Syntheses of Novel Metallofullerene Nano-Peapods

金属富勒烯-豆荚（碳纳米管包裹的富勒烯）如Gd@C_<82>豆荚的一个迷人的特点是，我们可以在富勒烯吸热插入的位置进行“局部带隙工程”。先前的TEM图像和电子能量损失谱表明，在高密度的“豆荚”结构中，金属富勒烯的间距可以有规律地接近1.1 nm，而在低密度的“豆荚”结构中经常观察到1.1-3 nm的间距。在目前的Gd@C_<82>豆荚样品中，200多个SWNT图像中约有10%显示局部修饰的半导体带隙。扫描隧道显微镜和光谱学（dI/dY）给出了碳纳米管在费米能级附近的偏压相关的地形图像和局域态密度（LDS）。在STS图中，可以清楚地看到两个强VHS峰对应于传导和价带边缘，并且在较高的偏置电压下可以看到两个较小的VHS峰。原来的0.43 eV的带隙被缩小到0.17 eV，在那里富勒烯有望出现。此外，Gd@C_<82>豆瓣具有双极FET行为，通过简单的静电栅极可以容易地获得n和p通道。由Gd@C_<82>豆荚组成的小束组成的10多个独立装置也获得了类似的结果。这种双极性行为从未在C_<60>的豆荚中观察到。TEM图像和电子能量损失谱显示，在高密度“豆荚”结构中，金属富勒烯的间距可达1.1 nm，而在低密度“豆荚”结构中，金属富勒烯的间距通常为1.1 ~ 3 nm。在目前的Gd@C_<82>豆荚样品中，200多个SWNT图像中约有10%显示局部修饰的半导体带隙。

One of the fascinating features of metallofullerene-peapods (CNT encaging fullerenes) such as Gd@C_<82> peapods is that we can perform a 'local band gap engineering' at the site where a fullerene is endothermally inserted. Previous TEM images and electron energy loss spectra suggested that the metallofullerenes can be spaced regularly as close as 1.1 nm in a high-density 'peapod' structure, while 1.1-3 nm spacing was often observed in a low-density peapod. In the present Gd@C_<82> peapod samples, about 10% of over 200 SWNT images showed locally modified semiconducting band gaps.Scanning tunneling microscopy and spectroscopy (dI/dY) give bias-dependent topographic images and local density of states (LDS) on carbon nanotubes near the fermi level. In the STS map, two strong VHS peaks corresponding to conduction and valence band edges are clearly seen with two smaller ones at higher bias voltages. The original band gap of 0.43 eV is narrowed down to 0.17 eV where the fullerene is expected to be located.Furthermore, Gd@C_<82> peapods exhibit ambipolar FET behavior with both n-and p-channels easily accessible by simple electrostatic gates. Similar results were obtained from more than 10 independent devices composed of a small bundle of Gd@C_<82> peapods. Such ambipolar behavior has never been observed for C_<60> peapods.TEM images and electron energy loss spectra suggested that the metallofullerenes can be spaced regularly as close as 1.1 nm in a high-density 'peapod' structure, while 1.1-3 nm spacing was often observed in a low-density peapod. In the present Gd@C_<82> peapod samples, about 10% of over 200 SWNT images showed locally modified semiconducting band gaps.