|AVS 57th International Symposium & Exhibition|
|Thin Film||Thursday Sessions|
|Session:||Modeling and Analysis of Thin Films|
|Presenter:||G. Lucovsky, North Carolina State University|
|Correspondent:||Click to Email|
Correlated atomic positions of Si-atoms bonded to 2-fold coordinated O-atoms are determined by Si 3d-dervied T2g states on these atoms . These states constrain dihedral angles contributing to medium range order with correlation lengths of ~0.4 and 0.45 nm, and, a coherence length of ~1 nm, each obtained from the first sharp diffraction peak in X-ray diffraction . O K edge soft X-ray SiO2 spectra reveal conduction band edge states with singly degenerate A1 symmetry, and stronger doubly and triply degenerate E and T2 d-state beginning at energies ~3 eV higher. This difference is smaller in c-Si, ~1 eV. Analysis of O K and L2,3 spectra are based on a charge transfer multiplet many electron theory . Energy differences are the same for band edge features obtained from transmission/reflectivity studies in the visible/VUV where the d-state character was not previously recognized . The correspondence derives from O 1s core hole localization, and a coherent process in which 1s core holes are filled by electrons from valence band O 2p p states, accounting for the one-to-one correspondence between sequenced features in the O K edge, and in the Si L2,3 spectrum of SiO2. L2,3 spectra, studied by electron energy loss spectroscopy (EELS), have not detected the weaker Si A1 features in the 100 to 104 eV regime of SiO2, or 98 to 100 eV regime of c-Si. The O K edge X-ray spectra of transition metal elemental and complex oxides are qualitatively different with either doubly or triply degenerate d-state derived spectral features at the band edge. This results in significant quantitative differences in (i) the high-spin excited d-states of O-atom vacancy occupied d2 states, and (ii) the negative ion electronically active d-state traps populated by charge injection. O-vacancy states in SiO2 are close to mid-gap, and do not contribute to gate stack tunneling processes. This explains the order of magnitude higher interfacial trap densities, dit, and trap-assisted tunneling in HfO2 gate stacks. It also accounts for significant differences in radiation hardness. XAS spectra are presented for the first time for remote plasma deposited GeO2. These deposited films display significantly different O K edge spectra than those obtained by oxidation of Ge; more importantly A1, and E and T2g features stronger and narrower than those of SiO2. Electrical data for deposited GeO2 dielectrics on Si and Ge substrates are compared for the first time with SiO2 test devices on the same substrates.
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