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Enhanced Seebeck coefficient of quantum-confined electrons in SrTiO_3/SrTi_0.8Nb_0.2O_3 superlattices Mune, Yoriko Ohta, Hiromichi Koumoto, Kunihito Mizoguchi, Teruyasu Ikuhara, Yuichi We report two-dimensional Seebeck coefficients (|S|_2D) of [(SrTiO_3)x/(SrTi_0.8Nb_0.2O_3)y]_20 (x=1–60, y=1–20) superlattices, which were grown on the (100) face of insulating LaAlO_3 substrates to clarify the origin of the giant |S|_2D values of the SrTiO_3 superlattices [H. Ohta et al., Nat. Mater. 6, 129 (2007)]. The |S|_2D values of the [(SrTiO_3)_17/(SrTi_0.8Nb_0.2O_3)y]_20 superlattices increased proportionally to y^{−0.5} and reached 320µVK^{−1} (y=1), which is approximately five times larger than that of the SrTi_0.8Nb_0.2O_3 bulk (|S|_3D=61µVK^{−1}). The slope of the log|S|_2D-log y plots was −0.5, proving that the density of states in the ground state for SrTiO_3 increases inversely proportionally to y. The critical barrier thickness for quantum electron confinement was also clarified to be 6.25nm (16 unit cells of SrTiO_3). journal article American Institite of Physics 2007-11-08 application/pdf APPLIED PHYSICS LETTERS 91 192105 192105 0003-6951 https://nagoya.repo.nii.ac.jp/record/10162/files/ApplPhysLett_91_192105.pdf http://hdl.handle.net/2237/11980 https://nagoya.repo.nii.ac.jp/records/10162 eng https://doi.org/10.1063/1.2809364 Copyright (2007) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.