Growth of high-quality epitaxial ZnO films on α-Al2O3

Fons, Paul; Iwata, K.; Niki, Shigeru; Yamada, A.; Matsubara, Koji

doi:10.1016/s0022-0248(98)01427-4

Cited by 184 publications

(97 citation statements)

References 12 publications

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“…Early growth experiments with magnetron sputtering [39,41], and chemical vapor deposition (CVD) [42][43][44] led to polycrystalline films. Later attempts led to high quality ZnO single-crystal films prepared by RF magnetron sputtering [45] and methods such as molecular beam expitaxy (MBE) [46,47], pulsed laser deposition (PLD) [48], metal-organic CVD (MOCVD) [49], and hydride or halide vapor phase epitaxy (HVPE) [50,51]. The improved quality of ZnO films allowed observation of optically pumped lasing at room temperature [52].…”

Section: Epitaxial Growth Of Zno Filmsmentioning

confidence: 99%

Preparation and properties of ZnO and devices

Izyumskaya

Avrutin

Özgür

et al. 2007

Physica Status Solidi (b)

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ZnO has gained interest in part because of its large exciton binding energy (60 meV), good for lasing with low threshold. The renewed interest in ZnO is fuelled by availability of high quality substrates, reports of p-type conductivity, and ferromagnetic behavior when doped with transitions metals. The field is also fuelled by theoretical predictions and perhaps experimental confirmation of ferromagnetism at room temperature for potential spintronics applications. Despite great strides there are still many challenges, the chief among them is the attainment of reproducibly low resistivity p-type ZnO. While ZnO already has many industrial applications owing to its piezoelectric properties and bandgap in the near UV, its applications to optoelectronic devices utilizing electrical injection has not yet been put to practice mainly due to the lack of p-type epitaxial layers. This review provides a discussion of some of the growth issues of ZnObased epitaxial and heteroepitaxial layers and their use in a variety of devices.

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Section: Epitaxial Growth Of Zno Filmsmentioning

confidence: 99%

Preparation and properties of ZnO and devices

Izyumskaya

Avrutin

Özgür

et al. 2007

Physica Status Solidi (b)

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“…In addition, multi-functionality of ZnO, such as large bandgap energy of 3.3eV for transparent electronics [4] and piezoelectricity for actuator [5], would be interesting for hybridization devices. From the viewpoint of biomedical applications, less hazardousness of oxides has attracted a great deal of attention, where other compound semiconductors cannot work.Recent progress on epitaxial growth of ZnO based semiconductors has been performed by molecular beam epitaxy (MBE) [6,7], pulsed laser deposition (PLD) [8,9] and metalorganic vapor phase epitaxy …”

mentioning

confidence: 99%

Characterization of undoped ZnO layers grown by molecular beam epitaxy towards biosensing devices

Ogata¹,

Komuro²,

Hama³

et al. 2004

Physica Status Solidi (b)

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Undoped ZnO layers grown by molecular beam epitaxy (MBE) were investigated aiming at biosensing devices based on organic/inorganic hybrid structures. Clear observation of free exciton emission in low temperature photoluminescence (PL) spectra and electron mobility as high as 114 cm 2 /Vs at room temperature indicate that the quality of the ZnO layers is applicable for biosensors. Surface bonding of the ZnO the layers, which is one of the key issues for hybridization, was examined by means of xray photoelectron spectroscopy (XPS). The XPS spectra of O 1s revealed that formation and desorption of hydroxyl (OH) bonds can be controlled by air exposure and thermal treatments. , establishment of hybridization between biofunctionalized molecules and inorganic semiconductor systems is of high importance. Until now, Si-based FETs are mainly utilized for them, however, compound semiconductors should be another candidates. In termes of fabrication of hybridized structures, their controllability of bandgap energies and lattice constants, which resulted in realization of laser diodes and high electron mobility transistors (HEMTs), would possess several potential. Among lots of compounds, i.e., numerous combinations of elements, we have chosen zinc oxide (ZnO) based semiconductors as materials for EnFET and biochemical sensors from the following reasons.One of the advantages of ZnO is expected to easily form direct bonding between organic molecules and the oxide surface. In case of non-oxide compounds, surface cleaning is necessary for precise bonding control, which can be realized by the removal of unintentionally formed amorphous oxide layer at the surface, while oxide surfaces are free from that. Considering that direct binding of biofunctional molecules on insulating gate layers in FETs is preferable for signal processing, availability of crystalline insulating layers of oxides is crucial for hybridization. Also it is expected that the techniques of selfassembled monolayer formation using organothiols on gold [3] would be applicable on oxide surfaces by the reaction between cation in oxide and S in molecules. In addition, multi-functionality of ZnO, such as large bandgap energy of 3.3eV for transparent electronics [4] and piezoelectricity for actuator [5], would be interesting for hybridization devices. From the viewpoint of biomedical applications, less hazardousness of oxides has attracted a great deal of attention, where other compound semiconductors cannot work.Recent progress on epitaxial growth of ZnO based semiconductors has been performed by molecular beam epitaxy (MBE) [6,7], pulsed laser deposition (PLD) [8,9] and metalorganic vapor phase epitaxy

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“…Due to a large lattice mismatch of 18%, however, ZnO films prepared on sapphire substrates have large crystal mosaics, high residual carrier concentrations, and low mobility, all of which make optoelectronic applications challenging. 14 One of the most promising means to improve the crystal quality of ZnO films is to prepare buffer layers prior to the crystal growth. Various types of ZnO buffer layers have been reported.…”

Section: Introductionmentioning

confidence: 99%

Off-axis sputter deposition of ZnO films on c-sapphire substrates by utilizing nitrogen-mediated crystallization method

et al. 2014

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Abstract. High-quality epitaxial ZnO films on c-plane sapphire substrates have been obtained by utilizing an offaxis sputtering configuration together with buffer layers prepared via nitrogen-mediated crystallization (NMC). The role of NMC buffer layers is to provide high density of nucleation site and, thus, to reduce the strain energy caused by the large lattice mismatch (18%) between ZnO and sapphire. The NMC buffer layers allow two-dimensional growth of subsequently grown ZnO films, being particularly enhanced by employing an off-axis sputtering configuration in which the substrate is positioned out of the high-energy particles, such as negative oxygen ions originating from the targets. As a result, ZnO films with smooth surfaces (root-mean-square roughness: 0.76 nm) and a high electron mobility of 88 cm 2 ∕V · s are fabricated. Photoluminescence spectra of the ZnO films show strong near-band-edge emission, and the intensity of the orange-red defect emission significantly decreases with increasing horizontal distance between the target and the substrate. From these results, we conclude that off-axis sputtering together with NMC buffer layers is a promising method for obtaining high-quality epitaxial ZnO films. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Growth of high-quality epitaxial ZnO films on α-Al2O3

Cited by 184 publications

References 12 publications

Preparation and properties of ZnO and devices

Preparation and properties of ZnO and devices

Characterization of undoped ZnO layers grown by molecular beam epitaxy towards biosensing devices

Off-axis sputter deposition of ZnO films on c-sapphire substrates by utilizing nitrogen-mediated crystallization method

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