【作者】 王颖；

【导师】 胡经国； Shiying Guo；

【作者基本信息】 扬州大学 ， 物理学， 2025， 硕士

【摘要】 实现具有低接触电阻和高电荷传输能力的金属-半导体接触是开发二维半导体器件的重要挑战。二维SnS₂具有合适的带隙和较高的电子迁移率,有希望取代硅基半导体成为场效应晶体管的新型沟道材料。然而,传统块体金属-半导体异质结通常会在界面处受到强费米能级钉扎效应的影响,导致存在不可调谐的肖特基势垒高度,影响器件性能并产生较高的能耗。使用二维金属构建范德华接触可以有效抑制金属诱导间隙态的产生,削弱费米能级钉扎效应。为了构建具有低接触电阻、高载流子注入速率的高质量金属-半导体界面,实现肖特基势垒的可调谐性,我们基于第一性原理计算方法对二维金属与二维SnS₂的界面接触特性进行探究。（1）首先构建了三维金属-SnS₂的异质结模型,SnS₂界面处S原子与界面的金属原子通过共价键连接,强烈的界面相互作用导致SnS₂金属化并产生了金属诱导间隙态,引起严重的费米能级钉扎效应。随后,我们构建了二维金属、半金属与SnS₂的金半接触结构,层间结合能和电荷转移表明界面接触类型为范德华接触,电子能带结构表明范德华界面结构有效抑制了金属诱导间隙态;然而,界面处的电荷转移导致界面偶极子的产生,利用界面电势差对费米能级钉扎因子进行修正,可以接近肖特基莫特极限,表明面偶极子的存在也会导致费米能级钉扎效应。在这些金属中,Bi、1TWTe₂、1TMo Te₂与SnS₂可以形成欧姆接触,隧穿概率分别为15.81%、12.48%、13.77%,可以作为二维SnS₂理想的金属电极材料。（2）利用表面功能化调控优化Mxene材料与二维SnS₂的界面接触特性。通过改变Mxene材料的表面官能团可以有效调控其功函数,从2.12 e V到5.95 e V,其中Ta₂CF₂、Ta₂C（OH）₂、Ti₂N（OH）₂和Nb₂C（OH）₂可以与SnS₂形成n型欧姆接触。有趣的是,层间距以及层间结合能表明OH官能团修饰的Mxene材料与SnS₂的界面相互作用明显强于O、F官能团修饰的Mxene材料,并且Ta₂C（OH）₂,Ti₂N（OH）₂和Nb₂C（OH）₂与SnS₂的界面隧穿概率远高于其余二维Mxene金属,特别是Ta₂C（OH）₂-SnS₂异质结的隧穿概率可以达到37.07%。此外,基于独立密度梯度模型研究,我们发现OH官能团修饰的MXene与SnS₂界面同时存在强氢键相互作用和范德华相互作用,而其他Mxene金属-SnS₂界面只存在范德华力,这表明氢键可以有效增强界面相互作用、提高金半接触的隧穿概率,这对提升界面载流子注入效率具有重要意义。更多还原

【Abstract】 Achieving efficient metal-semiconductor contacts with low contact resistance and high charge transfer ability is a major challenge in developing two-dimensional semiconductor devices.Two-dimensional SnS₂ has been considered as a promising candidate to field-effect transistors,due to its appropriate band gap and high carrier mobility.However,conventional metal-semiconductor junctions typically suffer from strong Fermi-level pinning effects,resulting in uncontrollable Schottky barrier heights that degrade device performance and lead to high energy consumption.Utilizing two-dimensional metals to construct van der Waals contacts can effectively suppress the generation of metal induced gap states,thereby weakening Fermi-level pinning.To construct high-quality metal-semiconductor interfaces with low contact resistance and high carrier injection rates while achieving tunability of Schottky barriers,we systematically investigate the interfacial characteristics between two-dimensional metals and monolayer SnS₂ based on the first-principles calculation.（1）The three-dimensional metal-SnS₂ heterojunctions are constructed firstly.Covalent bonding emerges between interfacial sulfur atoms of SnS₂ and metal atoms.The three-dimensional metal-SnS₂ suffers from serious metal induced gap states due to the strong coupling at the interface,result in strong Fermi-level pinning effects.Subsequently,we construct contacts between two-dimensional metals/semimetals and SnS₂.The interface binding energy and charge transfer demonstrate the formation of van der Waals contacts between 3D metal-SnS₂ heterojunction,which are effective nearly free of metal induced gap states,as evidenced by band structures.However,charge transfer leads to the interface dipoles.By modifying the Fermi-level pinning factor through interface potential difference,we achieved approximate Schottky-Mott limit,indicating that the Fermi-level pinning effects arising from interface dipoles.In these metals,Bi,1T-WTe₂,and 1T-Mo Te₂ are three excellent electrodes for n-type SnS₂ devices,because they can form Ohmic contact and high tunneling probabilities（15.81%,12.48%,and 13.77%）in the contact with SnS₂.（2）We use surface engineering to modify the interfacial properties of MXene and two-dimensional SnS₂.The changes of surface functional groups of Mxene materials can effectively regulate the work function.The work functions of surface engineered MXene ranges from 2.12～5.95 e V.Among these MXene,Ta₂CF₂,Ta₂C（OH）₂,Ti₂N（OH）₂ and Nb₂C（OH）₂ can form n-type Ohmic contact in the contact with SnS₂.Interestingly,the interface distance and binding energy indicate that OH-terminated MXene-SnS₂ contacts exhibit stronger interface coupling compared to O-and F-terminated contacts,accompanied by higher tunneling probability.Especially,the tunneling probability of Ta₂C（OH）₂-SnS₂interface is 37.07%.In addition,according to independent gradient model,OH-terminated MXene-SnS₂ contacts show strong hydrogen-bonding interactions and van der Waals interactions.O and F-terminated MXene-SnS₂ contacts only have weak van der Waals forces between the two layers.Hydrogen-bonding can strengthen interface coupling and enhance tunneling probability,which is significant to improve charge injection efficiency.更多还原