@article{lucovsky_seo_lee_fleming_ulrich_luning_lysaght_bersuker_2007, title={Intrinsic electronically active defects in transition metal elemental oxides}, volume={46}, ISSN={["0021-4922"]}, DOI={10.1143/JJAP.46.1899}, abstractNote={Densities of interfacial and bulk defects in high-κ dielectrics are typically about two orders of magnitude larger than those in Si–SiO2 devices. An asymmetry in electron and hole trapping kinetics, first detected in test capacitor devices with nanocrystalline ZrO2 and HfO2 dielectrics, is a significant potential limitation for Si device operation and reliability in complementary metal oxide semiconductor applications. There are two crucial issues: i) are the electron and hole traps intrinsic defects, or are they associated with processed-introduced impurities?, and ii) what are the local atomic bonding arrangements and electronic state energies of these traps? In this study, thin film nanocrystalline high-κ gate dielectrics, TiO2, ZrO2, and HfO2 (group IVB TM oxides), are investigated spectroscopically to identify the intrinsic electronic structures of valence and conduction band states, as well as those of intrinsic bonding defects. A quantitative/qualitative distinction is made between crystal field and Jahn–Teller (J–T) d-state energy differences in nanocrystralline TM elemental oxides, and noncrystalline TM silicates and Si oxynitrides. It is experimentally shown and theoretically supported that a length scale for nanocrystallite size <2–3 nm i) eliminates J–T d-state term splittings in band edge π-bonded d-states, and ii) represents a transition from the observation of discrete band edge defects to band-tail defects. Additionally, π-state bonding coherence can also be disrupted with similar effects on band edge and defect states in HfO2 films which have been annealed in NH3 at 700 °C, and display Hf–N bonds in N atom K1 edge X-ray absorption spectra.}, number={4B}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS}, author={Lucovsky, Gerald and Seo, Hyungtak and Lee, Sanghyun and Fleming, Leslie B. and Ulrich, Marc D. and Luning, Jan and Lysaght, Pat and Bersuker, Gennadi}, year={2007}, month={Apr}, pages={1899–1909} }
 @article{fleming_fulton_lucovsky_rowe_ulrich_luening_2007, title={Local bonding analysis of the valence and conduction band features of TiO2}, volume={102}, ISSN={["1089-7550"]}, DOI={10.1063/1.2764004}, abstractNote={An analysis of the valence and conduction band electronic structure of TiO2 as studied by ultraviolet photoemission spectroscopy (UPS) and x-ray absorption spectroscopy (XAS) using synchrotron radiation is reported. Valence band spectra from UPS have been deconvolved using a five-peak model. The spectra are interpreted based on the peak assignments to the XAS data and the symmetries of the valence band states. The interpretation is consistent with theoretical calculations of molecular orbitals found in the literature. The removal of the d-state degeneracies that arise from a collective Jahn–Teller splitting of the crystal field split t2g and eg states is observed and scales with the conduction band results from the absorption data. These Jahn–Teller derived energy separations are present in the O K1 and Ti L3 spectra but are not resolved in the photoemission valence band spectra. Two defect states are clearly observed ∼0.7 and 2.0 eV above the valence band edge and are attributed to the presence of oxygen atom vacancies that are described in terms of Ti3+ states.}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Fleming, I. and Fulton, C. C. and Lucovsky, G. and Rowe, J. E. and Ulrich, M. D. and Luening, J.}, year={2007}, month={Aug} }
 @article{lucovsky_luening_fleming_ulrich_rowe_seo_lee_lysaght_bersuker_2007, title={Spectroscopic studies of O-vacancy defects in transition metal oxides}, volume={18}, ISSN={["1573-482X"]}, DOI={10.1007/s10854-007-9192-x}, journal={JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS}, author={Lucovsky, G. and Luening, J. and Fleming, L. B. and Ulrich, M. D. and Rowe, J. E. and Seo, H. and Lee, S. and Lysaght, P. and Bersuker, G.}, year={2007}, month={Oct}, pages={S263–S266} }
