本文關鍵詞：準二維半導體材料的預測和應力調控的第一性原理研究　出處：《清華大學》2016年博士論文　論文類型：學位論文

  更多相關文章： 低維金屬鹵化物/硫化物 石墨烯 輸運性質 應力調控 第一性原理計算

【摘要】：探索具有高性能輸運特性和高柔韌性的新型準二維半導體材料是當前凝聚態(tài)物理領域的熱點研究課題之一�；诘谝恍栽碛嬎�,本論文研究了拉伸應變對單層硒化錫輸運性質的調控機制;預測了寬帶隙的準二維半導體單層碘化鉛和三碘化鉍,并研究其對應變的響應;提出了一種特殊的調控石墨烯帶隙的方法。首先,我們發(fā)現(xiàn)在零應變條件下,單層硒化錫是一種具有較高的電子遷移率的近直接帶隙準二維半導體,其可承受的雙軸拉伸應變極限約為12%。雙軸拉伸應變能夠有效調控單層硒化錫的帶隙大小,同時可在2%的應變下實現(xiàn)間接帶隙到直接帶隙的轉變并在較大的應變范圍內(2%～8%)保持直接帶隙的狀態(tài)。零應變下,單層硒化錫中電子比空穴更易于移動,其遷移率高達1.5×104cm~2V~(-1)s~(-1)。隨著雙軸應變的增加,單層硒化錫的電子遷移率會逐漸下降,但在8%的應變之前都保持在600 cm~2V~(-1)s~(-1)之上。其次,我們預測了寬帶隙半導體單層金屬鹵族化物(單層碘化鉛和三碘化鉍)的存在。單層碘化鉛是一個帶隙約為2.63 eV的間接帶隙半導體。我們指出量子尺寸效應導致碘化鉛從體的直接帶隙轉變到單層的間接帶隙。雙軸應變可以有效地調控該能隙大小,但無法實現(xiàn)從間接帶隙到直接帶隙的轉變,這可以通過應變會均勻地改變鉛和碘原子層之間的電場來理解。單層三碘化鉍可以通過剝離方法獲得。它也是一個間接帶隙半導體,其帶隙隨層厚的增加而減小。在雙軸拉伸應變下,單層、雙層和三層的碘化鉍帶隙都呈下降趨勢,這從側面反映了碘化鉍的層間耦合作用很弱。單層三碘化鉍、碘化鉛和石墨烯的復合結構都可以增強對可見光的吸收。最后,我們研究了在連續(xù)的石墨烯中形成的類似于zigzag-GNR的一維褶皺結構。提出了利用襯底作用和量子尺寸效應的聯(lián)合效應在連續(xù)的石墨烯中打開能隙的方案。通過第一性原理計算,我們證實通過褶皺結構彎曲部分與襯底之間的強相互作用能夠打開約0.7 eV的能隙。在不破壞完美石墨烯結構的情況下,實現(xiàn)金屬-半導體-金屬結,很好地解釋了實驗結果。
[Abstract]:It is one of the hot research topics in the field of condensed matter physics to explore new quasi-two-dimensional semiconductor materials with high performance transport characteristics and high flexibility. In this paper, the mechanism of the effect of tensile strain on the transport properties of monolayer tin selenide was studied. The quasi-two-dimensional semiconductor monolayer lead iodide and bismuth triiodide with wide band gap are predicted and their responses to strain are studied. A special method for controlling graphene band gap is proposed. Firstly, we find that the monolayer tin selenide is a near direct band gap quasi-two-dimensional semiconductor with high electron mobility under zero strain condition. The strain limit of biaxial tension is about 12. Biaxial tensile strain can effectively control the band gap of tin selenide monolayer. At the same time, the transition from indirect band gap to direct band gap can be realized at the strain of 2% and keep the state of direct band gap in a large strain range. It is easier to move electrons in monolayer tin selenide than holes, and its mobility is as high as 1.5 脳 10 ~ 4 cm ~ (2) C ~ (2) V ~ (-1) ~ (-1) ~ (-1) ~ 1 ~ (-1). The electron mobility of monolayer tin selenide decreases gradually, but before the strain of 8%, the electron mobility remains above 600cm ~ (2) V ~ (+) ~ (-1). We predicted the wide gap semiconductor monolayer metal halides (monolayer lead iodide and bismuth triiodide). Monolayer lead iodide is a band gap of about 2.63. We point out that the quantum size effect results in the transition of lead iodide from direct band gap to single layer indirect band gap. Biaxial strain can effectively regulate the size of the band gap. However, the transition from indirect band gap to direct band gap can not be realized. This can be understood by the fact that the strain changes the electric field between the lead and iodine atoms uniformly. The monolayer bismuth triiodide can be obtained by stripping. It is also an indirect band-gap semiconductor. The band gap decreases with the increase of layer thickness. Under biaxial tensile strain, the band-gap of bismuth iodide in single layer, double layer and three layer shows a downward trend, which reflects the weak interlaminar coupling of bismuth iodide. The composite structure of lead iodide and graphene can enhance the absorption of visible light. We have studied the one-dimensional fold structure similar to zigzag-GNR formed in continuous graphene. It is proposed that the energy gap is opened in continuous graphene by the combined effect of substrate action and quantum size effect. First principle calculation. It is shown that the energy gap of about 0.7 EV can be opened by the strong interaction between the bending part of the folded structure and the substrate, and the metal-semiconductor metal junction can be realized without destroying the perfect graphene structure. The experimental results are well explained.
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O469

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