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C. Y. Chang, Chi GC, Wang WM, Chen LC, Chen KH, Ren F, Pearton* SJ.  2005.  Transport properties of InN nanowires. Appl. Phys. Lett.. 87:093112-(1-3).
and C.-C. Chen*, Yeh C-C, Liang C-H, Lee C-C, Chen C-H, Yu M-Y, Liu H-L, Chen LC, Lin YS, Ma KJ, Chen KH.  2001.  Preparation and characterization of carbon nanotubes encapsulated GaN nanowires. J. Phys. Chem. of Solids. 62:1577-1586.
and C.H. Lin, KH, Chattopadhyay S, Hsu CW, Wu MH, Chen WC, Wu CT, Tsen SC, Lee JH, Chen CH, Chen CW, Chen LC, Chen* KH.  2009.  Enhanced charge separation by sieve-layer mediation in high efficiency inorganic-organic solar cell. Adv. Mater.. 21:259-263.
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, 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.

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, 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, 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, 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, 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, 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, YK, Hsieh HH, Pong WF, Tsai MH, Dann TE, Chien FZ, Tseng PK, Chen LC, Wei SL, Chen KH, Wu JJ, Chen YF.  1999.  X-ray-absorption of Si-C-N thin films: acomparison between crystalline and amorphous phases. J. Appl. Phys.. 86:5609-5613.
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, 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, 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, H-C, Chen T-H, Sankar R, Yang Y-J, Chen L-C, Chen K-H.  2020.  Highly improved thermoelectric performance of BiCuTeO achieved by decreasing the oxygen content, 2020. 15:100248. AbstractWebsite

BiCuTeO is a promising thermoelectric material owing to its intrinsically low thermal conductivity and high carrier concentration. This study investigated the influence of stoichiometric oxygen deficiencies on the thermoelectric performance of BiCuTeO. Bulk BiCuTeO1−x (0.16 ≥ x) samples were prepared by a conventional solid state reaction and pelleted by hot pressing. Synchrotron X-ray diffraction, electron probe X-ray microanalysis, scanning electron microscopy, and transmission electron microscopy characterized the samples. A maximum value of 1.06 was achieved for the dimensionless figure of merit ZT at 673 K for BiCuTeO0.88, which is approximately 49% better than the current maximal ZT value for BiCuTeO. The power factor was noticeably improved owing to increases in the electrical conductivity and Seebeck coefficient. Moreover, the optimal oxygen deficiency could introduce nanoparticles, resulting in reduced thermal conductivity. The findings will be important for the future development of metal oxide thermoelectric materials for use in practical thermoelectric devices.

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, CC, Lin CF, Chiou JM, Ho TH, Tai Y, Lee JH, Chen YF, Wang JK, Chen LC, Chen* KH.  2010.  Effects of cathode buffer layers on the efficiency of bulk-heterojunction solar cells. Appl. Phys. Lett.. 96:263506.
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, 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, 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, Lan TW, Chi GC, Chen* LC, Chen KH, Chen JJ, Jang S, Ren F, Pearton SJ.  2006.  Effect of ozone cleaning and annealing on Ti/Al/Pt/Au ohmic contacts on GaN nanowires. Electrochemical and Solid-State Lett.. 9:G155-G157.
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.