 @article{lucovsky_seo_fleming_luening_lysaght_bersuker_2007, title={Studies of bonding defects, and defect state suppression in HfO2 by soft X-ray absorption and photoelectron spectroscopies}, volume={601}, ISSN={["1879-2758"]}, DOI={10.1016/j.susc.2007.04.197}, abstractNote={This paper identifies two-different regimes of nano-crystallinity: (i) thin films with nano-crystallites >3 nm, that display coherent well-defined grain-boundaries, and (ii) thin films with nano-crystallites less than ∼2 nm, that display neither will-defined grain-boundaries nor lattice planes in high resolution transmission electron microscopy images, but yield an image indicative of clusters of small nano-crystallites with a length scale order of ∼2 nm. Near edge X-ray absorption spectroscopy, and soft-X-ray photoelectron spectroscopy, combined with visible and UV spectroscopic ellipsometry, provide an unambiguous way to distinguish between these two technologically important regimes of nano-crystalline order, yielding significant information on electronic structure of intrinsic band edge states and intrinsic electronically-active defects.}, number={18}, journal={SURFACE SCIENCE}, author={Lucovsky, G. and Seo, H. and Fleming, L. B. and Luening, J. and Lysaght, P. and Bersuker, G.}, year={2007}, month={Sep}, pages={4236–4241} }
 @article{ulrich_rowe_keister_2006, title={Comparison of ultrathin SiO2/Si(100) and SiO2/Si(111) interfaces from soft x-ray photoelectron spectroscopy}, volume={24}, ISSN={["2166-2746"]}, DOI={10.1116/1.2218865}, abstractNote={The limitations of soft x-ray photoelectron spectroscopy (SXPS) for determining structural information of the SiO2∕Si interface for device-grade ultrathin (∼6–22Å) films of SiO2 prepared from crystalline silicon by remote plasma assisted oxidation are explored. The main focus of this article is the limitation of data analysis and sensitivity to structural parameters. In particular, annealing data shows a significant decrease in the integrated density of suboxide bonding arrangements as determined from analysis of SXPS data. These decreases and changes are interpreted as evidence for reorganization of specific interface bonding arrangements due to the annealing process. Moreover, these results suggest that sample preparation and processing history are both critical for defining the nature of the SiO2∕Si interface, and therefore its electrical properties. Quantitative estimates of the interface state densities are derived from SXPS data revealing ∼2 monolayers (ML) of suboxide as prepared and ∼1.5 ML of suboxide after rapid thermal annealing at 900°C for both Si(100) and Si(111) substrates. Comparison of the individual suboxide bonding state densities indicate for both Si substrate crystallographic orientations that annealing causes a self-organization of the suboxide consistent with bond constraint theory.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Ulrich, M. D. and Rowe, J. E. and Keister, J. W.}, year={2006}, pages={2132–2137} }
 @article{lucovsky_seo_fleming_ulrich_luning_lysaght_bersuker_2006, title={Intrinsic bonding defects in transition metal elemental oxides}, volume={46}, ISSN={["0026-2714"]}, DOI={10.1016/j.microrel.2006.07.032}, abstractNote={Gate dielectrics comprised of nanocrystalline HfO2 in gate stacks with thin SiO2/SiON interfacial transition regions display significant asymmetries with respect to trapping of Si substrate injected holes and electrons. Based on spectroscopic studies, and guided by ab initio theory, electron and hole traps in HfO2 and other transition metal elemental oxides are assigned to O-atom divacancies, clustered at internal grain boundaries. Three engineering solutions for defect reduction are identified: i) deposition of ultra-thin, <2 nm, HfO2 dielectric layers, in which grain boundary formation is suppressed by effectively eliminating inter-primitive unit cell π-bonding interactions, ii) chemically phase separated high HfO2 silicates in which inter-primitive unit cell p-bonding interactions are suppressed by the two nanocrystalline grain size limitations resulting from SiO2 inclusions, and iii) non-crystalline Zr/Hf Si oxynitrides without grain boundary defects.}, number={9-11}, journal={MICROELECTRONICS RELIABILITY}, author={Lucovsky, G. and Seo, H. and Fleming, L. B. and Ulrich, M. D. and Luning, J. and Lysaght, P. and Bersuker, G.}, year={2006}, pages={1623–1628} }