@article{zhang_whitten_2009, title={Photoemission into Water Adsorbed on Metals: Probing Dissociative Electron Transfer Using Theory}, volume={109}, ISSN={["1097-461X"]}, DOI={10.1002/qua.22345}, abstractNote={Abstract}, number={15}, journal={INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY}, author={Zhang, Yu and Whitten, J. L.}, year={2009}, month={Dec}, pages={3541–3551} }
 @article{zhang_whitten_2009, title={Photoinduced dissociation of water adsorbed on a Ag cluster}, volume={903}, ISSN={["0166-1280"]}, DOI={10.1016/j.theochem.2008.12.050}, abstractNote={Theoretical electronic structure calculations are reported for the photoinduced dissociation of water adsorbed on a 31-atom silver cluster, Ag31 to produce H2 and adsorbed O. Both ground and excited electronic state processes are considered. The excited electronic state of interest is formed by photoemission of an electron from the Ag cluster and transient attachment of the electron to the adsorbed water molecule. A very large energy barrier for H2 formation (3.51 eV) is found for the ground state process while the barrier in the excited state is much smaller (0.47 eV). In the excited state, partial occupancy of an OH antibonding orbital facilitates OH stretch and the electron hole in the metal cluster stabilizes OH and O adsorbates. The excited state pathway for dissociation of water begins with the formation of an excited electronic state at 3.49 eV. Stretch of the OH bond up to 3.44 a.u. (1.82 Å) occurs with little change in energy. In this region of OH stretch the molecule must return to the ground state potential energy surface to dissociate fully and to form H2. Geometry optimizations are carried out using a simplex algorithm which allows the total energy to be calculated using configuration interaction theory.}, number={1-3}, journal={JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM}, author={Zhang, Yu and Whitten, Jerry L.}, year={2009}, month={Jun}, pages={28–33} }
 @article{zhang_whitten_2008, title={Photoinduced dissociation of water and transport of hydrogen between silver clusters}, volume={112}, ISSN={["1089-5639"]}, DOI={10.1021/jp800528j}, abstractNote={Theoretical electronic structure calculations are reported for the dissociation of water adsorbed on a 31-atom silver cluster, Ag31, and subsequent transfer of a H to a second Ag31 cluster leaving OH on the first cluster. Both ground and excited electronic state processes are considered for two choices of Ag cluster separation, 6.35 and 7.94 A, on the basis of preliminary calculations for a range of separation distances. The excited electronic state of interest is formed by photoemission of an electron from one Ag cluster and transient attachment of the photoemitted electron to the adsorbed water molecule. A very large energy barrier is found for the ground-state process (3.53 eV at a cluster separation of 6.35 A), while the barrier in the excited state is small (0.38 eV at a cluster separation of 6.35 A). In the excited state, partial occupancy of an OH antibonding orbital facilitates OH stretch and concomitant movement of the negatively charged OH toward the electron-hole in the metal cluster. The excited-state pathway for dissociation of water and transfer of H begins with the formation of an excited electronic state at 3.59-3.82 eV. Stretch of the OH bond occurs with little change in energy (0.38-0.54 eV up to a stretch of 1.96 A). In this region of OH stretch the molecule must return to the ground-state potential energy surface to fully dissociate and to transfer H to the other Ag cluster. Geometry optimizations are carried out using a simplex algorithm and a semigrid method. These methods allow the total energy to be calculated directly using configuration interaction theory.}, number={28}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Zhang, Yu and Whitten, Jerry L.}, year={2008}, month={Jul}, pages={6358–6363} }
