Elucidation of Surface Nano-hillocks by Localized Plasma Expansion
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RESEARCH ARTICLE-PHYSICS
Elucidation of Surface Nano-hillocks by Localized Plasma Expansion A. A. Almaaz1 · W. M. Moslem1,2
· M. El-Metwally2
Received: 15 April 2020 / Accepted: 29 August 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract For the time being, the creation of surface nano-structures has become an important technological process which plays a paramount role in the electronic devices, as it has a very remarkable feature that they are used in etching without using chemicals. Irradiation of silicon oxide single crystal with slow highly charged ions can produce surface nano-hillocks. The formation mechanism of the created nano-hillocks is a topic of debate. One of the suggested formation mechanisms is a plasma expansion approach. The latter will be used to explain the creation of surface nano-hillocks in silicon oxide single crystal using a fully classical plasma model. For this purpose, classical hydrodynamic ion fluid equations along with Maxwellian or non-Maxwellian electrons distributions are solved numerically to obtain the expansion profiles of the number density, fluid velocity, and electrostatic potential. The relevance of different plasma parameters such as temperature and density ratios, superthermal, and non-extensive parameters is highlighted on the expansion profiles. Keywords Surface nano-hillocks · Plasma expansion · Silicon oxide single crystal
1 Introduction In 1954, Landau and Lifshits studied the formation of a highdensity and temperature plasma [1]. They used an optical device to irradiate a target; therefore, the electrons are heated and expanded toward the vacuum. Later, plasma expansion approach was used to study many subjects in plasma physics (see e.g., Refs. [2–6]). Plasma expansion was used to explain the formation of surface nano-structures which have been created in different materials. Many efforts have been made to create surface nano-structures by irradiation with slow highly charged ions (HCIs) as a useful nano-technological tool which has not any chemical treatment [7]. The size and shape of nano-structures depend on the kind and particles beam parameters [8–11]. During the interaction of SiO2 surface by HCIs, the electrons are heated and expanded toward
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W. M. Moslem [email protected] A. A. Almaaz [email protected] M. El-Metwally [email protected]
1
Department of Physics, Faculty of Science, Port Said University, Port Said 42521, Egypt
2
Centre for Theoretical Physics, The British University in Egypt (BUE), El-Shorouk City 43, Cairo, Egypt
the vacuum. The ions follow the electrons producing nanostructuring in the surface. As the electrons have lighter mass than ions, they throw off the created plasma bulk region. Therefore, an ambipolar electric field is formed that accelerates the positive ions resulting in the breaking of the chemical bonds and explosion into plasma cloud of energetic ions with high rate. Eventually, an outward pressure results which leads to plasma expansion. The size and shape of the created nano-struc
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