Film Delamination Research Articles

Correction: High performance, binder-free electrodes with single atom catalysts on doped nanocarbons for electrochemical water splitting synthesized using one-step thermally controlled delamination of thin films

Correction for ‘High performance, binder-free electrodes with single atom catalysts on doped nanocarbons for electrochemical water splitting synthesized using one-step thermally controlled delamination of thin films’ by Efrat Shawat Avraham et al., J. Mater. Chem. A, 2024, https://doi.org/10.1039/D4TA04701J.

INFLUENCE OF BIAS VOLTAGE ON THE STRUCTURE AND MECHANICAL PROPERTIES OF Ti-Nb-C FILMS DEPOSITED BY DC DUAL MAGNETRON SPUTTERING

The films of the Ti-Nb-C system were deposited by direct current (DC) magnetron co-sputtering of composite Ti+Nb, and graphite targets onto Si substrates to which negative substrate bias in the range of -50÷-200 V was applied during film deposition. The microstructure, chemical bonds, and mechanical properties of films were comparatively investigated. The X-ray diffraction (XRD) analysis revealed that the peaks of the XRD spectra of the film obtained by co-spattering of the composite Ti+Nb and graphite targets are located in the intermediate region between the corresponding peaks of the Ti-C and Nb-C films. The X-ray photoelectron spectroscopy (XPS) showed that the Ti-C and Nb-C bonds prevail in the deposited Ti-Nb-C films. It was suggested that the Ti-Nb-C films are nanocomposite and consist of the crystallites of Ti<sub>1-x</sub>Nb<sub>x</sub>C<sub>y</sub> solid solutions surrounded by amorphous carbon-based matrix. The Knoop hardness of the Ti-Nb-C film is highest (37.5 GPa) in the film deposited at -50 V substrate bias. The average friction coefficient determined before film delamination was the lowest (0.12) in that Ti-Nb-C film.

High performance, binder-free electrodes with single atom catalysts on doped nanocarbons for electrochemical water splitting synthesized using one-step thermally controlled delamination of thin films

Developing high performance catalysts for electrochemical water splitting is critical for an efficient and sustainable route to hydrogen production.

Roll-to-plate 0.1-second shear-rolling process at elevated temperature for highly aligned nanopatterns

The shear-rolling process is a promising directed self-assembly method that can produce high-quality sub−10 nm block copolymer line-space patterns cost-effectively and straightforwardly over a large area. This study presents a high temperature (280 °C) and rapid (~0.1 s) shear-rolling process that can achieve a high degree of orientation in a single process while effectively preventing film delamination, that can be applied to large-area continuous processes. By minimizing adhesion, normal forces, and ultimate shear strain of the polydimethylsiloxane pad, shearing was successfully performed without peeling up to 280 °C at which the chain mobility significantly increases. This method can be utilized for various high-χ block copolymers and surface neutralization processes. It enables the creation of block copolymer patterns with a half-pitch as small as 8 nm in a unidirectional way. Moreover, the 0.1-second rapid shear-rolling was successfully performed on long, 3-inch width polyimide flexible films to validate its potential for the roll-to-roll process.

Sequential separation of battery electrode materials and metal foils in aqueous media

To recycle high-value lithium-ion battery components, it is imperative to efficiently separate electrode materials from current collector foils and to separate cathodes from anodes. This study investigates the delamination behaviors of cathodes and anodes from their respective current collectors in aqueous media. Whereas anode films can easily detach from copper foils in water, the delamination of cathode films does not exhibit the same behavior in water; instead, the cation exchange reaction results in lithium leaching and aluminum corrosion in the presence of water. A buffer solution with surfactant additives has been designed to prevent aluminum corrosion and to improve solution wetting behavior, thereby facilitating cathode delamination. The delamination difference enables the sequential recovery of electrode materials and metal foils at different separation stages, simplifying the traditionally intricate processes within a one-pot recovery system. The recovered materials retain their crystal structure and morphology, and there are no signs of aluminum corrosion or residues on the metal foils. The sequential separation technique achieves nearly 100% separation efficiency for electrode materials from metal foils and over 98% separation efficiency for cathode and anode materials.