 @article{lucovsky_fulton_zhang_luning_edge_whitten_nemanich_schlom_afanase'v_2005, title={Conduction band-edge d-states in high-k dielectrics due to Jahn-Teller term splittings}, volume={486}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2004.11.233}, abstractNote={X-ray absorption spectroscopy (XAS) is used to study conduction band edge electronic structure of high-k transition metal (TM) and trivalent lanthanide series rare earth (RE) oxide dielectrics. Empty TM/RE d-states are studied by intra-atomic transitions originating in core level spin-orbit split p-states, and conduction band states are studied in inter-atomic transitions which originate in the oxygen atom 1s core level state. In non-crystalline Zr and Hf silicate alloys, the local bonding symmetry, or crystal field splits these d-states into doubly and triply degenerate features. In nano-crystalline oxides, there are additional d-state splittings due to contributions of more distant neighbors that completely remove d-state degeneracies via the Jahn–Teller effect mechanism. This gives rise to highly localized band edge states that are electronically active in photoconductivity, internal photoemission, and act as bulk traps in metal oxide semiconductor (MOS) devices.}, number={1-2}, journal={THIN SOLID FILMS}, author={Lucovsky, G and Fulton, CC and Zhang, Y and Luning, J and Edge, L and Whitten, JL and Nemanich, RJ and Schlom, DG and Afanase'v, VV}, year={2005}, month={Aug}, pages={129–135} }
 @article{lucovsky_fulton_zhang_zou_luning_edge_whitten_nemanich_ade_schlom_et al._2005, title={Conduction band-edge states associated with the removal of d-state degeneracies by the Jahn-Teller effect}, volume={5}, ISSN={["1558-2574"]}, DOI={10.1109/TDMR.2005.845804}, abstractNote={X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-/spl kappa/ transition metal (TM) and trivalent lanthanide rare earth (RE) oxide gate dielectrics. The lowest conduction band d/sup */-states in TiO/sub 2/, ZrO/sub 2/ and HfO/sub 2/ are correlated with: 1) features in the O K/sub 1/ 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, E/sub opt/ (or equivalently, E/sub g/), and conduction band offset energy with respect to Si, E/sub B/, scale monotonically with the d-state energies of the TM/RE atoms. The multiplicity of d-state features in the Ti L/sub 2,3/ spectrum of TiO/sub 2/, and in the derivative of the O K/sub 1/ spectra for ZrO/sub 2/ and HfO/sub 2/ 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.}, number={1}, journal={IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY}, author={Lucovsky, G and Fulton, CC and Zhang, Y and Zou, Y and Luning, J and Edge, LF and Whitten, JL and Nemanich, RJ and Ade, H and Schlom, DG and et al.}, year={2005}, month={Mar}, pages={65–83} }
 @article{lucovsky_zhang_fulton_zou_nemanich_ade_whitten_2005, title={Final state effects in VUV and soft X-ray absorption spectra of transition metal oxides and silicate alloys: comparisons between experiment and ab initio calculations}, volume={144}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2005.01.251}, abstractNote={This paper uses X-ray absorption spectroscopy and vacuum ultra-violet spectroscopic ellipsometry to study the electronic structure of high-k transition metal (TM) oxide gate dielectrics. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d* states, which define the optical band gap, including their relationship to the band gap, Eg, of the oxide.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Lucovsky, G and Zhang, Y and Fulton, CC and Zou, Y and Nemanich, RJ and Ade, H and Whitten, JL}, year={2005}, month={Jun}, pages={917–919} }
 @article{lucovsky_zhang_luning_afanase'v_stesmans_zollner_triyoso_rogers_whitten_2005, title={Intrinsic band edge traps in nano-crystalline HfO2 gate dielectrics}, volume={80}, ISSN={["0167-9317"]}, DOI={10.1016/j.mee.2005.04.052}, abstractNote={Chemically pure thin films of HfO2, as well as other transition metal and rare earth elemental and complex oxides, e.g., LaScO3 and LaAlO3, are nanocrystalline as-deposited. The local bonding environments of the transition and rare earth atoms are distorted with respect to ideal octahedral or cubic bonding, and degeneracies of the respective band edge d-states are completely removed by Jahn-Teller (J-T) distortions. Spectroscopic studies have revealed these J-T term splittings, and also a band edge localized state which is assigned to an electronically-active bonding defect at nanocrystalline grain boundaries.}, journal={MICROELECTRONIC ENGINEERING}, author={Lucovsky, G and Zhang, Y and Luning, J and Afanase'v, VV and Stesmans, A and Zollner, S and Triyoso, D and Rogers, BR and Whitten, JL}, year={2005}, month={Jun}, pages={110–113} }
