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.
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Acknowledgements
This material is based upon work supported by the Defense Advanced Research Project Agency (DARPA) and Space and Naval Warfare Center, San Diego (SPAWARSYSCEN-SD) under contract N66001-08-C-2040. It is also supported by a grant from the Emerging Technology Fund of the State of Texas to the Atomically Precise Manufacturing Consortium.
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Choi, H., Huang, M., Ballard, J.B. et al. Theoretical and Experimental Study of Tip Electronic Structures in Scanning Tunneling Microscope. MRS Online Proceedings Library 1177, 1–6 (2009). https://doi.org/10.1557/PROC-1177-Z06-03
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DOI: https://doi.org/10.1557/PROC-1177-Z06-03