ESR and Electric Conductance Studies of the Fine-Powdered SnO<sub>2</sub>

Mizokawa, Yusuke; Nakamura, Shōgo

doi:10.1143/jjap.14.779

Cited by 50 publications

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“…We conclude that H O is stable enough to explain the observed unintentional n-type conductivity in SnO 2 [5,8]. Indeed, an increase in carrier concentration has been observed upon exposure to moist air or H 2 [12,13]. Nola et al [13] also reported a decrease in the number of donors upon annealing at 573 K, consistent with our calculated barrier of 2:2 eV for the motion of H O .…”

Section: Prl 101 055502 (2008) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 89%

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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Section: Prl 101 055502 (2008) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 89%

Sources of Electrical Conductivity inSnO2

et al. 2008

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“…If, instead, this level can be attributed to V O , which becomes more dominant once the hydrogen donors are removed, then our calculated value is also in good agreement with this result. We note that a level at 0.28-0.35 eV has been observed in many n-type samples [75,[164][165][166] (as has the ∼0.15 eV level) [73][74][75]167], and that, in a study on SnO 2 nanoparticles [168], a switching of activation energy from 0.11 to 0.35 eV was observed in the largest nanoparticle when changing from low to high temperature.…”

Section: Sn Omentioning

confidence: 51%

“…A clear increase in conductivity as P O 2 is decreased can be observed when temperature T > 1000 K, indicating the presence of a relatively deep donor [34]. From these data, a donor activation energy of 0.15 eV in the dilute limit has been derived [72][73][74], or possibly at ∼0.3 eV [75], but the majority of computational studies indicates that the most likely donor, the oxygen vacancy, is deeper with the (2+/0) transition occurring at about 1 eV below the conduction band minimum (CBM) [20,41,43].…”

Section: Introductionmentioning

confidence: 77%

“…Mizokawa and Nakamura [75] measured conductivities and carrier concentrations as a function of temperature in SnO 2 samples under different external conditions, finding an activation energy of 0.15 eV that increased to 0.3 eV after O 2 adsorption, with an associated reduction in carrier density. One would expect a significant concentration of vacancies on the surface of SnO 2 , where the lower coordination would reduce the electron ionization energy.…”

Section: Sn Omentioning

confidence: 99%

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Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Buckeridge

Catlow

Farrow

et al. 2018

Phys. Rev. Materials

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The source of n-type conductivity in undoped transparent conducting oxides has been a topic of debate for several decades. The point defect of most interest in this respect is the oxygen vacancy, but there are many conflicting reports on the shallow versus deep nature of its related electronic states. Here, using a hybrid quantum mechanical/molecular mechanical embedded cluster approach, we have computed formation and ionization energies of oxygen vacancies in three representative transparent conducting oxides: In 2 O 3 , SnO 2 , and ZnO. We find that, in all three systems, oxygen vacancies form well-localized, compact donors. We demonstrate, however, that such compactness does not preclude the possibility of these states being shallow in nature, by considering the energetic balance between the vacancy binding electrons that are in localized orbitals or in effective-mass-like diffuse orbitals. Our results show that, thermodynamically, oxygen vacancies in bulk In 2 O 3 introduce states above the conduction band minimum that contribute significantly to the observed conductivity properties of undoped samples. For ZnO and SnO 2 , the states are deep, and our calculated ionization energies agree well with thermochemical and optical experiments. Our computed equilibrium defect and carrier concentrations, however, demonstrate that these deep states may nevertheless lead to significant intrinsic n-type conductivity under reducing conditions at elevated temperatures. Our study indicates the importance of oxygen vacancies in relation to intrinsic carrier concentrations not only in In 2 O 3 , but also in SnO 2 and ZnO.

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“…According to electro-physical study data, ionized oxygen vacancies in tin dioxide form shallow donor levels with an energy of ~0.03 and ~0.15eV below the bottom of the CBM [9,10,11]. In electron spin resonance measurements, other authors have observed the existence of donor levels from ~0.15eV up to ~0.30eV underneath the CBM [12]. Note that the literature only shows how, for a given 4 sample, one (or several) discreet levels are placed around this 0.15eV broad energy region but does not suggest the existence of a continuous band 0.15eV wide.…”

Section: -Results and Discussionmentioning

confidence: 99%

Defect study of SnO2 nanostructures by cathodoluminescence analysis: Application to nanowires

Prades

Arbiol

Cirera

et al. 2007

Sensors and Actuators B: Chemical

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Abstract:Defects in SnO 2 nanowires have been studied by cathodoluminescence, and the obtained spectra have been compared with those measured on SnO 2 nanocrystals of different sizes in order to reveal information about point defects not determined by other characterization techniques. Dependence of the luminescence bands on the thermal treatment temperatures and pre-treatment conditions have been determined pointing out their possible relation, due to the used treatment conditions, with the oxygen vacancy concentration. To explain these cathodoluminescence spectra and their behavior, a model based on first-principles calculations of the surface oxygen vacancies in the different crystallographic directions is proposed for corroborating the existence of surface state bands localized at energy values compatible with the found cathodoluminescence bands and with the gas sensing mechanisms. CL bands centered at 1.90 eV and 2.20 eV are attributed to the surface oxygen vacancies 100º coordinated with tin atoms whereas CL bands centered at 2.37 eV and 2.75 eV are related to the surface oxygen vacancies 130º coordinated. This combined process of cathodoluminescence and ab initio calculations is shown to be a powerful tool for nanowire defect analysis. Key words:SnO 2 , CATHODOLUMINESCENCE, NANOSTRUCTURE, NANOWIRE, OXYGEN VACANCY, AB INITIO Manuscript 2 1.-Introduction:Tin dioxide (SnO 2 ) plays a key role in solid state gas sensors [1]. So a lot of experimental work has been done in order to characterize SnO 2 not only from the technological point of view as a sensor of different gases [2] but also from the materials science standpoint [3] so as to achieve improved performances by means of a better knowledge of the synthesized materials. The vacancy defects investigation deserves special attention as they have been clearly related to conductive and sensing properties of metal oxides [2]. This article will deal with the analysis of point defects using cathodoluminescence (CL) spectra of nanostructured SnO 2 , as this technique reveals complementary information about radiative transitions related to these point defects that is not determined by other characterization techniques This experimental procedure is not new. Since the mid-1970s, however, few works have been published presenting the CL spectra of SnO 2 with different morphologies [4,5,6,7]. In all known cases, several bands between 1.9 and 2.6eV have been reported but there still remains some uncertainty on their origin [6]. However, there are no systematic and detailed works considering nanowires and their comparison with nanoparticles of different sizes.On the other hand, first-principles methodologies based on the density functional theory (DFT) now provide precise calculations of the energetic properties of bulk materials and their surfaces in moderate computing times [8]. Consequently, it is attractive to link theoretical findings with unclearly interpreted experimental results in order to attain better materials knowledge with a straightforward technological ...

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ESR and Electric Conductance Studies of the Fine-Powdered SnO₂

Cited by 50 publications

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Sources of Electrical Conductivity inSnO2

Sources of Electrical Conductivity inSnO2

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Defect study of SnO2 nanostructures by cathodoluminescence analysis: Application to nanowires

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ESR and Electric Conductance Studies of the Fine-Powdered SnO2

Cited by 50 publications

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Sources of Electrical Conductivity inSnO2

Sources of Electrical Conductivity inSnO2

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Defect study of SnO2 nanostructures by cathodoluminescence analysis: Application to nanowires

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ESR and Electric Conductance Studies of the Fine-Powdered SnO₂