Browsing by Author "Chang, Lo-Yueh"

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Core-Level Shift of Graphene with Number of Layers Studied by Microphotoelectron Spectroscopy and Electrostatic Force Microscopy
(2014-10-30)
Lin, Chi-Yuan
;
Shiu, Hung-Wei
;
Chang, Lo-Yueh
;
Chen, Chia-Hao
;
Chang, Chen-Shiung
The dependence of C-1s core-level shift (CLS) of graphene on the number of layer (NL) is significant information to derive the coordination-resolved C1s core-level energy (E-1s) of carbon allotropes. To observe the variation of CLS of graphene with NL, binding energy and work function of graphene with various NL were examined by scanning photoelectron microscopy/spectroscopy and electrostatic force microscopy. E1s of grounded graphene decreased as NL increased. The E-1s of single-layer graphene and multilayer graphene (MLG) is 289.42 and 289.13 eV, respectively. Based on the NL-dependent E1s of graphene, the CLS of C-1s between a free carbon atom and diamond is 0.74 eV, calculated by the bond-order-length-strength correlation theory. The CLS of graphene with NL supported the existence of surface core-level shift (SCLS) on graphite. The magnitude of SCLS in MLG was +0.09 eV. The effective coordination number is 3.68 for bilayer graphene and 4.31 for the surface carbon layer in MLG.
Direct spectroscopic evidence of charge reversal at the Pb(Zr(0.2)Ti(0.8))O(3)/La(0.7)Sr(0.3)MnO(3) heterointerface
(2011-01-21)
Wu, Chung-Lin
;
Lee, Pei-Wei
;
Chen, Yi-Chun
;
Chang, Lo-Yueh
;
Chen, Chia-Hao
At the heterointerface of a top ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) (PZT) ultrathin film and a bottom La(0.7)Sr(0.3)MnO(3) (LSMO) electrode, we used continuous synchrotron-radiation photoelectron spectroscopy to probe in situ and demonstrated that the interfacial charges are reversible and their affected valence-band barrier height becomes modulated upon switching the polarization in the top layer. By monitoring the core-level shifting of the buried LSMO layer under continuous illumination of synchrotron radiation, we directly observed a temporal screening of polarization induced by the photon-generated carriers in the top PZT layer. This dynamic characterization of the core-level shifting of the buried layer demonstrates an effective method to probe the electric conduction and ferroelectric polarization of an ultrathin ferroelectric oxide thin film.
Direct spectroscopic evidence of charge reversal at the Pb(Zr0.2Ti0.8)O-3/La0.7Sr0.3MnO3 heterointerface
(2011-01-21)
Wu, Chung-Lin
;
Lee, Pei-Wei
;
Chen, Yi-Chun
;
Chang, Lo-Yueh
;
Chen, Chia-Hao
At the heterointerface of a top ferroelectric Pb(Zr0.2Ti0.8)O-3 (PZT) ultrathin film and a bottom La0.7Sr0.3MnO3 (LSMO) electrode, we used continuous synchrotron-radiation photoelectron spectroscopy to probe in situ and demonstrated that the interfacial charges are reversible and their affected valence-band barrier height becomes modulated upon switching the polarization in the top layer. By monitoring the core-level shifting of the buried LSMO layer under continuous illumination of synchrotron radiation, we directly observed a temporal screening of polarization induced by the photon-generated carriers in the top PZT layer. This dynamic characterization of the core-level shifting of the buried layer demonstrates an effective method to probe the electric conduction and ferroelectric polarization of an ultrathin ferroelectric oxide thin film.