Argonne National Laboratory

Synchrotron X-ray Scanning Tunneling Microscopy (SX-STM)

Synchrotron X-ray Scanning Tunneling Microscopy (SX-STM)

Specialized smart tips and topographic filters are used to fully realize high spatial resolution and high chemical sensitivity imaging with synchrotron X-ray scanning tunneling microscopy.

Synchrotron light sources contribute uniquely to many research fields including physics, chemistry, materials science, biology, medicine, geology, and cultural heritage. Synchrotron X-ray scanning tunneling microscopy (SX-STM) is an imaging technique combining the best of two worlds: the exceptional chemical, magnetic, and structural sensitivity of X-rays combined with the unparalleled ability of scanning probe microscopy to resolve and manipulate surfaces down to single atoms.

A joint effort between the Center for Nanoscale Materials (CNM) and Argonne’s Advanced Photon Source (APS) recently developed the technique of synchrotron X-ray scanning tunneling microscopy with innovations including specialized smart tips and topographic filters. With these advances, we have demonstrated direct elemental imaging on the atomic scale. For instance, we have achieved a lateral resolution of 2 nm and a vertical resolution of a single atomic layer (i.e., the ultimate limit) at room temperature. Polarized X-rays also can be employed to simultaneously probe the magnetic, elemental, chemical, and topographic properties of a surface.

To make the SX-STM technique available to the wider scientific community, the CNM and APS are constructing a dedicated synchrotron beamline branch at Sector 4 of the APS. This branch will be known as XTIP and will become operational in 2018. Until then, we provide limited beamtime to users for early-science SX-STM experiments. These experiments will focus on the study of chemical and magnetic properties of nanoscale materials using SX-STM at photon energies between 500 to 2500 eV.

In addition, a newly developed low-temperature SX-STM will provide researchers access to a one-of-a-kind instrument. By pairing the capabilities of synchroton X-ray analysis with extremely precise microscopy in XTIP, we will offer a new way to simultaneously determine the physical structure, chemical makeup, and magnetic properties of materials at close to atomic scale. In turn, this will open up unique ways of exploring novel phenomena and the fabrication of next-generation nanoscale materials.