اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدEffects of Strain and Film Thickness on the Stability of the Rhombohedral Phase of HfO2
56
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The discovery of ferroelectric polarization in HfO2-based ultrathin films has spawned a lot of interest due to their potential applications in data storage. Recently, a new R3m rhombohedral phase was proposed to be responsible for the emergence of ferroelectricity in the [111]-oriented Hf0.5Zr0.5O2 thin films, but the fundamental mechanism of ferroelectric polarization in such films remains poorly understood. In this paper, we employ density-functional-theory calculations to investigate structural and polarization properties of the R3m HfO2 phase. We find that the film thickness and in-plane compressive strain effects play a key role in stabilizing the R3m phase leading to robust ferroelectricity of [111]-oriented R3m HfO2.
قيم البحث
اقرأ أيضاً
We report on the behavior of Ge-Ge, Ge-Sn, Sn-Sn like and disorder-activated vibrational modes in GeSn semiconductors investigated using Raman scattering spectroscopy. By using an excitation wavelength close to E1 gap, all modes are clearly resolved
and their evolution as a function of strain and Sn content is established. In order to decouple the individual contribution of content and strain, the analysis was conducted on series of pseudomorphic and relaxed epitaxial layers with a Sn content in the 5-17at.% range. All vibrational modes were found to display the same qualitative behavior as a function of content and strain, viz. a linear downshift as the Sn content increases or the compressive strain relaxes. Simultaneously, Ge-Sn and Ge-Ge peaks broaden, and the latter becomes increasingly asymmetric. This asymmetry, coupled with the peak position, is exploited in an empirical method to accurately quantify the Sn composition and lattice strain from Raman spectra.
We present a segregrated strain model that describes the thickness-dependent dielectric properties of ferroelectric films. Using a phenomenological Landau approach, we present results for two specific materials, making comparison with experiment and
with first-principles calculations whenever possible. We also suggest a smoking gun benchtop probe to test our elastic scenario.
The quest towards expansion of the MAX design space has been accelerated with the recent discovery of several solid solution and ordered phases involving at least two MAX end members. Going beyond the nominal MAX compounds enables not only fine tunin
g of existing properties but also entirely new functionality. This search, however, has been mostly done through painstaking experiments as knowledge of the phase stability of the relevant systems is rather scarce. In this work, we report the first attempt to evaluate the finite-temperature pseudo-binary phase diagram of the Ti2AlC-Cr2AlC via first-principles-guided Bayesian CALPHAD framework that accounts for uncertainties not only in ab initio calculations and thermodynamic models but also in synthesis conditions in reported experiments. The phase stability analyses are shown to have good agreement with previous experiments. The work points towards a promising way of investigating phase stability in other MAX Phase systems providing the knowledge necessary to elucidate possible synthesis routes for MAX systems with unprecedented properties.
The electronic interconnections in the state-of-the-art integrated circuit manufacturing have been scaled down to the micron or sub-micron scale. This results in a dramatic increase in the current density passing through interconnections, which means
that the electromigration (EM) effect plays a significant role in the reliability of products. Although thorough studies and reviews of EM effects have been continuously conducted in the past 60 years, some parts of EM theories lack clear elucidation of the electric current-induced non-directional effects, including electric current-induced phase equilibrium changes. This review article is intended to provide a broad picture of electric current-induced lattice stability changes and to summarize the existing literature on EM-related phenomena, EM-related theoretical models, and relevant effects of the electroplastic (EP) effect in order to lead to a better understanding of electric current-induced effects on materials. This article also posits that EM is either part of the EP effect or shares the intrinsic electric current-induced plastic deformation associated with the EP effect. This concept appears to contribute to the missing parts of the EM theories.
Applying external strain is an efficient way to manipulate the site preference of dopants in semiconductors, however, the validity of the previous continuum elastic model for the strain influence on the doping forma- tion energy is still under debate
. In this paper, by combining quantum mechanical theoretical analysis and first-principles calculations, we show that if the occupation change of different orbitals caused by the strain is negligible, the continuum elastic model is valid, otherwise it will fail. Our theory is confirmed by first-principles calculation of Mn-doped GaAs system. Moreover, we show that under compressive strain the hole density, thus the Curie temperature TC can increase in Mn-doped spintronic materials.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
