The Effect of Y Doping on Monoclinic, Orthorhombic, and Cubic Polymorphs of HfO2: A First Principles Study

Abstract

HfO2 can assume different crystalline structures, such as monoclinic, orthorhombic, and cubic polymorphs, each one characterized by unical properties. The peculiarities of this material are also strongly related to the presence of doping elements in the unit cell. Thus, the present paper has the main purpose of studying and comparing twelve different systems characterized by diverse polymorphs and doping percentages. In particular, three different crystalline structures were considered: the monoclinic P21/c, the orthorhombic Pca21, and the cubic Fm3m phases of HfO2. Each one has been studied by using Y as a doping agent with three different contents: 0% Y:HfO2, 8% Y:HfO2, 12% Y:HfO2, and 16% Y:HfO2. For all the systems, density functional theory (DFT) methods based on PBE/GGA, and on the HSE hybrid functionals were used to optimize the geometry as well as to study their optical properties. Depending on the polymorphs, Y affects the formation energy in different ways and causes changes in the optical properties. When the percentage of Y did not exceed 12%, a stabilization of the cubic phase fraction and an increase of the dielectric constant was observed. Additionally, the calculated optical bandgap energies and the refractive index are examined to provide an overview of the systems and are compared with experimental data. The bandgaps obtained are in perfect agreement with the experimental values and show a slight increase as the doping percentage grows, while only minor differences are found between the three polymorphs in terms of both refractive index and optical band gap. The adopted first principles study generates a reasonable prediction of the physical-chemical properties of all the systems, thus identifying the effects of doping phenomena.

Adsorption of Polylactic-co-Glycolic Acid on Zinc Oxide Systems: A Computational Approach to Describe Surface Phenomena

“…The optimized structures of the polymorphs were then used to generate polymer–ZnO systems and to simulate the adsorption of PLGA and its mechanical properties. The single particle wave functions were expanded using the plane wave (PW) method in the PW basis set [ 25 ] for all the Zn, O, C, and H entities. Perdew–Burke–Ernzerhof’s (PBE) GGA density functional theory [ 26 ] was used for the electron exchange–correlation (xc) of energy.…”

Quantum tunnelling in hafnia-based metal-insulator-metal diodes: atomistic-to-continuum modelling approach and experimental validation

“…Since the introduction by Intel in a manufacturing process in 2007, HfO 2 is nowadays used as high-κ material, thus revealing a full CMOS (complementary metal-oxide-semiconductor) compatibility. HfO 2 has a relatively wide bandgap (5.6 eV) [11], large band offset with Si, i.e., less parasitic leakage, large coercive field (at least 1 MV cm −1 ), and medium-high permittivity. Moreover, the absence of an interfacial dead layer in HfO 2 makes this material a promising candidate in thin-film technology, unlike perovskites-based material, and the mid-range dielectric constant allows the switching at reasonable voltage values [12][13][14][15].…”

First principles study of WSe2 and the effect of V doping on the optical and electronic properties

“…A Quantum Atomistic ToolKit (ATK) atomic-scale modeling platform has been used to model all the WSe 2 structures and to perform all calculations. [26][27][28] Our work aims to understand how the properties of such an innovative material can be modified by the presence of a doping agent such as V, already discussed in the literature and previously tested experimentally. We aim to understand how different percentages of V can help to alter the geometric structure of the material and therefore influence its optical and electronic properties in order to improve its applicability in the new generation of devices and for applications in the field of THz telecommunications.…”