Non-destructive depth profile evaluation of multi-layer thin film stack using simultaneous analysis of data from multiple X-ray photoelectron spectroscopy instruments

Non-destructive depth profile evaluation of multi-layer thin film stacks using simultaneous analysis of angle-resolved x-ray photoelectron spectroscopy data from multiple instruments is demonstrated. The data analysis algorithm, called the maximum smoothness method, was originally designed to handle data from a single XPS instrument with a single x-ray energy; in this work, the algorithm is extended to provide a simultaneous analysis tool which can handle data from multiple instruments with multiple x-ray energies. The analysis provides depth profiles for multilayer stacks that cannot be obtained by conventional data analysis methods. In this paper, metal multi-layer stack samples with total thickness greater than 10 nm are analyzed with the maximum smoothness method to nondestructively obtain depth profiles, with precise information on the chemical states of atoms in the surface layer (< 2 nm) and the overall layer stack structure, which can only be obtained by analyzing the data from multiple instruments.

Research on Failure Mechanism and Thermal Stress of Thin-film Thermocouple at High Temperature

Aiming at the reliability of thin-film thermocouples applied to turbine blades at high temperatures, combined with high-temperature tests and finite element analysis, this paper studies its failure mechanism and thermal stress under thermal load. Multi-layer thin-film thermocouple samples were prepared on ceramic substrate, and high-temperature tests were carried out under different temperature loads, and the phenomenon of film shedding and cracking was observed using electron microscope. This paper analyzes the failure mechanism of the film sensor based on the function and structure, and uses ANSYS to analyze the thermal stress distribution of the film under high temperature load. Combining several existing theoretical models, this paper analyzes the factors affecting the thermal stress of the film and conducts simulation verification.

Playing Ping Pong With Light: Directional Emission of White Light

Over the last decades, light-emitting diodes (LED) have replaced common light bulbs in almost every application, from flashlights in smartphones to automotive headlights. Illuminating nightly streets requires LEDs to emit a light spectrum that is perceived as pure white by the human eye. The power associated with such a white light spectrum is not only distributed over the contributing wavelengths but also over the angles of vision. For many applications, the usable light rays are required to exit the LED in forward direction, namely under small angles to the perpendicular. In this work, we demonstrate that a specifically designed multi-layer thin film on top of a white LED increases the power of pure white light emitted in forward direction. Therefore, the deduced multi-objective optimization problem is reformulated via a real-valued physics-guided objective function that represents the hierarchical structure of our engineering problem. Variants of Bayesian optimization are employed to maximize this non-deterministic objective function based on ray tracing simulations. Eventually, the investigation of optical properties of suitable multi-layer thin films allowed to identify the mechanism behind the increased directionality of white light: angle and wavelength selective filtering causes the multi-layer thin film to play ping pong with rays of light.

Hydrophobicity and Macroscale Tribology Behavior of Stearic Acid/Hydroxypropyl Methylcellulose Dual-Layer Composite

Hydroxypropyl methylcellulose (HPMC) and stearic acid (SA) are integrated to fabricate a double-layer thin film composite material with potential applications in sustainable packaging and coating materials. The effect of SA concentration on the moisture and wear resistance at the macroscale of the composite are studied. The amount of SA on the surface (>SA5H) is beneficial in increasing anti-wear behavior and reducing the friction coefficient by 25%. The petal-shaped crystals formed by SA are distributed on the surface of the double-layer film, increasing its hydrophobicity. When subjected to wear, the SA crystals on the surface of the double-layer film are fractured into debris-like abrasive particles, forming an optimal third-body of moderate shape and particle size, and imparting anti-wear and lubricating characteristics.

Piezoelectric properties of PZT by an ethylene glycol-based chemical solution synthesis

We have investigated a water-stable sol–gel method based on ethylene glycol as a solvent and bridging ligand for the synthesis of ferroelectric lead zirconate titanate in bulk and thin film forms. This method offers lower toxicity of the solvent, higher stability toward atmospheric moisture and a simplified synthetic procedure compared to traditional sol–gel methods. However, the piezoelectric properties of products produced using this method have yet to be systematically studied. We have measured the ferroelectric and piezoelectric properties and compared them to existing literature using different synthesis techniques. Ceramic pellets of Nb-doped lead zirconate titanate (PNZT) in the tetragonal phase were produced with high density and good piezoelectric properties, comparable to those reported in the literature and those found in commercial piezoelectric elements. In addition, a nine-layer thin film stack was fabricated by spin coating onto platinized silicon substrates. The films were crack-free and showed a perovskite grain structure with a weak (111) orientation. Piezoelectric measurements of the film showed a piezoelectric coefficient comparable to literature values and good stability toward fatigue.

Multi-layer thin-film deposition for high-performance X-ray field-emission characteristics

In this study, we developed a nanoscale emitter having a multi-layer thin-film nanostructure in an effort to maximize the field-emission effect with a low voltage difference. The emitter was a sapphire board on which tungsten–DLC multi-player thin film was deposited using PVD and CVD processes. This multi-layer thin-film emitter was examined in a high-vacuum X-ray tube system. Its field-emission efficiency according to the applied voltage was then analyzed.