P-N Junction Effect of Metal Oxides inside Carbon Nanotubes on NO_2 detection

在p型碳纳米管(CNTs)内部沉积了不同带隙的N型半导体氧化物(TiO2：3.0 eV，SnO2：3.7 eV)。结果表明，这些材料对1ppm NO2的电阻变化取决于氧化物的带隙与p-n结的大小相对应。此外，利用扫描隧道谱(STS)研究了碳纳米管和SnO_2-碳纳米管的偏压导通电流。结果表明，从碳纳米管和SnO_2-碳纳米管的禁带宽度来看，SnO_2-CNTs形成了p-n结。

N-type semiconductor oxides with different band gap (TiO_2: 3.0 eV, SnO_2: 3.7 eV) were deposited inside p-type carbon nanotubes (CNTs). It was clarified that the resistance changes of these materials to 1 ppm NO_2 depended on band-gap of oxides corresponded to the magnitude of p-n junction. Besides, the current differentiated by bias voltage was examined for CNTs and SnO_2-CNTs by means of scanning tunneling spectroscopy (STS). As the result, the formation of p-n junction for SnO_2-CNTs was confirmed from the band-gap evaluated from CNTs and SnO_2-CNTs.