Ion tracks as electrically conducting nanowires

物质中的离子径迹是在快速重离子辐照过程中通过高的和非常局部的电子能量损失而产生的。以这种方式引起的结构变化通常产生无定形径迹或缺陷富集的潜在径迹。在极少数情况下，人们发现从电绝缘相到导电相的局部相变。这是四面体无定形碳（ta-C）的情况，其在用例如GeV 238U离子照射时局部转化为sp2键合的导电相。导电轨道的直径仅为8nm。因此，导电离子轨道具有实现新型纳米级电子器件的潜力。似乎除了ta-C之外，其他材料如VO2、稀土镍酸盐和Fe3O4也适合于产生导电离子轨道，这些材料经历作为温度的函数的绝缘体-金属转变。这样的系统可能是感兴趣的全氧化物电子器件，因为它们的热电行为。该提案的目的是调整ta-C中的轨道电导率，使其具有欧姆传导的高且均匀的电导率。这将通过用合适的金属原子掺杂ta-C基质以及通过用高电荷态离子（高能量损失）进行离子辐照来实现。此外，还将研究VO2薄膜中导电离子径迹的形成、微观结构和性质。应研究离子轨道电子学的潜力，用于通过照射ta-C和绝缘BN间隔层的分层膜结构制备的中断轨道。以这种方式，导电离子轨道提供了尺寸为几nm 3的小体积的接触，其甚至在室温下也可以表现出库仑阻塞效应。

Ion tracks in matter are generated during irradiation with swift heavy ions by high and very local electronic energy loss. The structural changes induced in this way often yield to amorphous tracks or defect enriched latent tracks. In very few cases one finds a local phase transformation form an electrically insulating to a conductive phase. This is the case for tetrahedral amorphous carbon (ta-C) which locally converts to a sp2 bonded conductive phase upon irradiation with e.g. GeV 238U ions. The diameter of the conducting tracks is only 8 nm. Thus, conducting ion tracks possess the potential to realize novel nanoscale electronic devices. It seems that beside ta-C other materials like VO2 , rare earth nickelates and Fe3O4, which undergo an insulator-metal transition as function of temperature, are also suited to generate conducting ion tracks. Such systems may be of interest for all-oxide electronic devices and because of their thermoelectric behaviour. The aim of the proposal is to tailor the track conductivity in ta-C towards high and uniform conductivity with Ohmic conduction. This shall be achieved by doping of the ta-C matrix with suited metal atoms and also by ion irradiation with high charge state ions (high energy loss). Furthermore, the formation, the microstructure and the properties of conducting ion tracks in VO2 thin films shall be investigated. The potential of ion track electronics shall be studied for interrupted tracks, prepared by irradiating layered film structures of ta-C and insulating BN spacer layers. In this way conducting ion tracks provide the contacts to a small volume of few nm3 in size which may exhibit Coulomb blockade effects even at room temperature.