HfO2 Thin Film for Microelectromechanical Systems Application
Iniewski Krzysztof in Integrated Microsystems, 2017
The surface damage inherent in a sputtering PVD process and device morphology inherent to the scaling process generally rule out PVD deposition approaches. Within all the manufacturing options, chemical vapor deposition-based methods, ALD and MOCVD, draw the highest industrial interest for deposition of high-k dielectrics. ALD approaches appear to be promising, because of its precision in layer growth and high layer uniformity in large deposition areas such as 300 mm wafer technology. However, the generation of polycrystalline dielectrics in the manufacturing environment may cause high leakage currents and a possible diffusion path for dopants along its grain boundaries. Another major disadvantage of ALD is the long processing time, which makes it an expensive tool to operate. Besides, the demand for complex precursors decreases its flexibility for using in material research. The other technique is MOCVD, because of its good film conformality and control on deposition rates. However, choice of the precursor, deposition temperature, and incorporation of carbon impurities are major concerns in this technique.
Introduction to Report
Kitsakorn Locharoenrat in Research Methodologies for Beginners, 2017
So far, different methods have been carried out for such films, such as, halide vapor phase epitaxy (HVPE) [3], metal-organic chemical vapor deposition (MOCVD) [4], pulsed laser deposition (PLD) [5], molecular beam epitaxy (MBE) [6], single ion beam sputtering (SIBS) [7], and double ion beam sputtering (DIBS) [8]. However, they have drawback because the specimens have been prepared under high temperature conditions. This might lead to degradation of the substrates and the films during deposition. Therefore, low temperature preparations of the AlN films are more attractive and very important. In this contribution, we then introduce radio frequency reactive magnetron sputtering to fabricate the AlN films under low temperature conditions.
Toxicity Analysis of Ag and Au Nanoparticles
Suresh C. Pillai, Yvonne Lang in Toxicity of Nanomaterials, 2019
Thin films of Ag, Au, TiO2-Ag, and TiO2-Au prepared on different substrates (glass, plates, textiles, and polymers) is an emerging area of interest with respect to antibacterial surfaces [1,2]. Commercial products based on the traditional sol-gel method are known for some decades. Ag, Au, TiO2, ZnO, ZrO2, and many other thin films were prepared on heat-resistant substrates using the sol-gel method [3–5]. Nevertheless, the thickness of these coatings is not reproducible, the coatings were not mechanically stable, and they have exhibited low adhesion to the substrate. Colloid depositions on substrates require a temperature of a few hundred degrees for an adequate adherence to the selected substrate. Many research groups reported the preparation of Ag thin films by chemical vapour deposition or physical vapour deposition. These last two methods lead to controllable thin film growth, high reproducibility, and mechanical stability [23,24]. The renewed interest in silver-based antibacterial solutions is due to the decline of antibiotic efficacy together with the emergence of stable coated surfaces killing bacteria by contact. Contact killing was defined by Espirito Santo et al. (2011) as damages on the cell-wall membrane occurring after the contact of the microbe with a surface, plus an increase of the intracellular ion content [25]. These films/coatings have been shown to kill bacteria in the minute range without loss of the content (TiO2, Ag, Au) [26]. Ballo et al. reported sputtered Ag and Cu on flexible substrates showing quasi-instantaneous pathogens inactivation [27]. The prepared thin films were reported to kill Staphylococcus aureus. The latter microorganism represents the second pathogen causing hospital-acquired infections (HAIs) as reported by the Centers for Disease Control and Prevention, 2011–2014 [28].
Characterization, antibacterial, total antioxidant, scavenging, reducing power and ion chelating activities of green synthesized silver, copper and titanium dioxide nanoparticles using Artemisia haussknechtii leaf extract
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Mehran Alavi, Naser Karimi
In order to prepare metallic NPs, several methods have been applied. For example, using a various chemicals as precursors and more amounts of surfactants as stabilizing agents is one of the common methods in NPs synthesis. In this way, there are the different preparation methods in the synthesis of metallic NPs from several materials [4]. Today, the way of NP synthesis with a small size is important part of nanotechnology function [5]. There are several ways for NPs synthesis such as chemical, physical, biological and enzymatic methods. Physical vapour deposition (PVD), atomic layer deposition, spay pyrolysis, ball milling, laser desorption, lithographic methods, layer by layer growth, ultra-thin films and molecular beam epitaxy are some examples of physical methods. Also, chemical methods include chemical vapour deposition (CVD), wet chemical and co-precipitation. In contrast to these two basic methods, biological synthesis ways of NPs have less energy need and are eco-friendly methods [6].
Green nanotechnology-based drug delivery systems for osteogenic disorders
Published in Expert Opinion on Drug Delivery, 2020
David Medina-Cruz, Ebrahim Mostafavi, Ada Vernet-Crua, Junjiang Cheng, Veer Shah, Jorge Luis Cholula-Diaz, Gregory Guisbiers, Juan Tao, José Miguel García-Martín, Thomas J. Webster
Consequently, one of most critical problems with NMs-based drug delivery approaches is the production of delivery vehicles. Traditional synthesis of NMs relies upon physicochemical processes, which are hindered by several drawbacks – such as harsh processing conditions, production and release of toxic by-products or lack of desired biocompatibility – leading to unwanted cytotoxic profiles upon contact with biological tissue [91–93]. Furthermore, unique instrumentation is often required for the production of the carriers, such as chemical vapor deposition (CVD) chambers or ultra-high vacuum systems. Additional drawbacks are observed during the aggregation of NPs after synthesis, which can impede both the purification and characterization of the systems, as well as compromise the effectiveness of the newly-synthesized NMs (for biomedical applications) [94]. As a consequence of the synthesis method, some of these NMs might degrade once released in the body, leading to an unwanted production of toxic degradation products that may be harmful to body tissues, or locally lower the pH. Therefore, using these materials in a large dose could prove defiant. Moreover, due to the complexity of bone tissue, most of the drug delivery systems exhibit poor targeting efficiency and uncontrolled drug release. Therefore, to increase the efficiency of therapy and improve its biomedical outcomes, new targeted drug delivery systems have been intensively pushed forward as potential strategies, avoiding the limitations aforementioned.
Modeling the antifouling properties of atomic layer deposition surface-modified ceramic nanofiltration membranes
Published in Biofouling, 2022
Welldone Moyo, Nhamo Chaukura, Machawe M. Motsa, Titus A. M. Msagati, Bhekie B. Mamba, Sebastiaan G. J. Heijman, Thabo T. I. Nkambule
Surface modifications such as pore size tuning are important for engineering the selectivity and flux of membranes. Commonly used modification methods include electroless gold deposition and polymer grafting (Sun et al. 2013; Mustafa et al. 2016). However, these methods are laborious, time consuming and involve the use of hazardous chemicals, hence their application is limited (Sun et al. 2013). Vapor deposition techniques such as physical vapor deposition (PVD), chemical vapor deposition (CVD) and atomic layer deposition (ALD) offer better alternatives for surface and pore size modification because they are not specific to the chemistry of the substrate material (Kim and Oh 2014). Moreover, the thickness of the coating can be manipulated over a wide range (Kim and Oh 2014).