New challenges on gallium-doped zinc oxide films prepared by r.f. magnetron sputtering

Assunção, V.; Fortunato, Elvira; Marques, A.; Gonçalves, A.; Ferreira, I.; Águas, Hugo; Martins, Rodrigo

doi:10.1016/s0040-6090(03)00955-6

Cited by 93 publications

(47 citation statements)

References 12 publications

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“…On the other hand, the ZGO films are polycrystalline with a preferred (0002) grain orientation and a roughness above 15-18 nm that is enhanced as the annealing temperature increases. This behavior is ascribed to the increase of the crystalline size [15]. Similar results were found for ZnO.…”

Section: Methodssupporting

confidence: 83%

“…Due to cost increase of indium and the need to have films able to sustain a hydrogen plasma discharge during the deposition process [8], zinc aluminum oxide (ZAO) [9][10][11][12][13] and zinc gallium oxide (ZGO) have been developed as a promising alternative to ITO, since zinc (Zn) is a quite abundant (about 10 3 more than In [14]) and "green" material. Besides that, gallium (Ga) has a better doping efficiency than aluminum (Al), allowing room temperature processing [12,15,16]. For these films, the conductivity improvement has been associated with the crystal order and corresponding grain size.…”

mentioning

confidence: 99%

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Oxide semiconductors: Order within the disorder

Fortunato

Pereira

Barquinha

et al. 2009

Philosophical Magazine

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Section: Methodssupporting

confidence: 83%

mentioning

confidence: 99%

Oxide semiconductors: Order within the disorder

Fortunato

Pereira

Barquinha

et al. 2009

Philosophical Magazine

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“…[10] These depositions were also carried out at room temperature. Figure 5a shows the source-to-drain current (I DS ) as a function of the gate voltage (V GS ).…”

Section: ±2mentioning

confidence: 99%

Fully Transparent ZnO Thin‐Film Transistor Produced at Room Temperature

Fortunato¹,

et al. 2005

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Functional oxide materials currently represent a key challenge as well as a promising powerful tool for both fundamental understanding and technological development of the next generation of transparent electronics, such as field-effect transistors.[1] Here, we report a fully transparent ZnO thin-film transistor (ZnO-TFT) with a transmittance above 80 % in the visible part of the spectrum, including the glass substrate, fabricated by radiofrequency (rf) magnetron sputtering at room temperature, with a bottom gate configuration. ), the opacity of polysilicon TFTs limits the aperture ratio for active matrix arrays; this is highly important, for instance, when OLEDs have to be addressed. Also, if flexible substrates based on polymers are intended to be used, the processing temperature is quite a limiting factor.One possible way to overcome such problems is the utilization of efficient and reliable oxide-based thin-film transistors. Transparent-oxide-semiconductor-based transistors have recently been proposed, using intrinsic zinc oxide (ZnO) as an active channel.[3±8] One of the main advantages exhibited by these transistors lies in the magnitude of the electron-channel mobility, leading to higher drive currents and faster device operating speeds. The mobility reported in the literature ranges from 0.2±7 cm 2 V ±1 s ±1, with an on/off current ratio from 10 5 ±10 7 , and a threshold voltage (V TH ) between ±1 V and 15 V. Until now, most ZnO channel layers have been deposited using substrate heating or subjected to post-thermal annealing, mainly in order to increase the crystallinity of the ZnO layer and thus the mobility in the film. The purpose of this work is to demonstrate the possibility of fabricating high-mobility ZnO thin-film transistors at room temperature by rf magnetron sputtering with improved performances and highly compatible with the fabrication technologies used for flexible electronics. By doing so, we overcome processing-temperature limitations, making it possible for the devices to be used in a wide range of applications where the mobility is no longer a limitation, such as for use in so-called fast and invisible electronics. Figure 1 shows the dependence of the electrical resistivity (r) and the average optical transmittance in the visible spectra (between 400±700 nm) as a function of rf power density (P). The highest resistivity (» 10 8 X cm) was obtained for, the films were close to being stoichiometric with few structural defects and a consequently higher resistivity. As we decreased or increased the rf power density from 5 W cm ±2 , a deviation from stoichiometry was obtained, accompanied by a decrease in electrical resistivity due to a lower carrier concentration and/or electron mobility. This was also confirmed by a decrease in the optical transmittance, especially for rf power densities lower than 5 W cm ±2 .COMMUNICATIONS 590

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“…Gallium is less reactive and more resistant to oxidation compared with aluminium [77,78]. Recently it was demonstrated by the present authors that doping with gallium led to films with low resistivity associated with a high transmittance in the visible region [79][80][81][82][83], even when processed at room temperature. Several techniques have also been used like MOCVD, evaporation, magnetron sputtering, sol gel and plasma assisted molecular beam epitaxy [84].…”

Section: Transparent Oxide Semiconductorsmentioning

confidence: 58%