Excited Cr impurity states in Al<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>from constraint density functional theory

Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; T, Ito; Freeman, Arthur J

doi:10.1103/physrevb.87.205113

Cited by 22 publications

(11 citation statements)

References 32 publications

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“…∆SCF calculations of excited states for systems with reduced dimensions abound (e.g., Refs. [38][39][40]), and the ∆SCF method as implemented in the ABINIT code [41] is employed to predict structural effects of direct optical transitions at the valley edges of ferroelectric SnS and SnSe monolayers here. Calculations were performed with GBRV projected-augmented-wave [42] pseudopotentials [43] of the PBE type [44], which are known to underestimate the electronic band gap.…”

Section: Görling Formulated the Interacting Photoexcitedmentioning

confidence: 99%

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

et al. 2017

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Photostriction is predicted for SnS and SnSe monolayers, two-dimensional ferroelectrics with rectangular unit cells (the lattice vector a1 is larger than a2) and an intrinsic dipole moment parallel to a1. Photostriction in these two-dimensional materials is found to be related to the structural change induced by a screened electric polarization in the photoexcited electronic state (i.e., a converse piezoelectric effect) that leads to a compression of a1 and a comparatively smaller increase of a2 for a reduced unit cell area. The structural change documented here is ten times larger than that observed in BiFeO3, making monochalcogenide monolayers an ultimate platform for this effect. This structural modification should be observable under experimentally feasible densities of photexcited carriers on samples that have been grown already, having a potential usefulness for light-induced, remote mechano-opto-electronic applications.A truly novel opto-mechanical coupling in twodimensional (2D) ferroelectric materials awaits to be discovered.Photostriction -the creation of nonthermal strain upon illumination [1-4]-has been welldocumented in three-dimensional ferroelectrics such as SbSI [5] and BiFeO 3 [6,7]. It has been suggested to be driven by the large voltage build-up caused by a photovoltaic effect and the resulting converse piezoelectricity [8], and it may be useful for applications such as remotely-switchable memory devices [9] and lightinduced actuators [10]. The earliest studied photostrictive material, SbSI, transitions from a ferroelectric onto a paraelectric at a critical temperature T c < 300 K. As photostrictive effects are larger in the ferroelectric phase, T c can be increased above 300 K on SbSI ceramics which have smaller domain sizes and display a non-uniform stoichiometry nevertheless. The photostriction response time increases with sample thickness due to a reduced penetration depth, being a few seconds on bulk samples [5]. On the other hand, ferroelectric films show photostriction within a few picoseconds [11][12][13][14][15], and even when the photoexcited electron-hole pair is localized [16,17].The growing interest on the interactions of light with 2D materials [18-21] makes a study of illumination leading to non-trivial structural deformations an interesting and timely endeavor. As long as a photoexcited state induces some amount of charge redistribution -which is a quite reasonable physical assumption-any material is expected to change shape as the structure is let to relieve the stress induced by the photoexcited carriers. Here, the surprising result is the rather large magnitude of such structural change for 2D ferroelectrics, that originates from an inverse piezoelectric effect upon illumination.Two-dimensional ferroelectrics in the group IV monochalcogenide family (GeS, GeSe, SnS, SnSe, among others) [22][23][24][25][26][27][28][29][30][31] undergo a ferroelectric-to-paraelectric transition with a transition temperature that is tunable by atomic number [25]. Following the numerical approach...

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Section: Görling Formulated the Interacting Photoexcitedmentioning

confidence: 99%

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

et al. 2017

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“…[15][16][17][18] Generally, Cr 3+ with 3d 3 electron configuration exhibits a broad emission band (650~1600 nm) ascribing to the 4 T 2 → 4 A 2 transition, or a narrow emission band (~700 nm) due to the 2 E→ 4 A 2 radiation, which strongly depends on the crystal-field environment of the host lattices. In the intermediate or high-strength crystal filed, such as in ruby and alexandrite, 19, 20 2 E is the lowest excited state and the transition of 2 E→ 4 A 2 is doubly forbidden by parity and spin, which shows a long decay lifetime; while in a low-strength crystal field, 4 T 2 is the lowest excited state and the transition of 4 T 2 → 4 A 2 is spin-allowed, which results in a short decay lifetime. As a consequence, significant variety in temperature-dependent lifetime can be expected and a useful level control is made possible by modifying the crystal-field strength via the variation of the host material.…”

