Fabrication of locally defined Ge:Mn-Hybridstructures with self organized processes during pulsed laser annealing

本研究计划涉及自组织Ge:Mn杂化结构的制备和表征。这些杂化结构是在脉冲激光照射下锗锰合金表面熔化过程中由于Mullins-Sekerka不稳定性而形成的。在短脉冲准分子激光熔化过程中，不大可能发生Mullins-Sekerka不稳定性。我们使用脉冲长度在300 ~ 1200 ns之间的固体激光器，制备了一种渗透的、铁磁性的、富锰的、非晶的Ge:Mn纳米网络，其纳米线直径小于10 nm，嵌入在缺乏锰的晶体锗中。高于临界Mn浓度时，锰在熔融Ge-Mn合金的再结晶过程中不能完全融入结晶锗中，而在Ge-Mn合金的液相中积累。在富锰区，Ge-Mn合金的熔化温度局部降低。如果由于特定激光脉冲长度导致的Ge-Mn合金液相局部温度低于其局部熔化温度，则制备了本构过冷熔体。这种过冷液体的再结晶是高度不稳定的，这是制造锗锰杂化结构的主要要求。下一步，通过脉冲激光处理前形成周期性的Mn分布，以及脉冲激光处理后对Ge-Mn合金富锰区进行选择性化学蚀刻，形成有序的Ge:Mn杂化结构。结构的锗表面显示出与Ge-Mn合金中蚀刻富锰区域相同的结构尺寸。这种小于10nm的结构是传统光学光刻技术无法实现的，对纳米压印光刻技术具有重要意义。此外，我们已经证明了渗透锗：锰纳米的磁化强度和反常霍尔效应是密切相关的。这种特殊的性质只有从众所周知的稀释铁磁半导体GaAs:Mn中才知道。因此，渗透铁磁纳米网的制备代表了自旋电子学将磁性和半导体性质结合起来进行信息处理的新途径。本课题涉及纳米压印技术和磁性纳米结构中自旋极化载流子输运的研究工作。

The research proposal is related to the fabrication and characterization of self-organized Ge:Mn hybrid structures. Those hybrid structures are formed due to the Mullins-Sekerka instability during melting of the surface of a germanium-manganese (Ge-Mn)-alloy by pulsed laser irradiation. The occurrence of an Mullins-Sekerka instability is rather unlikely during melting with short pulses of excimer lasers. We used a solid-state laser with pulse lengths between 300 ns and 1200 ns and fabricated a percolating, ferromagnetic, manganese-rich, amorphous Ge:Mn nanonet with nanowire diameters below 10 nm embedded in manganese-poor, crystalline germanium.Above a critical Mn concentration, the manganese is not completely incorporated into the crystalline germanium during recrystallization of the molten Ge-Mn alloy and accumulates in the liquid phase of the Ge-Mn alloy. In the Mn-rich area the melting temperature of the Ge-Mn alloy locally decreases. If the local temperature in the liquid phase of the Ge-Mn alloy due to the specific laser pulse length lies below its local melting temperature, a constitutional supercooled melt is fabricated. The recrystallization of such a supercooled liquid is highly instable which is the main requirement to fabricate Ge:Mn hybrid structures. In the next step ordered Ge:Mn hybrid structures will be created by forming a periodic Mn distribution before pulsed laser treatment and by selective chemical etching of manganese-rich regions of the Ge-Mn alloy after pulsed laser treatment. The structured germanium surface reveals the same structure size as the etched manganese-rich regions of the Ge-Mn alloy. Such structure sizes < 10 nm cannot be fabricated by conventional optical lithography and are important for the nanoimprint lithography.Moreover, we have shown that the magnetization and anomalous Hall effect of percolating Ge:Mn nanonets are strongly correlated. This specific property has only been known from the well known diluted ferromagnetic semiconductor GaAs:Mn. Therefore, the fabrication of percolating ferromagnetic nanonets represents a new approach in spintronics for the combination of magnetic and semiconducting properties for information processing. The presented proposal is related to research work on nanoimprint-lithography and on transport of spinpolarized charge carriers in magnetic nanostructures.