Large disparity between optical and fundamental band gaps in layered 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>In</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Se</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Li, Wei; Sabino, Fernando P.; Lima, Felipe Crasto de; Wang, Tianshi; Miwa, R. H.; Janotti, Anderson

doi:10.1103/physrevb.98.165134

Cited by 52 publications

(50 citation statements)

References 51 publications

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“…By increasing the thickness of β′-In 2 Se 3 film, the valence band (VB) gradually shifts to higher energy while the conduction band (CB) oppositely moves toward lower energy, resulting in a decreased band gap size of 1.87 and 1.68 eV, respectively, for 2 and 3 QL surface. Such an inverse thickness-dependence of electronic properties is in accordance with previous results, [32][33][34] but the band gap of single QL β′-In 2 Se 3 films has not been reported in experiment so far. The tendency of increased band gap in thinner films can be understood in the framework of quantum confinement effect and electron correlations.…”

Section: Resultssupporting

confidence: 92%

Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

et al. 2021

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BiFeO 3 ). [8,9] The polarization instability with depolarization field in ultrathin ferroelectrics thus critically limit their applications in nanoelectronics. [10] With the help of strong anisotropy and lower free carrier density, 2D vdW materials and heterostructures may overcome these obstacles, as demonstrated in CuInP 2 S 6 , [11] WTe 2 , [12] MoTe 2 . [13] and SnSe. [14] 2D ferroelectricity has been established as an advantageous property that inspires broad applications in high-density capacitors, piezoelectric sensors, and field effect transistors. [15] As a typical representative of III-VI semiconductor, a branch of In 2 Se 3 -based vdW family has been theoretically predicted [16] and experimentally verified [17][18][19] to host intrinsic room-temperature ferroelectricity down to the 2D limit, where reversible spontaneous electric polarization is expected in both out-of-plane and in-plane orientations. For the polymorphic structure of bulk In 2 Se 3 , there exist about five stable phases at ambient pressure: α-, β-, γ-, δ-, and κ-In 2 Se 3 , among which only the α and β phases can be stabilized in nature as vdW materials that are easily exfoliated or synthetized into thin films. [20] Within a primitive unit cell (UC), both αand β-In 2 Se 3 are constituted of bonded quintuple layer (QL) in a sequence of Se-In-Se-In-Se, but vertically stack in different orders. While α-In 2 Se 3 has a zincblende crystal structure and possesses outof-plane ferroelectricity with dipole locking in both bulk and nanoflake forms, [18,19,21,22] there is still no consensus on the precise alignments of the atomic layers in β-In 2 Se 3 . [23][24][25] Theoretically speaking, the pristine β-In 2 Se 3 is arranged in a facecentered cubic (fcc) order with a metastable nature, and can easily evolve into an unsymmetric fcc′ structure (β′-In 2 Se 3 ) by slightly shifting the central Se layer in horizontal direction away from the ideal fcc positions, [16] as compared in Figure 1a,b. The total energy of β′-In 2 Se 3 is only 0.057 eV per UC higher than α-In 2 Se 3 , however, its ferroelectricity is much more complex, partially due to its structural ambiguity and environmentdependent phase transition among variant metastable states. [16] Robust ferroelectricity has been experimentally confirmed in both αand β′-In 2 Se 3 down to the single layer limit and can survive at room temperature. [23,26] However, very recent optical and electron microscopy measurements argue that β′-In 2 Se 3 is in an in-plane anti-ferroelectric order that is featured by anisotropic nanostriped surface morphology. [24] Moreover, a 2D ferroelectrics have received wide interest due to the remarkable quantum states of emerging physics at reduced dimensionality, associated with their exotic properties in high-performance and nonvolatile functional devices. Here, by combing molecular beam epitaxy synthesis and scanning tunneling microscopy characterization, two metastable phases of layered In 2 Se 3 films: β′and β*-In 2 Se 3 are reported, which develop different types of in...

