本文選題：五邊形石墨烯 + 第一原理計(jì)算��； 參考：《長春大學(xué)》2017年碩士論文

【摘要】：自從2004年海姆和諾沃肖洛夫利用機(jī)械剝離法成功制備石墨烯以來,一系列新型二維材料(單層六方氮化硼、單層二硫化鉬、鍺烯、黑磷烯、硼烯等)的相關(guān)研究已成為材料科學(xué)和凝聚態(tài)物理學(xué)等領(lǐng)域的研究熱點(diǎn)之一。2015年,研究人員又發(fā)現(xiàn)了一種新型的二維碳同素異形體五邊形石墨烯,其完全由碳五元環(huán)構(gòu)成,為準(zhǔn)直接帶隙半導(dǎo)體材料,具有較好的熱穩(wěn)定性和機(jī)械穩(wěn)定性,具有負(fù)泊松比和超高的力學(xué)強(qiáng)度。隨著計(jì)算機(jī)技術(shù)的飛速發(fā)展,計(jì)算材料學(xué)在材料科學(xué)研究中占有越來越重要的地位。為了進(jìn)一步探討五邊形石墨烯在微電子器件領(lǐng)域的潛在應(yīng)用,從理論上研究五邊形石墨烯的電子結(jié)構(gòu)調(diào)控就顯得非常必要。在本論文中,我們采用第一原理密度泛函理論研究堿金屬原子吸附和外加應(yīng)變對五邊形石墨烯幾何結(jié)構(gòu)和電子結(jié)構(gòu)的影響,為進(jìn)一步研究五邊形石墨烯的性能提供理論指導(dǎo)。具體研究工作和主要結(jié)論概括如下。(1)研究了五邊形石墨烯的幾何結(jié)構(gòu)和電子結(jié)構(gòu)。研究表明五邊形石墨烯呈褶皺結(jié)構(gòu),由sp3雜化碳原子和sp2雜化碳原子構(gòu)成。電子結(jié)構(gòu)計(jì)算表明五邊形石墨烯為帶隙寬度3.22 eV的準(zhǔn)直接帶隙半導(dǎo)體。(2)研究了堿金屬原子(Li、Na和K)吸附對五邊形石墨烯的幾何結(jié)構(gòu)和電子結(jié)構(gòu)的影響。吸附能計(jì)算表明五邊形石墨烯第三層碳原子之間的橋位(B33)是堿金屬原子最穩(wěn)定的吸附位置,電荷由吸附的堿金屬原子轉(zhuǎn)移到五邊形石墨烯上。堿金屬原子吸附后,五邊形石墨烯的導(dǎo)帶和價(jià)帶都向下移動(dòng),這說明費(fèi)米能級向上移動(dòng)。隨著吸附的堿金屬原子的原子序數(shù)逐漸增大,五邊形石墨烯的功函數(shù)單調(diào)降低。計(jì)算結(jié)果表明當(dāng)K原子在五邊形石墨烯表面吸附時(shí),其吸附能最大,吸附最強(qiáng),五邊形石墨烯的功函數(shù)降低最多,K原子與五邊形石墨烯之間的電荷轉(zhuǎn)移最大。(3)研究了外加拉伸和壓縮應(yīng)變對五邊形石墨烯的幾何結(jié)構(gòu)和電子結(jié)構(gòu)的影響。研究表明外加應(yīng)變對五邊形石墨烯中的sp3雜化碳原子的影響最大,在-10%到25%的應(yīng)變范圍內(nèi)五邊形石墨烯發(fā)生的是彈性形變。施加應(yīng)變后,五邊形石墨烯由準(zhǔn)直接帶隙半導(dǎo)體完全轉(zhuǎn)變?yōu)殚g接帶隙半導(dǎo)體。在外加壓縮應(yīng)變下,五邊形石墨烯的帶隙逐漸變小;在外加拉伸應(yīng)變下,帶隙隨拉伸應(yīng)變的增大先緩慢增加后急劇減小。
[Abstract]:Since Heym and Novosholov successfully prepared graphene by mechanical stripping in 2004, a series of novel two-dimensional materials (monolayer hexagonal boron nitride, monolayer molybdenum disulfide, germanium enene, black phosphorene) have been prepared. In 2015, researchers discovered a new two-dimensional carbon isomorphism pentagonal graphene, which is composed entirely of carbon quintuple rings. Quasi-direct band-gap semiconductor material has good thermal stability and mechanical stability, with negative Poisson ratio and ultra-high mechanical strength. With the rapid development of computer technology, computational materials science plays an increasingly important role in material science research. In order to further explore the potential applications of pentagonal graphene in the field of microelectronic devices, it is necessary to study the electronic structure regulation of pentagonal graphene theoretically. In this thesis, we use the first principle density functional theory to study the effect of alkali metal atomic adsorption and applied strain on the geometry and electronic structure of pentagonal graphene, which provides theoretical guidance for further study on the properties of pentagonal graphene. The geometrical and electronic structures of pentagonal graphene are studied. The results show that pentagonal graphene has a fold structure consisting of sp3 hybrid carbon atom and sp2 hybrid carbon atom. The electronic structure calculation shows that pentagonal graphene is a quasi-direct band-gap semiconductor with a band gap width of 3.22 EV). The effect of the adsorption of alkaline-metal atoms on the geometric and electronic structures of pentagonal graphene was studied. The calculation of adsorption energy shows that the bridge position B33 between the third layer carbon atoms of pentagonal graphene is the most stable adsorption position of alkali metal atom and the charge is transferred from the adsorbed alkali metal atom to the pentagonal graphene. After alkali atom adsorption, the conduction band and valence band of pentagonal graphene move downward, which indicates that the Fermi energy level moves upward. The work function of pentagonal graphene decreases monotonously with the increase of atomic number of the adsorbed alkali metal atom. The results show that when K atom is adsorbed on the surface of pentagonal graphene, the adsorption energy is the largest and the adsorption is the strongest. The maximum charge transfer between pentagonal graphene and pentagonal graphene was studied. The effect of tension and compression strain on the geometry and electronic structure of pentagonal graphene was studied. The results show that the effect of applied strain on the sp3 hybrid carbon atoms in pentagonal graphene is the greatest, and the deformation of pentagonal graphene is elastic in the range of -10% to 25%. After applied strain, pentagonal graphene completely changed from quasi direct band gap semiconductor to indirect band gap semiconductor. The band gap of pentagonal graphene decreases gradually under the applied compressive strain, and the band gap increases slowly at first and then decreases sharply with the increase of tensile strain.
【學(xué)位授予單位】：長春大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O613.71

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