Suppr超能文献

准金属和半导体碳纳米管 pn 结中光电流机制的比较。

A Comparison of Photocurrent Mechanisms in Quasi-Metallic and Semiconducting Carbon Nanotube pn-Junctions.

机构信息

Department of Electrical Engineering University of California , Los Angeles, California 90095, United States.

King Abdulaziz City for Science and Technology , Riyadh 12612, Saudi Arabia.

出版信息

ACS Nano. 2015 Dec 22;9(12):11551-6. doi: 10.1021/acsnano.5b03873. Epub 2015 Oct 28.

Abstract

We present a comparative study of quasi-metallic (Eg ∼ 100 meV) and semiconducting (Eg ∼ 1 eV) suspended carbon nanotube pn-junctions introduced by electrostatic gating. While the built-in fields of the quasi-metallic carbon nanotubes (CNTs) are 1-2 orders of magnitude smaller than those of the semiconducting CNTs, their photocurrent is 2 orders of magnitude higher than the corresponding semiconducting CNT devices under the same experimental conditions. Here, the large exciton binding energy in semiconducting nanotubes (∼400 meV) makes it difficult for excitons to dissociate into free carriers that can contribute to an externally measured photocurent. As such, semiconducting nanotubes require a phonon to assist in the exciton dissociation process, in order to produce a finite photocurrent, while quasi-metallic nanotubes do not. The quasi-metallic nanotubes have much lower exciton binding energies (∼50 meV) as well as a continuum of electronic states to decay into and, therefore, do not require the absorption of a phonon in order to dissociate, making it much easier for these excitons to produce a photocurrent. We performed detailed simulations of the band energies in quasi-metallic and semiconducting nanotube devices in order to obtain the electric field profiles along the lengths of the nanotubes. These simulations predict maximum built-in electric field strengths of 2.3 V/μm for semiconducting and 0.032-0.22 V/μm for quasi-metallic nanotubes under the applied gate voltages used in this study.

摘要

我们提出了通过静电门控引入的准金属(Eg ∼ 100 meV)和半导体(Eg ∼ 1 eV)悬浮碳纳米管 pn 结的对比研究。虽然准金属碳纳米管(CNT)的内置场比半导体 CNT 的内置场小 1-2 个数量级,但在相同的实验条件下,它们的光电流比相应的半导体 CNT 器件高 2 个数量级。在这里,半导体纳米管中较大的激子结合能(∼400 meV)使得激子难以离解成自由载流子,这些自由载流子可以对外测量的光电流做出贡献。因此,半导体纳米管需要声子来协助激子离解过程,以产生有限的光电流,而准金属纳米管则不需要。准金属纳米管具有较低的激子结合能(∼50 meV)以及连续的电子态可以衰减,因此不需要吸收声子就可以离解,从而使这些激子更容易产生光电流。我们对准金属和半导体纳米管器件的能带能量进行了详细的模拟,以获得纳米管长度上的电场分布。这些模拟预测,在本研究中使用的门电压下,半导体纳米管的最大内置电场强度为 2.3 V/μm,而准金属纳米管的最大内置电场强度为 0.032-0.22 V/μm。

文献AI研究员

20分钟写一篇综述,助力文献阅读效率提升50倍。

立即体验

用中文搜PubMed

大模型驱动的PubMed中文搜索引擎

马上搜索

文档翻译

学术文献翻译模型,支持多种主流文档格式。

立即体验