Dielectric response and transport properties of silicon films nano-textured by random voids
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Dielectric response and transport properties of silicon films nano-textured by random voids Mohamed Shaker Salem1,*, Gamal Madboly Naser1, and Abear Abdullah El-Gamal1,*
1
Physics Department, Faculty of Science, Cairo University, Giza 12613, Egypt
Received: 30 April 2020
ABSTRACT
Accepted: 18 September 2020
Silicon films decorated with random nano-voids and having variable porosities are produced by the electrochemical polarization of heavily doped singlecrystalline silicon substrates. Optical characterizations of the structure are investigated using the FTIR and photoluminescence measurements. The electrical conductivity, dielectric constant, and electric modulus are explored in the frequency range from 10 Hz to 10 MHz and in the temperature range from 300 to 475 K. The frequency-dependent conductivity is well agreed with the Jonscher’s power law. The temperature dependence of the dc conductivity is analyzed using Arrhenius relationship. The dielectric response of the films is influenced by the porosity and temperature. A dielectric relaxation process is observed with activation energy nearly equal to that of dc conduction. The relaxation time gets slightly longer as the porosity increases. A conduction mechanism based on the thermally activated jumps of electrons near the Fermi edge is proposed.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction Due to their outstanding mechanical and optical stabilities, silicon nano-architectures are of substantial interest in reducing the scale of integrated circuits and maintaining the high performance of the siliconbased devices. Bulk silicon has poor optical properties because of its indirect bandgap. Nano-structured silicon, on the other hand, has a large direct bandgap associated with the quantum confinement of carriers at small dimensions approaching Bohr radius. When the size of the silicon crystals is reduced, the electronic band structure of bulk silicon undergoes a
transition to a direct bandgap. A microscopic explanation of such a transition has been performed using ground-state density functional theory calculations of the electronic structure and absorption spectra of silicon nanostructures [1]. The presences of direct bandgap in silicon nanostructures makes them promising candidates for photonic and optoelectronic devices [2, 3]. Silicon nanostructures can be fabricated by various routes which display compatibility with the technology used for developing silicon-based devices. These methods include electron beam lithography [4], ion beam implantation [5], and plasma-assisted chemical vapor deposition [6]. One
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https://doi.org/10.1007/s10854-020-04511-3
J Mater Sci: Mater Electron
of the extremely simple and inexpensive approaches for fabricating an array of silicon nanostructures is the electrochemical anodization of silicon in hydrofluoric acid (HF) electrolyte [7, 8]. This process creates randomly distributed voids extending from the out
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