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Theoretical and Experimental Study of Tip Electronic Structure in Scanning Tunneling Microscope

Published online by Cambridge University Press:  31 January 2011

HeeSung Choi,
Min Huang,
Joshua B Ballard,
Kevin T He,
Scott W Schmucker,
Joseph N Lyding,
John N Randall and
Kyeongjae Cho
HeeSung Choi
Affiliation:
hschoi@utdallas.eduhschoi07@gmail.com, University of Texas at Dallas, Department of Materials Science & Engineering and Department of Physics, Richardson, Texas, United States
Min Huang
Affiliation:
minhuang@utdallas.edu, University of Texas at Dallas, Department of Materials Science & Engineering and Department of Physics, Richardson, Texas, United States
Joshua B Ballard
Affiliation:
jballard@zyvexlabs.com, Zyvex Labs, Richardson, Texas, United States
Kevin T He
Affiliation:
kevinhe@uiuc.edu, University of Illinois Urbana-Champaign, Department of Electrical and Computer Engineering and Bechman Institute, Urbana, Illinois, United States
Scott W Schmucker
Affiliation:
sschmuc2@uiuc.edu, University of Illinois Urbana-Champaign, Department of Electrical and Computer Engineering and Bechman Institute, Urbana, Illinois, United States
Joseph N Lyding
Affiliation:
lyding@uiuc.edu, University of Illinois Urbana-Champaign, Department of Electrical and Computer Engineering and Bechman Institute, Urbana, Illinois, United States
John N Randall
Affiliation:
jrandall@zyvexlabs.com, Zyvex Labs, Richardson, Texas, United States
Kyeongjae Cho
Affiliation:
kjcho@utdallas.edu, University of Texas at Dallas, Department of Materials Science & Engineering and Department of Physics, Richardson, Texas, United States
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Abstract

The atomic and electronic structures of pyramidal model STM tips of transition metals (W, Rh, Pd, Ir and Pt) were investigated using density functional theory (DFT) method. The calculated density of states show that d electrons of the apex atoms in the M4 (M = W, Rh, Pd, Ir, Pt) model tips behave differently near the Fermi level, with the dz2 state being dominant only for W tip. The electronic structures of pyramid structures of W and Pd single-atom tips with larger sizes are studied and compared. The density of states of Pd apex atom and W apex atom show different occupation of d-bands leading to asymmetric density of states for Pd tip. The asymmetric tunneling currents measured by W and Pt-Ir STM tips are explained by the calculated electronic structures of W and Pd model tips.

Keywords

scanning tunneling microscopy (STM)simulationelectronic structure

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