AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM+AS-ThM

Paper EM+AS-ThM7
Line-Width and Symmetry Changes in Jahn Teller Term-Split Sc 3d-States in LaScO3 as a Function of Deposition and Annealing Temperatures

Thursday, November 16, 2006, 10:00 am, Room 2003

Session: High-k Dielectric Characterization
Presenter: H. Seo, NC State University
Authors: H. Seo, NC State University
L.F. Edge, Penn State University
D.G. Schlom, Penn State University
N.A. Stoute, NC State University
G. Lucovsky, NC State University
Correspondent: Click to Email
LaScO@sub 3@ conduction band states are derived in part from Jahn-Teller-split Sc 3d-states in distorted octahedral arrangements of O-neighbors. Conventional XRD for films deposited at ~300°C, and annealed to 700°C display no evidence for crystallinity, while films annealed to >800°C display strong crystalline features. New studies of conduction band states by i) vacuum ultra-violet spectroscopic ellipsometry (VUV SE), and ii) x-ray absorption spectra (XAS) for transitions from (a) spin-orbit split Sc 2p core states (Sc L@sub 2,3@) and (b) the O 1s core state (O K@sub 1@), are compared, providing insights into scales of order. XRD results are indicative of grain sizes >5 nm for >800°C anneals, but do not distinguish between i) amorphous films, and ii) nanocrystalline films with grain sizes <5 nm. The new spectroscopic studies provide evidence for crystallinity in as-deposited films, and films annealed at 700°C, indicating a significant decrease in Sc 3d feature line-widths for annealing between 700°C and 1000°C. These changes are also evident in VUV SE spectra for transitions between de-localized O 2p valence band edge states, and empty O-atom molecular orbitals (MO) with Sc and La d-state contributions. The empty MO states for Sc L@sub 2,3@ and O K@sub 1@ core level excitations are essentially the same, but with significantly different matrix elements. Results of photoconductivity and internal photoemission studies are revisited and reinterpreted, providing a quantitative basis for strong matrix element effects that distinguish between a band gap at 6.0 eV for the onset of strong optical absorption, and weaker transitions at ~4.6-5 eV that define band offset energy thresholds at internal dielectric interfaces.