We performed room-temperature far-infrared ($40–650{\mathrm{cm}}^{-1}$) transmission measurements on undoped and bromine-doped powder samples of carbon nanofibers in stacked-cup cone geometry. The transmission spectra show enhanced transmittance after bromine doping and all spectra were fit to a Drude-Lorentz (DL) model. A decreased metallic conductivity along with a redshift of the lowest semiconducting gap was found with doped samples. A significant decrease in the scattering rate upon heavy doping has been qualitatively explained as partial ordering of intercalated dopant ions. Absorption spectra were derived from the transmission spectra under the assumption of nondispersive reflectance and subsequently compared with DL-model-derived spectra. The free-carrier density of the $n$-type powder and the electronic mean free path were estimated and compared with reported values for single-walled nanotubes and pyrolytic graphite.

中文翻译：

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叠杯锥构型中未掺杂和掺Br的碳纳米纤维粉末的远红外吸收

我们进行了室温远红外（$40–650{\mathrm{厘米}}^{-\mathrm{1个}}$）在堆积杯锥几何形状的碳纳米纤维的未掺杂和溴掺杂粉末样品上的透射率测量。溴掺杂后的透射光谱显示出增强的透射率，所有光谱均符合Drude-Lorentz（DL）模型。发现掺杂样品的金属电导率降低，同时最低半导体间隙出现红移。定性地解释了重掺杂时散射速率的显着降低是嵌入的掺杂离子的部分排序。吸收光谱是在非色散反射率的假设下从透射光谱得出的，然后与DL模型衍生的光谱进行比较。的自由载流子密度$ñ$估算了粉末类型和电子平均自由程，并将其与单壁纳米管和热解石墨的报道值进行了比较。