TY - JOUR
T1 - Conduction band-edge states associated with the removal of d-state degeneracies by the Jahn-Teller effect
AU - Lucovsky, Gerald
AU - Fulton, C. C.
AU - Zhang, Y.
AU - Zou, Y.
AU - Luning, J.
AU - Edge, L. F.
AU - Whitten, J. L.
AU - Nemanich, R. J.
AU - Ade, H.
AU - Schlom, D. G.
AU - Afanase'v, V. V.
AU - Stesmans, A.
AU - Zollner, S.
AU - Triyoso, D.
AU - Rogers, B. R.
N1 - Funding Information:
Manuscript received September 28, 2004; revised January 11, 2005. The work of G. Lucovsky was supported by the Office of Naval Research (ONR), the Air Force Office of Scientific Research (AFOSR), the Semiconductor Research Corporation (SRC), and the SRC/International SEMATECH Front End Processes (FEP) Center. G. Lucovsky, C. C. Fulton, Y. Zhang, Y. Zou, R. J. Nemanich and H. Ade are with the Department of Physics, North Carolina State University, Raleigh, NC 27695 USA (e-mail: lucovsky@ncsu.edu). J. Luning is with the Stanford Synchrotron Radiation Laboratories, Menlo Park, CA 94025 USA. L. F. Edge and D. G. Schlom are with the Department of Materials Science and Engineering, Pennsylvania State University, State College, PA 16801 USA. J. L. Whitten is with the Department of Chemistry, North Carolina State University, Raleigh, NC 27695 USA. V. V. Afanase’v and A. Stesmans are with the Department of Physics, University of Leuven, Leuven, Belgium. S. Zollner and D. Triyoso are with Freescale Semiconductor, Inc., Tempe, AZ 85284 USA. B. R. Rogers is with the Department of Chemical Engineering, Vanderbilt University, Nashville, TN 37235 USA. Digital Object Identifier 10.1109/TDMR.2005.845804
PY - 2005/3
Y1 - 2005/3
N2 - X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-κ transition metal (TM) and trivalent lanthanide rare earth (RE) oxide gate dielectrics. The lowest conduction band d* -states in TiO2, ZrO2 and HfO2 are correlated with: 1) features in the O K1 edge, and 2) transitions from occupied Ti 2p, Zr 3p and Hf 4p states to empty Ti 3d-, Zr 4d-, and Hf 5d-states, respectively. The relative energies of d-state features indicate that the respective optical bandgaps, Eopt (or equivalentiy, Eg), and conduction band offset energy with respect to Si, EB, scale monotonically with the d-state energies of the TM/RE atoms. The multiplicity of d-state features in the Ti L2,3 spectrum of TiO2, and in the derivative of the O K1 spectra for ZrO2 and HfO2 indicate a removal of d-state degeneracies that results from a static Jahn-Teller effect in these nanocrystalline thin film oxides. Similar removals of d-state degeneracies are demonstrated for complex TM/RE oxides including Zr and Hf titanates, and La, Gd and Dy scandates. Analysis of XAS and band edge spectra indicate an additional band edge state that is assigned Jahn-Teller distortions at internal grain boundaries. These band edges defect states are electronically active in photoconductivity (PC), internal photoemission (IPE), and act as bulk traps in metal oxide semiconductor (MOS) devices, contributing to asymmetries in tunneling and Frenkel-Poole transport that have important consequences for performance and reliability in advanced Si devices.
AB - X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-κ transition metal (TM) and trivalent lanthanide rare earth (RE) oxide gate dielectrics. The lowest conduction band d* -states in TiO2, ZrO2 and HfO2 are correlated with: 1) features in the O K1 edge, and 2) transitions from occupied Ti 2p, Zr 3p and Hf 4p states to empty Ti 3d-, Zr 4d-, and Hf 5d-states, respectively. The relative energies of d-state features indicate that the respective optical bandgaps, Eopt (or equivalentiy, Eg), and conduction band offset energy with respect to Si, EB, scale monotonically with the d-state energies of the TM/RE atoms. The multiplicity of d-state features in the Ti L2,3 spectrum of TiO2, and in the derivative of the O K1 spectra for ZrO2 and HfO2 indicate a removal of d-state degeneracies that results from a static Jahn-Teller effect in these nanocrystalline thin film oxides. Similar removals of d-state degeneracies are demonstrated for complex TM/RE oxides including Zr and Hf titanates, and La, Gd and Dy scandates. Analysis of XAS and band edge spectra indicate an additional band edge state that is assigned Jahn-Teller distortions at internal grain boundaries. These band edges defect states are electronically active in photoconductivity (PC), internal photoemission (IPE), and act as bulk traps in metal oxide semiconductor (MOS) devices, contributing to asymmetries in tunneling and Frenkel-Poole transport that have important consequences for performance and reliability in advanced Si devices.
KW - Complex oxides
KW - Conduction band edge states
KW - D-state degeneracy
KW - High-κ dielectrics
KW - Jahn-Teller splittings
KW - Photoconductivity
KW - Spectroscopic ellipsometry
KW - X-ray absorption spectroscopy
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U2 - 10.1109/TDMR.2005.845804
DO - 10.1109/TDMR.2005.845804
M3 - Article
AN - SCOPUS:20444477165
SN - 1530-4388
VL - 5
SP - 65
EP - 83
JO - IEEE Transactions on Device and Materials Reliability
JF - IEEE Transactions on Device and Materials Reliability
IS - 1
ER -