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

该研究计划涉及自组织Ge：Mn杂化结构的制备和表征。这些混杂结构是由于脉冲激光熔化锗锰(Ge-Mn)合金表面过程中的Mullins-Sekerka不稳定性造成的。在准分子激光的短脉冲熔化过程中，不太可能发生Mullins-Sekerka不稳定性。我们使用脉冲长度在300 ns到1200 ns之间的固体激光，制备了渗流、铁磁性、富锰、非晶态的Ge：Mn纳米网，纳米线直径小于10 nm，嵌入在贫锰的晶态Ge中。在一个临界的锰浓度下，在熔融的Ge-Mn合金的再结晶过程中，锰没有完全融入到晶态Ge中，而积累在Ge-Mn合金的液相中。在富锰区，Ge-Mn合金的熔化温度局部降低。如果由于特定的激光脉冲长度导致Ge-Mn合金液相局部温度低于其局部熔化温度，则形成成分过冷熔体。这种过冷液的再结晶是高度不稳定的，这是制备Ge：Mn杂化结构的主要要求。在下一步中，通过在脉冲激光处理前形成周期性的Mn分布以及在脉冲激光处理后选择性地对Ge-Mn合金的富锰区进行化学腐蚀，将形成有序的Ge：Mn杂化结构。结构良好的锗表面显示出与Ge-Mn合金蚀刻富锰区相同的结构尺寸。这样的结构尺寸&lt；10 nm不能用传统的光学光刻方法来制造，这对于纳米压印光刻是很重要的。此外，我们还证明了渗透Ge：Mn纳米网络的磁化强度和反常霍尔效应之间存在很强的相关性。这一特殊性质仅从众所周知的稀磁半导体GaAs：Mn中得知。因此，渗流铁磁纳米网的制备代表了自旋电子学的一种新方法，它将磁性和半导体特性结合起来用于信息处理。该方案涉及纳米压印光刻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.