Experimental Confirmation of the Predicted Shallow Donor Hydrogen State in Zinc Oxide

Cox, S.F.J.; Davis, E. A.; Cottrell, Stephen P.; King, P.J.C.; Lord, J. S.; Gil, J. M.; Alberto, H. V.; Vilão, R. C.; Duarte, J. Piroto; Campos, N. Ayres de; Weidinger, A.; Lichti, R.L.; Irvine, S.J.C.

doi:10.1103/physrevlett.86.2601

Cited by 430 publications

(258 citation statements)

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“…While hydrogen can be difficult to directly assess spectroscopically, the well-defined creation and decay properties of muons has led to significant success in the use of µSR as a spectroscopic probe of isolated defect centres in semiconductors that differ from hydrogen only by a mass factor (m Mu /m H ≈ 1/9) and the associated small difference in zero-point energy [85]. While µSR studies of conventional semiconductors such as Si [86] or GaAs [87] found charge transition levels for muonium lying deep within the band gap, as would be expected for the conventional behaviour of hydrogen in these materials, such measurements [84] provided the first spectroscopic evidence of the donor-nature of hydrogen in ZnO, summarized in Fig. 5.…”

Section: Donor Nature Of Hydrogenmentioning

confidence: 99%

“…Cox et al [84] performed muon spin rotation and relaxation spectroscopy (µSR) measurements on ZnO, investigating muonium (Mu = [µ + , e − ]) as a lightisotope analogue of hydrogen. While hydrogen can be difficult to directly assess spectroscopically, the well-defined creation and decay properties of muons has led to significant success in the use of µSR as a spectroscopic probe of isolated defect centres in semiconductors that differ from hydrogen only by a mass factor (m Mu /m H ≈ 1/9) and the associated small difference in zero-point energy [85].…”

Section: Donor Nature Of Hydrogenmentioning

confidence: 99%

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Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

226

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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Section: Donor Nature Of Hydrogenmentioning

confidence: 99%

Section: Donor Nature Of Hydrogenmentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

226

180

View full text Add to dashboard Cite

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“…1,2 However, several experimental studies have shown that the dominant native shallow donor in ZnO is hydrogen, as predicted by calculations. [3][4][5] One of the major efforts in semiconductor technology during the recent years was the realization of ptype conductivity in ZnO, leading to optoelectronic devices in the blue spectral range like high-power light-emitting diodes. It is required to suitable compensate the incorporated defects in ZnO resulting in highly resistive material even at high dopant concentrations.…”

Section: Introductionmentioning

confidence: 99%

Study of the photoluminescence emission line at 3.33 eV in ZnO films

Yalishev

Kim

Deng

et al. 2012

Journal of Applied Physics

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We study properties of the line at 3.33 eV observed in photoluminescence (PL) emission spectra of various ZnO films prepared using pulsed laser deposition method. The influence of deposition parameters, such as oxygen pressure, laser fluence, post-annealing, and electric field exposure on intensity of this luminescence band has been investigated. The recombination characteristics are probed by temperature and excitation dependent PL spectroscopy. The obtained experimental data suggest that the 3.33 eV luminescence line in ZnO depends strongly on surface band bending and originates from recombination of bound excitons (BEs) complex located near the surface and grain boundaries. The anomalously small thermal activation energy of BE in comparison with the localization energy is explained by decreasing of the interface barrier. Possible nature of defects that bind free excitons and cause the 3.33 eV emission line in ZnO is proposed. V C 2012 American Institute of Physics. [http://dx

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“…A particularly relevant case is the doping character of H in semiconductors and oxides [3][4][5][6], where practically all calculations refer to the electronic structure of H whereas most experimental information comes from μSR [7][8][9][10][11][12][13]. Overlapping data exist only for ZnO where proton-ENDOR (electron-nuclear double resonance) data [14] can be compared directly with μSR results [15][16][17][18]. A number of properties (e.g., ionization energy) are indeed similar for the two species.…”

mentioning

confidence: 99%

Muonium donor in rutileTiO2and comparison with hydrogen

et al. 2015

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Muonium, a positive muon and an electron, is often used as an experimentally accessible substitute for hydrogen in materials research. In semiconductors and insulators, a large amount of information on the hydrogen behavior is deduced from this analogy; however, it is seldom demonstrated that this procedure is justified. We show here, via a comparison of the hyperfine interactions, that in TiO 2 muonium and hydrogen form the same configuration with the same basic electronic structure. A detailed description of the bonding characteristics of the muon to the Ti 3+ polaron is presented. The special role of muon motion within the so-called oxygen channel in the rutile structure, which occurs at a lower temperature than for hydrogen, is emphasized. Muonium (Mu) is a pseudoisotope of hydrogen in which the proton is replaced by a positive muon (μ + ), with a factor of 9 lighter mass. Muon spin spectroscopy (μSR) uses muons implanted with 100% spin polarization and offers a very sensitive method to study the properties of this isolated pseudohydrogen in solids [1,2]. It is usually assumed that information obtained from μSR can be transferred with appropriate modifications to H. However, overlapping experiments to support this assumption are scarce. A particularly relevant case is the doping character of H in semiconductors and oxides [3][4][5][6], where practically all calculations refer to the electronic structure of H whereas most experimental information comes from μSR [7][8][9][10][11][12][13]. Overlapping data exist only for ZnO where proton-ENDOR (electron-nuclear double resonance) data [14] can be compared directly with μSR results [15][16][17][18]. A number of properties (e.g., ionization energy) are indeed similar for the two species. However, the measured hyperfine interaction (hfi), scaled with the magnetic moments, differs by almost a factor of 10. This raised the question of whether the same configuration is measured, or if the H center may involve an additional defect [19,20].Here, we report a case where the same configuration can be established for H and Mu. We compare the hfi of the μSR experiment with the proton-ENDOR result, both for rutile TiO 2 . The H center in TiO 2 was extensively studied by Brant et al.[21] using electron paramagnetic resonance (EPR) and ENDOR, who found that the electron is located at the Ti ion reducing it from Ti 4+ to Ti 3+ . H is bound to one of the six O atoms surrounding Ti and the magnetic interaction between the proton and the electron is mainly dipolar. This specific hfi permits a sensitive comparison of the two experiments. We have observed a dramatic change of the μSR spectra with increasing temperature and a complete disappearance of the hyperfine splitting at 10 K. We show that this is due to rapid jumps of the muon between neighboring bonding positions to O atoms around Ti 3+ . The very strong angle dependence of the dipolar interaction and the averaging over values in different * ruivilao@fis.uc.pt positions lead to the reduction and final disappearance of the hfi...

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Experimental Confirmation of the Predicted Shallow Donor Hydrogen State in Zinc Oxide

Cited by 430 publications

References 10 publications

Conductivity in transparent oxide semiconductors

Conductivity in transparent oxide semiconductors

Study of the photoluminescence emission line at 3.33 eV in ZnO films

Muonium donor in rutileTiO2and comparison with hydrogen

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