Complex centers of hydrogen in tin dioxide

Abstract

Tin dioxide is a wide band-gap semiconductor and is part of a class of promising transparent conducting oxides. It shows n-type conductivity, even when not intentionally doped, and is usually attributed to intrinsic defects. Theoretically, the unintentional doping with hydrogen, either at interstitials or at O sites, has been proposed to provide the shallow donors for the n-type conductivity of SnO2. Since H is an electrically active impurity present in many growth environments, a deeper theoretical understanding of the hydrogen and H-related complexes in SnO2 is highly welcome. We present here the results of ab initio studies, based on self-consistent electronic structure calculations, based on Perdew, Burke and Ernzerhof plus the on-site Coulomb correction and Heyd–Scuseria–Ernzerhof hybrid functional approaches, for several H-related defect centers in SnO2. Isolated substitutional (HO) and interstitial (Hi) impurities, as well as some complexes related to them, like 2H, HO–H VSn–H, VSn–2H, VO–H2, VO–2H and Sni–H, have been analyzed from structural and electronic properties, formation energy and vibrational frequencies. A comparison of our calculated vibrational frequencies with recent infrared measurements (IR) allowed us to ascribe the observed IR peaks to the H-related centers. This, added to the low formation energy of the VO–H2 center, and nudged-elastic band method-based calculations, is a strong indication for this center to be the source of hidden hydrogen in SnO2.