Elasticity, electronic structure, and dielectric property of cubic SrHfO₃ from first‐principles

Abstract

Recently, SrHfO3 compound was proposed as a potential gate dielectric to fabricate metal–oxide–semiconductor field‐effect transistors (MOSFET) with equivalent oxide thickness (EOT) below 1 nm. Here we report the elasticity, electronic structure, and dielectric property of cubic SrHfO3 from first‐principle study based on the plane‐wave pseudopotential method within the local density approximation (LDA). The independent elastic constants of cubic SrHfO3 are derived from the derivative of total energy as a function of lattice strain. The elastic modulus is predicted from Voight‐Hill bounds. The Born effective charges, electronic dielectric tensors, long wavelength phonon frequencies, and LO–TO splitting of cubic SrHfO3 are computed by linear response with density functional perturbation theory (DFPT). The calculated lattice constant and bulk modulus of cubic SrHfO3 are in good agreement with the available experimental data and other theoretical results. Our results show cubic SrHfO3 is a ductile insulator with an indirect band gap of 3.74 eV (LDA value) and electric dielectric tensor of 4.43, Hf 5d states and O 2p states exhibit a strong hybridization, and cubic SrHfO3 can be mechanically stable. In addition, the phonon frequency of ‘soft mode' at zone‐center also agrees well with previous theoretical value. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermodynamic Stability and Vacancy Defect Formation Energies in SrHfO3

“…CBM is dominated by the Hf-5d orbitals with minor contribution coming from strontium 4s orbitals. The direct (Γ–Γ) band gap between the O-2p and Hf-5d orbital amounts to 3.776 eV, which is comparable with earlier DFT reports (3.67 eV and 3.74 eV). However, this band gap is underestimated as compared to the experimental value of 6.1 eV and will be taken into account during the computation of defect formation energies.…”

First-Principles Prediction of Two-Dimensional Electron Gas Driven by Polarization Discontinuity in Nonpolar/Nonpolar AHfO3/SrTiO3 (A = Ca, Sr, and Ba) Heterostructures

“…When the film thickness reaches the critical thickness, δ z increases drastically, and as n further increases, δ z changes slightly. The calculated Z i * are listed in Table and are in good agreement with the previous results from DFT calculations. , The estimated polarization in each AHfO 3 /SrTiO 3 HS model is shown in Figure c. The polarization is negligible until the AHfO 3 film thickness reaches its critical thickness.…”

First-principles study of structural and vibrational properties of SrHfO3 compared to SrZrO3

“…These modes correspond to rotations of oxygen octahedra as it will be discussed in the next Section. The present calculation of zone center phonons of cubic SrHfO 3 shows an unstable TO mode as an imaginary frequency mode with the value of 49i cm À1 , in agreement with what has been predicted by Stachiotti et al [9] (76i cm À1 ), Vali [10] (61i cm À1 ), Hou [11] (66.9i cm À1 ) and Sinha [19] (75i cm À1 ). This G 4 À unstable mode was not observed by Yangthaisong [20] who worked within the LDAÀPZ and GGAÀPBE.…”