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We elucidate the doping mechanism of suitable elements into borophene with first‐principles density functional theory calculation. During doping with nitrogen (N), the sp2 orbitals are responsible for arranging themselves to accommodate the electron of the N atom. Doping dramatically changes structure and electronic properties from corrugated and metallic borophene to flat and insulating h‐BN with 100 % N‐doping. We extend the mechanism of N‐doping in borophene to doping of non‐metallic and metallic ad‐atoms on borophene. Our findings will help to design boron‐based 2D materials. [ABSTRACT FROM AUTHOR]

The low-frequency Raman signals of single-wall carbon nanotubes (SWNTs), appearing in the range of 100–300 cm−1, have been interpreted as radial-breathing mode (RBM) comprising pure radial Eigenvectors. Here, we report that most of the low-frequency and intermediate-frequency signals of SWNTs are radial-tangential modes (RTMs) coexisting radial and tangential Eigenvectors, while only the first peak at the low-frequency side is the RBM. Density functional theory simulation for SWNTs of ~ 2 nm in diameter shows that dozens of RTMs exhibit following the RBM (~ 150 cm−1) up to G-mode (~ 1592 cm−1) in order with Landau regulation. We specify the RBM and the RTM on Raman spectra obtained from SWNTs, where both appear as prominent peaks between 149 and 170 cm−1 and ripple-like peaks between 166 and 1440 cm−1, respectively. We report that the RTMs have been regarded as RBM (~ 300 cm−1) and ambiguously named as intermediate-frequency mode (300–1300 cm−1) without assignment. The RTMs gradually interlink the RBM and the G-mode resulting in the symmetric Raman spectra in intensity. We reveal high-resolution transmission microscope evidence for a helical structure of SWNTs, informing the typical diameter of commercial SWNTs to be 1.4–2 nm. [ABSTRACT FROM AUTHOR]

By utilizing ab initio density functional theory, the structural and electronic properties of novel silicene/ZnI2 heterobilayers (HBLs) were investigated. Constructing HBLs with ZnI2 in different stacking configurations leads to direct bandgap opening of silicene at K point, which ranges from 138.2 to 201.2 meV. By analyzing the projected density of states and charge density distribution, we found that the predicted HBLs conserve the electronic properties of silicene and ZnI2 can serve as a decent substrate. The tunability of electronic properties can be achieved by enforcing biaxial strain and by varying interlayer distance where bandgap can get as low as zero to as high as 318.8 meV and 290.7 meV, respectively depending on the stacking patterns. Maintenance of the remarkable features of silicene, high mobility of charge carriers, and fine-tuning of bandgap pave the way to construct new nanoelectronic devices using these novel silicene/ZnI2 HBLs. [ABSTRACT FROM AUTHOR]

Of late, two-dimensional van der Waals heterostructures (vdWHs) have gained tremendous attention for water-splitting to produce hydrogen (H 2) fuel. This work demonstrates various configurations of vdWHs made up of monolayer boron arsenide (BAs) and germanium carbide (GeC) that exhibit outstanding photocatalytic properties in the water-splitting process to generate H 2 fuel. The absorption coefficient of the proposed BAs/GeC vdWHs is more than 105 cm−1, which exceeds the extensive conversion efficiency of optoelectronic materials. The absorption coefficient can be further tuned and reaches a maximum value of 2.6 × 10 5 cm−1 when applying an external strain. Dynamically tunable bandgaps in the range of 0.78–2.02 eV are found in these vdWHs by applying a biaxial strain. A strong photocatalytic water splitting action throughout the ultraviolet to optical spectrum region is found when a biaxial strain of −6% to +6% is applied. The favorable characteristics of the proposed BAs/GeC vdWHs could help enhance H 2 fuel generation via water splitting. • Model I-III of BAs/GeC vdWHs possesses a direct bandgap. • A wide direct bandgap is advantageous and desired for the applications of photocatalysis. • The photocatalytic water splitting of H 2 production is examined by calculated the band edge position of the suggested BAs/GeC vdWHs. • The biaxial strain can significantly increase their absorbance. [ABSTRACT FROM AUTHOR]