Publication

Band gaps and dielectric constants of amorphous hafnium silicates: A first-principles investigation

Alfredo Pasquarello
2007
Journal Articles

Abstract

Electronic band gaps and dielectric constants are obtained for amorphous hafnium silicates using first-principles methods. Models of amorphous (HfO2)(x)(SiO2)(1-x) for varying x are generated by ab initio molecular dynamics. The calculations show that the presence of Hf gives rise to low-lying conduction states which explain the experimentally observed nonlinear dependence of the band gap on hafnium content. Static dielectric constants are found to depend linearly on x, supporting recent experimental data. (c) 2007 American Institute of Physics.

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https://infoscience.epfl.ch/entities/publication/98eeb6bf-8027-447b-8e7d-c235c0f6a810

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Alfredo Pasquarello
2007
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/98eeb6bf-8027-447b-8e7d-c235c0f6a810

About this result

Related concepts (32)

Band gap

In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band.

Electronic band structure

In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called band gaps or forbidden bands). Band theory derives these bands and band gaps by examining the allowed quantum mechanical wave functions for an electron in a large, periodic lattice of atoms or molecules.

Direct and indirect band gaps

In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone. If the k-vectors are different, the material has an "indirect gap". The band gap is called "direct" if the crystal momentum of electrons and holes is the same in both the conduction band and the valence band; an electron can directly emit a photon.

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Band gaps and dielectric constants of amorphous hafnium silicates: A first-principles investigation

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