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Journal Article
Fathabadi, M, Qorbani M, Sabbah A, Quadir S, Huang C-Y, Chen KH, Chen L-C, Naseri N.  2022.  Ultrathin amorphous defective co-doped hematite passivation layer derived via in-situ electrochemical method for durable photoelectrochemical water oxidation, 2022. Journal of Materials Chemistry A. :-.: The Royal Society of Chemistry AbstractWebsite

Although hematite (i.e., α-Fe2O3) has been widely investigated in photoelectrochemical water oxidation studies due to its high theoretical photocurrent density, it still suffers from serious surface charge recombination and low photoelectrochemical stability. Here we report an in-situ electrochemical method to form a uniform and ultrathin (i.e., 3–5 nm) passivation layer all over the porosities of the optimized ~3.2% Ti-doped α-Fe2O3 photoanode. We unveil the amorphous and defective nature of the in-situ derived layer assigning to a high concentration of oxygen vacancy and intercalated potassium atoms there, i.e., the formation of Ti/K co-doped defective α-Fe2O3-x. Owing to the efficient passivation of surface states, alleviated surface-potential fluctuations, and low charge-transfer resistance at the interface, photoanodes show an average of ~60% enhancement in the photoelectrochemical performance, applied bias absorbed photon-to-current efficiency of 0.43%, and Faradaic efficiency of ~88%. Moreover, the passivation layer prevents direct contact between the electrode material and electrolyte, resulting in less degradation and outstanding photoelectrochemical stability with photocurrent retention of ~95% after ~100 hours, albeit by performing several successive in-situ electrochemical passivation processes. This work presents an industrially scalable method to controllably engineer the interfaces of semiconductors–electrolytes with precious metal-free defective hematite-based co-catalysts for sustainable photoelectrochemical solar-to-fuel conversion applications.

Daichakomphu, N, Abbas S, Chou T-L, Chen L-C, Chen K-H, Sakulkalavek A, Sakdanuphab R.  2022.  Understanding the effect of sputtering pressures on the thermoelectric properties of GeTe films. Journal of Alloys and Compounds. 893:162342. AbstractWebsite

In this work, we study the effect of sputtering pressures on the thermoelectric properties of GeTe films. The working pressures were differentiated from 3 to 30 mTorr, and the as-deposited films were annealed at 623 K for 10 min in Ar atmosphere. The results show that the working pressure has a significant effect on the Ge content and crystalline size. The turning trend of the Seebeck coefficient with different sputtering pressures corresponds to the Ge content. The surface morphology of annealed film will change from cracks to voids with increasing sputtering pressure. This behavior can be explained by the growth mechanisms model. The voids and relatively low crystalline size of GeTe films affect to the reduction of the electrical conductivity. In addition, the void content decreased as film thickness was increased. Therefore, controlling the working pressures in the sputtering process and film thickness is important for the thermoelectric performance of GeTe thin film. In our work, we prove that the thermoelectric properties of GeTe films could be optimized effectively by simply tuning different sputtering conditions.

Roy, P, Kumar, Haider G, Chou T-chin, Chen K-H, Chen L-C, Chen Y-F, Liang C-T.  2019.  Ultrasensitive Gas Sensors Based on Vertical Graphene Nanowalls/SiC/Si Heterostructure, 2019. ACS SensorsACS Sensors. 4(2):406-412.: American Chemical Society AbstractWebsite
Liu, YL, Yu CC, Fang CY, Chen HL, Chen CW, Kuo CC, Chang CK, Chen LC, Chen KH.  2013.  Using optical anisotropy as a quality factor to rapidly characterize structural qualities of large-area graphene films. Analytical Chemistry.
Chen, CP, Ganguly A, Chen RS, Fischer W, Chen LC, Chen KH.  2011.  Ultra-sensitive in situ label-free DNA detection using GaN nanowires-based extended-gate field-effect-transistor sensor. Anal. Chem.. 83:1938-1943.
Fang*, WC, Leu MS, Chen KH, Chen LC.  2008.  Ultrafast charging-discharging capacitive property of RuO2nanoparticles on carbon nanotubes using nitrogen incorporation. J. Electrochem. Soc.. 155:K15-K18.
Chen, RS, Chen HY, Lu CY, Chen CP, Chen LC, Yang YJ, Chen* KH.  2007.  Ultrahigh photocurrent gain in m-axial GaN nanowires. Appl. Phys. Lett.. 91:223106.
Sun, CL, Chen* LC, Su MC, Hong LS, Chyan O, Hsu CY, Chen KH, Chang TF, Chang L.  2005.  Ultrafine platinum nanoparticles uniformly dispersed on arrayed CNx nanotubes with high electrochemical activity. Chem.of Mater.. 17:3749-3753.
Chen, LC, Lu TR, Bhusari DM, Wu JJ, Chen KH, Kuo CT, Chen TM.  1998.  The Use of a Bio-molecular Target for Crystalline Carbon Nitride Film Deposition by Ar Ion-Beam Sputtering without Other Source of Nitrogen. Appl. Phys. Lett.. 72:3449.