关键词： Tensile strain  

摘要： Polyaniline (PANI) has been extensively studied in the past few decades owing to its broad applications in electronic devices. However, two dimensional PANI was not realized until very recently. In this work, the thermal transport properties of one of the newly synthesized 2D PANI structures, C3N, are systematically investigated using classical molecular dynamics simulations. The in-plane thermal conductivity (.) of monolayer and bilayer C3N structures is computed, and the. values for infinite-length systems are found to be as high as 820 and 805 W m-1 K-1, respectively. Both the values are markedly higher than those of many prevailing 2D semiconducting materials such as phosphorene, hexagonal boron nitride, MoS2 and MoSe2. The effects of different modulators, such as system dimension, temperature, interlayer coupling strength and tensile strain, on the calculated thermal conductivity are evaluated. Monotonic decreasing trends of thermal conductivity with temperature and tensile strain are found, while a positive correlation between the thermal conductivity and system dimension is revealed. Interlayer coupling strength is found to have negligible effects on the in-plane thermal conductivity of bilayer C3N. The cross-plane interfacial thermal resistance (R) between two adjacent C3N layers is evaluated in the temperature range from 100 to 500 K and at different coupling strengths. The predicted R at temperature 300 K equals 3.4 x 10-8 K m-2 W-1. The maximum reductions of R can amount to 59% and 68% with respect to temperature and coupling strength, respectively. Our results provide theoretical guidance to future applications of C3N-based low-dimensional materials in electronic devices.

关键词： Monolayers  

摘要： We propose a two-dimensional (2D) tetragonal material: an yttrium nitride (t-YN) monolayer, with a distinguished combination of mechanical and electronic properties based on first-principles calculations. We find that the t-YN monolayer is a low direct band gap semiconductor (0.55 eV) with strong anisotropic mechanical and electronic properties. We also identify that the t-YN monolayer to be a 2D ferroelastic material with a reversible strain of about 14.4%, indicating that the anisotropic properties of the t-YN monolayer can be switched by applying external stress. Furthermore, the moderate-switching barrier (33 meV/atom) of ferroelastic lattice rotation renders the switchable anisotropic properties accessible experimentally. These outstanding properties make the t-YN monolayer a promising switchable anisotropic 2D material for electronic and mechanical applications.

关键词： BORON   QUASIPARTICLES (Physics)   HEXAGONAL crystal system   ENERGY gaps (Physics)   SUBSTRATES (Materials science)   ELECTRONIC apparatus & appliances  

摘要： The two-dimensional boron monolayers were reported to be metallic both in previous theoretical predictions and experimental observations. Unexpectedly, we have first found a family of boron monolayers with the novel semiconducting property as confirmed by the first-principles calculations with the quasi-particle G(0)W(0) approach. We demonstrate that the connected network of hexagonal vacancies dominates the gap opening for both the in-plane s+p(x,y), and p(z) orbitals, with which various semiconducting boron monolayers are designed to realize the band gap engineering for the potential applications in electronic devices. The semiconducting boron monolayers in our predictions are expected to be synthesized on the proper substrates, due to the similar stabilities to the ones observed experimentally.

关键词： Mn-doped GaN monolayer   Magnetic properties   Electronic structure   First principle calculationa  

摘要： To meet the need of low-dimensional spintronic devices, we investigate the electronic structure and magnetic properties of Mn-doped GaN monolayer using first-principles method. We find the nonmagnetic GaN monolayer exhibits half-metallic ferromagnetism by Mn doping due to double-exchange mechanism. Interestingly, the ferromagnetic coupling in Mn-doped GaN monolayer is enhanced with tensile strain and weakened with compressive strain. What is more, the ferromagnetic-antiferromagnetic transformation occurs under compressive strain of-9.5%. These results provide a feasible approach for fabrication of a new GaN monolayer based diluted magnetic semiconductor. (C) 2016 Elsevier B.V. All rights reserved.

关键词： flexible photodetectors   all-inorganic perovskites   layered materials   optoelectronics   two-dimensional materials   CsPbBr3  

摘要： Printed flexible photodetectors based on 2D inorganic perovskites with atomic thickness show excellent photosensing with fast rise and decay response times. As-synthesized nanosheets can easily be dispersed in various solvents, leading to large-area, crack-free, low-roughness, flexible films after printing. This study demonstrates that all-inorganic perovskite CsPbX3 nanosheets as a new class of 2D semiconductors have huge potential for flexible optoelectronic applications.

关键词： Monolayers   MOSFETs   Effective mass   Tunneling   Anisotropy  

摘要： Ballistic transport characteristics of metal-oxide semiconductor field effect transistors (MOSFETs) based on anisotropic two-dimensional materials monolayer HfS2 and phosphorene are explored through quantum transport simulations. We focus on the effects of the channel crystal orientation and the channel length scaling on device performances. Especially, the role of degenerate conduction band (CB) valleys in monolayer HfS2 is comprehensively analyzed. Benchmarking monolayer HfS2 with phosphorene MOSFETs, we predict that the effect of channel orientation on device performances is much weaker in monolayer HfS2 than in phosphorene due to the degenerate CB valleys of monolayer HfS2. Our simulations also reveal that at 10 nm channel length scale, phosphorene MOSFETs outperform monolayer HfS2 MOSFETs in terms of the on-state current. However, it is observed that monolayer HfS2 MOSFETs may offer comparable, but a little bit degraded, device performances as compared with phosphorene MOSFETs at 5 nm channel length. (C) 2015 AIP Publishing LLC.

关键词： Heterojunctions   Band gap   Monolayers   Field effect transistors   Tunneling  

摘要： A vertical transistor based on a double gated, atomically thin heterojunction is theoretically examined. Both p-type and n-type transistor operations can be conveniently achieved by using one of the two gates as the switching gate. The transistor shows excellent saturation of output I-V characteristics due to drain-induced depletion and lack of tunneling barrier layers. The subthreshold slope could be below the thermionic limit due to band filtering as the switching mechanism. The atomically thin vertical PN heterojunction can be electrostatically modulated from a type II heterojunction to a broken bandgap alignment, which is preferred for maximizing the on-current. (C) 2014 AIP Publishing LLC.

关键词： Molybdenum   Monolayers   Band gap   Semiconductors   Photoluminescence  

摘要： Monolayer Mo1-xWxSe2 (x = 0, 0.14, 0.75, and 1) alloys were experimentally realized from synthesized crystals. Mo1-xWxSe2 monolayers are direct bandgap semiconductors displaying high luminescence and are stable in ambient. The bandgap values can be tuned by varying the W composition. Interestingly, the bandgap values do not scale linearly with composition. Such non-linearity is attributed to localization of conduction band minimum states around Mo d orbitals, whereas the valence band maximum states are uniformly distributed among W and Mo d orbitals. Results introduce monolayer Mo1-xWxSe2 alloys with different gap values, and open a venue for broadening the materials library and applications of two-dimensional semiconductors. (C) 2014 AIP Publishing LLC.