Zanin D A, De Pietro L G, Peter Q, Kostanyan A, Cabrera H, Vindigni A, Bähler Th, Pescia D, Ramsperger U
Laboratory for Solid State Physics , ETH Zurich , 8093 Zurich, Switzerland.
Proc Math Phys Eng Sci. 2016 Nov;472(2195):20160475. doi: 10.1098/rspa.2016.0475.
We perform scanning tunnelling microscopy (STM) in a regime where primary electrons are field-emitted from the tip and excite secondary electrons out of the target-the scanning field-emission microscopy regime (SFM). In the SFM mode, a secondary-electron contrast as high as 30% is observed when imaging a monoatomic step between a clean W(110)- and an Fe-covered W(110)-terrace. This is a figure of contrast comparable to STM. The apparent width of the monoatomic step attains the 1 mark, i.e. it is only marginally worse than the corresponding width observed in STM. The origin of the unexpected strong contrast in SFM is the material dependence of the secondary-electron yield and not the dependence of the transported current on the tip-target distance, typical of STM: accordingly, we expect that a technology combining STM and SFM will highlight complementary aspects of a surface while simultaneously making electrons, selected with nanometre spatial precision, available to a macroscopic environment for further processing.
我们在一种模式下进行扫描隧道显微镜（STM）实验，即一次电子从针尖场发射出来并激发靶材中的二次电子——扫描场发射显微镜模式（SFM）。在SFM模式下，当对清洁的W(110)和覆盖Fe的W(110)平台之间的单原子台阶进行成像时，观察到高达30%的二次电子对比度。这是一个与STM相当的对比度数值。单原子台阶的表观宽度达到1埃，即仅略差于STM中观察到的相应宽度。SFM中意外出现的强对比度的起源是二次电子产率的材料依赖性，而非STM中典型的传输电流对针尖 - 靶材距离的依赖性：因此，我们预计将STM和SFM相结合的技术将突出表面的互补特性，同时使具有纳米空间精度选择的电子可用于宏观环境进行进一步处理。
