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arXiv 2602.12944cond-mat.mes-hallcond-mat.mtrl-sci
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关于石墨烯纳米带边缘效应与体效应的影响

Electrostatic edge effects versus edge doping in graphene nanoribbons: a scanning gate microscopy and modelling study

Colm Durkan, Xiao Liu, Ed Saunders

AI总结:

本文通过计算和实验研究了石墨烯纳米带边缘与体效应在电中性点切换中的影响,发现边缘电场增强导致CNP移动,但无符号变化,可能源于能带结构变化。

摘要:

最近的研究表明,当石墨烯纳米带(GNRs)的宽度低于约50纳米时,其电学性质在电阻率、电中性点(CNP)和能带结构方面表现出尺寸依赖性。观察到当GNR宽度低于某一值时,CNP的符号会切换。在本文中,我们通过AFM尖端存在下的电场和导电性计算模型来探索这一现象。我们证明,由于边缘附近电场显著增强,GNR宽度减小时,CNP预计将向更低值移动,但符号变化并不预期出现。我们还通过高分辨率扫描门显微镜(SGM)实验表明,GNR的边缘和体部之间似乎没有显著差异,表明CNP的切换并非由于差异掺杂,而可能是由于尺寸函数的能带结构变化所致。

英文摘要:

The charge neutrality point (CNP) of graphene nanoribbons (GNRs) patterned by oxygen plasma etching moves towards zero as the ribbon narrows and, on 300 nm SiO2, changes sign below a crossover width of ~ 50 nm: an observation previously attributed to n-type edges surrounding a p-type bulk. We test this edge-doping hypothesis in three ways. First, finite element modelling of complete GNR transistors with uniform doping shows that fringing of the gate field at the edges reproduces the trend of the measured CNP with width down to ~ 50nm without any edge doping, while producing a bias-dependent inversion of the carrier type at the edges that mimics n-type edges in scanned-probe measurements. Second, fitting the CNP of ribbons on 90 nm and 300 nm SiO2 with the gate capacitance of a finite strip, which fixes the electrostatic contribution with no adjustable parameter other than the bulk doping, shows that fringing accounts for most of the width dependence and isolates the remainder as an edge charge. This is acceptor-like (0.24 e/nm per edge) in the present ribbons, which therefore have no n-type edges, and donor-like but small in devices on 300 nm SiO2; no single edge-charge, field-coupled or contact-doping mechanism describes both. Third, scanning gate microscopy finds no edge contrast of the sign expected for n-type edges. The width dependence of the CNP is therefore predominantly electrostatic, and n-type edges are not an intrinsic consequence of oxygen-plasma etching. A design map shows that fringing dominates the width dependence whenever the gate dielectric is thicker than 30-50 nm, whereas in scaled high-K transistors, edge charge dominates and would shift the threshold voltage of a 10 nm ribbon by ~ 0.1-0.15 V. Fitting the CNP versus width with the strip capacitance provides a simple test for edge doping in any gated two-dimensional nanostructure

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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