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European Microscopy Congress 2016: Proceedings || Microstructural evolution and thermal stability of nitride-based metal/semiconductor superlattices for thermoelectric and hard-coating applications
摘要： A detailed analysis on the quality and microstructure of various metal/semiconductor superlattices employing HR(S)/TEM (high-resolution (scanning)/transmission electron microscopy) imaging and energy dispersive x-ray spectroscopy (EDX) mapping on as-deposited and annealed samples is presented. Epitaxial metal/semiconductor superlattices are known to be promising candidates for compounds in electronic, photonic, and plasmonic devices, but are also of interest for applications as hard coatings, and in thermoelectric materials [1]. The crystalline quality of the superlattices, in terms of their defect density, phase purity, interface roughness, and stoichiometry of the individual layers, plays a crucial role with respect to the physical properties and thus the applicability of such superlattice stacks. It was recently shown that metal/semiconductor superlattices based on (Al,Sc)N as the semiconductor component can be grown epitaxially with low-defect densities by magnetron sputtering on [001]MgO substrates [2]. Phase formation and thermal stability studies of as-deposited and long-time annealed cubic TiN/(Al,Sc)N superlattices employing a combination of HR(S)/TEM and EDX mapping revealed intermixing of the TiN and (Al,Sc)N layers by interdiffusion of the metal atoms with increased annealing time [3]. Improved (Ti,W)N/(Al,Sc)N [4] and (Hf,Zr)N/ScN [5] superlattices were grown by magnetron sputtering and analyzed with various TEM methods, and their microstructural evolution as well as thermal stability becomes presented here. An example is show in Figure 1, which shows an overview of an improved cubic (Ti,W)N/(Al,Sc)N superlattice stack in cross-section STEM (a), and a typical HRTEM micrograph of the metal/semiconductor interface region, demonstrating the high epitaxial quality of the growth [4]. Figure 2 demonstrates the superior thermal stability of the (Zr,Hf)N- based systems as compared to previous TiN- based superlattices. EDX mapping at high-resolution before and after annealing at 950 °C for 120 hours reveals diffusion of the metal atoms in the TiN/AlScN system (b), while the Hf0.5Zr0.5N/ScN superlattice stays intact (d). All experiments were conducted at Link?ping’s image- and probe-corrected and monochromated FEI Titan3 60-300 microscope equipped with a Gatan Quantum ERS GIF, high-brightness XFEG source, and Super-X EDX detector, operated at 300 kV [6].
关键词： Nitrides,superlattices,EDX mapping
更新于2025-09-23 15:23:52
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Triple stimuli-responsive ZnO quantum dots-conjugated hollow mesoporous carbon nanoplatform for NIR-induced dual model antitumor therapy
摘要： Aiming at the inef?ciency and toxicity in traditional antitumor therapy, a novel multifunctional nanoplat-form was constructed based on hollow mesoporous carbon (HMC) to achieve triple stimuli response and dual model antitumor therapy via chemo-photothermal synergistic effect. HMC was used as an ideal nanovehicle with a high drug loading ef?ciency as well as a near-infrared (NIR) photothermal conversion agent for photothermal therapy. Acid-dissoluble, luminescent ZnO quantum dots (QDs) were used as the proper sealing agents for the mesopores of HMC, conjugated to HMC via disul?de linkage to prevent drug (doxorubicin, abbreviated as Dox) premature release from Dox/HMC-SS-ZnO. After cellular endocytosis, the Dox was released in a pH, GSH and NIR laser triple stimuli-responsive manner to realize accurate drug delivery. Moreover, the local hyperthermia effect induced by NIR irradiation could promote the drug release, enhance cell sensitivity to chemotherapeutic agents, and also directly kill cancer cells. As expected, Dox/HMC-SS-ZnO exhibited a high drug loading capacity of 43%, well response to triple stimuli and excellent photothermal conversion ef?ciency g of 29.7%. The therapeutic ef?cacy in 4T1 cells and multicellular tumor spheroids (MCTSs) demonstrated that Dox/HMC-SS-ZnO + NIR had satisfactory chemo-photothermal synergistic effect with a combination index (CI) of 0.532. The cell apoptosis rate of the combined treatment group was more than 95%. The biodistribution and pharmacodynamics studies showed its biosecurity to normal tissues and synergistic inhibition effect to tumor cells. These distinguished results indicated that the Dox/HMC-SS-ZnO nanoplatform is potential to realize ef?cient triple stimuli-responsive drug delivery and dual model chemo-photothermal synergistic antitumor therapy.
关键词： Chemo-photothermal synergistic therapy,Triple stimuli-responsive,Hollow mesoporous carbon nanoparticles,TEM-EDX mapping,ZnO quantum dots
更新于2025-09-19 17:13:59