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Chang, H-C, You H-J, Sankar R, Yang Y-J, Chen L-C, Chen K-H.  2019.  Enhanced Thermoelectric Performance via Oxygen Manipulation in BiCuTeO, 2019. MRS Advances. 4(8):499-505.: Materials Research Society AbstractWebsite

BiCuTeO is a potential thermoelectric material owing to its low thermal conductivity and high carrier concentration. However, the thermoelectric performance of BiCuTeO is still below average and has much scope for improvement. In this study, we manipulated the nominal oxygen content in BiCuTeO and synthesized BiCuTeOx (x = 0.94–1.06) bulks by a solid-state reaction and pelletized them by a cold-press method. The power factor was enhanced by varying the nominal oxygen deficiency due to the increased Seebeck coefficient. The thermal conductivity was also reduced due to the decrease in lattice thermal conductivity owing to the small grain size generated by the optimal nominal oxygen content. Consequently, the ZT value was enhanced by ∼11% at 523 K for stoichiometric BiCuTeO0.94 compared to BiCuTeO. Thus, optimal oxygen manipulation in BiCuTeO can enhance the thermoelectric performance. This study can be applied to developing oxides with high thermoelectric performances.

Chang, CK, Kataria S, Kuo CC, Ganguli A, Wang BY, Hwang JY, Huang KJ, Yang WH, Wang SB, Chuang CH, Chen M, Huang CI, Pong WF, Song KJ, Chang SJ, Guo J, Tai Y, Tsujimoto M, Isoda S, Chen CW, Chen LC, Chen KH.  2013.  Band gap engineering of chemical vapor deposited graphene by in-situ BN doping. ACS Nano. 7:1333-1341.
Chang, ST, Wang CH, Du HY, Hsu HC, Kang CM, Chen CC, Wu CS, Yen SC, Huang WF, Chen LC, Lin MC, Chen KH.  2012.  Vitalizing fuel cells with a vitamin: pyrolyzed vitamin B12 as non-precious catalyst for enhanced oxygen reduction reaction. Energy & Environ. Sci.. 5:5305-5314.
Chang, CY, Tsao FC, Pan CJ, Chi GC, Wang HT, Chen JJ, Ren F, Norton DP, Pearton* SJ, Chen KH, Chen LC.  2006.  Electroluminescence from ZnO nanowire/polymer composite p-n junction. Appl. Phys. Lett.. 88:173503-(1-3).
Chang, HJ, Chen CH, Chen* YF, Lin TY, Chen LC, Chen KH, Lan ZH.  2005.  Responseto “Comment on ‘Direct evidence of nanocluster-induced luminescence in InGaNepifilms. Appl. Phys. Lett.. 87:136102-(1-2).
Chang, CK, Hwang JY, Lai WJ, Chen CW, Huang CI, Chen KH, Chen LC.  2010.  Influence of solvent on the dispersion of single-walled carbon nanotubes in polymer matrix and the photovoltaic performance. J. Phys. Chem.. C114:10932-10936.
Chang, YK, Hsieh HH, Pong* WF, Tsai M-H, Chien FZ, Tseng PK, Chen LC, Wang TY, Chen KH, Bhusari DM, Yan JR, Lin ST.  1999.  Quantum confinement effect in diamond nanocrystals studied by X-Ray-absorption spectroscopy. Phys. Rev. Lett.. 82:5377-5380.
Chang, CS, Chattopadhyay S, Chen* LC, Chen KH, Chen CW, Chen YF, Collazo R, Sitar Z.  2003.  Band gap dependence of field emission from one dimensional nanostructures grown on n-type and p-type silicon substrates. Phys. Rev.. B68:125322-(1-5).
Chang, H-C, You H-J, Sankar R, Yang Y-J, Chen L-C, Chen K-H.  2019.  Enhanced thermoelectric performance of BiCuTeO by excess Bi additions, 2019. 45(7, Part A):9254-9259. AbstractWebsite

Thermoelectric (TE) devices used to convert waste heat directly into electricity are highly desirable for alleviating the prevailing energy crisis and global climate-change issues. Among the various TE materials available, metal oxides exhibit high thermal and chemical stabilities in air, and are hence, preferred for use in many TE applications. However, most of them possess TE figures of merit (ZT) that are below the applicable value of 2, in the mid-temperature region (from 250 to 600 °C). In a previous work, the removal of a small amount of Bi from BiCuSeO was found to improve the ZT of BiCuSeO. In this work, we pursue another track and study the TE performance of BiCuTeO after the addition of up to 6% excess Bi. Bi1+xCuTeO (x = 0.00–0.06) samples were prepared by solid-state reactions, followed by hot-pressing to form pellets. By adding a stoichiometric excess of Bi into BiCuTeO, 16% enhancement in power factor was achieved at 450 °C. This enhancement can be attributed to the increase in the Seebeck coefficient because of the appearance of secondary phases. Detailed characterizations and discussions of the effect of the nominal excess Bi in BiCuTeO are presented in this paper. The findings of this study can be applied in the investigation of novel high-performance TE materials.

