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测量了石墨和纳米碳样品沿不同方向的正电子湮没辐射Doppler展宽谱,研究样品中电子动量分布.结果表明,纳米碳样品的缺陷浓度高于石墨;石墨中自由电子的平均动量高于纳米碳.石墨晶体中的自由电子动量分布表现出显著的各向异性:沿石墨晶体的[0001]方向的自由电子(即2Pz电子)的动量最大;偏离该方向越大,自由电子的动量越小;垂直于[0001]方向的自由电子的动量最小.而且,Doppler展宽谱的S参数与cos2θ呈线性关系(θ是石墨[0001]晶向与探头方向的夹角);而纳米碳中自由电子动量的分布不存在明显的各向异性.
The Doppler broadening spectrum of positron annihilation radiation in different directions of graphite and nanocarbon samples was measured to study the electron momentum distribution in the samples.The results showed that the concentration of defects in nanocarbon samples was higher than that of graphite.The average momentum of free electrons in graphite was higher than that of nanocarbon The free electron momentum distribution in graphite crystals shows significant anisotropy: the momentum of free electrons (ie, 2Pz electrons) along the [0001] direction of graphite crystals is the largest; the larger the deviation from this direction, the smaller the momentum of free electrons; The momentum of free electrons perpendicular to the [0001] direction is minimal, and the S-parameter of Doppler broadening spectrum is linear with cos2θ (θ is the angle between the crystal orientation of [0001] and the probe); while the free electron momentum There is no obvious anisotropy in the distribution.