 @article{fulton_lucovsky_zhang_zou_nemanich_ade_whitten_2005, title={Studies of the coupling of final d*-states in mixed Hf and Ti oxides (HfO2)(x)(TiOx)(1-x) and other complex oxides}, volume={144}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2005.01.098}, abstractNote={Abstract X-ray absorption spectroscopy and vacuum ultra-violet spectroscopic ellipsometry are used to study the electronic structure of complex oxides comprised of mixed TM/TM and TM/RE oxides. Experimental spectra for HfTiO 4 and Gd(Dy)ScO 3 indicate multiple d-state features in the O K 1 edge. These are compared with the empirical models for atomic d-state mixing. It is concluded that a mean field, virtual alloy model does not apply, and that the effects associated with the differences in atomic coordination and deviations from ideal octahedral or cubic bonding play a determinant role in d-state atom mixing. The results are applied band edge engineering options for high- k dielectric applications.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Fulton, CC and Lucovsky, G and Zhang, Y and Zou, Y and Nemanich, RJ and Ade, H and Whitten, JL}, year={2005}, month={Jun}, pages={913–916} }
 @article{lucovsky_zhang_whitten_schlom_freeouf_2004, title={Separate and independent control of interfacial band alignments and dielectric constants in transition metal rare earth complex oxides}, volume={72}, ISSN={["0167-9317"]}, DOI={10.1016/j.mee.2004.01.006}, abstractNote={Spectroscopic studies of transition metal (Tm) and rare earth (Re) oxides, combined with ab initio theory, identify the band edge electronic structure of alternative high-k dielectrics. The lowest conduction band states are derived from anti-bonding transition metal d*-states with a π symmetry and show strong final state effects. Applied to the complex Tm/Re mixed oxides of the general form ReTmO3, this approach identifies a novel way for obtaining separate and independent control of band gap energies and dielectric constants through local bonding arrangements in which Tm and Re atoms are nearest neighbors to the same oxygen atom.}, number={1-4}, journal={MICROELECTRONIC ENGINEERING}, author={Lucovsky, G and Zhang, Y and Whitten, JL and Schlom, DG and Freeouf, JL}, year={2004}, month={Apr}, pages={288–293} }
 @article{lucovsky_zhang_whitten_schlom_freeouf_2004, title={Spectroscopic studies of the electrical structure of transition metal and rare earth complex oxides}, volume={21}, ISSN={["1386-9477"]}, DOI={10.1016/j.physe.2003.11.111}, abstractNote={Spectroscopic studies of transition metal (Tm) and rare earth (Re) oxides, combined with ab initio theory identify the band edge electronic structure of high-K dielectrics. The lowest conduction band states are derived from anti-bonding Tm (Re) d∗-states. A novel method for obtaining independent control of band gap energies and dielectric constants in complex oxides, ReTmO3, results from coupling of Tm and Re atom d-states bonded to the same oxygen atom.}, number={2-4}, journal={PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES}, author={Lucovsky, G and Zhang, Y and Whitten, JL and Schlom, DG and Freeouf, JL}, year={2004}, month={Mar}, pages={712–716} }
 @article{lucovsky_rayner_zhang_appel_whitten_2003, title={Band offset energies in zirconium silicate Si alloys}, volume={216}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(03)00429-X}, abstractNote={Transition metal silicates, (ZrO2)x(SiO2)1−x, with dielectric constants, k>10 have been proposed as alternative dielectrics for advanced Si devices. Studies by X-ray absorption, X-ray photoelectron and Auger electron spectroscopy are combined to identify the compositional variation of the valence and conduction band offset energies with respect to Si in Zr silicate alloys. The minimum conduction band offset energy, associated with localized Zr 4d∗-states, is ∼1.4 eV, and is independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO2 content. Differences between the coupling of tunneling electrons to localized Zr 4d∗ and extended Si 3s∗ states, characterized by respective tunneling masses of ∼0.5mo and ∼0.2mo, combine to contribute to a minimum in the direct tunneling current in the mid-silicate-alloy composition range, x∼0.4–0.6.}, number={1-4}, journal={APPLIED SURFACE SCIENCE}, author={Lucovsky, G and Rayner, B and Zhang, Y and Appel, G and Whitten, J}, year={2003}, month={Jun}, pages={215–222} }
 @article{lucovsky_raynor_zhang_fulton_nemanich_appel_ade_whitten_2003, title={Electronic structure of transition metal high-k dielectrics: interfacial band offset energies for microelectronic devices}, volume={212}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(03)00055-2}, abstractNote={Transition metal silicates, (ZrO2)x(SiO2)1� x, have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to}, number={2003 May 15}, journal={APPLIED SURFACE SCIENCE}, author={Lucovsky, G and Raynor, GB and Zhang, Y and Fulton, CC and Nemanich, RJ and Appel, G and Ade, H and Whitten, JL}, year={2003}, month={May}, pages={563–569} }
