Tin monoxide as an s‐orbital‐based p‐type oxide semiconductor: Electronic structures and TFT application

Ogo, Yoichi; Hiramatsu, Hidenori; Nomura, Kenji; Yanagi, Hiroshi; Kamiya, Toshio; Kimura, Mutsumi; Hirano, Masahiro; Hosono, Hideo

doi:10.1002/pssa.200881792

Cited by 232 publications

(213 citation statements)

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“…This mechanism is greatly exemplified by tin monoxide (SnO), which shows a high contribution of delocalized Sn 5s states to the VB and of likewise delocalized Sn 5p states to the CB (right-hand side of Figure 1), making the material a promising candidate for transparent applications. 7,11,12 In spite of great improvements in recent years, an even better hole mobility is required for more complex applications. In this direction, recent reports have demonstrated that SnO films deposited in a very Sn-rich environment exhibit a high hole mobility.…”

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confidence: 99%

“…13,24,25 Because the metal states are more spatially spread than the oxygen states, the metallic contribution to the VB renders the good hole mobility of SnO. 9,11,12 Therefore, an increase in the metallic contributions to the VB edge is expected to further enhance the hole mobility. Figure 4 presents the calculated electronic structures of SnO with V Sn , O i , V O , and Sn i defects, focusing on the region from À2 to 2 eV.…”

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confidence: 99%

“…As discussed previously, this is expected to increase the mobility of the holes because of the more dispersive character of the metallic bands. 7,9,11,12 FIG. 2.…”

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Enhancement of p-type mobility in tin monoxide by native defects

Granato

Caraveo-Frescas

Alshareef

et al. 2013

Applied Physics Letters

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Transparent p-type materials with good mobility are needed to build completely transparent p-n junctions. Tin monoxide (SnO) is a promising candidate. A recent study indicates great enhancement of the hole mobility of SnO grown in Sn-rich environment [E. Fortunato et al., Appl. Phys. Lett. 97, 052105 (2010)]. Because such an environment makes the formation of defects very likely, we study defect effects on the electronic structure to explain the increased mobility. We find that Sn interstitials and O vacancies modify the valence band, inducing higher contributions of the delocalized Sn 5p orbitals as compared to the localized O 2p orbitals, thus increasing the mobility. This mechanism of valence band modification paves the way to a systematic improvement of transparent p-type semiconductors.

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Enhancement of p-type mobility in tin monoxide by native defects

Granato

Caraveo-Frescas

Alshareef

et al. 2013

Applied Physics Letters

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“…5,7 However, SnO TFTs generally operate in the depletion mode and have a high off-state current owing to the high hole concentration and the low resistivity of the SnO films. 7−11 It is reported that the conductivity in SnO is related to tin vacancy and controllable also by impurity doping.…”

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confidence: 99%

Effects of Pb Doping on Hole Transport Properties and Thin-Film Transistor Characteristics of SnO Thin Films

Liao

Xiao

Ran

et al. 2015

ECS J. Solid State Sci. Technol.

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Effects of Pb doping on the microstructural, optical, and hole transport properties of Sn 1−xf Pb xf O films fabricated by pulsed laser deposition were investigated. It was found that Pb was not solved in bulk ceramic samples, while solved up to x f = 0.035 in the thin films. The Pb doping enlarged the optical bandgap, decreased the hole concentration, and reduced the Hall mobility (μ Hall , from 1.95 to 0.68 cm 2 V −1 s −1 up to x f = 0.035) as x f increased. The field-effect mobility in thin-film transistors also decreased with x f (μ lin , from 0.34 to 0.0024 cm 2 V −1 s −1 ), but the deterioration of μ lin was significantly larger than that of μ Hall . It is speculated that the deterioration of μ Hall would be due to the increase in grain boundary potential barriers. Oxide semiconductors have attracted considerable attention as next-generation channel materials to replace amorphous silicon and polycrystalline silicon for thin-film transistors (TFTs), because of their high electron mobilities >10 cm 2 V −1 s −1 and excellent electrical properties due to the large bandgaps.1−3 However, the reported oxide-based TFTs with excellent performance show n-type characteristics only. The lack of high-performance p-type oxide-based TFTs impedes the realization of transparent low-power-consumption complementary circuits in various TFT applications. 4,5 It is known that the valence band maximum (VBM) of most oxide semiconductors is mainly composed of fully occupied 2p orbitals of oxygen ions with a large electronegativity. 5,6 Hence the dispersion of the VBM band is in general small (i.e., the hole effective mass is large) and the ionization potential is large (i.e., the holes are energetically unstable), causing difficulty in p-type doping for oxide semiconductors.Fortunately, effective p-type doping and relatively high hole mobility is attained in SnO due to the hole contribution through the VBM composed of 5s 2 orbitals of Sn 2+ . 5,7 However, SnO TFTs generally operate in the depletion mode and have a high off-state current owing to the high hole concentration and the low resistivity of the SnO films.7−11 It is reported that the conductivity in SnO is related to tin vacancy and controllable also by impurity doping.5,12−14 However, the previous reports on doping effects are not consistent with each other. Guo et al. reported that doping in SnO with large size dopants such as Sb or Y enhances their hole mobilities and hole concentrations, 13 the latter of which is opposite to usual concept of aliovalent ion doping (i.e., substitutions of the Sn 2+ sites by Sb 3+ /Y 3+ ions are expected to be n-type doping). In contrast, Hosono et al. gave a clear evidence that Sb 3+ doping decreases the hole mobility and the hole concentration in SnO and finally converts the carrier polarity to n-type. 5Liang et al. demonstrated that doping of SnO with Y decreases the field-effect mobility but suppresses the off-state current in SnO TFTs, even though the mechanism for the reduction in the off-state current is not clarified.14 Like SnO, ...

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“…Tin oxide (SnO) applied for p-type semiconductor has a large electronic conductivity due to 5s orbital structure of Sn in valence band maximum. SnO has been attracting immense attention as transparent devices such as thin films transistor [3] . When the zinc tin oxide (ZTO) was synthesized using Zn and Sn, it showed the reduction of significant oxygen vacancy [4] .…”

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confidence: 99%

Fabrication of ZnSn Thin Films Obtained by RF co-sputtering

Lee¹,

Park²,

Kang³

et al. 2016

Journal of the Chosun Natural Science

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The Zn, Sn, and ZnSn thin films were deposited on Si(100) substrate using radio frequency (RF) magnetron cosputtering method. A surface profiler and X-ray photoelectron spectroscopy (XPS) were used to investigate the Zn, Sn, and ZnSn thin films. Thickness of the thin films was measured by a surface profiler. The deposition rates of pure Zn and Sn thin films were calculated with thickness and sputtering time for optimization. From the survey XPS spectra, we could conclude that the thin films were successfully deposited on Si(100) substrate. The chemical environment of the Zn and Sn was monitored with high resolution XPS spectra in the binding energy regions of Zn 2p, Sn 3d, O 1s, and C 1s.

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Tin monoxide as an s‐orbital‐based p‐type oxide semiconductor: Electronic structures and TFT application

Cited by 232 publications

References 20 publications

Enhancement of p-type mobility in tin monoxide by native defects

Enhancement of p-type mobility in tin monoxide by native defects

Effects of Pb Doping on Hole Transport Properties and Thin-Film Transistor Characteristics of SnO Thin Films

Fabrication of ZnSn Thin Films Obtained by RF co-sputtering

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