer thickness corresponding to lowest material removal depended on scratch depth, with 3 nm and 7.5 nm layer thickness for 3 and 5 nm depths, respectively. Metallic layers reduced stiffness and drove material downward over piling up. Quantifying scratch resistance versus geometric parameters elucidates fundamental physics to facilitate superior CMNL coating fabrication. Full article

This article explores the utilization of cathodic-arc deposition Cr-Al overlay coatings as oxidation protection for Ti-Al-Nb intermetallic alloys. The primary objective is to investigate PVD Al-Cr coatings deposited via cathodic-arc deposition without subsequent vacuum annealing. The microstructure, phase, and chemical composition of the coatings were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis. Isothermal exposure of samples in a laboratory air furnace was conducted, revealing the efficacy of Cr-Al coatings in protecting the Ti49-11Al-40Nb-1.5Zr-0.75V-0.75Mo-0.2Si (mass%) intermetallic alloy VTI-4 against oxidation. The findings highlight that the as-deposited coatings possess a layered structure and contain Al-Cr intermetallics. Post-exposure to the furnace without prior vacuum annealing results in coatings exhibiting a porous microstructure, raising concerns regarding oxidation protection. This investigation of Cr-Al coatings on a VTI-4 alloy substrate yields valuable insights into their nanolaminate structure and challenges associated with aluminum droplet fractions. The proposed additional vacuum heat treatment at 650 °C for 500 h effectively homogenizes the coating, leading to predominant Cr₂Al and Ti-Al phases. Additionally, the formation of diffusion layers at the “coating–substrate” interface and the presence of oxide barriers contribute to the coatings’ heat resistance. Our research introduces possibilities for tailoring coating properties for specific high-temperature applications in aerospace, energy, or industrial contexts. Further refinement of the heat treatment process offers the potential for developing advanced coatings with enhanced performance characteristics. Full article