Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

Alema, Fikadu; Ledyaev, Oleg; Miller, Ross A.; Beletsky, Valeria; Osinsky, A.; Schoenfeld, Winston V.

doi:10.1016/j.jcrysgro.2015.11.012

Cited by 34 publications

(24 citation statements)

References 29 publications

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“…87 The data shown in Figures 5a and 5b seem to confirm the general validity of the correlation between E g and the square of the difference of Pauling electronegativity between oxygen and the cationic average electronegativity initially proposed 9 We like to stress that: a) theoretical data calculated by using Eq. 7 (green triangles in Figure 6a) are close to experimental values of mixed oxides in both crystallographic systems (rock-salt structure up to 50at% in Mg content for stable phases and wurtzite structure with Mg content ≤ 20at%) by using as electronegativity parameters 83 Data shown in Figure 6a support the usefulness of the use of Eq. 7 in predicting, with reasonable accuracy, the optical bandgap values of non-regular mixed oxides provided that the bandgap value of both pure oxides can be expressed by means of Eq.…”

supporting

confidence: 81%

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

Quarto

Zaffora

Franco

et al. 2017

J. Electrochem. Soc.

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A critical assessment of the Photocurrent Spectroscopy (PCS) Technique for the semi-quantitative characterization of passive film and corrosion layers composition is carried out. We take into account more than three decades of PCS usage as "in-situ" analytical technique and related results as well as the criticism of the underlying semi-empirical correlation relating the measured optical bandgap (E g ) to the passive film composition. The discrepancies between the experimental data, gathered by PCS measurements, and E g estimates originating from recently developed Density Functional Theory based modeling of solid state properties are stressed with particular emphasis on the case of anodic passive film grown on technologically important alloys (Fe-Cr and stainless steels). The extension of this correlation to mixed oxides and its use for relating the oxide composition to the bandgap values is critically reviewed by comparing the predicted E g of mixed oxides with the experimental values. Suggestions on how to account for different bandgap values of oxide polymorphs and how to correlate the E g values to the composition of mixed s,p-d-metal oxides are presented and discussed on the basis of experimental results reported in the literature. On the basis of this assessment, the ability of PCS in providing quantitative information on the composition of passive film and corrosion layer is generally confirmed. Fujimoto (fujimoto@mat.eng.osaka-u.ac.jp) and HeeJin Jang (heejin@chosun.ac.kr). . This paper is a Critical Review in Electrochemical and Solid State Science and Technology (CRES 3 T). This article was reviewed by ShinjiPhotocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their bandgap is a prerequisite to any possible application in different fields such as solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials). 1,2In the last 20-30 years an increasing number of electrochemists working in the field of corrosion have been attracted by this technique owing to its versatility and ability to scrutinize "in-situ" corrosion layers and passive films having semiconducting or insulating behavior. In previous as well as in very recent works 3-7 we have shown that PCS is able to provide detailed information on characteristic energy levels of passive film/electrolyte junctions (flatband potential: U FB ; internal photoemission threshold: E th ; bandgap value: E g ). Such information is necessary for a deeper understanding of the possible mechanisms of charge transfer (electrons and ions) at the metal/corrosion layer/electrolyte interface. Further advantages stem from the fact that the PCS technique does not require particular surface finishing control, it can be used both on large areas as well as in microscopic regions of the electrode, and can reach high sensitivity by using a lock-in amplifier coupled to a mec...

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supporting

confidence: 81%

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

Quarto

Zaffora

Franco

et al. 2017

J. Electrochem. Soc.

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“…The MSM devices were connected in series with a load resistance of 464 Ω and biased at 6 V. extending well into the solar blind spectral window (long wavelength cutoff < 290 nm). The decrease in the peak responsivity wavelength ( P ) with the Mg content in the film is shown in Figure 2 (b, red) and is in agreement with the blue shift in the absorption edge observed for these films [22].…”

