Synthesis and wavelength-sensitive near-infrared photodetection performance of large-diameter single-walled carbon nanotubes with tailored bandgap distribution

单壁碳纳米管（SWCNT）以不同的电子类型存在，根据其结构具有可调的带隙。半导体（S-）SWCNT还能够选择性地吸收近红外（NIR）范围内的光，从低于一微米一直到技术上重要的电信波段高达几微米。因此，单壁碳纳米管被认为是一种理想的材料，波长敏感的近红外光电探测，这是预计将用于新一代的光电导体，光学二极管和光学晶体管。然而，基于SWCNT的检测器的性能受到限制，主要是由于这样的事实，即生长的SWCNT通常含有金属和S-纳米管，并且前者对于有效的光电检测是非常不期望的。因此，我们建议使用具有定制带隙分布的大直径s-SWCNTs来制造波长敏感的近红外光电探测器，并研究所获得的器件的性能和工作机制。这项工作将是IMR团队和达姆施塔特/卡尔斯鲁厄团队的联合研究工作，将他们在控制合成单壁碳纳米管和将单壁碳纳米管集成到设备架构中的独特专业知识引入其中。我们将建立一种浮动催化剂化学气相沉积方法，通过结合催化剂设计和原位蚀刻，连续，可控地合成具有定制带隙的高质量s-SWCNTs。通过杂原子掺杂或液相色谱法可以进一步优化带隙分布。我们将制作光电探测器使用大直径的s-SWCNT定制的带隙分布的基础上的s-SWCNT薄膜或从溶液通过介电泳，测量空间和光谱分辨的光电流响应，从而揭示光电流产生的机制。我们开发了一种器件架构，允许有效地将光转换为目标波长范围的电流，并将开发具有良好再现性和长期稳定性的优化SWCNT基NIR光电探测器。除了解决与大直径半导体单壁碳纳米管的可控合成以及从具有小带隙的单壁碳纳米管在NIR中产生光电流相关的基本问题之外，具有波长特异性吸收的NIR光电探测器的开发将构成无分散元件的NIR光谱法的重要一步。

Single-walled carbon nanotubes (SWCNTs) exist in different electronic types with tunable band gaps depending on their structure. Semiconducting (s-) SWCNTs are also able to selectively absorb light in the near-infrared (NIR) range from below one micron all the way through the technologically important telecom band up to several microns. In consequence, SWCNTs have been regarded as an ideal material for wavelength-sensitive NIR photodetection, which are expected to be used in new-generation photoconductors, optical diodes, and optical transistors. However, the performance of SWCNT-based detectors has been limited mainly due to the fact that as-grown SWCNTs usually contain both metallic and s- nanotubes, and the former is highly undesirable for efficient photodetection. Therefore, we propose to fabricate wavelength-sensitive NIR photodetectors using large-diameter s-SWCNTs with tailored band gap distributions and to study the performance and working mechanism of the devices obtained. This work will be a joint research effort of the IMR team and the Darmstadt/Karlsruhe team, bringing in their unique expertise in the controlled synthesis of SWCNTs and the integration of SWCNTs into device architectures. We will establish a floating catalyst chemical vapor deposition approach for the continuous, controllable synthesis of high-quality s-SWCNTs with tailored band gaps by combining catalyst design and in-situ etching. The band gap distribution will be further optimized by hetero-atom doping or liquid phase chromatography. We will fabricate photodetectors using large-diameter s-SWCNTs with tailored band gap distributions either on the basis of s-SWCNT films or from solution via dielectrophoresis, measure the spatially and spectrally resolved photocurrent response, and thereby reveal the mechanism of photocurrent generation. We develop a device architecture that allows efficient conversion of light into current for the targeted wavelength range will be developed and optimized SWCNT-based NIR photodetectors with good reproducibility and long term stability are targeted. Besides addressing fundamental questions related to the controlled synthesis of large-diameter, semiconducting SWCNTs and the photocurrent generation in the NIR from SWCNTs with small bandgap, the development of NIR photodetectors with wavelength-specific absorption will constitute an important step towards NIR spectrometry without dispersing elements.