FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands.
Nano Lett. 2013;13(12):5925-30. doi: 10.1021/nl402978s. Epub 2013 Nov 7.
We present a comparative study of the ultrafast photoconductivity in two different forms of one-dimensional (1D) quantum-confined graphene nanostructures: structurally well-defined semiconducting graphene nanoribbons (GNRs) fabricated by a "bottom-up" chemical synthesis approach and semiconducting carbon nanotubes (CNTs) with a similar bandgap energy. Transient photoconductivities of both materials were measured using time-resolved terahertz spectroscopy, allowing for contact-free measurements of complex-valued photoconductivity spectra with subpicosecond time-resolution. We show that, while the THz photoresponse seems very different for the two systems, a single model of free carriers experiencing backscattering when moving along the long axis of the CNTs or GNRs provides a quantitative description of both sets of results, revealing significantly longer carrier scattering times for CNTs (ca. 150 fs) than for GNRs (ca. 30 fs) and in turn higher carrier mobilities. This difference can be explained by differences in band structures and phonon scattering and the greater structural rigidity of CNTs as compared to GNRs, minimizing the influence of bending and/or torsional defects on the electron transport.
我们对两种不同形式的一维（1D）量子限制石墨烯纳米结构中的超快光导率进行了比较研究：通过“自下而上”的化学合成方法制造的结构明确的半导体石墨烯纳米带（GNRs）和具有相似能带隙能量的半导体碳纳米管（CNTs）。使用太赫兹时域光谱法测量了这两种材料的瞬态光导率，允许以亚皮秒时间分辨率进行无需接触的复值光导率光谱测量。我们表明，虽然两种系统的太赫兹光响应看起来非常不同，但当自由载流子沿 CNT 或 GNR 的长轴移动时经历背散射的单个模型为两组结果提供了定量描述，表明 CNT 的载流子散射时间明显长于 GNR（约 150 fs），而载流子迁移率则更高。这种差异可以通过能带结构和声子散射的差异以及与 GNR 相比 CNT 更高的结构刚性来解释，从而最小化了弯曲和/或扭转缺陷对电子输运的影响。