Chemically-stable flexible transparent electrode: gold-electrodeposited on embedded silver nanowires

Silver nanowires (AgNWs) with a low diameter, high aspect ratio, stable suspension, and easy synthesis have recently attracted the optoelectronic industry as a low-cost alternative to indium tin oxide transparent conductive films. However, silver nanowires are not chemically stable, and their conductivity diminishes over time due to reactions with atmospheric components. This is a bottleneck for their wide industrial applications. In this study, we aim to address this issue by synthesizing silver nanowires with an average diameter of approximately 65 nm and a length of approximately 13 µm. The prepared Ag nanowires are then applied to fabricate transparent, flexible, and chemically stable conductive films. The fabrication includes spraying of silver nanowires suspension on a glass substrate followed by Dr. blade coating of polystyrene (PS) solution and delamination of the PS-AgNWs film. The resulting film exhibits an optimum sheet resistance of 24 Ω/□ and transmittance of 84%. To further enhance the stability of the transparent conductive film, the facial and scalable double pulse electrodeposition method is used for coating of gold on the exposed surface of the AgNWs embedded in PS. The final transparent film with gold coating demonstrates a remarkable stability under harsh conditions including long exposure to UV light and nitric acid solution. After 100 min of UV/Ozone treatment, the increase in sheet resistance of the optimal PS-AgNW@Au sample is 15.6 times lower than the samples without gold coating. In addition, the change in sheet resistance after 2000 bending cycles in the optimal PS-AgNW@Au electrode is measured and it showed an increase of only 22% of its initial sheet resistance indicating its good flexibility. The proposed electrode performs an excellent chemical stability, good conductivity, transparency, and flexibility that makes it a potential candidate for various optoelectronic devices.

Precise quantification of the adhesion between metallic thin films and silicon wafer

The performance and reliability of integrated circuits depend on the mechanical and electrical properties of the interfaces between thin films and the silicon wafer. One of the essential properties of the interface is its adhesion energy. However, conventional adhesion characterization methods could be further improved, especially in providing repeatable and reliable measurements. In this paper, we measured the adhesive strength of the interface between tungsten thin films and silicon wafers in micro-sized specimens using a direct push-to-pull device built into a nano-indenter. A scratch method with a transparent theoretical model was applied to quantify the same interfaces' adhesive strength, adhesion energy, and fracture resistance. Microscopic and mechanical analysis clarified the physical origin of thin film delamination. The current method precisely quantified the interfaces' adhesive strength and fracture resistance. This method is promising for sub-micron thin film designs in the semiconductor industry with its superior repeatability, reliability, and ease of operation.

Controllable Delamination of CNT-Reinforced Carbon Fiber Films by Harnessing Mechanical and Topological Characteristics of the Composites

Controllable Delamination of CNT-Reinforced Carbon Fiber Films by Harnessing Mechanical and Topological Characteristics of the Composites

Water nanolayer facilitated solitary-wave-like blisters in MoS2 thin films

Solitary waves are unique in nonlinear systems, but their formation and propagation in the nonlinear fluid-structure interactions have yet to be further explored. As a typical nonlinear system, the buckling of solid thin films is fundamentally related to the film-substrate interface that is further vulnerable to environments, especially when fluids exist. In this work, we report an anomalous, solitary-wave-like blister (SWLB) mode of MoS2 thin films in a humid environment. Unlike the most common telephone-cord and web buckling deformation, the SWLB propagates forward like solitary waves that usually appear in fluids and exhibits three-dimensional expansions of the profiles during propagation. In situ mechanical, optical, and topology measurements verify the existence of an interfacial water nanolayer, which facilitates a delamination of films at the front side of the SWLB and a readhesion at the tail side owing to the water nanolayer-induced fluid-structure interaction. Furthermore, the expansion morphologies and process of the SWLB are predicted by our theoretical model based on the energy change of buckle propagation. Our work not only demonstrates the emerging SWLB mode in a solid material but also sheds light on the significance of interfacial water nanolayers to structural deformation and functional applications of thin films.

