Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size
Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size
复制标题
DOI：
10.1103/physrevb.76.064304
复制
发表时间：
2007-08-01
影响因子：
3.7
通讯作者：
Pimenta, M. A.
中科院分区：
文献类型：
--
作者：
Cancado, L. G.;Jorio, A.;Pimenta, M. A.
在本文中，报道了纳米石墨的 D、G、D-' 和 G(') 波段的微分拉曼截面 β 对激发激光能量以及微晶尺寸的依赖性。我们证明，β(G) 与激发激光能量 (E-l) 的四次方成正比，正如拉曼散射理论所预测的那样。对于由双共振机制（D、D-'和G(')）产生的谱带，微分截面不依赖于E-l，这解释了I-D/I-G之比对拉曼实验中使用的激发激光能量E-l的强烈依赖性。测量了 D 和 D-' 能带微分截面的 L-a 依赖性，证实了与 L-a(-1) 成正比的 I-D/I-G 比例源于 beta(D) 对微晶尺寸倒数的强烈依赖性。在 G(') 带情况下，数据表明其微分截面随着微晶尺寸 L-a 的增加而增加，与无序诱导的 D 和 D-' 带相比，遵循相反的行为。对 D、G、D-' 和 G(') 能带的半高全宽 (Gamma) 对纳米石墨微晶尺寸 L-a 的依赖性进行了分析，结果表明声子寿命与微晶尺寸成正比。
In this paper, the dependence of the differential Raman cross section beta of the D, G, D-', and G(') bands of nanographites on the excitation laser energy and also on the crystallite size is reported. We show that beta(G) is proportional to the fourth power of the excitation laser energy (E-l), as predicted by the Raman scattering theory. For the bands which arise from the double-resonance mechanism (D, D-', and G(')), the differential cross section does not depend on E-l, explaining the strong dependence of the ratio I-D/I-G on the excitation laser energy E-l used in the Raman experiment. The L-a dependence of D and D-' band differential cross sections is measured, confirming that the proportionality I-D/I-G proportional to L-a(-1) originates from the strong dependence of beta(D) on the inverse of the crystallite size. In the G(') band case, the data show that its differential cross section increases with the increasing crystallite size L-a, following an opposite behavior when compared with the disorder induced D and D-' bands. An analysis on the dependence of the full width at half maximum (Gamma) of the D, G, D-', and G(') bands on the crystallite size L-a of nanographites is performed, showing that the phonon lifetime is proportional to the crystallite size.