skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Ultra-High Vacuum Compatible Optical Chopper System for Synchrotron X-ray Scanning Tunneling Microscopy

Abstract

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division; Argonne National Laboratory - Advanced Photon Source
OSTI Identifier:
1400397
DOE Contract Number:
AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 12th International Conference on X-Ray Microscopy , 10/26/14 - 10/31/14, Melbourne, Australia
Country of Publication:
United States
Language:
English

Citation Formats

Chang, Hao, Cummings, Marvin L., Shirato, Nozomi, Stripe, Benjamin D., Rosenmann, Daniel, Preissner, Curt A., Freeland, John W., Kersell, Heath R., Hla, Saw Wai, and Rose, Volker. Ultra-High Vacuum Compatible Optical Chopper System for Synchrotron X-ray Scanning Tunneling Microscopy. United States: N. p., 2015. Web. doi:10.1063/1.4937495.
Chang, Hao, Cummings, Marvin L., Shirato, Nozomi, Stripe, Benjamin D., Rosenmann, Daniel, Preissner, Curt A., Freeland, John W., Kersell, Heath R., Hla, Saw Wai, & Rose, Volker. Ultra-High Vacuum Compatible Optical Chopper System for Synchrotron X-ray Scanning Tunneling Microscopy. United States. doi:10.1063/1.4937495.
Chang, Hao, Cummings, Marvin L., Shirato, Nozomi, Stripe, Benjamin D., Rosenmann, Daniel, Preissner, Curt A., Freeland, John W., Kersell, Heath R., Hla, Saw Wai, and Rose, Volker. Thu . "Ultra-High Vacuum Compatible Optical Chopper System for Synchrotron X-ray Scanning Tunneling Microscopy". United States. doi:10.1063/1.4937495.
@article{osti_1400397,
title = {Ultra-High Vacuum Compatible Optical Chopper System for Synchrotron X-ray Scanning Tunneling Microscopy},
author = {Chang, Hao and Cummings, Marvin L. and Shirato, Nozomi and Stripe, Benjamin D. and Rosenmann, Daniel and Preissner, Curt A. and Freeland, John W. and Kersell, Heath R. and Hla, Saw Wai and Rose, Volker},
abstractNote = {High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.},
doi = {10.1063/1.4937495},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2015},
month = {Thu Jan 01 00:00:00 EST 2015}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beammore » attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less
  • Epitaxial graphene, grown by thermal decomposition of the SiC (0001) surface, is a promising material for future applications due to its unique and superlative electronic properties. However, the innate chemical passivity of graphene presents challenges for integration with other materials for device applications. Here, we present structural characterization of epitaxial graphene functionalized by the organic semiconductor perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). A combination of ultra-high vacuum scanning tunneling microscopy (STM) and high-resolution X-ray reflectivity (XRR) is used to extract lateral and vertical structures of 0, 1, and 2 monolayer (ML) PTCDA on epitaxial graphene. Both Fienup-based phase-retrieval algorithms and model-based least-squares analysesmore » of the XRR data are used to extract an electron density profile that is interpreted in terms of a stacking sequence of molecular layers with specific interlayer spacings. Features in the STM and XRR analysis indicate long-range molecular ordering and weak π–π* interactions binding PTCDA molecules to the graphene surface. The high degree of both lateral and vertical ordering of the self-assembled film demonstrates PTCDA functionalization as a viable route for templating graphene for the growth and deposition of additional materials required for next-generation electronics and sensors.« less
  • We have developed a very compact (60 {times} 60 {times} 75 mm{sup 3}), vacuum compatible, large format (25 {times} 25 mm{sup 2}, 1024 {times} 1024 pixels) CCD camera for digital imaging of visible and ultraviolet radiation, soft to penetrating x-rays ({le}20 keV), and charged particles. This camera provides a suitable replacement for film with a linear response, dynamic range and intrinsic signal-to- noise response superior than current x-ray film, and provides real- time access to the data. The spatial resolution of the camera (< 25 {mu}m) is similar to typical digitization slit or step sizes used in processing film data.more » This new large format CCD camera has immediate applications as the recording device for steak cameras or gated microchannel plate diagnostic, or when used directly as the detector for x-ray, xuv, or optical signals. This is especially important in studying high-energy plasmas produced in pulse-power, ICF, and high powered laser-plasma experiments, as well as other medical and industrial applications.« less
  • A variety of defects on {100} cleavage surfaces of pyrite (FeS2) are observed directly using ultra high vacuum scanning tunneling microscopy. Step edges are aligned along <10> and <11> surface directions. Atomic scale images indicate that the atomic structure, with a respect to the Fe lattice, and local density of occupied states is unchanged at a step edge, including kink and corner sites. The inferred presence of monosulfides at step edges, based on X-ray photoelectron spectra on similar surfaces elsewhere, does not lead to occupied states higher in energy that dz2 dangling bond states at Fe sites. A sequence ofmore » consecutive images at the atomic scale captured evidence of dynamic structural changes at defects on this surface at room temperature. Step edges are seen to be generally stable over the course of the STM observations, whereas vacancies, their surrounding sites, and corner step edge sites are not. Theoretical maps of the attachment energy for an Fe adatom over a {100} surface cell indicate the presence of low energy diffusion channels along the topology of the closest S atoms in the uppermost atomic S monolayer. Calculation of the activation energy barriers for the self-diffusion of an Fe adatom over a {100} terrace predict low 0.1 eV diffusion barriers along channels and 0.24 eV across channels. Subsequently, calculated Fe adatom mobilities over the time scale of the STM observations are very high, ranging from 105-106 ? over the course of one minute, calculated for room temperature and depending on the diffusion direction. The structural changes documented in the STM images are explained as resulting from the natural process of surface self-diffusion.« less