Parameters influencing the fracture of Mo films and their wider significance

Fragmentation testing has been used for decades to assess thin film fracture and delamination. Hooke’s law is generally used to determine a film fracture stress from the crack onset strain observed in micrographs or measured as an electrical resistance increase. While this method is in theory suitable in the elastic regime, it neglects important film characteristics, such as residual stress, microstructure, or film architecture. Thus, there is a need to improve fracture analysis using fragmentation to avoid significant errors in measuring fracture stress or apparent fracture toughness of thin films. In-situ X-ray diffraction fragmentation experiments can measure the film fracture stress even for individual layers being part of a multilayer. Which characteristics influence the apparent fracture behavior will be demonstrated on Mo thin films on polyimide.Graphical abstract

Effect of the deposition process on the stability of Ti3C2T x MXene films for bioelectronics

Ti3C2T x MXene is emerging as the enabling material in a broad range of wearable and implantable medical technologies, thanks to its outstanding electrical, electrochemical, and optoelectronic properties, and its compatibility with high-throughput solution-based processing. While the prevalence of Ti3C2T x MXene in biomedical research, and in particular bioelectronics, has steadily increased, the long-term stability and degradation of Ti3C2T x MXene films have not yet been thoroughly investigated, limiting its use for chronic applications. Here, we investigate the stability of Ti3C2T x films and electrodes under environmental conditions that are relevant to medical and bioelectronic technologies: storage in ambient atmosphere (shelf-life), submersion in saline (akin to the in vivo environment), and storage in a desiccator (low-humidity). Furthermore, to evaluate the effect of the MXene deposition method and thickness on the film stability in the different conditions, we compare thin (25 nm), and thick (1.0 μm) films and electrodes fabricated via spray-coating and blade-coating. Our findings indicate that film processing method and thickness play a significant role in determining the long-term performance of Ti3C2T x films and electrodes, with highly aligned, thick films from blade coating remarkably retaining their conductivity, electrochemical impedance, and morphological integrity even after 30 d in saline. Our extensive spectroscopic analysis reveals that the degradation of Ti3C2T x films in high-humidity environments is primarily driven by moisture intercalation, ingress, and film delamination, with evidence of only minimal to moderate oxidation.

Flexible all-organic photodetectors via universal water-assisted transfer printing

Transfer printing of small-molecular organic semiconductors often faces challenges due to surface adhesion mismatch. Here, we developed a sacrificing-layer-assisted transfer printing technique for the deposition of small-molecular thin films. High-boiling-point ethylene glycol (EG) was doped in aqueous solution poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the sacrificing layer to manipulate residual water in film, which allowed chlorobenzene solution to spontaneously spread and form uniform film. The residual water guaranteed film delamination from the stamp, allowing for its transfer onto various substrates and seeding layers. As a proof of concept, laterally conductive organic photodetectors using recyclable EG-PEDOT:PSS electrodes and a small-molecular active layer were consecutively fabricated via transfer printing in ambient air. The resulting device exhibited a high on/off ratio of 711 and a fast rise time of 0.5ms. Notably, the polymer electrode and the bulk heterojunction demonstrated unique repairability and recyclability.

Quantifying Degradation Mechanisms in a High-Performance Parallel Hybrid Lithium-Ion Supercapacitor Induced by Long Term Cycling at High Current Rates

Understanding the degradation pathways of electrode materials is a key to develop more reliable Li-ion technologies along with an increased energy density and power rate. This study aims to demonstrate the benefits of the combined use of X-ray based characterization techniques and electrochemical assessment for thorough multi-scale analysis to elucidate the aging mechanisms of a Li4Ti5O12/AC//LiMn2O4/AC parallel hybrid lithium-ion supercapacitor. Analyses performed on samples extracted from full stack representative of industrial battery application, show that irreversible modifications are observed at all length scales on both electrodes. At the negative, the disaggregation and corrosion of the LTO active material, as well as AC particle cracking and electrode film delamination have been observed. In the meantime, drastic cracking of the AC and LMO active material along with important micro-strain increase at the crystallite level for LMO as well as Mn3+ dissolution are reported at the positive. The formation of a cathode electrolyte interface (CEI) is also reported. These structural and chemical changes have been identified as precursors to important polarization increase, Li inventory loss and furthermore capacity fading leading thus to device failure.

