Non-equilibrium phase transitions in crystalline semiconductors under swift heavy ion irradiation

快速重离子束是一种有用的工具，用于高局部电子能量沉积对固体结构和性质修改的影响的单独研究。在大多数绝缘体和金属中，由于快速重离子照射而引起的高电子激发已知会导致离子轨迹周围的无定形轨道形成。这种效应通常在热尖峰模型的框架中解释，假设材料熔化，然后快速冷却和再凝固。在与技术相关的半导体领域，情况就不那么明朗了。特别是缺乏足够可靠的实验数据，到现在为止，阻止了对过程的最终理解以及没有矛盾的理论描述。因此，拟议的研究的主要目标是进一步澄清物理过程，特别是证明在快速重离子辐照下半导体中可能存在熔融相。为此，在快速重离子辐照半导体（Si，GaAs，InP）的不同掺杂类型和浓度的损伤演化和退火将作为电子能量沉积，离子质量和离子速度，以及在不同的辐照温度下的碰撞离子的电荷状态的函数进行研究。实验将伴随着模型模拟的框架内的热尖峰模型，使，在连接的实验数据，结论发生在高电子激发下的相变。除了基本方面，关于实现深埋改性层，纳米结构的合成和超高能粒子加速器和空间应用中的快速离子诱导设备故障的研究的实际相关性是显而易见的。

Swift heavy ion beams are a useful tool for a separate study of the effect of high local electronic energy deposition on structural and property modifications in solids. In most insulators and metals the high electronic excitation due to swift heavy ion irradiation is known to result in amorphous track formation around the ion trajectories. This effect is commonly explained in the framework of a thermal spike model assuming melting of the material followed by fast cooling and re-solidification. In the technologically relevant semiconductors the situation is much less clear. Especially the lack of sufficiently reliable experimental data up to now prevents the final understanding of the processes as well as a theoretical description free of contradictions. It is therefore the main goal of the proposed research to contribute to a further clarification of the physical processes, particularly to proof the possible existence of a melt phase in semiconductors under swift heavy ion irradiation. For this purpose, the damage evolution and annealing in swift heavy ion irradiated semiconductors (Si, GaAs, InP) of different doping type and concentration will be studied as a function of the electronic energy deposition, the ion mass and ion velocity, and the charge state of the impinging ions at different irradiation temperatures. The experiments will be accompanied by model simulations in the framework of the thermal spike model enabling, in connection with the experimental data, conclusions about the phase transitions occurring under high electronic excitation. Apart from the basic aspect, the practical relevance of the research with regard to the realisation of deeply buried modified layers, the synthesis of nanostructures and swift ion induced device failure in super-high energy particle accelerators and space applications is obvious.