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.
AbstractIn 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.
Das, S, Valiyaveettil SM, Chen K-H, Suwas S, Mallik RC.
2019.
Thermoelectric properties of Mn doped BiCuSeO, 2019. Materials Research Express. 6(8):086305.: IOP Publishing
AbstractBiCuSeO is a promising thermoelectric material having earth-abundant non-toxic constituents and favourable thermoelectric properties like ultra-low thermal conductivity. In this study, Mn+2 has been introduced at the Bi+3 site to increase hole concentration as well as Seebeck coefficient, through aliovalent doping and magnetic impurity incorporation respectively. Samples were prepared through two-step solid state synthesis with the composition Bi1-xMnxCuSeO (x = 0.0, 0.04, 0.06, 0.08, 0.10 and 0.12). X-ray diffraction patterns confirmed the tetragonal (space group: P4/nmm) crystal structure of BiCuSeO as well as phase purity of the samples. The Seebeck coefficient and electrical resistivity had a decreasing trend with increasing doping fraction owing to the generation of charge carriers. The samples with x = 0.04 and 0.06 showed temperature independent Seebeck coefficient above 523 K, which is a signature of small polaron hopping. While the Seebeck coefficient of the samples with x = 0.08, 0.10 and 0.12 increased above 523 K due to the combination of localized and extended states. The thermal conductivity was dominated by the lattice part of the thermal conductivity. As a result of moderate Seebeck coefficient and low electrical resistivity, the highest power factor of 0.284 mW m−1-K2 was obtained for the Bi0.92Mn0.08CuSeO at 773 K, leading to a maximum zT of 0.4 at 773.
Das, CR, Hsu HC, Dhara S, Bhaduri AK, Raj B, Chen LC, Chen KH, Albert SK, Ray A, Tzeng Y.
2010.
A complete Raman mapping of phase transitions in Si under indentation. J. Raman Spectroscopy. 41:334.
Datta, A, Dhara* S, Muto S, Hsu CW, Wu CT, Shen CH, Tanabe T, Maruyama T, Chen KH, Chen LC, Wang YL.
2005.
Formation and in-situ dynamics of metallic nanoblisters in self-ion-implanted GaN nanowires. Nanotechnology. 16:2764-2769.
Dhara, SK, Magudapathy P, Kesavamoorthy R, Kalavathi S, Nair KGM, Hsu GM, Chen LC, Chen* KH, Santhakumar K, Soga T.
2006.
Nitrogen ion beam synthesis of InN in InP(100) at elevated temperature. Appl. Phys. Lett.. 88:241904-(1-3).
Dhara, SK, Datta A, Wu CT, Lan ZH, Chen* KH, Wang YL, Chen LC, Hsu CW, Lin HM, Chen CC.
2003.
Enhanced dynamic annealing in self-ion implanted GaN nanowires. Appl. Phys. Lett.. 82:451-453.
Dhara, SK, Datta A, Lan ZH, Chen* KH, Wang YL, Shen CS, Chen LC, Hsu CW, Lin HM, Chen CC.
2004.
Blue shift of yellow band in self-ion beam irradiated GaN nanowires. Appl. Phys. Lett.. 84:3486-3488.