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Methods of Thin Film Deposition
Published in Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu, Thin Film Coatings, 2022
Fredrick Madaraka Mwema, Tien-Chien Jen, Lin Zhu
Atomic layer deposition (ALD) is a gas phase thin film deposition method, which is based on sequential, self-limited, and surface-controlled reactions. In this process, two or more reactants, known as precursor chemicals, each consisting of different chemical compositions of the desired thin film material, are introduced onto the surface of the substrate one at a time. In this process, each precursor is introduced into the reaction chamber and allowed to saturate (this means that the precursor reacts or consumes all the active sites of the substrate) on the surface of the substrate to form a monolayer of material. Most of the ALD systems utilise inert gases as carriers of the precursors during the thin film deposition process. In most cases, nitrogen gas is used as the carrier gas, and it is mostly maintained at the pressure of about 1 mbar.
2 Synthesis
Published in Yi Long, Yanfeng Gao, Vanadium Dioxide-Based Thermochromic Smart Windows, 2021
Shancheng Wang, Dimitra Vernardou, Charalampos Drosos, Yi Long
Atomic layer deposition (ALD) is consider a special type of CVD technique due to its unique character. Different from other CVD techniques, the precursor of ALD has to be introduced into the reaction chamber separately due to its self-limited reaction [12]. The self-limited growth is the core of ALD. Under this condition, the amount of thin film deposited on the substrate is fixed (theoretically one atomic layer per deposition). Because of its ability to precisely control the film thickness, ALD is able to form a very high-quality thin film. However, the reaction cycle must be repeated several times to deposit a thicker film, which makes ALD a slow and high-cost CVD technique.
Nanostructure Thin Films: Synthesis and Different Applications
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
Ho Soon Min, Debabrata Saha, J.M. Kalita, M.P. Sarma, Ayan Mukherjee, Benjamin Ezekoye, Veronica A. Ezekoye, Ashok Kumar Sharma, Manesh A. Yewale, Ayaz Baayramov, Trilok Kumar Pathak
Over the past two decades, atomic layer deposition (ALD), which is a unique modification of the conventional chemical vapor deposition (CVD) technique, has emerged as a promising method to grow metal oxides, nitrides, sulfides, selenides, tellurides, and pure metals [Riikka and Puurunena, 2005; George, 2010]. Thin-film deposition in ALD relies on the alternate exposure of precursors separated by an inert gas purging step [Riikka, 2005; George, 2010]. The complementary and self-limiting surface chemical reactions during film growth provide atomic level control over film thickness and uniformity over a large deposition area [Riikka, 2005; George, 2010]. In addition, ALD offers a number of industrially and technologically important characteristics, which include excellent conformal depositions on high aspect ratio structures, easy thickness control, pinhole-free dense coatings, and relatively low deposition temperature [Riikka, 2005; George, 2010].
Experimental investigation of the EDM tools coated with nano-alumina film
Published in Surface Engineering, 2023
Shu-Yu Gui, Hu Gong, Yi-Jia Sun, Chong Feng
Currently, insulating film coating on electrodes has been used in some fields [19,20]. Common coating methods include sputtering [21], chemical vapour deposition [22], atomic layer deposition [23] and others. Among other methods suitable for modifying surface properties, ALD, in particular, enables dense coating to grow on substrates with nanometer precision [24]. ALD can meet the structure of large aspect ratio and complex surface due to its atomic-level thickness and high conformality with the coating surface. Industrial applications of ALD include Micro-Electro-Mechanical System (MEMS), thin film magnetic heads, optoelectronic devices, etc. [25]. Al2O3 is a commonly used insulating material and many scholars have studied the characteristics of Al2O3 films deposited by ALD. Kukli et al. [24] proved that Al2O3 coatings of nm thickness by ALD method can provide a certain insulating effect and enhance the surface hardness. Huang et al. deposited Al2O3 film on 925 silvers by ALD to enhance its anti-tarnish performance and anti-scratch performance [26].
Influence of ALD-Al2O3 film on anti-scratch and anti-tarnish of silver
Published in Surface Engineering, 2021
Jiankang Huang, Xiang Yu, P. W. Shum, Zhifeng Zhou, Yijie Ma
Sterling silver (925 silver) is the mainstream material in the fashion jewellery market, with an annual demand of over 5 million kg [1], but suffers from tarnish and scratches during usage. The exposure to environments that contain sulphur compounds (such as sweat) makes the silver surface susceptible to tarnishing [2], and scratches always appear on its surface due to its soft texture. This may provoke the loss of the lustre of silver ornaments, which might be critical for silver cultural relics [3, 4]. Currently, available protection methods are precious metal films prepared by electrodeposition [5], metal oxide films prepared by physical vapour deposition (PVD) [6], and nitrocellulose lacquers [7]. However, these approaches have limitations: electrodeposition is expensive and may lead to opacity, PVD films are prone to defects like pores and discontinuities [8, 9], and nitrocellulose lacquers suffer from difficulties in achieving a uniform film. Nano Al2O3 films prepared by atomic layer deposition (ALD) technique are good candidates to overcome these hurdles [10, 11]. Based on sequential and self-limiting nature, ALD can also provide atomic-level control of film thickness and allow for conformal deposition on complex shapes. The deposition of Al2O3 films by the ALD technique on the silver surface enhances the resistance to tarnishing and scratching, while being accompanied by the inevitable colour difference, which is closely related to the film thickness.
Medicinal stability of vitamin C coated with TiO2 by ALD
Published in Particulate Science and Technology, 2018
M. J. Haghshenas-Lari, N. Mostoufi, R. Sotudeh-Gharebagh
Few researchers have used the ALD method in pharmaceutical industries. ALD, unlike chemical vapor deposition (CVD), has self-limiting surface reactions that can produce high-quality thin films coated on surfaces. Also, in the CVD process, side reactions occur whose products are not acceptable to be found in drugs. Another method of coating is the sol–gel method, which is not feasible for drugs (like vitamin C) because the drug is soluble in the solvent and becomes decomposed. Therefore, the ALD, as a new method, was investigated in the present work and it can be further applied in the pharmaceutical industries. The aim of this study was to investigate the coating of vitamin C powder with TiO2 in a fluidized-bed reactor by the ALD method. The effects of TiCl4 injection time, regime of fluidization and temperature on the loading of TiO2 and stability of the coated vitamin C against temperature and humidity were also investigated. Drug stability in humidity and high-temperature condition are important in pharmacy. TiO2 is a stable, colorless, odorless and harmless product to the human body, which makes it a good candidate for stabilizing of vitamin C. Therefore, in the present work, vitamin C was coated by TiO2 to investigate its effect on the stability of this material.