离子径迹电光学性质的太赫兹时域光谱

THz-TDS study of the electrical and optical properties of ion tracks

为了深入研究离子径迹的电光学性质,室温下用太赫兹时域光谱(THz-TDS)测量高能重离子辐照的聚苯乙烯(PS)和聚乙烯(PE),获得了辐照样品的光学常数。研究发现,在离子沉积能量或离子剂量较高时,辐照PS和PE的吸收系数相比未辐照样品都有显著增加,这是由于辐照产生的碳团聚体对太赫兹波有吸收作用;对折射率而言,辐照PS的折射率增加而辐照PE的折射率降低,这与2种聚合物的结构有关。用有效介质理论提取出辐照聚合物中离子径迹的光学常数,并用Drude-Lorentz模型对其进行拟合,由拟合参数计算出了离子径迹的直流电导率。与常规接触测量法获得的离子径迹的电学参数进行比较,发现2种测量结果的差异是由于沿径迹方向能量沉积的不均匀性造成,THz-TDS测量结果更能反映高能量沉积区域物质的电学性质。

The electrical and optical properties of ion tracks in PS and PE irradiated with high energy heavy ions were investigated by Terahertz Time-Domain Spectroscopy（THz-TDS）.It was found that the refractive index and absorption coefficient in THz frequency range of ion track in irradiated PS were larger than those of virgin PS,while the refractive index of ion track in irradiated PE lower than that of virgin PE,and the absorption coefficient of track in irradiated PE larger than that of virgin PE.The different change trends of refractive index of ion track in PS and PE were attributed to the polymer structures.The optical constants of ion track were extracted using Effective Medium Theory（EMT）.The DC resistivity and carrier mobility of ion track were obtained by analyzing the results with Drude-Lorentz theory.The difference of the electrical constants obtained from this method and contacting measurements was attributed to the discontinuity of the energy density deposited by the ions.The THz-TDS results could be related to the electrical properties of ion track with the higher energy density.