4th Physical Institute, University of Göttingen, 37077 Göttingen, Germany.
Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Science. 2014 Jul 11;345(6193):200-4. doi: 10.1126/science.1250658.
Two-dimensional systems such as surfaces and molecular monolayers exhibit a multitude of intriguing phases and complex transitions. Ultrafast structural probing of such systems offers direct time-domain information on internal interactions and couplings to a substrate or bulk support. We have developed ultrafast low-energy electron diffraction and investigate in transmission the structural relaxation in a polymer/graphene bilayer system excited out of equilibrium. The laser-pump/electron-probe scheme resolves the ultrafast melting of a polymer superstructure consisting of folded-chain crystals registered to a free-standing graphene substrate. We extract the time scales of energy transfer across the bilayer interface, the loss of superstructure order, and the appearance of an amorphous phase with short-range correlations. The high surface sensitivity makes this experimental approach suitable for numerous problems in ultrafast surface science.
二维体系，如表面和分子单层，表现出多种有趣的相和复杂的转变。超快结构探测可以提供关于内部相互作用和与衬底或体相支撑的耦合的直接时域信息。我们已经开发了超快低能电子衍射，并通过透射研究了从平衡态激发的聚合物/石墨烯双层系统中的结构弛豫。激光泵浦/电子探针方案解析了由折叠链晶体组成的聚合物超结构的超快熔化，该超结构被记录在一个独立的石墨烯衬底上。我们提取了双层界面能量传递、超结构有序损失和具有短程相关性的非晶相出现的时间尺度。高的表面灵敏度使得这种实验方法适用于超快表面科学中的许多问题。
