V2NO2/ TiSi2N4异质结界面性质调控的理论研究
2024-02-21冯继辰马宁牛丽
冯继辰,马宁,牛丽
V2NO2/ TiSi2N4异质结界面性质调控的理论研究
冯继辰1,马宁2,牛丽1
(哈尔滨师范大学 1. 物理与电子工程学院,2. 计算机科学与信息工程学院,黑龙江 哈尔滨 150025)
MXenes;异质结;肖特基势垒;第一性原理;MA2Z4
1 计算方法
2 结果与讨论
2.1 电子结构特性
在建立V2NO2/TiSi2N4异质结模型之前,研究了V2NO2和TiSi2N4单层的结构信息及电子结构.V2NO2中的氧原子在晶胞中具有三个不同的结合位点:直接占据上面V原子的表面空位(构型I);在N原子的顶部和由三个相邻的V原子形成的三角形的中空处(构型II);在底部V原子的顶部和三个相邻的N原子的中心上(构型III).计算结果与文献[9]相同,构型III具有最低的能量,说明构型III比V2NO2其他两种构型更稳定.优化后的最稳定结构见图1a,V2NO2纳米单层的空间群为164(3),晶格参数为2.91 nm-1.
V2NO2的能带结构见图1b,通过能带图可知V2NO2保留了V2N的金属性质,考虑到构型III在能量上是最有利结构并且保持了体系类金属性质,构型III的V2NO2是用于构建金属-半导体异质结构的理想构型.
图2 V2NO2/ TiSi2N4异质结的六种堆叠方式(分别称为Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵ)
当两个层堆叠形成异质结构时,会发生电荷的重新分布和转移,为了分析其相互作用,计算了异质结构中的三维电荷密度差分,结果见图3.图3a中黄色和淡蓝色区域分别表示电荷积累和耗尽.黄色区域正好在V2NO2层表面之下,这表明电子在V2NO2层周围积累;而TiSi2N4层的表面被淡蓝色区域包围,这意味着空穴在TiSi2N4层周围积聚.而静电势也能看出这一点(见图3b),电子从静电势低的一端向高的一端转移,即由TiSi2N4层向V2NO2层转移.电子局域函数(ELF)也绘制在图3c中,可以看到靠近TiSi2N4层的Ti原子周围的局域电子形状与另一侧的Ti原子周围的局域电子形状明显不同,这表明异质结构中存在层间范德瓦尔斯相互作用.
图3 V2CO2/TiSi2N4异质结电子性质
2.2 外加电场对肖特基势垒的调控
施加不同外电场时V2NO2/TiSi2N4肖特基结的投影能带结构(外电场施加范围为-0.5~+0.5 V/nm-1)见图4b.计算结果表明,在正的外加电场调节下,VBM和CBM先上升后下移;在负的外加电场调节下,其VBM和CBM的总体趋势为下移趋势.在正负外加电场作用下,单层TiSi2N4保持了原间接带隙半导体的特性.
图4 异质结在外电场作用下的肖特基势垒和能带结构的变化
3 结语
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Theoretical study of the modulation of interfacial properties of V2NO2/ TiSi2N4heterojunctions
FENG Jichen1,MA Ning2,NIU Li1
(1. School of Physics and Electronic Engineering,2. School of Computer Science and Information Engineering,Harbin Normal University,Harbin 150025,China)
MXenes;heterojunctions;Schottky barriers;first principles;MA2Z4
O469
A
10.3969/j.issn.1007-9831.2024.01.010
1007-9831(2024)01-0051-05
2023-06-26
冯继辰(1999-),男,黑龙江牡丹江人,在读硕士研究生,从事凝聚态物理研究.E-mail:1141117031@qq.com
马宁(1981-),男,黑龙江哈尔滨人,副教授,博士,从事第一性原理计算研究.E-mail:maninghsd@163.com