 @article{lucovsky_whitten_zhang_2002, title={A molecular orbital model for the electronic structure of transition metal atoms in silcate and aluminate alloys}, volume={190}, ISSN={["1873-5584"]}, DOI={10.1016/S0169-4332(01)00835-2}, abstractNote={Applied to transition metal oxides and silicate and aluminate alloys, a classification scheme that separates non-crystalline dielectrics into three groups with different amorphous morphologies, demonstrates a direct correlation between stability against crystallization and oxygen atom coordination. It also provides a local bonding model for molecular orbital (MO), calculations that are based on the coordination and symmetry of transition metal atoms and the orbital energies of their oxygen neighbors. These calculations provide important insights into the electronic structure of transition metal dielectrics, e.g. the role of anti-bonding d-states in determining conduction band offset energies with respect to Si.}, number={1-4}, journal={APPLIED SURFACE SCIENCE}, author={Lucovsky, G and Whitten, JL and Zhang, Y}, year={2002}, month={May}, pages={48–55} }
 @article{lucovsky_whitten_zhang_2002, title={A molecular orbital model for the electronic structure of transition metal atoms in silicate and aluminate alloys}, volume={46}, ISSN={["1879-2405"]}, DOI={10.1016/S0038-1101(02)00160-0}, abstractNote={A classification scheme that separates non-crystalline dielectrics into three groups with different amorphous morphologies reveals an approximately linear relationship between oxygen atom coordination and average bond ionicity. When applied to transition metal (TM) and rare earth (RE) lanthanide oxides, and their silicate and aluminate alloys, this approach demonstrates a correlation between stability against crystallization and oxygen atom coordination. It also provides a local bonding model for local molecular orbital calculations that are based on the coordination and symmetry of TM and RE atoms and the orbital energies of their oxygen neighbors. These calculations provide important insights into the electronic structure of TM and RE dielectrics, and in particular the role of atomic d-state energies in providing a scaling parameter for conduction band offset energies between gate dielectrics and the Si substrate.}, number={11}, journal={SOLID-STATE ELECTRONICS}, author={Lucovsky, G and Whitten, JL and Zhang, Y}, year={2002}, month={Nov}, pages={1687–1697} }
 @article{lucovsky_zhang_rayner_appel_ade_whitten_2002, title={Electronic structure of high-k transition metal oxides and their silicate and aluminate alloys}, volume={20}, number={4}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Lucovsky, G. and Zhang, Y. and Rayner, G. B. and Appel, G. and Ade, H. and Whitten, J. L.}, year={2002}, pages={1739–1747} }
 @article{rayner_kang_zhang_lucovsky_2002, title={Nonlinear composition dependence of x-ray photoelectron spectroscopy and Auger electron spectroscopy features in plasma-deposited zirconium silicate alloy thin films}, volume={20}, ISSN={["2166-2746"]}, DOI={10.1116/1.1493788}, abstractNote={The local bonding of Zr, Si, and O atoms in plasma-deposited, and post-deposition annealed Zr silicate pseudobinary alloys [(ZrO2)x(SiO2)1−x] was studied by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Systematic decreases in XPS binding energies, and increases in AES kinetic energies with alloy composition x are consistent with an empirical chemical bonding model based on electronegativity equalization; however, there are significant departures from the predicted linear composition dependencies of that model. Deviations from linearity in the XPS compositional dependencies are correlated with dipolar network atom fields as determined from ab initio calculations. The nonlinearities in the x dependence of ZrMVV and OKVV AES spectral features are determined primarily by oxygen–atom coordination dependent shifts in valence band offset energies. The energy spread in the compositional dependence of binding energies (∼1.85 eV) for the XPS Zr 3d5/2 and Si 2p features combined with x-ray absorption spectroscopy data indicates that the conduction band offset energies between the Si substrate and Zr silicate dielectrics are alloy composition independent. Changes in O 1s XPS features in alloys with x∼0.3 to 0.6 as function of annealing temperature are consistent with a previously identified chemical phase separation that occurs after 60 s anneals at 900 °C in a nonoxidizing ambient, Ar.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Rayner, GB and Kang, D and Zhang, Y and Lucovsky, G}, year={2002}, pages={1748–1758} }
