Investigation Of Electronic And Optical Properties Of Several Novel Two-Dimensional VA-Compound Semiconductors Via First-principles Calculations

Graphene has been regarded as the most promising candidate for future nano-electronics and optoelectronics since it has been successfully fabricated.However,the gapless nature makes the pristine graphene almost impossible to develop in optoelectronic and logic electronic devices.After the graphene and the transition metal dichalcogenides?TMDCs?,the two-dimensional compounds containing VA elements have drawn extensive interests.Among them,phosphorene possesses a layered nature and ultra-high carrier mobility,providing a promising approach for future applications in the field of electronic device and energy storage.Nevertheless,the instability and short lifetime in the air still dramatically obstruct phosphorene and its devices to use in high-volume practical applications.Owing to the difficulty in the synthesis of arsenene,there are few reports on the work of the arsenene experimentally.Besides,the reserve of antimony is limited and the antimonene is an indirect bandgap semiconductor.Thus,it is significant to explore the two-dimensional?2D?materials based on the group VA elements.At present,using the theoretical methods to explore the electronic and optical properties of 2D materials has become a hot-topic in 2D materials and devices.In this paper,we investigate the the electronic properties and the optical properties of novel two-dimensional materials and heterostructures by using first-principles calculations,and explored their potential applications in high-speed switching devices and solar energy conversion.The main results of this thesis are summarized as follows:?1?Firstly,the first-principles method was performed to predict the 2D hexagonal YN?h-YN?.By assessing the phonon spectrum,ab initio molecule dynamics and elastic constants,the h-YN monolayer is proved to own satisfying thermal,dynamic and mechanical stability.Distinguishing from the most reported 2D transition metal mononitrides which exhibit metallic,monolayer h-YN is a semiconductor with an indirect bandgap of 2.322 eV.In particular,h-YN presents unusually insensitive responses of electronic structures to tensile or compressive strain due to the valence orbital hybridization.Carrier mobility calculations suggest that monolayer h-YN possesses high electron mobility of up to 10⁴ cm² V^–1s^–1and hole mobility of up to 10³cm²V^–1s^–1 in zigzag and armchair orientations.Moreover,few-layer h-YN displays evident semiconductor performances and dispersive conductive bands,indicating light electron effective masses and excellent electron transport capabilities.Such pronounced carrier mobility,insensitive electronic responses to strain together with light electron effective masses of few-layer structures endow h-YN a promising candidate in future high-speed electronic devices in high-strain conditions.?2?Herein,we propose a novel 2D pentagonal SiAs₂?penta-SiAs₂?with favorable suitability for water splitting based on the first-principles calculations.By using hybrid functional,we demonstrate the bandgap of 2D penta-SiAs₂ is 2.35 eV and its band-edges perfectly stride the redox potential of water.Most importantly,this material possesses both highly desirable carrier mobilities and strong light absorption in the visible and ultraviolet?UV?regions,which are superior to most previously reported 2D materials.Furthermore,the reaction coordinates suggest that it is feasible for water decomposing and hydrogen evolution on the surface of penta-SiAs₂.These extraordinary characteristics endow the penta-SiAs₂ a promising 2D material for overall photocatalytic water splitting,and also provide a possible route for future experiment scheme.?3?In the end,we theoretically predict the indium selenide/antimonene heterostructure as a promising candidate for optoelectronic applications by using density functional theory method.By assessing the binding energy and interlayer distances,the pattern AC is demonstrated as the most energetically stable configuration.Remarkably,indium selenide/antimonene heterostructure presents a direct bandgap of0.97 eV at the HSE06 level.Additionally,indium selenide/antimonene heterostructure exhibits a type-II band alignment,indicating its favorable capability of electron-hole separation.Carrier mobility computations show that the electron mobility and hole mobility of indium selenide/antimonene heterostructure are both up to 10³cm²V^–1s^–1,which are superior than these of individual InSe monolayer and/or antimonene.The power-conversion efficiency of InSe/antimonene thin-film solar cell is calculated as17.2%.These desirable electronic and optical properties endow the indium selenide/antimonene heterostructure a potential candidate for multifunctional optoelectronic applications.