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利用紫外激光直接改变材料电导率,具有广泛的应用前景,现正日益引起人们的重视。目前,在这一领域的研究大多集中于各种有机高分子聚合物,C_(60)是最近才出现的新材料。根据能带理论计算,C_(60)晶体为典型的直接能隙半导体,其能隙宽度为1.5eV。但多晶C_(60)薄膜却是良好的绝缘体,其本正电导率低于10~(-7)S·cm~(-1)。最近,Phillips等报道了用248nm的KrF准分子激光提高C_(60)薄膜电导率的实验研究,并提出电导率变化的主要机制是激光诱导的绝缘体-金属相变。 本文进行了准分子激光诱导C_(60)薄膜电导率提高的实验研究。在低于刻蚀阈值的激光脉冲照射下,C_(60)薄膜电导率提高了6个数量级。Raman谱的研究表明:电导率变化的主要机制是C_(60)被光致氧化分解为无定形碳,在较低能流密度的情况下,观察到微晶石墨及C_(60)聚合团簇的形成。
The use of UV laser to directly change the conductivity of materials, has a wide range of applications, is now increasingly aroused people’s attention. At present, most of the research in this field focuses on a variety of organic polymers, C_ (60) is a new material recently appeared. According to the energy band theory calculation, C_ (60) crystal is a typical direct gap semiconductor with an energy gap width of 1.5eV. However, the polycrystalline C 60 thin film is a good insulator and its positive conductivity is lower than 10 -7 S · cm -1. Recently, Phillips et al. Reported an experimental study on increasing the conductivity of a C_ (60) thin film by using a KrF excimer laser at 248 nm. The main mechanism of the conductivity change is laser-induced insulator-metal phase transition. In this paper, an experimental study on the increase of conductivity of C_ (60) film induced by excimer laser was carried out. Under the pulse of laser pulse lower than the etching threshold, the conductivity of C 60 films increased by six orders of magnitude. The Raman spectra show that the main mechanism of the electrical conductivity change is that C 60 is decomposed to amorphous carbon by photooxidation. At lower energy flux density, microcrystalline graphite and C 60 polycrystalline clusters are observed Formation.