Photo electron emission microscopy of polarity-patterned materials

W. C. Yang, B. J. Rodriguez, A. Gruverman, Robert Nemanich

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

This study presents variable photon energy photo electron emission microscopy (PEEM) of polarity-patterned epitaxial GaN films, and ferroelectric LiNbO3 (LNO) single crystals and PbZrTiO3 (PZT) thin films. The photo electrons were excited with spontaneous emission from the tunable UV free electron laser (FEL) at Duke University. We report PEEM observation of polarity contrast and measurement of the photothreshold of each polar region of the materials. For a cleaned GaN film with laterally patterned Ga- and N-face polarities, we found a higher photoelectric yield from the N-face regions compared with the Ga-face regions. Through the photon energy dependent contrast in the PEEM images of the surfaces, we can deduce that the threshold of the N-face region is less than ∼4.9 eV while that of the Ga-face regions is greater than 6.3 eV. In both LNO and PZT, bright emission was detected from the negatively poled domains, indicating that the emission threshold of the negative domain is lower than that of the positive domain. For LNO, the measured photothreshold was ∼4.6 eV at the negative domain and ∼6.2 eV at the positive domain, while for PZT, the threshold of the negative domain was less than 4.3 eV. Moreover, PEEM observation of the PZT surface at elevated temperatures displayed that the domain contrast disappeared near the Curie temperature of ∼300 °C. The PEEM polarity contrast of the polar materials is discussed in terms of internal screening from free carriers and defects and the external screening due to adsorbed ions.

Original languageEnglish (US)
JournalJournal of Physics Condensed Matter
Volume17
Issue number16
DOIs
StatePublished - Apr 27 2005
Externally publishedYes

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Electron emission
electron emission
polarity
Microscopic examination
microscopy
Screening
Photons
thresholds
Spontaneous emission
Epitaxial films
Free electron lasers
screening
Curie temperature
Ferroelectric materials
photons
Single crystals
ultraviolet lasers
Ions
free electron lasers
polar regions

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Photo electron emission microscopy of polarity-patterned materials. / Yang, W. C.; Rodriguez, B. J.; Gruverman, A.; Nemanich, Robert.

In: Journal of Physics Condensed Matter, Vol. 17, No. 16, 27.04.2005.

Research output: Contribution to journalArticle

Yang, W. C. ; Rodriguez, B. J. ; Gruverman, A. ; Nemanich, Robert. / Photo electron emission microscopy of polarity-patterned materials. In: Journal of Physics Condensed Matter. 2005 ; Vol. 17, No. 16.
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