Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application

Jayaraj, M. K.; Saji, K. J.; Nomura, Kenji; Kamiya, Toshio; Hosono, Hideo

doi:10.1116/1.2839860

Cited by 97 publications

(70 citation statements)

References 32 publications

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“…1), an increase of O 2 flow does not seem to have a significant effect on the band gap. Such a small change in band gap is also reported by Jayaraj et al for a-ZTO prepared by PLD with O 2 partial pressures between 2 and 9 Pa. 28 Likewise, annealing the ZTO and ZnO at 500 C in air for 1 h only slightly decreases the optical band gap (<0.1 eV) as shown in Fig. 3.…”

Section: -supporting

confidence: 78%

“…Attempts to determine Hall mobility and carrier concentration of these highly resistive films are not successful as they are beyond the detection range of the Hall instrument. A slightly more conductive film (resistivity $ 4 X cm) of ZTO sputtered with 25 sccm O 2 from 33% Sn target shows a Hall mobility of 5.7 cm 2 V À1 s À1 which is comparable to $8 cm 2 V À1 s À1 reported for a-ZTO 28 and a-IGZO. 37 The carrier concentration of this ZTO is 2.5 Â 10 17 cm…”

Section: Resultssupporting

confidence: 49%

“…Re-crystallization of ZTO films has been reported to start at $600 C in RF magnetron sputtering, 20 and <450 C in -PLD. 28 Jayaraj et al have attributed this difference to the difference in growth kinetic energies, where a higher kinetic energy in PLD produces film which recrystallizes at lower temperatures. 28 Therefore, it is reasonable to assume that in the HiTUS sputtered films, recrystallization will occur at annealing temperatures higher than 500 C. There is no significant difference in the diffraction peaks in ZTO films despite having different tin compositions.…”

Section: -4mentioning

confidence: 99%

“…20 In addition, Gorrn et al have investigated the stability of a-ZTO TFTs under gate bias stress and showed a small threshold voltage shift of 30 mV after 1000 min stressing, 21 thereby demonstrating that ZTO TFTs are suitable as current drivers for transparent active matrix OLED displays. 22 Various deposition techniques, such as sol-gel, 23,24 atomic layer deposition (ALD), 25,26 metal organic chemical vapour deposition (MOCVD), 27 and pulsed laser deposition (PLD), 21,28 have been reported for ZTO, however, rf or dc magnetron sputtering is most commonly used. [6][7][8][9][10]20,[29][30][31][32] Ceramic ZTO targets with at.…”

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confidence: 99%

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Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

Niang

Cho

Heffernan

et al. 2016

Journal of Applied Physics

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The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ∼90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 108, a sub-threshold slope of 0.55 V dec−1, and a field effect mobility of 15 cm2 V−1 s−1, which is a sharp increase from 0.8 cm2 V−1 s−1 obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm2 V−1 s−1, but the sub-threshold slope is slightly deteriorated to 0.65 V dec−1. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn2SnO4 and ZnSnO3 phases.

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Section: -supporting

confidence: 78%

Section: Resultssupporting

confidence: 49%

Section: -4mentioning

confidence: 99%

mentioning

confidence: 99%

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Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

Niang

Cho

Heffernan

et al. 2016

Journal of Applied Physics

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“…Binary compounds like doped indium oxide, zinc oxide, and tin oxide are widely used because they present unique electrical and optical properties. Zinc indium tin oxide (ZITO) alloys have been previously studied and improvements in electrical 3,4 and mechanical 5 properties compared to indium tin oxide (ITO) were reported for certain compositions. The objective of the presented experiments was to characterize the electronic structure (i.e., work function and band edge energies) of ZITO thin films in order to assess their suitability for electrode applications.…”

Section: Introductionmentioning

confidence: 99%

The electronic structure of co-sputtered zinc indium tin oxide thin films

Carreras

Gutmann

Antony

et al. 2011

Journal of Applied Physics

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Spin polarization and charge transmission for a waveguide on surface of topological insulator Appl. Phys. Lett. 99, 153104 (2011) Behavior of nitrogen atoms in SiC-SiO2 interfaces studied by electrically detected magnetic resonance Appl. Phys. Lett. 99, 142105 (2011) Influence of deep levels on capacitance-voltage characteristics of AlGaN/GaN heterostructures J. Appl. Phys. 110, 073702 (2011) Electronic states at the interface between indium tin oxide and silicon J. Appl. Phys. 110, 074503 (2011) Improved calculation of vacancy properties in Ge using the Heyd-Scuseria-Ernzerhof range-separated hybrid functional J. Appl. Phys. 110, 063534 (2011) Additional information on J. Appl. Phys. Zinc indium tin oxide (ZITO) transparent conductive oxide layers were deposited via radio frequency (RF) magnetron co-sputtering at room temperature. A series of samples with gradually varying zinc content was investigated. The samples were characterized with x-ray and ultraviolet photoemission spectroscopy (XPS, UPS) to determine the electronic structure of the surface. Valence and conduction bands maxima (VBM, CBM), and work function were determined. The experiments indicate that increasing Zn content results in films with a higher defect rate at the surface leading to the formation of a degenerately doped surface layer if the Zn content surpasses $50%. Furthermore, the experiments demonstrate that ZITO is susceptible to ultraviolet light induced work function reduction, similar to what was earlier observed on ITO and TiO 2 films.

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Transparent OLED Displays

Riedl

2010

Transparent Electronics

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Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application

Cited by 97 publications

References 32 publications

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

The electronic structure of co-sputtered zinc indium tin oxide thin films

Transparent OLED Displays

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