Unleashing the Quadratic Nonlinear Optical Responses of Graphene by Confining White-Graphene (h-BN) Sections in Its Framework

Abstract

In an attempt to diversify the options in designing graphene-based systems bearing large second order nonlinear optical (NLO) responses of octupolar and/or dipolar character, the subject of the quadratic NLO properties of hybrid boron nitride (BN) graphene flakes is opened up. State of the art ab initio and density functional theory methods applied on a toolbox of book-text octupolar and arbitrary dipolar planar hybrid h-BN-graphene nanosized systems reveal that by confining finite h-BN sections in the internal network of graphene, the capacity of the π-electron network of graphene species in delivering giant second order NLO responses could be fully exploited. Configuration interaction (CIS) and time-dependent density functional (TD) computations, within the sum-overstate (SOS) perturbational approach, expose that the prevailing (hyper)polarization mechanism, lying under the sizable computed octupolar hyperpolarizabilities, is fueled by alternating positive and negative atomic charges located in the internal part of the hybrid flakes, and more precisely at the BN/graphene intersections. This type of charge transfer mechanism distinguishes, in fact, the elemental graphene dipoles/octupoles we report here from other conventional NLO dipoles or octupoles. More interestingly, it is shown that by controlling the shape, size, and covering area of the h-BN domain (or domains), one can effectively regulate "à volonté" both the magnitudes and types of the second order NLO responses switching from dipolar to octupolar and vice versa. Especially in the context of the latter class of NLO properties, this communication brings into surface novel, graphene-based, octupolar planar or quasiplanar motifs. The take home message of this communication is summarized as follows: When the right BN segment is incorporated in the right section of the right graphene flake, systems of giant quadratic NLO octupolar and/or dipolar responses may emerge.

Inducing a Finite In-Plane Piezoelectricity in Graphene with Low Concentration of Inversion Symmetry-Breaking Defects

“…20 Apart from atom adsorption, other techniques can be used to break the inversion symmetry of graphene sheets, such as hole formation, 21 stacking control in graphene bilayers, 22 application of non-homogeneous strain, 23 and chemical doping. [24][25][26] Among these strategies, chemical doping seems the most promising as it already represents an effective experimental mean for tuning structural and electronic properties (such as band gap and work function) of graphene. 24,25,[27][28][29] Boron nitride (BN) chemical doping of graphene has recently been successfully achieved in different configurations and concentrations: semiconducting atomic layers of hybrid h-BN and graphene domains have been synthesized, 27 low-pressure chemical-vapor-deposition (CVD) synthesis of large-area few-layer BN doped graphene (BNG) has been presented, leading to BN concentrations as high as 10%; the BN content in BNG layers has been discussed to be related to the heating temperature of the precursor, as confirmed by X-ray photoelectron spectroscopy measurements.…”

Nonlinear optical response and transparency of hexagonal boron nitride hybrid graphene nanoribbons

“…Recently, many studies [10,27] have demonstrated that for the evaluation of the NLO properties of BCN-related species, a longrange corrected DFT method, for example CAM-B3LYP, can provide more reasonable and accurate predictions. Su et al used the CAM-B3LYP method to calculate NLO properties of h-BN-CNTs.…”

“…More recently, Karamanis et al [10] have reported the secondorder NLO responses of a series of coronene-shape h-B 12 N 12 inserting graphene nanoribbons of C n , in which the hybrid substrates of C n are hexagonal GNRs with armchair edges. However, in our study, the hybrid substrates of C n are a rectangle with the zigzag and armchair edges.…”

“…The hexagonal boron nitride (BN) hybrid graphene nanoribbons (h-BN-GNRs) as novel nanomaterials have attracted great attention [1][2][3][4][5][6][7][8][9][10][11] from theoretical and experimental chemists and physicists due to their novel structural, optical, and electronic properties. The h-BN-GNRs have complementary electronic properties of pure graphene and h-BN and it is most likely that new properties would be created from the hybridized graphene and h-BN because of the tunable electronic energy gap [12][13][14].…”

“…Therefore, more and more attention is paid to investigate nonlinear optical responses of h-BN-GNRs. More recently, Karamanis et al [10] have studied the second-order NLO responses of a series of hexagonal boron nitride coronene (B 12 N 12 ) hybrid hexagonal graphene nanoribbons, in which the ˇ0 value of h-B 12 N 12 C 84 is 7.3 × 10 3 au at the CAM-B3LYP level. However, the ˇ0 value of hexagonal boron-nitride hybrid carbon nanotube (h-B 10 N 10 C 30 ) is 1.05 × 10 4 au at the same level of theory reported by Su et al [27].…”