Pong, WF, Chang YK, Hsieh HH, Tsai MH, Lee KH, Dann TE, Chien FZ, Tseng PK, Tsang KL, Su WK, Chen LC, Wei SL, Chen KH, Bhusari DM, Chen YF.
1998.
Electronic and Atomic Structures of Si-C-N Thin Film by X-ray-absorption Spectroscopy. J. Electron Spectroscopy and Related Pheno.. 92:115.
Ray, SC, Tsai HM, Bao CW, Chiou JW, Jan JC, Kumar K, Pong* WF, Tsai M-H, Chattopadhyay S, Chen LC, Chien SC, Lee MT, Lin ST, Chen KH.
2004.
Electronic and bonding structures of B-C-N thin films by X-ray absorption and photoemission spectroscopy. J. Appl. Phys. . 96:208-211.
Pao, CW, Babu PD, Tsai HM, Chiou JW, Ray SC, Yang SC, Chien FZ, Pong* WF, Tsai M-H, Hsu CW, Chen LC, Chen KH, Lin H-J, Lee JF, Guo JH.
2006.
Electronic structure of group-III-nitride nanorods studied by x-ray absorption, x-ray emission, and Raman spectroscopy. Appl. Phys. Lett.. 88:223113-(1-3).
Bayikadi, KS, Sankar R, Wu CT, Xia C, Chen Y, Chen L-C, Chen K-H, Chou F-C.
2019.
Enhanced thermoelectric performance of GeTe through in situ microdomain and Ge-vacancy control, 2019. Journal of Materials Chemistry A. 7(25):15181-15189.: The Royal Society of Chemistry
AbstractA highly reproducible sample preparation method for pure GeTe in a rhombohedral structure without converting to the cubic structure up to ∼500 °C is reported to show control of the Ge-vacancy level and the corresponding herringbone-structured microdomains. The thermoelectric figure-of-merit (ZT) for GeTe powder could be raised from ∼0.8 to 1.37 at high temperature (HT) near ∼500 °C by tuning the Ge-vacancy level through the applied reversible in situ route, which made it highly controllable and reproducible. The enhanced ZT of GeTe was found to be strongly correlated with both its significantly increased Seebeck coefficient (∼161 μV K−1 at 500 °C) and reduced thermal conductivity (∼2.62 W m−1 K−1 at 500 °C) for a sample with nearly vacancy-free thicker herringbone-structured microdomains in the suppressed rhombohedral-to-cubic structure phase transformation. The microdomain and crystal structures were identified with HR-TEM (high-resolution transmission electron microscopy) and powder X-ray diffraction (XRD), while electron probe micro-analysis (EPMA) was used to confirm the stoichiometry changes of Ge : Te. Theoretical calculations for GeTe with various Ge-vacancy levels suggested that the Fermi level shifts toward the valence band as a function of increasing the Ge-vacancy level, which is consistent with the increased hole-type carrier concentration (n) and effective mass (m*) deduced from the Hall measurements. The uniquely prepared sample of a near-vacancy-free GeTe in a rhombohedral structure at high temperature favoured an enhanced Seebeck coefficient in view of the converging L- and Σ-bands of the heavy effective mass at the Fermi level, while the high density domain boundaries for the domain of low carrier density were shown to reduce the total thermal conductivity effectively.
Valiyaveettil, SM, Qorbani M, Hsing C-R, Chou T-L, Paradis-Fortin L, Sabbah A, Srivastava D, Nguyen D-L, Ho T-T, Billo T, Ganesan P, Wei C-M, Chen L-C, Chen K-H.
2022.
Enhanced thermoelectric performance of skutterudite Co1−yNiySn1.5Te1.5−x with switchable conduction behavior, 2022. Materials Today Physics. 28:100889.
AbstractA fine control of carriers in solids is the most essential thing while exploring any functionality. For a ternary skutterudite like CoSn1·5Te1.5−x, which has been recently recognized as a potential material for thermoelectric conversion, the dominant carrier could be either electrons or holes via chemically tuning the quaternary Sn2Te2 rings in the structure. Both theoretical calculation and different spectroscopic probes, such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) were employed to unveil the conduction type switching details. On the other hand, a Ni-for-Co substitution was applied to enhance electronic transport, and thereby the thermoelectric power factor. Thanks to the substantial cut-off of lattice thermal conductivity by the characteristic Sn2Te2 rings in the skutterudite structure, ultimately a 70-fold increase in the dimensionless figure-of-merit (zT) is achieved at 723 K with the nominal composition Co0·95Ni0·05Sn1·5Te1.5.
Syum, Z, Billo T, Sabbah A, kumar Anbalagan A, Quadir S, Hailemariam AG, Sabhapathy P, Lee C-H, Wu H-L, Chen L-C, Chen K-H.
2023.
Enhancing the lithium-ion storage capability of Cu2ZnSnS4 anodes via a nitrogen-doped conductive support, 2023. Chemical Engineering Journal. 465:142786.
AbstractAchieving lithium-ion batteries with both excellent electrochemical performance and cycling stability is a top priority for their real-world applications. This work reports high-performance and stable Cu2ZnSnS4 (CZTS) anode materials encapsulated by nitrogen-doped carbon (CZTS@N-C) for advanced lithium-ion battery application. Ex-situ X-ray photoelectron spectroscopy and transmission electron microscopy revealed that the nitrogen-doped carbon network features a more conducive solid-electrolyte interphase that enables lower charge-transfer resistance and fast Li+ diffusion kinetics with negligible initial irreversible capacity loss. As a result, the CZTS@N-C electrode delivers a significantly enhanced capacity of 710 mAh g−1 with 73% capacity retention after 220 cycles at a current rate of 0.5 mA g−1 and superior rate performance compared to that of unmodified CZTS. Additionally, the study sheds light on the fast lithiation dynamics chemistry of CZTS@N-C through kinetics analysis, explored by in-situ Raman, ex-situ X-ray absorption, and in-situ electrochemical impedance. This study provides a new approach for fabricating high-performance, durable conductive polymer-encapsulated low-cost transition-metal-sulfide anode materials.