 @article{lucovsky_rayner_kang_appel_johnson_zhang_sayers_ade_whitten_2001, title={Electronic structure of noncrystalline transition metal silicate and aluminate alloys}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1404997}, abstractNote={A localized molecular orbital description (LMO) for the electronic states of transition metal (TM) noncrystalline silicate and aluminate alloys establishes that the lowest conduction band states are derived from d states of TM atoms. The relative energies of these states are in agreement with the LMO approach, and have been measured by x-ray absorption spectroscopy for ZrO2–SiO2 alloys, and deduced from an interpretation of capacitance–voltage and current–voltage data for capacitors with Al2O3–Ta2O5 alloy dielectrics. The LMO model yields a scaling relationship for band offset energies providing a guideline for selection of gate dielectrics for advanced Si devices.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Lucovsky, G and Rayner, GB and Kang, D and Appel, G and Johnson, RS and Zhang, Y and Sayers, DE and Ade, H and Whitten, JL}, year={2001}, month={Sep}, pages={1775–1777} }
 @article{urquhart_ade_rafailovich_sokolov_zhang_2000, title={Chemical and vibronic effects in the high-resolution near-edge X-ray absorption fine structure spectra of polystyrene isotopomers}, volume={322}, DOI={10.1016/s0009-2614(00)00441-3}, abstractNote={This Letter presents the high-resolution C 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of hydrogenated and deuterated polystyrene. The differences between these spectra provide unambiguous evidence for the presence of a significant vibronic contribution to the shape and structure of the C 1s(C–H) →1π∗CC transition in polystyrene. High-resolution NEXAFS spectra, spectroscopic simulations and ab initio calculations are used to help resolve the relative contributions of chemical shifts and vibronic excitation to the shape of the characteristic C 1s(C–H) →1π∗CC transition.}, number={5}, journal={Chemical Physics Letters}, author={Urquhart, S. G. and Ade, Harald and Rafailovich, M. and Sokolov, J. S. and Zhang, Y.}, year={2000}, pages={412–418} }
 @article{zhang_chung_1998, title={2s(2)2p P-2(o) triply excited state of He-}, volume={58}, ISSN={["1094-1622"]}, DOI={10.1103/PhysRevA.58.3336}, abstractNote={The triply excited ${2s}^{2}2p{}^{2}{P}^{o}$ state of ${\mathrm{He}}^{\ensuremath{-}}$ is studied by using the saddle-point complex-rotation method. The energy and Auger width of this resonance are calculated. Relativistic corrections are evaluated with the first-order perturbation theory, and the mass-polarization effect is also included. The partial Auger widths are calculated for the individual open channels. The total width is obtained by coupling the important open channels and summing over the other channels. These results are compared with the theoretical and experimental data in the literature.}, number={4}, journal={PHYSICAL REVIEW A}, author={Zhang, Y and Chung, KT}, year={1998}, month={Oct}, pages={3336–3337} }
 @article{zhang_chung_1998, title={Even-parity triply excited states of lithium}, volume={58}, ISSN={["1094-1622"]}, DOI={10.1103/PhysRevA.58.1098}, abstractNote={In this work, 14 even-parity ${2l2l}^{\ensuremath{'}}{\mathrm{nl}}^{\ensuremath{''}}$ $(ng~3)$ resonances of lithium are calculated by using the saddle-point complex-rotation method. Among the 14 resonances, four are ${}^{2}P$ resonances, four are ${}^{2}D$ resonances, and six are ${}^{2}S$ resonances. Relativistic corrections are evaluated with the first-order perturbation theory and the mass-polarization effect is also included. The Auger widths are studied. The partial Auger widths are calculated for the individual open channels and the total width is obtained by coupling the important open channels. These results are compared with recent theoretical and experimental data in the literature.}, number={2}, journal={PHYSICAL REVIEW A}, author={Zhang, Y and Chung, KT}, year={1998}, month={Aug}, pages={1098–1102} }