Effect of interlayer carbon nanotube films on the quasi-static and dynamic mode Ⅰ fracture behavior of laminated composites – An experimental and numerical investigation

A combined experimental and numerical study was conducted to investigate the quasi-static and dynamic mode Ⅰ fracture behavior of laminated composites toughened by carbon nanotube (CNT) films. Fracture tests under quasi-static and dynamic loading conditions were carried out by using electronic universal testing machine and electromagnetic Hopkinson bar device respectively. It’s illustrated that the CNT films can suppress the propagation of interlayer cracks effectively. Dynamic strengthening effect was also observed for CNT toughened composites during tests. For numerical simulations, the three-linear cohesive zone model (CZM) was proposed to simulate the Mode I delamination of CNT films toughened composites under quasi-static loading condition. Furthermore, rate-dependent parameters were introduced into this model by user-defined subroutine to describe the dynamic fracture behavior of toughened composites. This developed numerical model was validated by comparing with dynamic crack propagating speeds obtained from experimental tests. During the dynamic delaminating process, the average crack propagation rate of toughened composites decreased while the energy release rate increased, indicating that the interlayer CNT films can hinder the dynamic delamination effectively.

Delamination from an adhesive sphere: Curvature-induced dewetting versus buckling

Everyday experience confirms the tendency of adhesive films to detach from spheroidal regions of rigid substrates-what is a petty frustration when placing a sticky band aid onto a knee is a more serious matter in the coating and painting industries. Irrespective of their resistance to bending, a key driver of such phenomena is Gauss' Theorema Egregium, which implies that naturally flat sheets cannot conform to doubly curved surfaces without developing a strain whose magnitude grows sharply with the curved area. Previous attempts to characterize the onset of curvature-induced delamination, and the complex patterns it gives rise to, assumed a dewetting-like mechanism in which the propensity of two materials to form contact through interfacial energy is modified by an elastic energy penalty. We show that this approach may characterize moderately bendable sheets but fails qualitatively to describe the curvature-induced delamination of ultrathin films, whose mechanics is governed by their propensity to buckle and delaminate partially, under minute levels of compression. Combining mechanical and geometrical considerations, we introduce a minimal model for curvature-induced delamination accounting for the two buckling motifs that underlie partial delamination: shallow "rucks" and localized "folds". We predict nontrivial scaling rules for the onset of curvature-induced delamination and various features of the emerging patterns, which compare well with experiments. Beyond gaining control on the use of ultrathin adhesives in cutting-edge technologies such as stretchable electronics, our analysis is a significant step toward quantifying the multiscale morphology that emerges upon imposing geometrical and mechanical constraints on highly bendable solid objects.

Evaluation of Corrosion Resistance and Surface Film Analysis after Corrosion Testing of Materials Coated by Chemical Densified Coating Method under Boiling Sulfuric Acid Environment

For the purpose of developing metallic materials with excellent corrosion resistance under boiling sulfuric acid environment, the coated materials were evaluated for their corrosion resistance and the differences in surface morphology were investigated. As a result, the corrosion resistance of SUS304 coated and sintered eight times by chemical densified coating method (S-ZAC) was maintained at the point after 12h corrosion test, but the corrosion rate rapidly increased after 100h corrosion test. The cross-sectional microstructural analysis of the specimens showed that only a small amount of SiO2 remained on the surface, while Cr2O3 completely disappeared. The mechanism of film delamination in S-ZAC is assumed to be due to the thermal expansion caused by heating, which resulted in curvature of the thick film and cracks at the Cr2O3 and SiO2 interfaces. On the other hand, SUS304 coated with higher density of Cr2O3 by repeating the coating and sintering eleven times (MS-ZAC) showed excellent corrosion resistance as well as SiC even after 100h corrosion test. The results of cross-sectional microstructural analysis showed that MS-ZAC had higher Cr2O3 concentration, finer SiO2 grain size, and fewer porosity than S-ZAC. In particular, the mechanism of film maintenance in MS-ZAC is assumed to be the formation of a stacked structure in Cr2O3 particle layer, in addition to the thinning of the entire film.

