Strong polaronic effects on rutile TiO2 electronic band edges

Clas Perssona!

 Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden

Antonio Ferreira da Silva

Instituto de Fisica, Universidade Federal da Bahia, Campus Ondina, 40210-340 Salvador-BA, Brazil

sReceived 29 December 2004; accepted 25 April 2005; published online 3 June 2005d

Abstract:

Thin TiO2 films are prepared by dc magnetron sputtering as well as by the sol-gel technique, and the optical band edge absorption asvd is obtained from transmission spectroscopy. The electronic structure and optical properties are studied employing a first-principle linearized augmented plane-wave method within the local density approximation (LDA), improved by an on-site Coulomb self-interaction potential (LDA+USIC). We show that the correction potential, the polaronic screening, and the spin-orbit interaction are crucial for determining the TiO2 effective electron and hole masses. The dielectric function «svd=«1svd+i«2svd and the high-frequency constant «s0!v!Eg /"d show pronounced anisotropy. The electron-optical phonon interaction affects «sv<0d strongly

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In this letter, we study the electronic band edge structure of rutile sD4h 14d TiO2 by means of a fully relativistic, fullpotential linearized augmented plane-wave sFPLAPWd method,6 using the LDA potential VsLDAd in combination with a modeled on-site self-interaction correction sSICd potential.7

 Vl sLDA + USICd = VsLDAd + Ul 2 S1−2o m,s nm,sD, s1d

where nm,s is the occupancy of the l orbitals. We show that this LDA+USIC approach is suitable for studying the bandedge properties of TiO2.