Section: Introductionmentioning

confidence: 99%

Dual-Phase Glass Ceramic: Structure, Dual-Modal Luminescence, and Temperature Sensing Behaviors

Chen

Wan

Zhou

et al. 2015

ACS Appl. Mater. Interfaces

260

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Yb(3+)/Er(3+)/Cr(3+) triply doped transparent bulk glass ceramic containing orthorhombic YF3 and cubic Ga2O3 nanocrystals was fabricated by a melt-quenching route to explore its possible application in optical thermometry with high spatial and temperature resolution. It was experimentally observed that Yb(3+)/Er(3+) ions incorporated into the precipitated YF3 nanophase, while Cr(3+) ions partitioned into the crystallized Ga2O3 nanophase after glass crystallization. Importantly, such spatial isolation strategy efficiently suppressed adverse energy transfer among different active ions. As a consequence, intense green anti-Stokes luminescence originated from Er(3+): (2)H11/2,(4)S3/2 → (4)I15/2 transitions, and deep-red Stokes luminescence transitions assigned to Cr(3+): (2)E → (4)A2 radiation were simultaneously realized. Impressively, the intermediate crystal-field environment for Cr(3+) in Ga2O3 made it possible for lifetime-based temperature sensing owing to the competition of radiation transitions from the thermally coupled Cr(3+) (2)E and (4)T2 excited states. In the meantime, the low-phonon-energy environment for Er(3+) in YF3 was beneficial for upconversion fluorescence intensity ratio-based temperature sensing via thermal population between the (2)H11/2 state and (4)S3/2 state. The Boltzmann distribution theory and the two-level kinetic model were adopted to interpret these temperature-dependent luminescence of Er(3+) and Cr(3+), respectively, which gave the highest temperature sensitivities of 0.25% K(-1) at 514 K for Er(3+) and 0.59% K(-1) at 386 K for Cr(3+).

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“…Previous studies concerning the defect structure of sapphire and other polymorphs of Al 2 O 3 have been essential in understanding its optical properties and methods to optimise its functionality. [4][5][6][7][8][9] These studies, however, have not connected the multiple optical processes that occur within and between these cation impurities in a complete analysis.…”

Section: Introductionmentioning

confidence: 99%

Defect chemistry of Ti and Fe impurities and aggregates in Al₂O₃

et al. 2014

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We report a theoretical evaluation of the properties of iron and titanium impurities in sapphire (corundum structured α-Al2O3). Calculations using analytical force fields have been performed on the defect structure with the metals present in isolated, co-doped and tri-cluster configurations. Crystal field parameters have been calculated with good agreement to available experimental data. When titanium and iron are present in neighbouring face and edge-sharing orientations, the overlap of the d-orbitals facilitates an intervalence charge transfer (FeIII/TiIII → FeII/TiIV) with an associated optical excitation energy of 1.85 eV and 1.76 eV in the respective configurations. Electronic structure calculations based on density functional theory confirm that FeIII/TiIII is the ground-state configuration for the nearest-neighbour pairs, in contrast to the often considered FeII/TiIV pair. Homonuclear intervalence charge transfer energies between both FeIII/FeII and TiIV/TiIII species have also been calculated, with the energy lying in the infra-red region. Investigation of multiple tri-clusters of iron and titanium identified one stable configuration, TiIII–(TiIV/FeII), with the energy of electron transfer remaining unchanged

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Excited Cr impurity states in Al2O3from constraint density functional theory

Cited by 22 publications

References 32 publications

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

Dual-Phase Glass Ceramic: Structure, Dual-Modal Luminescence, and Temperature Sensing Behaviors

Defect chemistry of Ti and Fe impurities and aggregates in Al₂O₃

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Excited Cr impurity states in Al2O3from constraint density functional theory

Cited by 22 publications

References 32 publications

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

Photostrictive Two-Dimensional Materials in the Monochalcogenide Family

Dual-Phase Glass Ceramic: Structure, Dual-Modal Luminescence, and Temperature Sensing Behaviors

Defect chemistry of Ti and Fe impurities and aggregates in Al2O3

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Product

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Defect chemistry of Ti and Fe impurities and aggregates in Al₂O₃