Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0012037

Semiconducting Characteristics of Magnesium-Doped Al2O3 Single Crystals

M. Tardio·R. Ramirez·R. Gonzalez·Y. Chen·M. R. Kokta
View original source ↗Read source document ↗Export metadata ↓

Abstract

DC and AC electrical measurements were performed to investigate the electrical conductivity of alpha-Al2O3:Mg samples with different concentrations of [Mg]^0 centers .The concentration of [Mg]^0 centers was monitored by the opticalabsorption peak at 2.56 eV. At low electrical fields, DC measurements reveal blocking contacts. Steady electroluminescence is emitted at the negative electrodeindicating that the majority of carriers are holes. Low voltage AC measurements show that the equivalent circuit for the sample is the bulk resistance in series with the junction capacitance connected in parallel with a capacitance, which represents the dielectric constant of the sample. The values determined for the bulk resistance in both DC and AC experiments are in good agreement. The electrical conductivity of Al2O3:Mg crystals increases linearly with the concentration of [Mg]^0 centers, regardless of the amount of other impurities also present in the crystals, and is four times higher in the $c_{\perpendicular}$ than in the $c_{\parallel}$ direction. The conductivity is thermally activated with an activation energy of 0.68 eV, which is independent of: 1) the [Mg]^0 content, 2) the crystallographic orientation, and 3) the concentration of other impurities. These results favor the {\it small-polaron-motion} mechanism.

Explore related subjects

cond-mat.mtrl-scicond-mat.soft

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M. Tardio, R. Ramirez, R. Gonzalez, Y. Chen, M. R. Kokta. 2000-12-04. Semiconducting Characteristics of Magnesium-Doped Al2O3 Single Crystals. https://doi.org/10.1063/1.1384481

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Dynamic Peach-Koehler self-force, inertia, and radiation damping of a regularized dislocation

The elastodynamic Peach-Koehler force is computed for a fully-regularized straight dislocation with isotropic core in continuum isotropic elastic elasticity, in compact forms involving partial mass or impulsion functions relative to shear and compressional waves. The force accounts for both dynamic radiation damping and inertia. The expressions are valid indifferently for subsonic or supersonic velocities. Results are compared with the case of a flat-core dislocation of the Peierls-Eshelby type, for a motion of jump from rest to constant velocity. In the steady-state limit, the Lagrangian function relevant to expressing the force in the flat-core case must be replaced by a related but different function for the regularized dislocation. However, by suitably defining the regularizing dislocation width, the steady-state limits of the force for the fully-regularized and flat-core dislocations can be matched exactly.

cond-mat.mtrl-sci↗
arXiv2026

LightPFP: A Lightweight Route to Ab Initio Accuracy at Scale

Machine learning interatomic potentials (MLIPs) bridge the gap between quantum-mechanical accuracy and scalable molecular simulations. However, a fundamental trade-off persists: universal MLIPs (u-MLIPs) offer broad transferability but are computationally expensive, whereas task-specific MLIPs (ts-MLIPs) achieve high efficiency at the expense of costly DFT training data. Here we introduce LightPFP, a data-efficient knowledge distillation framework. Instead of relying on expensive DFT calculations, LightPFP constructs a distilled ts-MLIP by using a u-MLIP to generate high-quality, material-specific training data, while employing a pre-trained lightweight model to further improve data efficiency. Across diverse material systems, LightPFP reduces model development time by approximately three orders of magnitude compared with DFT-based workflows, while maintaining DFT-level accuracy. Combined with a LAMMPS/Kokkos inference backend, LightPFP achieves more than three orders of magnitude higher inference efficiency than u-MLIP baselines while enabling simulations of systems thousands of times larger. When the teacher exhibits systematic bias, LightPFP supports few-shot precision correction using as few as 10 high-accuracy DFT configurations, as demonstrated by reproducing MgO's experimental melting point. This u-MLIP-driven distillation establishes a scalable route to high-fidelity, data-efficient MLIPs, accelerating the pace of materials discovery and design.

cond-mat.mtrl-sci↗
arXiv2026

First-order polarization process as an alternative to antiferroelectricity

Antiferroelectrics generate significant interest since their polarization versus electric field (P-E) curves show typical double-hysteresis loops appealing for various applications. Unfortunately, antiferroelectrics are rare. In magnetic compounds, magnetization versus magnetic field (M-H) curves can show analogous double hysteresis loops not only in antiferromagnets but also in systems exhibiting field-induced first-order reorientation of the magnetization through a so-called first-order magnetization process. Here, we show that appealing double-hysteresis P-E loops can also appear from an unprecedented first-order polarization process. Focusing on non-polar CaTiO3, which can be turned ferroelectric under tensile strain, we study epitaxial thin films on differently-oriented NdGaO3 substrates using a combination of theoretical and experimental techniques. We uncover that a certain configuration exhibits double-hysteresis P-E loops that we rationalize from a field-induced abrupt rotation of the polarization. Such a first-order polarization process establishes a promising alternative pathway to achieve double hysteresis P-E loops appealing for practical applications.

cond-mat.mtrl-sci↗