Nanoscale Imaging and Spectroscopy with XPEEM

Abstract

The continuous miniaturization and increasing complexity of the materials used in modern technology requires to have access to chemical composition, electronic structure, magnetization, and fluctuations in these properties at sub-micron and nanometer scales. X-ray photoemission electron microscopy (XPEEM) can provide this information. The recent years have seen a strong increase in XPEEM activities worldwide. This paper reviews the present situation and future developments of XPEEM in combination with synchrotron radiation. In particular, the role of energy filtering, aberration correction, and temporal resolution is discussed. 1．IntroductionX-ray photoelectron spectroscopy (XPS) and the related technique , X-ray absorption spectroscopy (XAS), are powerful tools for the analysis of surfaces, as widely discussed in this issue. In a traditional experimental setup, the spectroscopic signal is obtained from a spot of some 100 µm to millimeters in diameter, and therefore averages over this area. On the other hand, the progress in modern nanotechnology has fueled an evergrowing demand to perform XPS and XAS from areas as small as the smallest building blocks of those nanostructures . This has triggered the development of special instruments which combine spectroscopy and microscopy and allow to perform XPS and XAS with the highest possible lateral resolution of less than 100 nm. 1)More than 10 years ago, two basic, complemetary design principles have been identified to achieve this goal:2) the scanning and the direct imaging type instruments. In the scanning type instruments the photon beam is demagnified, i.e. the X-rays are focused by an optical system (like a Fresnel zone plate or a Schwarzschild objective) on a small spot on the sample. The photoelectrons excited from this area are then collected by a detector. The lateral resolution of the instrument is given by the size of the illuminated area. A surface map can be obtained by scanning the sample relative to the beam. More details of this kind of instruments can be found in the article of T. Munakata in this issue.

Compositional mapping of semiconductor quantum dots and rings

“…The technique with the highest lateral resolution obtained so far is photoemission electron microscopy (PEEM) which has been discussed in detail in Refs. [43,44]. It can reach a resolution of 20 nm which makes it suitable for compositional mapping of quantum dots.…”

Emerging surface characterization techniques for carbon steel corrosion: a critical brief review

“…(h) X-ray photoemission electron microscopy Submicrometre and nanometre imaging is possible through XPEEM. The details about operating procedures and principles are discussed by Heun et al [68]. New-generation XPEEM is represented by an instrument that is equipped with bandpass energy filter and is capable of providing high lateral resolution at around 0.5 µm with an X-ray source [69,70].…”

Lateral inhomogeneity of the Mg/(Zn+Mg) composition at the (Zn,Mg)O/CuIn(S,Se)2 thin-film solar cell interface revealed by photoemission electron microscopy

“…For samples with a pronounced surface roughness like the thin-film solar cell samples investigated in this study, PEEM is challenging since the contrast mechanisms described above can be dominated by topographical contrast, which will be discussed in conjunction with the data presented below. More detailed information on the PEEM technique [12][13][14][15] and its application to applied materials science [16][17][18][19] and thin-film solar cell structures 8,[20][21][22][23] can be found in respective literature. collecting all emitted electrons.…”