The structures of boron clusters, such as flat clusters and fullerenes, resemble those of carbon. Various two‐dimensional (2D) borophenes have been proposed since the production of graphene. The recent successful fabrication of borophene sheets has prompted extensive researches, and some unique properties are revealed. In this review, the recent theoretical and experimental progress on the structure, growth, and electronic and thermal transport properties of borophene sheets is summarized. The history of prediction of boron sheet structures is introduced. Existing with a mixture of triangle lattice and hexagonal lattice, the structures of boron sheets have peculiar characteristics of polymorphism and show significant dependence on the substrate. Due to the unique structure and complex BB bonds, borophene sheets have many interesting electronic and thermal transport properties, such as strong nonlinear effect, strong thermal transport anisotropy, high thermal conductance in the ballistic transport and low thermal conductivity in the diffusive transport. The growth mechanism and synthesis of borophene sheets on different metal substrates are also presented. The successful prediction and synthesis will shed light on the exploration of new novel materials. Besides, the outstanding and peculiar properties of borophene make them tempting platform for exploring novel physical phenomena and extensive applications.
We present that the asymmetrical and mixed functionalized double MXenes possess novel bipolar antiferromagnetic semiconductor (BAFS) feature, opening a new opportunity for the realization of antiferromagnetic spin field effect transistors.
Inspirited by the wide range of applications of graphene and the similarity between boron and carbon, 2D boron sheets have gained extensive research interest. In this work, using first-principles combined with a nonequilibrium Green's function method, thermal conductance of fully hydrogenated borophene, named borophane, is studied. Interestingly and in contrast to widely perceived sense, at 300 K, it is found that the thermal conductance of borophane in the armchair direction is remarkably larger than that of graphene. More interesting, a dimensionality crossover is observed in phonon transmission where low-frequency phonons exhibit 2D characteristic, while high-frequency phonons behave like a 1D system, oriented along armchair direction, which results in the ultrahigh thermal conductance. An anomalous increase of thermal conductance with uniaxial tensile strain is observed, which is well explained by the unique puckered structure and chemical bonding in borophane. The excellent in-plane stiffness and flexibility together with the high thermal conductance suggest that borophane is promising for soft thermal channel. Moreover, this unique dimensionality crossover in phonon transmission offers a perfect platform for studying the effect of phonon population in mode space, which is of primary importance for thermal transport in low-dimensional systems.
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