Abstract:A robust hydrophobic Y2O3 coating at high temperatures is important for industrial applications. In this study, Y2O3 thin films on Si substrates were prepared by reactive direct current magnetron sputtering. By changing the deposition power, Y2O3 thin films with different microstructures were obtained in poison mode and metallic mode, respectively. In order to understand the effect of heat treatment on the microstructure and hydrophobicity of Y2O3, the samples were annealed at 400 C in the air. Compared to metallic mode, no crack was formed on the surface of the Y2O3 film prepared in poison mode. In addition, the water contact angle on the surface of the Y2O3 thin film deposited in poison mode was above 90 before and after annealing at 400 C. It has been demonstrated that the initial high concentration of physically absorbed oxygen and its slow desorption process in a Y2O3 thin film prepared in poison mode contributes to the hydrophobicity of the thin film at high temperatures. These results can provide insights into the large-scale fabrication of hydrophobic Y2O3 coatings for high-temperature applications.Keywords: Y2O3 thin film; heat treatment; wettability; reactive magnetron sputtering
Usually, high-resolution and large-area NIL molds are expensive and difficult to fabricate. Even though they are typically made of silicon or other hard materials like nickel or quartz, after a number of imprinting cycles, they start cracking and, therefore, become unusable. In order to preserve the mold without affecting the throughput, intermediate molds were introduced. Intermediate molds are replicas of the original mold that are themselves used as molds to transfer the topographies to the final material. This interest is also present at an industrial level. For example, the company Obducat AB has recently patented [3] an imprinting apparatus to perform a two-step process involving intermediates for typical topographies ranging from gratings of 80 nm linewidth up to micrometric pillars.
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Intermediate molds are generally produced in plastic or soft materials by soft-lithography techniques and must guarantee high-fidelity copies and a sufficiently high number of processes before undergoing degradation [4]. While polymers such as poly-(methyl-methacrylate) (PMMA) or polystyrene (PS) are frequently used in thermal NIL, they are not recommended as material for intermediate molds because they are generally sticky and tend to crack during the release step [5]. Differently, beyond the ease of fabrication, elastomeric materials can ensure good elastic adaptation and conformal contact with the substrate, which leads to intimate contact without voids [6].
3D AFM reconstructions in Figure 3c show a larger view of the topographies, which confirms the satisfactory compliance of each transfer step to the previous and highlighting the consistent profiles of the original mold and COC replica. Owing to the possibility to fabricate more copies of the same initial mold and to the fact that a single PFPE intermediate mold can sustain tents of thermal imprint cycles without cracking or affecting the final feature resolution, the entire process yield is considerably increased.
Failure of the bonded dissimilar materials generally initiates near the interface, or just from the interface edge due to the stress singularity at the interface edge. In this study, the stress intensity factor of an edge crack close to the interface between the dissimilar materials is analyzed. The small edge crack is strongly dominated by the singular stress field near the interface edge. The analysis of stress intensity factor of small edge crack near the interface in bi-material and butt joint plates is carried out by changing the length and the location of the crack and the region dominated by the interface edge is examined. It is found that the dimensionless stress intensity factor of small crack, normalized by the singular stress at the crack tip point in the bonded plate without the crack, is equal to 1.12, independent of the material combination and adhesive layer thickness, when the relative crack length with respect to the crack location is less than 0.01. The adhesive strength of the bonded plate with various adhesive layer thicknesses can be expressed as the constant critical stress intensity factor of the small edge crack.
The effect of distributed coseismic slip on progressive, near-field edge waves is examined for continental shelf tsunamis. Detailed observations of edge waves are difficult to separate from the other tsunami phases that are observed on tide gauge records. In this study, analytic methods are used to compute tsunami edge waves distributed over a finite number of modes and for uniformly sloping bathymetry. Coseismic displacements from static elastic theory are introduced as initial conditions in calculating the evolution of progressive edge-waves. Both simple crack representations (constant stress drop) and stochastic slip models (heterogeneous stress drop) are tested on a fault with geometry similar to that of the M w = 8.8 2010 Chile earthquake. Crack-like ruptures that are beneath or that span the shoreline result in similar longshore patterns of maximum edge-wave amplitude. Ruptures located farther offshore result in reduced edge-wave excitation, consistent with previous studies. Introduction of stress-drop heterogeneity by way of stochastic slip models results in significantly more variability in longshore edge-wave patterns compared to crack-like ruptures for the same offshore source position. In some cases, regions of high slip that are spatially distinct will yield sub-events, in terms of tsunami generation. Constructive interference of both non-trapped and trapped waves can yield significantly larger tsunamis than those that produced by simple earthquake characterizations.
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