A wrinkling-assisted strategy for controlled interface delamination in mechanically-guided 3D assembly

Mechanically-guided three-dimensional (3D) assembly is a recently established method for the fabrication of 3D structures and devices at micro/nanoscale. Such assembly methods typically involve a process of compressive buckling in a patterned high-modulus thin film integrated with a low-modulus elastomer substrate at selective regions. A successful assembly requires, simultaneously, a sufficiently strong interface in selective regions to stay undelaminated, and a sufficiently weak interface in remaining regions to be fully separated. However, such requirements are very challenging to meet for highly flexible 3D mesostructures or those with large-area suspended features. Here, we propose a wrinkling-assisted strategy to substantially facilitate the delamination at desired regions of the film/substrate system. An additional assisting layer is introduced such that a weaker film/assisting-layer interface replaces the original film/substrate interface, and the wrinkles formed in the assisting layer induce additional driving forces to separate the film/assisting-layer interface. An analytical model is developed to capture the delamination of the thin film from the wrinkled assisting layer, which is validated by both experiments and finite element analyses (FEA). The model shows that a combined material/geometry parameter governs the process of delamination in the bilayer film/substrate system, offering a useful design reference for the mechanically-guided 3D assembly. Furthermore, our experiments and FEA demonstrate that the wrinkling-assisted strategy can enable the assembly of highly flexible 3D mesostructures and those with large areas attached to the substrate in the initial configuration, which are particularly challenging to achieve by using previous strategies.

Coarse-grained molecular dynamics simulation of oil film formation and delamination in boundary lubrication

Coarse-grained molecular dynamics simulation of oil film formation and delamination in boundary lubrication

THREE-DIMENSIONAL STRAIN/STRESS FIELDS IN BERKOVICH/VICKERS INDENTATION: COMPARISONS WITH THIN FILM DELAMINATION AND SHEAR BAND FORMATION

Starting from the simple assumption that the displacement field underneath a pyramidal (Berkovich/Vickers) tip for very shallow indents is described by the Boussinesq solution, while for deeper ones is dictated by the tip's specific geometry, a combination of the two leads to a combined displacement field for the material at contact with the tip. Continuum mechanics is then utilized for the calculation of the strain tensor, while gradient elasticity theory is adopted for the determination of the stress tensor underneath the tip. Gradient elasticity was assumed in order for the gradient term to be able to model, in this case, the inhomogeneously applied load due to the specific tip geometry, which is different than a flat punch. The thus calculated stress component along the loading (vertical) direction is a parametric function of the material's elastic constants (Poisson's ratio, Lame constants), as well as of the maximum elastic deformation and the gradient coefficient. By appropriately modifying these parameters, the proposed formulation seems to be able to predict the mechanical response of the material underneath the indenter for the specific pyramidal tip geometry (Berkovich or Vickers), without any approximations or empirical relations. The validity of the proposed formulation's predictions was checked against thin film delamination and shear band formation AFM/SEM micrographs, which showed a very good qualitative as well as quantitative comparison with the theoretical predictions.

Experimental Evaluation of the Impact of Rapid Environmental Changes on Stress Distribution in Tablet Coatings.

Drying-induced cracks in tablet coatings are undesirable as they not only affect tablet's appearance, but they may also interfere with its function. While it is well known that tensile stresses in the coating are responsible for coating failures, few have measured the stress in tablet coatings, especially when exposed to rapid environmental changes. In this study, two commercial tablet coatings based on Hydroxy Propyl Methyl Cellulose (HPMC) and Poly Vinyl Alcohol (PVA) are exposed to rapid variations in temperature and humidity to observe the variation in residual stress. Reducing temperature at a fixed humidity or reducing humidity at fixed temperature, both lead to high residual stresses. When both the humidity and temperature were reduced together, the residual stresses were very high causing delamination in the PVA-based film and cracking in the HPMC-based film. The changes in residual stress are almost instantaneous for the HPMC-based film while it is slower for the PVA-based film. The results highlight the importance of environmental conditions on the residual stress in the film and the resulting coating failure.