Hydrogen multicentre bonds

Janotti, Anderson; Walle, Chris G. Van de

doi:10.1038/nmat1795

Cited by 692 publications

(577 citation statements)

References 25 publications

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“…We find that (i) intrinsic point defects, such as V O and Sn i , are unlikely to be the cause of n-type conductivity in as-grown or annealed SnO 2 , and (ii) instead, this conductivity can be explained by inadvertent incorporation of impurities, in particular, hydrogen, which is generally difficult to detect but very likely to be present in the growth and/or processing environments. Besides incorporating on interstitial sites, hydrogen can also replace oxygen in SnO 2 and form a multicenter bond with its three Sn nearest neighbors [11]. Substitutional hydrogen has a low formation energy, acts as a shallow donor, and consistently explains experimental observations [12 -14].…”

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confidence: 62%

Sources of Electrical Conductivity inSnO2

et al. 2008

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SnO 2 is widely used as a transparent conductor and sensor material. Better understanding and control of its conductivity would enhance its performance in existing applications and enable new ones, such as in light emitters. Using density functional theory, we show that the conventional attribution of n-type conductivity to intrinsic point defects is incorrect. Unintentional incorporation of hydrogen provides a consistent explanation of experimental observations. Most importantly, we find that SnO 2 offers excellent prospects for p-type doping by incorporation of acceptors on the Sn site. Specific strategies for optimizing acceptor incorporation are presented.

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confidence: 62%

Sources of Electrical Conductivity inSnO2

et al. 2008

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“…From DFT calculations, Van de Walle and colleagues [79,82,83] showed that interstitial hydrogen can indeed act as a donor even in n-type ZnO, finding that the H + charge state is stable for all Fermi level positions within the band gap (see Fig. 4(b)).…”

Section: Donor Nature Of Hydrogenmentioning

confidence: 99%

“…Janotti and Van de Walle [83] showed that substitutional hydrogen on the oxygen site in ZnO also forms a shallow donor, in a so-called multicentre bond configuration (see Fig. 4).…”

Section: Stabilitymentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

224

180

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Abstract. Despite an extensive research effort for over 60 years, an understanding of the origins of conductivity in wide band-gap transparent conducting oxide (TCO) semiconductors remains elusive. While TCOs have already found widespread use in device applications requiring a transparent contact, there are currently enormous efforts to (i) increase the conductivity of existing materials, (ii) identify suitable alternatives, and (iii) attempt to gain semiconductor-engineering levels of control over their carrier density, essential for the incorporation of TCOs into a new generation of multifunctional transparent electronic devices. These efforts, however, are dependent on a microscopic identification of the defects and impurities leading to the high unintentional carrier densities present in these materials. Here, we review recent developments towards such an understanding. While oxygen vacancies are commonly assumed to be the source of the conductivity, there is increasing evidence that this is not a sufficient mechanism to explain the total measured carrier concentrations. In fact, many studies suggest that oxygen vacancies are deep, rather than shallow, donors, and their abundance in as-grown material is also debated. We discuss other potential contributions to the conductivity in TCOs, including other native defects, their complexes, and in particular hydrogen impurities. Convincing theoretical and experimental evidence is presented for the donor nature of hydrogen across a range of TCO materials, and while its stability and the presence of interstitial and substitutional species are still somewhat open questions, it is one of the leading contenders for unintentional conductivity in TCOs. We also review recent work indicating that the surfaces of TCOs can support very high carrier densities, opposite to the case of conventional semiconductors. In thin-film materials/devices and, in particular, nanostructures, the surface can have a large impact on the total conductivity in TCOs. We discuss models that attempt to explain both the bulk and surface conductivity based on features of the bulk band structure common across the TCOs, and compare these materials to other semiconductors. Finally, we briefly consider transparency in these materials, and its interplay with conductivity. Understanding this interplay, as well as the microscopic contenders for the conductivity of these materials, will prove essential to the future design and control of TCO semiconductors, and their implementation into novel multifunctional devices.

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“…In recent studies, however, hydrogen impurities have been found to be the dominant shallow donors in several important cases. [5][6][7][8][9][10] In 2 O 3 , a prototypical transparent conducting oxide, has the cubic bixbyite structure with a conventional unit cell that contains 80 atoms. 11 The oxygen sites are all equivalent.…”

Section: Introductionmentioning

confidence: 99%