Nanoscale Chemical Imaging by Scanning Tunneling Microscopy Assisted by Synchrotron Radiation

Abstract

Nanoscale chemical imaging using scanning tunneling microscopy is demonstrated with a core-level excitation of the probed element by a synchrotron radiation light. Pronounced element-specific contrasts were observed in the spatial resolution of approximately 10 nm on checkerboard-patterned Ni and Fe samples in differential photoinduced current images taken with the scanning tunneling microscopy tip under the synchrotron radiation irradiation whose photon energies are above and below the Ni (Fe) L absorption edge. The local detection of the photoinduced secondary electrons through the surface barrier lowered by the proximate tip and/or via the tunneling process probably plays an important role in achieving the high-spatial resolution.

Compositional mapping of semiconductor quantum dots and rings

“…Elemental sensitivity can be achieved by tuning the photon energy across the absorption edge of an element and acquiring difference images above and below the edge. This has recently been demonstrated on a test sample with a lateral resolution of 25 to 35 nm [171]. Although the technique is still in its infancy, this value is already comparable with the spatial resolution of chemical imaging by XPEEM.…”

X-ray Assisted Scanning Tunneling Microscopy and Its Applications for Materials Science: The First Results on Cu Doped ZrTe3

“…For example, Okuda et al showed~10 nm mapping on checkerboard-patterned Ni and Fe samples when X-ray photon energies were tuned to above and below the Ni (Fe) L absorption edge. The research team utilized glass-coated W tips [41]. Saito et al showed that Cu islands (>100 nm 2 ) embedded into Ge(111) 2 × 8 surface can be spatially resolved by detecting changes in the tip current (∼10 pA) when scanned laterally [42].…”

Observation of Micro-Magnetic Structures by Synchrotron Radiation Photoelectron Emission Microscopy

“…In order to improve the spatial resolution, some studies for further developments are underway worldwide not only for the PEEM apparatus but also for other SR assisted spectro-microscopy systems. [119][120][121] For the development of PEEM, aberration correction is the key technology. Spherical aberration as well as the chromatic aberration should be corrected.…”