Zone-Plate-Based Scanning Photoelectron Microscopy at Srrc: Performance and Applications

Abstract

Adapting classical spectroscopic methods to the new challenge of studying nanomaterials, imaging techniques are the trendsetter in recent years. Among them is scanning photoelectron microscopy (SPEM) with submicron spatial resolution, where the sample surface is raster-scanned by a focused soft X-ray beam, and the emitted photoelectrons are collected at each point by the input optics of an electron energy analyzer. We have constructed such a station at SRRC in Taiwan, which is now fully in operation. In this paper, we introduce the specific features of the instrument and discuss application examples on the characterization of scanning-probe-induced Si3N4 to SiOx conversion and electron-and plasma-induced chemical changes in alkanethiols self-assembled monolayers. In combining two-dimensional imaging and micro-photoemission, SPEM can reveal valuable information on the chemical and electronic properties of structured and multiphase materials.

Electrical control of nanoscale functionalization in graphene by the scanning probe technique

“…The detailed specifications of each beamline can be found in previous publications. 19,20 In both of the beamlines, a wide range of photon energy from 250 to 800 eV is available to collect photoelectrons from the sample using a hemispherical sector electron analyzer with multichannel detection (MCD) capability. The two-dimensional maps are obtained by scanning the sample with respect to the beam.…”

Graphene as tunable transparent electrode material on GaN: Layer-number-dependent optical and electrical properties

“…The soft X-ray beam utilized in these experiments, of photon energy 380 eV, was focused with Fresnel zone-plate optics; the spatial resolution is about 100 nm. 8 The photon energy was calibrated with the C 1s core-level line of exfoliated graphite sheets at binding energy (BE) 284.4 eV. 9 The overall energy resolution is better than 100 meV.…”

Scanning Photoelectron Microscopy for the Characterization of Novel Nanomaterials

“…By raster scanning the sample with respect to the focused photon beam and collecting the photoelectrons emitted from the illuminated microspot in a synchronized manner, a two-dimensional distribution of photoelectron intensity can be constructed. The three major components of an SPEM system are (i) focusing optics, (ii) electron energy analyzer, and (iii) sample scanning mechanism [3,4]. A schematic drawing of ZP-based SPEM system is illustrated in Figure 4.9; the detailed explanation is given in the following sections.…”

“…The respective signals can be used for image formation. For example, the SPEM at NSRRC has a 16-channel detector that allows a simultaneous acquisition of a set of 16 images corresponding to different KEs of photoelectrons in a single scan [3][4][5]. The images can be further processed including summing of all channels and the selection and subtraction of individual channels.…”

“…In order to manipulate and scan the sample surface in both millimeter-and micrometer scales, SPEM stations are generally equipped with two sets of sample positioning and scanning mechanisms; a mechanical step motor platform and an ultrahigh vacuum (UHV) compatible piezoelectric-driven stage [1,3]. Both scanning mechanisms are operated under computer control and synchronized with the data acquisition.…”