Chang, YS, Chien CT, Chen* CW, Chu TY, Chiang HH, Ku CH, Wu JJ, Lin CS, Chen LC, Chen KH.  2007.  Structural and optical properties of single crystal Zn1-xMgxO nanorods-experimental and theoretical studies. J. Appl. Phys.. 101:033502.
Chang, YK, Hsieh HH, Pong WF, 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 SiCN Thin Film by X-ray Absorption Spectroscopy and Theoretical Calculations. Phys. Rev.. B58:9018.
Chang, CY, Pearton* SJ, Huang PJ, G.C. Chi H, Wang T, Chen JJ, Ren F, Chen KH, Chen LC.  2007.  Control of nucleation site density of GaN nanowires. Appl. Surf. Sci.. 253:3196-3200.
Chang, HJ, Chen CH, Chen* YF, Lin TY, Chen LC, Chen KH, Lan ZH.  2005.  Direct evidence of nanocluster-induced luminescence in InGaN epifilms. Appl. Phys. Lett.. 86:021911-(1-3).
Chang, CY, Chi GC, Wang WM, Chen* LC, Chen KH, Ren F, Pearton SJ.  2006.  Electrical transport properties of single GaN and InN nanowires. J. Electronic Materials. 35:738-743.
Chang, M-C, Ho P-H, Tseng M-F, Lin F-Y, Hou C-H, Lin I-K, Wang H, Huang P-P, Chiang C-H, Yang Y-C, Wang I-T, Du H-Y, Wen C-Y, Shyue J-J, Chen C-W, Chen K-H, Chiu P-W, Chen L-C.  2020.  Fast growth of large-grain and continuous MoS2 films through a self-capping vapor-liquid-solid method, 2020. 11(1):3682. AbstractWebsite

Most chemical vapor deposition methods for transition metal dichalcogenides use an extremely small amount of precursor to render large single-crystal flakes, which usually causes low coverage of the materials on the substrate. In this study, a self-capping vapor-liquid-solid reaction is proposed to fabricate large-grain, continuous MoS2 films. An intermediate liquid phase-Na2Mo2O7 is formed through a eutectic reaction of MoO3 and NaF, followed by being sulfurized into MoS2. The as-formed MoS2 seeds function as a capping layer that reduces the nucleation density and promotes lateral growth. By tuning the driving force of the reaction, large mono/bilayer (1.1 mm/200 μm) flakes or full-coverage films (with a record-high average grain size of 450 μm) can be grown on centimeter-scale substrates. The field-effect transistors fabricated from the full-coverage films show high mobility (33 and 49 cm2 V−1 s−1 for the mono and bilayer regions) and on/off ratio (1 ~ 5 × 108) across a 1.5 cm × 1.5 cm region.

Chatterjee, A, Chattopadhyay S, Hsu CW, Shen CH, Chen* LC, Chen CC, Chen KH.  2004.  Growth and characterization of GaN nanowires produced on different sol-gel derived catalyst dispersed in TiO2 and polyvinyl alcohol matrix. J. Mater. Res.. 19:1768-1774.
Chatterjee, A, Shen CH, Ganguly A, Chen* LC, Hsu CW, Hwang JY, Chen KH.  2004.  Strong room-temperature UV emission of nanocrystalline ZnO films derived from a polymeric solution. Chem. Phys. Lett.. 391:278-282.
Chattopadhyay, S, Chen LC, Chen KH.  2011.  Energy production and conversion applications ofone-dimensional semiconductor nanostructures. NPG Asia Mater.. 3:74-81.
Chattopadhyay, S, Chen* LC, Wu CT, Chen KH, Wu JS, Chen YF, Lehmann G, Hess P.  2001.  Thermal diffusivity in amorphous silicon carbon nitride thin films by the traveling wave technique. Appl. Phys. Lett.. 79:332-334.
Chattopadhyay, S, Chen* LC, Chien SC, Lin ST, Wu CT, Chen KH.  2002.  Phase and thickness dependence of thermal diffusivity in SiCxNy and BCxNy,. Thin Solid Films. 420:205-211.
Chattopadhyay, S, Shi SC, Wu CT, Chen LC, Chen CH, Chen* KH.  2006.  Self selected apex angle distribution of the nanotips. Appl. Phys. Lett.. 89:143105-(1-3).
Chattopadhyay, S, Chen* LC, Chien SC, Lin ST, Chen KH.  2002.  Bonding characterization, density measurement and thermal diffusivity studies of amorphous silicon carbon nitride and boron carbon nitride thin films. J. Appl. Phys.. 92:5150-5158.
Chattopadhyay*, S, Shi SC, Lan ZH, Chen CF, Chen KH, Chen LC.  2005.  Molecular sensing with ultrafine silver crystals on hexagonal aluminum nitridenanorodtemplate. J. Am. Chem. Soc.. 127:2820-2821.
Chattopadhyay*, S, Lo HC, Hsu CH, Chen LC, Chen KH.  2005.  Surface enhanced Raman spectroscopy using self assembled silver nanoparticulates on silicon nanotips. Chem. Mater.. 17:553-559.
Chattopadhyay*, S, Chien SC, Chen LC, Chen KH, Lehmann G, Hess P.  2002.  Thermal diffusivity in diamond, SiCxNy and BCxNy. Diamond Relat. Mater. 11:708-713.