Long-Term Operational Stability of Ta/Pt Thin-Film Microheaters: Impact of the Ta Adhesion Layer

Microheaters with long-term stability are crucial for the development of a variety of microelectronic devices operated at high temperatures. Structured Ta/Pt bilayers, in which the Ta sublayer ensures high adhesion of the Pt resistive layer, are widely used to create microheaters. Herein, a comprehensive study of the microstructure of Ta/Pt films using high-resolution transmission electron microscopy with local elemental analysis reveals the twofold nature of Ta after annealing. The main fraction of Ta persists in the form of tantalum oxide between the Pt resistive layer and the alumina substrate. Such a sublayer hampers Pt recrystallization and grain growth in bilayered Ta/Pt films in comparison with pure Pt films. Tantalum is also observed inside the Pt grains as individual Ta nanoparticles, but their volume fraction is only about 2%. Microheaters based on the 10 nm Ta/90 nm Pt bilayers after pre-annealing exhibit long-term stability with low resistance drift at 500 °C (less than 3%/month)

Control of Columnar Grain Microstructure in CSD LaNiO₃ Films

Conductive LaNiO3 (LNO) films with an ABO3 perovskite structure deposited on silicon wafers are a promising material for various electronics applications. The creation of a well-defined columnar grain structure in CSD (Chemical Solution Deposition) LNO films is challenging to achieve on an amorphous substrate. Here, we report the formation of columnar grain structure in LNO films deposited on the Si-SiO2 substrate via layer-by-layer deposition with the control of soft-baking temperature and high temperature annealing time of each deposited layer. The columnar structure is controlled not by typical heterogeneous nucleation on the film/substrate interface, but by the crystallites’ coalescence during the successive layers’ deposition and annealing. The columnar structure of LNO film provides the low resistivity value ρ~700 µOhm·cm and is well suited to lead zirconate-titanate (PZT) film growth with perfect crystalline structure and ferroelectric performance. These results extend the understanding of columnar grain growth via CSD techniques and may enable the development of new materials and devices for distinct applications

Roughness Factors of Electrodeposited Nanostructured Copper Foams

Copper-based electrocatalytic materials play a critical role in various electrocatalytic processes, including the electroreduction of carbon dioxide and nitrate. Three-dimensional nanostructured electrodes are particularly advantageous for electrocatalytic applications due to their large surface area, which facilitates charge transfer and mass transport. However, the real surface area (RSA) of electrocatalysts is a crucial parameter that is often overlooked in experimental studies of high-surface-area copper electrodes. In this study, we investigate the roughness factors of electrodeposited copper foams with varying thicknesses and morphologies, obtained using the hydrogen bubble dynamic template technique. Underpotential deposition (UPD) of metal adatoms is one of the most reliable methods for estimating the RSA of highly dispersed catalysts. We aim to illustrate the applicability of UPD of lead for the determination of the RSA of copper deposits with hierarchical porosity. To find the appropriate experimental conditions that allow for efficient minimization of the limitations related to the slow diffusion of lead ions in the pores of the material and background currents of the reduction of traces of oxygen, we explore the effect of lead ion concentration, stirring rate, scan rate, monolayer deposition time and solution pH on the accuracy of RSA estimates. Under the optimized measurement conditions, Pb UPD allowed to estimate roughness factors as high as 400 for 100 µm thick foams, which translates into a specific surface area of ~6 m2·g−1. The proposed measurement protocol may be further applied to estimate the RSA of copper deposits with similar or higher roughness

Hybrid Core–Shell Microparticles Based on Vaterite Polymorphs Assembled via Freezing-Induced Loading

The hybrid core–shell system was fabricated based on pre-synthesized vaterite microparticles and iron oxide nanoparticles applying two technical approaches: physical adsorption of the nanoparticles from a suspension at room temperature and a newly developed method of freezing-induced loading. A combination of transmission electron microscopy and X-ray diffraction paired with precision nanomanipulation allows us to analyze the inner structure of the hybrid system, indicating that both vaterite and calcite phases were covered by Fe3O4 shells. The freezing-induced loading was found to be more preferable due to the formation of the core–shell nanoparticles in a more stable polymorphic composition of calcium carbonate when compared to physical adsorption

Permeability of the Composite Magnetic Microcapsules Triggered by a Non-Heating Low-Frequency Magnetic Field

Nanosystems for targeted delivery and remote-controlled release of therapeutic agents has become a top priority in pharmaceutical science and drug development in recent decades. Application of a low frequency magnetic field (LFMF) as an external stimulus opens up opportunities to trigger release of the encapsulated bioactive substances with high locality and penetration ability without heating of biological tissue in vivo. Therefore, the development of novel microencapsulated drug formulations sensitive to LFMF is of paramount importance. Here, we report the result of LFMF-triggered release of the fluorescently labeled dextran from polyelectrolyte microcapsules modified with magnetic iron oxide nanoparticles. Polyelectrolyte microcapsules were obtained by a method of sequential deposition of oppositely charged poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) on the surface of colloidal vaterite particles. The synthesized single domain maghemite nanoparticles integrated into the polymer multilayers serve as magneto-mechanical actuators. We report the first systematic study of the effect of magnetic field with different frequencies on the permeability of the microcapsules. The in situ measurements of the optical density curves upon the 100 mT LFMF treatment were carried out for a range of frequencies from 30 to 150 Hz. Such fields do not cause any considerable heating of the magnetic nanoparticles but promote their rotating-oscillating mechanical motion that produces mechanical forces and deformations of the adjacent materials. We observed the changes in release of the encapsulated TRITC-dextran molecules from the PAH/PSS microcapsules upon application of the 50 Hz alternating magnetic field. The obtained results open new horizons for the design of polymer systems for triggered drug release without dangerous heating and overheating of tissues