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Section: Resultssupporting

confidence: 92%

Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

et al. 2021

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“…In 2 Se 3 has four polymorphs (a, b, d, g phase). 151 Its 2D structures (a, b, d phase) are composed of Se-In-Se-In-Se layers, but have different stacking orders. These 2D structures are promising for random access memory, thermoelectrics, and photodetectors.…”

Section: Nismentioning

confidence: 99%

Atomic Layer Deposition of Two-Dimensional Layered Materials: Processes, Growth Mechanisms, and Characteristics

Cai

Han

Wang

et al. 2020

Matter

119

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Since the discovery of graphene, there has been an ever-increasing interest in two-dimensional (2D) layered materials with exceptional properties. To this end, a variety of synthesis methods have been developed. However, it is still challenging to produce large-scale high-quality single-crystalline 2D materials. In this regard, atomic layer deposition (ALD) has recently shown great promise and has stimulated more and more research efforts, ascribed to its unique growth mechanism and distinguished capabilities to achieve nanoscale films with excellent uniformity, unrivaled conformality, and atomic-scale controllability. This review comprehensively summarizes recent progress on ALD for 2D atomic sheets, including 25 different materials and more than 80 ALD processes. This work highlights different technical routes to ALD, their precise controllability, and their underlying principles for 2D materials. It is expected that this work will help boost more research efforts for controllable growth of high-quality 2D materials via ALD.

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“…Importantly, fundamental electronic properties in these phases of In2Se3 such as the carrier effective mass, as well as direct and indirect electronic bandgaps have yet to be measured experimentally. This, along with wide-ranging values reported for the optical bandgap between 1.2 eV and 1.8 eV [15][16][17][18], mandates a precise and direct experimental determination of the electronic structure of In2Se3.…”

Section: Introductionmentioning

confidence: 99%

Electronic Band Structure of In-Plane Ferroelectric van der Waals β′-In₂Se₃

Collins

Wang

Tadich

et al. 2020

ACS Appl. Electron. Mater.

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Layered indium selenides (In2Se3) have recently been discovered to host robust out-of-plane and inplane ferroelectricity in the α and β´ phases, respectively. In this work, we utilise angle-resolved photoelectron spectroscopy to directly measure the electronic bandstructure of β´-In2Se3, and compare to hybrid density functional theory (DFT) calculations. In agreement with DFT, we find the band structure is highly two-dimensional, with negligible dispersion along the c-axis. Due to n-type doping we are able to observe the conduction band minima, and directly measure the minimum indirect (0.99 eV) and direct (1.53 eV) bandgaps. We find the Fermi surface in the conduction band is characterized by anisotropic electron pockets with sharp in-plane dispersion about the M ̅ points, yielding effective masses of 0.21 m0 along KM ̅̅̅̅̅ and 0.33 m0 along ΓM ̅̅̅̅ . The measured band structure is well supported by hybrid density functional theory calculations. The highly two-dimensional (2D) bandstructure with moderate bandgap and small effective mass suggest that β´-In2Se3 is a potentially useful new van der Waals semiconductor. This together with its ferroelectricity makes it a viable material for highmobility ferroelectric-photovoltaic devices, with applications in non-volatile memory switching and renewable energy technologies.

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Large disparity between optical and fundamental band gaps in layered In2Se3

Cited by 52 publications

References 51 publications

Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

Atomic Layer Deposition of Two-Dimensional Layered Materials: Processes, Growth Mechanisms, and Characteristics

Electronic Band Structure of In-Plane Ferroelectric van der Waals β′-In₂Se₃

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Large disparity between optical and fundamental band gaps in layered In2Se3

Cited by 52 publications

References 51 publications

Atomic Visualization and Switching of Ferroelectric Order in β‐In2Se3 Films at the Single Layer Limit

Atomic Visualization and Switching of Ferroelectric Order in β‐In2Se3 Films at the Single Layer Limit

Atomic Layer Deposition of Two-Dimensional Layered Materials: Processes, Growth Mechanisms, and Characteristics

Electronic Band Structure of In-Plane Ferroelectric van der Waals β′-In2Se3

Contact Info

Product

Resources

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Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

Atomic Visualization and Switching of Ferroelectric Order in β‐In₂Se₃ Films at the Single Layer Limit

Electronic Band Structure of In-Plane Ferroelectric van der Waals β′-In₂Se₃