Section: Methodssupporting

confidence: 84%

“…Mg x Zn 1-x O films (450 nm-890 nm) with Mg content between x=0.0 and x=0.51 were grown on ZnO (~30nm)/AlN (~25 nm)/Al 2 O 3 (0001) substrates via the PMOCVD method. Details of the experimental procedure for the growth of the MgZnO films can be found elsewhere [22,24]. The response spectra of the devices were measured using a 150 W Xenon lamp as an excitation source.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, the authors have reported on the growth of a record high Mg content (51 %) wurtzite phase MgZnO epitaxial film with a band gap of ~ 4.50 eV (276 nm) which is well within the solar blind spectral window [22,23]. This was achieved via the pulsed metal organic chemical vapor deposition (PMOCVD) method in which fast periodic transitions between MgZnO layer growth and oxidation create a far from equilibrium process, resulting in high Mg content wurtzite MgZnO without phase segregation [24,25].…”

Section: Introductionmentioning

confidence: 98%

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High responsivity solar blind photodetector based on high Mg content MgZnO film grown via pulsed metal organic chemical vapor deposition

Alema

Hertog

Ledyaev

et al. 2016

Sensors and Actuators A: Physical

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Metal-semiconductor-metal (MSM) structured solar blind photodetectors were fabricated based on various Mg content wurtzite Mg x Zn 1-x O epitaxial films grown via pulsed metal organic chemical vapor deposition. The response spectra of the devices showed a peak position that shifts from ~383 nm to 276 nm for Mg content, x, between 0.0 and 0.51, covering a wide portion of the ultraviolet spectral region, extending well into the solar blind window. At 10 V bias, a large responsivity of ~1.8x10 4 A/W was obtained at 276 nm for a device based on a high Mg content (x=0.51) MgZnO film. To the best of our knowledge, this responsivity is the highest ever reported for a MgZnO based device and its origin is attributed to large internal gain resulting from carrier trapping at the MgZnO/Ni/Au interface. This is confirmed by the presence of an asymmetric Schottky barrier height on the two MSM contacts. Conversely, the response speed of the devices was slow with the 10%-90% rise and fall times measured to be in the millisecond range. The results reported in this work show the realization of high responsivity MgZnO based solar blind photodetectors, providing a significant step in the development of MgZnO alloy based of detector.

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“…Previous study on Mg x Zn 1−x O thin films, deposited via pulsed laser deposition (PLD), has found that this alloys were single-phase with the wurtzite structure up to a Mg composition x ~ 0.33; above that the alloys were found to be phase separated [1]. Single-phase wurtzite with high Mg composition x = 0.5 were also grown via molecular beam epitaxy [12], while more recent work used pulsed metal organic chemical vapor deposition to achieve single phase wurtzite alloys up to x = 0.51 [13]. The crystallization of single phase wurtzite alloys with large Mg composition, as opposed to that of the ceramics, was attributed to the nonequilibrium nature of the deposition methods thus enabling the growth of metastable alloys.…”

Section: Introductionmentioning

confidence: 99%

Thermal stability of ultra-wide-bandgap MgZnO alloys with wurtzite structure

Thapa

Huso

Lapp

et al. 2018

J Mater Sci: Mater Electron

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Mg x Zn 1−x O thin films were grown as metastable alloys via a sputtering technique in order to achieve single-phase wurtzite alloys with deep-UV optical bandgaps. As-grown alloys with Mg composition range 0-72% resulted in optical bandgaps spanning the UV-range of 3.3-4.4 eV. The thermal stability of the alloys was studied via post-growth controlled annealing experiments up to 900 °C. Alloys with low Mg up to 34% were found to be highly stable and retained their optical and material properties; however, alloys with higher Mg, up to 72%, were found to be unstable and were phase separated into wurtzite and cubic structural phases with respective optical bandgaps at ~ 3.5 and 6.0 eV. Both the as-grown and annealed alloys were studied using X-ray diffraction for structural identification, transmission spectroscopy for bandgap analysis, and Raman scattering for mapping the phonon mode-behavior. The experimental value for the solubility limit was found to be ~ 30%. A straightforward model calculation based on the Raman-mode saturation behavior yielded a similar value for the solubility limit of the alloys. The results are discussed in terms of available phase-diagrams for stable-state ceramics alloys that were grown under thermodynamics equilibrium conditions.

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Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

Cited by 34 publications

References 29 publications

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

High responsivity solar blind photodetector based on high Mg content MgZnO film grown via pulsed metal organic chemical vapor deposition

Thermal stability of ultra-wide-bandgap MgZnO alloys with wurtzite structure

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