Li Hu, Zhang Jiawei, Gholizadeh A Baset, Brownless Joseph, Fu Yangming, Cai Wensi, Han Yuanyuan, Duan Tianbo, Wang Yiming, Ling Haotian, Leifer Klaus, Curry Richard, Song Aimin
Department of Electrical and Electronic Engineering, University of Manchester, M13 9PL Manchester, U.K.
State Key Laboratory of Crystal Materials, Shandong Technology Centre of Nanodevices and Integration and School of Microelectronics, Shandong University, 250101 Jinan, China.
ACS Appl Mater Interfaces. 2021 Nov 10;13(44):52892-52900. doi: 10.1021/acsami.1c14597. Epub 2021 Oct 30.
The lack of a sizeable band gap has so far prevented graphene from building effective electronic and optoelectronic devices despite its numerous exceptional properties. Intensive theoretical research reveals that a band gap larger than 1 eV can only be achieved in sub-3 nm wide graphene nanoribbons (GNRs), but real fabrication of such ultranarrow GNRs still remains a critical challenge. Herein, we demonstrate an approach for the synthesis of ultranarrow and photoluminescent semiconducting GNRs by longitudinally unzipping single-walled carbon nanotubes. Atomic force microscopy reveals the unzipping process, and the resulting 2.2 nm wide GNRs are found to emit strong and sharp photoluminescence at ∼685 nm, demonstrating a very desirable semiconducting nature. This band gap of 1.8 eV is further confirmed by follow-up photoconductivity measurements, where a considerable photocurrent is generated, as the excitation wavelength becomes shorter than 700 nm. More importantly, our fabricated GNR field-effect transistors (FETs), by employing the hexagonal boron nitride-encapsulated heterostructure to achieve edge-bonded contacts, demonstrate a high current on/off ratio beyond 10 and carrier mobility of 840 cm/V s, approaching the theoretical scattering limit in semiconducting GNRs at room temperature. Especially, highly aligned GNR bundles with lengths up to a millimeter are also achieved by prepatterning a template, and the fabricated GNR bundle FETs show a high on/off ratio reaching 10, well-defined saturation currents, and strong light-emitting properties. Therefore, GNRs produced by this method open a door for promising applications in graphene-based electronics and optoelectronics.
尽管石墨烯具有许多优异的特性，但迄今为止，由于缺乏可观的带隙，它仍无法用于制造有效的电子和光电器件。大量的理论研究表明，只有在宽度小于3nm的石墨烯纳米带（GNR）中才能实现大于1eV的带隙，但实际制造这种超窄GNR仍然是一项严峻的挑战。在此，我们展示了一种通过纵向打开单壁碳纳米管来合成超窄且具有光致发光特性的半导体GNR的方法。原子力显微镜揭示了打开过程，并且发现所得的宽度为2.2nm的GNR在约685nm处发射出强烈而尖锐的光致发光，这表明其具有非常理想的半导体性质。后续的光电导率测量进一步证实了1.8eV的带隙，当激发波长小于700nm时会产生可观的光电流。更重要的是，我们通过采用六方氮化硼封装的异质结构来实现边缘键合接触，制造的GNR场效应晶体管（FET）显示出超过10的高电流开/关比和840cm²/V·s的载流子迁移率，接近室温下半导体GNR的理论散射极限。特别是，通过预先图案化模板还实现了长度达一毫米的高度对齐的GNR束，并且制造的GNR束FET显示出高达10的高开/关比、明确的饱和电流和强烈的发光特性。因此，通过这种方法生产的GNR为基于石墨烯的电子学和光电子学中的潜在应用打开了一扇门。
