Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials

Barraza‐Lopez, Salvador; Xia, Fengnian; Zhu, Wenjuan; Wang, Han

doi:10.1063/5.0030751

Cited by 19 publications

(10 citation statements)

References 60 publications

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“…It reminisces of the 2D transformations discussed in Refs. [27][28][29]31] and [30] for other 2D materials in which a double-well potential with a small barrier is crossed at finite temperature, unleashing 2D transformations of the order-by-disorder type. Indeed, close observation to fluctuations of lattice parameters in Refs.…”

Section: Transformation Onto a Planar Two-dimensional Silicene On Ave...mentioning

confidence: 99%

“…In fact, the buckled structure of silicene, germanene, and stanene gives a reason to expect structural transformations: the atomistic energy remains the same upon a mirror reflection with respect to the two-dimensional plane, making these materials structurally degenerate. Structural degeneracies have been found to give rise to structural phase transitions [27][28][29][30][31][32][33][34], to non-harmonic phonon modes [35], and to softened elastic constants [36,37].…”

Section: Introductionmentioning

confidence: 99%

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Thermally-driven phase transitions in freestanding low-buckled silicene, germanene, and stanene

Davis¹,

Orozco-Galvan²,

Barraza-Lopez³

2023

Preprint

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Low-buckled silicene, germanene, and stanene are group−IV graphene allotropes. They form a honeycomb lattice out of two interpenetrating (A and B) triangular sublattices that are vertically separated by a small distance ∆z. The atomic numbers Z of silicon, germanium, and tin are larger to carbon's (ZC = 6), making them the first experimentally viable two-dimensional topological insulators. Those materials have a twice-energy-degenerate atomistic structure characterized by the buckling direction of the B sublattice with respect to the A sublattice [whereby the B−atom either protrudes above (∆z > 0) or below (∆z < 0) the A−atoms], and the consequences of that energy degeneracy on their elastic and electronic properties have not been reported thus far. Here, we uncover ferroelastic, bistable behavior on silicene, which turns into an average planar structure at about 600 K. Further, the creation of electron and hole puddles obfuscates the zero-temperature SOC induced band gaps at temperatures as low as 200 K, which may discard silicene as a viable two-dimensional topological insulator for room temperature applications. Germanene, on the other hand, never undergoes a low-buckled to planar 2D transformation, becoming amorphous at around 675 K instead, and preserving its SOC-induced bandgap despite of band broadening. Stanene undergoes a transition onto a crystalline 3D structure at about 300 K, preserving its SOC-induced electronic band gap up to that temperature. Unlike what is observed in silicene and germanene, stanene readily develops a higher-coordinated structure with a high degree of structural order. The structural phenomena is shown to have deep-reaching consequences for the electronic and vibrational properties of those two dimensional topological insulators.

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Section: Transformation Onto a Planar Two-dimensional Silicene On Ave...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermally-driven phase transitions in freestanding low-buckled silicene, germanene, and stanene

Davis¹,

Orozco-Galvan²,

Barraza-Lopez³

2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Ever since the successful isolation of graphene in 2004 that proves its stability [4], other 2D materials such as antimonene [5][6][7][8][9], phosphorene [10][11][12], arsenene [13][14][15], germanene [16], monolayer MoS 2 [17][18][19], 2D ferroelectrics including SnS, SnSe, and SnTe [20], and 2D magnets [21] have sparked much interest. The reduced symmetries of these emerging materials lead to inhomogeneous electron distribution, different optical, valley, and spin responses, and properties including ferroelectricity, magnetism, and superconductivity [22]. These properties are different from those of the bulk and may offer more possibilities for next-generation electronic applications.…”

Section: Introductionmentioning

confidence: 99%

Highly stable electronic properties of rippled antimonene under compressive deformation

et al. 2022

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Antimonene has attracted much attention for its high carrier mobility and suitable band gap for electronic, optoelectronic, and even spintronic devices. To tailor its properties for such applications, strain engineering may be adopted. However, such two-dimensional (2D) crystals may prefer to exist in the rippled form because of the instability of long-range orders, and rippling has been shown to have a contrasting, significant impact on the electronic properties of various 2D materials, which complicates the tuning process. Hence, the effects of rippling on the electronic properties of antimonene under strain are herein investigated by comparing antimonene in its rippled and flat forms. Density functional theory calculations are performed to compute the structural and electronic parameters, where uniaxial compression of up to 7.5% is applied along the armchair and zigzag directions to study the anisotropic behavior of the material. Highly stable properties such as the work function and band gap are obtained for the rippled structures, where they are fully relaxed, regardless of the compression level, and these properties do not deviate much from those of the pristine structure under no strain. In contrast, various changes are observed in their flat counterparts. The mechanisms behind the different results are thoroughly explained by analyses of the density of states and structure geometry. The out-of-plane dipole moments of the rippled structures are also presented to give further insights into potential applications of rippled antimonene in sensors, actuators, triboelectric nanogenerators, etc. This work presents extensive data and thorough analysis on the effect of rippling on antimonene. The identification of optimal ripple amplitudes for which the electronic properties of the pristine condition can be recovered will be highly significant in guiding the rational design and architecture of antimonene-based devices.

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“…Etching is a reversible process of growth and exists simultaneously with growth during the fabrication of 2D materials. [24][25][26][27][28] It is noteworthy that the etching process has a direct impact on the nucleation control, growth evolution and structural regulation of 2D materials. Thus, it can be an indirect top-down method to deepen the understanding of growth mechanism and promote the fabrication of large-sized and high quality 2D materials and 2D heterostructures.…”

mentioning

confidence: 99%

From Top to Down—Recent Advances in Etching of 2D Materials

Fan

et al. 2022

Adv Materials Inter

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Etching, considered as the reverse process of growth, has drawn intensive interests in the past decades. Rather from offering building blocks for formation of materials, etching is served as removing basic units from the matrix. Generally, etching plays a critical role in three aspects: first, it can serve as direct top‐down method to precisely make designed patterns for electronic devices. Second, it can offer an indirect way to probe the detailed growth mechanism of 2D materials, enhancing understanding of growth process. Finally, it can be an efficient and facile way to visualize grain boundaries. Herein, several commonly used etching techniques for 2D materials are presented of which chemical vapor deposition etching has attracted the most intensive attentions. Thereafter, the typical etching modes of 2D materials are demonstrated, wherein linear etching, anisotropic etching, and fractal etching are comprehensively exhibited, respectively. Furthermore, the etching mechanism of 2D materials is elucidated, thereby offering a guideline for probing their in‐depth etching dynamics and kinetics. Finally, relevant concerns regarding uniformity and reproducibility within etching process are discussed and the expected future is envisaged.

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Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials

Cited by 19 publications

References 60 publications

Thermally-driven phase transitions in freestanding low-buckled silicene, germanene, and stanene

Thermally-driven phase transitions in freestanding low-buckled silicene, germanene, and stanene

Highly stable electronic properties of rippled antimonene under compressive deformation

From Top to Down—Recent Advances in Etching of 2D Materials

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