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Etching
Published in Eiichi Kondoh, Micro- and Nanofabrication for Beginners, 2021
The term ‘remote plasma’ is used for plasma techniques that do not use the substrate/workpiece bias. The bombardment by ions from the plasma is suppressed (the ion incidence due to the intrinsic voltage difference between the surface and the plasma—sheath potential—cannot be eliminated but it is much gentler than the intentional negative biasing), which allows minimizing the physical effects to etching. This method is called chemical dry etching (CDE) in a narrow sense, and is sometimes called after-glow etching, although this definition is somewhat less rigorous.
Cleaning of Organic Objects and Materials
Published in Radko Tiňo, Katarina Vizárová, František Krčma, Milena Reháková, Viera Jančovičová, Zdenka Kozáková, Plasma Technology in the Preservation and Cleaning of Cultural Heritage Objects, 2021
Radko Tiňo, Katarina Vizárová, František Krčma, Milena Reháková, Viera Jančovičová, Zdenka Kozáková
Other alternative methods include low-pressure plasma and laser cleaning. However, their efficiency is limited (Grieten et al., 2017). The corrosion removal was accompanied by sputtering by the collision of ions against the original surface of the daguerreotype. The sputtering results in optical changes, including permanent matting effect (Daniels, 1981; Golovlev et al., 2000; Golovlev et al., 2003; Turovets et al., 1998). The use of non-thermal remote atmospheric plasma cleaning was introduced as a new method for corrosion removal (Boselli et al., 2016; Siliprandi 2007). Boselli (M. Boselli et al., 2016) used both a commercial plasma jet source (kINPen 09, Neoplas Tools GmbH) and a specially designed DBD plasma source operated within a controlled volume at atmospheric pressure. The argon–hydrogen gas mixture (hydrogen content: 35% vol.) was used to remove corrosion products, without immersion of the substrate in solvents or chemicals. The concept of the remote plasma treatment is that gas is channeled through the source and exits through a nozzle and indirectly treats the surface in the afterglow (Grieten et al., 2017). Treatment in the afterglow eliminates the reactive species such as ions, which are considered the main cause of the non-selective physical etching of the surface by low-pressure plasmas, from the interaction volume (Grieten et al., 2017). As there is no mechanical contact with the surface of the daguerreotype, the risk of mechanical damage is significantly reduced as well. Moreover, plasma cleaning is considered an eco-sustainable method, compared to conventional solvent-based conservation-restoration techniques. Grieten et al., 2017 at all evaluated the plasma cleaning at three different levels. They focused on the chemical and physical differences introduced by the plasma jet afterglow treatment. The selectivity of remote plasma treatment was proved, as only the oxidized species formed during the corrosion process have been transformed while the original surface remained unaffected. This resulted in a partial regeneration of the original image. The effects of plasma treatment are influenced by the exact chemical build-up of the daguerreotype, which depends on the exact technological procedure used by the author. A different approach may result in different types of corrosion products and influence the thickness of the corrosion layer as well. Atmospheric plasma treatment is a potential alternative for currently used cleaning techniques and that it is worth further exploring. The long-term stability of daguerreotypes treated with a plasma afterglow was not studied, and this is a significant evaluation criterion for the conservation–restoration community. The corrosion process results in a displacement of atoms, and any kind of cleaning technique cannot recover the original position of these atoms. While some techniques can remove these displaced atoms, atmospheric plasma only changes the oxidation state of atoms by (partially) reducing corrosion products to their metallic state. The claims were supported by results from STEM, SEM, EELS, EDX and XAFS (Grieten et al., 2017).
Hydrogen-terminated diamond MOSFETs on (0 0 1) single crystal diamond with state of the art high RF power density
Published in Functional Diamond, 2022
Cui Yu, Chuangjie Zhou, Jianchao Guo, Zezhao He, Mengyu Ma, Hao Yu, Xubo Song, Aimin Bu, Zhihong Feng
Some promising results have realized on H-diamond FETs [9–12]. Jingu et al. developed a remote plasma processing method [13] to get H-diamond surface after source and drain electrodes lithography, and Imanishi et al. got a maximum output power density of 3.8 W/mm at 1 GHz for the diamond metal-oxide-semiconductor FETs (MOSFETs) using this technique on a (1 1 0) preferential polycrystalline diamond [9]. Kudara et al. also obtained output power densities of 2.5 W/mm at 1 GHz, and 1.5 W/mm at 3.6 GHz for the diamond MOSFETs with 200 nm Al2O3 gate dielectric on a (1 1 0) preferential polycrystalline diamond [14]. Kudara et al. fabricated diamond MOSFETs with regrown P++-diamond layers as the source and drain regions on the chemical vapor deposition (CVD) IIa (1 1 1) single crystal diamond substrate [15]. A current density of 1 A/mm and an output power density of 3.6 W/mm at 1 GHz were obtained.