Browsing by Author "Pao, CW"

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Comparison of the electronic structures of AIN nanotips grown on p- and n-type Si substrates
(2005-12-07)
Chiou, JW
;
Tsai, HM
;
Pao, CW
;
Dong, CL
;
Chang, CL
At and N K-edge x-ray absorption near-edge structure (XANES), scanning photoelectron microscopy (SPEM) and x-ray emission measurements were performed on AIN nanotips grown on p- and n-type Si substrates (p-AIN and n-AIN). Features and intensities in the Al and N K-edge XANES spectra of these AIN nanotips overall are similar. In contrast, the intensities of the valence-band SPEM spectra of p-AIN are apparently larger than those of n-AIN, which indicates that the valence-band density of states of p-AIN exceeds that of n-AIN. This result may be related to the observed enhancement of field-emission intensity of AIN nanotips grown on the p-type Si substrate.
Direct experimental evidence of hybridization of Pb states with O 2p states in ferroelectric perovskite oxides
(2005-07-04)
Jan, JC
;
Tsai, HM
;
Pao, CW
;
Chiou, JW
;
Asokan, CK
This work presents the O K- and Ti L-3,L-2-edge x-ray absorption near-edge structure (XANES) spectra of PbxSr1-xTiO3 (PxSTO) and BaxSr1-xTiO3 (BxSTO) compounds with various Pb and Ba concentrations. The result provides direct evidence that the Pb-O bonding strongly affects O 2p-Ti 3d hybridization in the TiO6 octahedron of PxSTO. In contrast, the Ba-O bonding does not substantially affect O 2p-Ti 3d hybridization in BxSTO. The Ti L-3-edge XANES spectra show the splitting of the e(g) band for PxSTO with x greater than or similar to 0.5, which provides an evidence of Pb-induced tetragonal distortion in the TiO6 octahedron. In contrast, e(g) band splitting is absent in BxSTO. (c) 2005 American Institute of Physics.