Soncini Cristian, Bondino Federica, Magnano Elena, Bhardwaj Sunil, Kumar Manvendra, Cepek Cinzia, Pedio Maddalena
Istituto Officina Materiali (CNR-IOM), Laboratorio TASC, I-34149 Trieste, Italy.
Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy.
Nanotechnology. 2021 Mar 5;32(10):105703. doi: 10.1088/1361-6528/abce30.
The relation between morphology and energy level alignment in carbon nanotubes (CNT) is a crucial information for the optimization of applications in nanoelectronics, optics, mechanics and (bio)chemistry. Here we present a study of the relation between the electronic properties and the morphology of single wall CNT (SWCNT), aligned multi wall CNT (MWCNT) and unaligned MWCNT. The CNT were synthesized via catalytic chemical vapor deposition in ultra-high vacuum conditions. Combined ultraviolet photoemission and inverse photoemission (IPES) spectra reveal a high sensitivity to the nanotube morphology. In the case of unaligned SWCNT the distinctive unoccupied Van Hove singularities (vHs) features are observed in the high resolution IPES spectra. Those features are assigned to semiconducting and metallic SWCNT states, according to calculated vHs DOS. The two MWCNT samples are similar in the diameter of the tube (about 15 nm) and present similar filled and empty electronic states, although the measured features in the aligned MWCNT are more defined. Noteworthy, interlayer states are also revealed. Their intensities are directly related to the MWCNT alignment. Focussing and geometrical effects associated to the MWCNT alignment are discussed to account the spectral differences.
碳纳米管（CNT）的形态与能级排列之间的关系是优化纳米电子学、光学、力学及（生物）化学应用的关键信息。在此，我们展示了一项关于单壁碳纳米管（SWCNT）、取向多壁碳纳米管（MWCNT）和非取向MWCNT的电子性质与形态之间关系的研究。这些碳纳米管是在超高真空条件下通过催化化学气相沉积法合成的。结合紫外光电子能谱和逆光电子能谱（IPES）揭示了对纳米管形态的高灵敏度。在非取向SWCNT的情况下，在高分辨率IPES谱中观察到独特的未占据范霍夫奇点（vHs）特征。根据计算出的vHs态密度，这些特征被归因于半导体和金属SWCNT态。两个MWCNT样品的管径相似（约15纳米），并且呈现出相似的填充和空电子态，尽管在取向MWCNT中测量到的特征更明确。值得注意的是，还揭示了层间态。它们的强度与MWCNT的取向直接相关。讨论了与MWCNT取向相关的聚焦和几何效应，以解释光谱差异。
