In-situ formation of MgO2 thin films on MgO single-crystal surfaces at high temperatures

Wang, Zhong Lin; Bentley, J.; Kenik, E.A.; Horton, L.L.; McKee, R. A.

doi:10.1016/0039-6028(92)90278-e

Cited by 31 publications

(9 citation statements)

References 26 publications

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“…2c arise because of the double diffraction of these two phases. Similar types of diffraction pattern and orientation relationships between the MgO and MgO 2 phases were also reported by Wang et al 19 The diffraction streaks in Fig. 2c are along <110> and are suggested to be produced by the strain field effect along <110> arising because of the lattice mismatch between the MgO and MgO 2 phases.…”

Section: Resultssupporting

confidence: 72%

Growth and Characterization of Pulsed-Laser-Deposited Ilmenite–Hematite Thin Films

Kale

Padmini

Dou

et al. 2007

Journal of Elec Materi

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The ilmenite-hematite (1 -x) FeTiO 3 Á xFe 2 O 3 solid solution system is considered to be a novel material for spin-electronics, microelectronics, hightemperature electronics, and radhard electronics. This paper focuses on thin films of composition x = 0.33 grown on (100) MgO single-crystal substrates using pulsed-laser deposition (PLD) under different argon-oxygen mixtures. The surface of the MgO was found to possess MgO 2 crystals, yielding an orientation relationship, [001] MgO k [011] MgO 2 and (100)MgO k (110) MgO 2 . The structural characterizations show that the films are crystalline and homogeneous without any secondary phase. The films show a weak and inclined (1120) growth epitaxy. A bandgap of 3.4-3.7 eV was obtained for these films from optical measurements carried out in the UV-visible region. Electrical measurements confirmed the semiconducting behavior. However, the resistivity was found to increase substantially on the slightest addition of oxygen into the chamber.

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Section: Resultssupporting

confidence: 72%

Growth and Characterization of Pulsed-Laser-Deposited Ilmenite–Hematite Thin Films

Kale

Padmini

Dou

et al. 2007

Journal of Elec Materi

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“…This motif has the same surface stoichiometry as Mg-O 3 -2×2; its surface energy is 0.23 eV per 1×1 cell higher. Although not favored in (111) surface, it might exist in some other surfaces, such as the (100) surface 40 ). This type of motif can provide a hint for experimental growth of the crystal MgO 2 , which is calculated to be stable at high pressure 41 .…”

Section: B Mgo (111)mentioning

confidence: 99%

Evolutionary method for predicting surface reconstructions with variable stoichiometry

et al. 2013

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We present a specially designed evolutionary algorithm for the prediction of surface reconstructions. This new technique allows one to automatically explore all the low-energy configurations with variable surface atoms and variable surface unit cells through the whole chemical potential range. The power of evolutionary search is demonstrated by the efficient identification of diamond 2×1 (100) and 2×1 (111) surfaces with a fixed number of surface atom and a fixed cell size. With further variation of surface unit cells, we study the reconstructions of the polar surface MgO (111). Experiment has detected an oxygen trimer (ozone) motif (Plass et al, 1998). We predict a new version of this motif which can be thermodynamically stable at extreme oxygen rich condition. Finally, we perform a variable stoichiometry search for a complex ternary system: semi-polar GaN (1011) with and without adsorbed oxygen. The search yields a non-intuitive reconstruction based on N3-trimers. These examples demonstrate that an automated scheme to explore the energy landscape of surfaces will improve our understanding of surface reconstructions. The method presented in this report can be generally applied to binary and multi-component systems.

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“…Following in-situ annealing (figure 2) the bright-field image shows ~100-nm grains on the specimen surfaces, the SAD pattern has the same features as in Wang et al [1] (extra reflections at 3/2{100} (type 1) and {110} (type2) plus double diffraction), and EELS shows Si, possibly Al, and lower Mg relative to O. Quantification yields Mg/O = 0.50 ± 0.05 and Si/Mg = 0.49 ± 0.05, consistent with forsterite Mg 2 SiO 4 . Upon additional annealing in air at 1623 K for 15 min the polycrystalline film dewets the surface and forms small islands with moiré fringes visible on some particles [3].…”

mentioning

confidence: 61%

“…

Wang et al previously annealed MgO in the TEM to ~1500 K, observed a phase transformation at the surface, and identified the phase as MgO 2 [1]. They primarily studied bulk, cleaved {100} surfaces in the reflection geometry (REM, RHEED, and REELS), but also studied thin cleavage fragments by transmission electron microscopy (TEM), selected area diffraction (SAD), and transmission electron energy-loss spectroscopy (EELS).

…”

mentioning

confidence: 98%

Forsterite Formed on MgO Single Crystals During In-Situ Annealing

et al. 2006

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Wang et al. previously annealed MgO in the TEM to ~1500 K, observed a phase transformation at the surface, and identified the phase as MgO 2 [1]. They primarily studied bulk, cleaved {100} surfaces in the reflection geometry (REM, RHEED, and REELS), but also studied thin cleavage fragments by transmission electron microscopy (TEM), selected area diffraction (SAD), and transmission electron energy-loss spectroscopy (EELS). In light of the extensive use of annealed single crystal MgO as a substrate for epitactic growth, numerous previous studies of MgO surfaces, and especially the seemingly unlikely formation of MgO 2 (stable only at high oxygen partial pressures) in the vacuum of the TEM, additional in-situ annealing studies have been performed. Single-crystal {001} MgO TEM specimens, prepared following an involved and proven protocol [2], were annealed in situ with the use of a Gatan model 628 single-tilt heating holder. Most anneals employed a Philips CM30; additional anneals used an oil-free, dry-pumped Philips CM200-FEG. Specimens were heated in situ to ~1500 K at ~1 x 10 -7 Torr, held at that temperature for a few minutes, and cooled. Other than preliminary experiments to determine appropriate conditions, in-situ anneals were performed with specimens kept out of the electron beam. Comparison specimens were annealed in a vacuum furnace at 10 -5 to 10 -6 Torr, but no second phase formed.In figure 1, the weak-beam image shows a contamination-free, step-terrace structure, the SAD pattern shows only expected MgO reflections, and the EELS shows only O and Mg edges, quantified with Gatan EL/P software to yield Mg/O = 1.0 ± 0.1. Following in-situ annealing (figure 2) the bright-field image shows ~100-nm grains on the specimen surfaces, the SAD pattern has the same features as in Wang et al. [1] (extra reflections at 3/2{100} (type 1) and {110} (type2) plus double diffraction), and EELS shows Si, possibly Al, and lower Mg relative to O. Quantification yields Mg/O = 0.50 ± 0.05 and Si/Mg = 0.49 ± 0.05, consistent with forsterite Mg 2 SiO 4 . Upon additional annealing in air at 1623 K for 15 min the polycrystalline film dewets the surface and forms small islands with moiré fringes visible on some particles [3]. Large-area SAD patterns exhibit the same features as after in-situ annealing, except 4-fold spots around MgO reflections (possibly <111> relrods from defects on {111}) are no longer present. Tilting experiments (on carefully selected individual particles) around 13 -0 f (type 1)//200 M reflections to [312] (10°) and [311] (25°) forsterite zones and around 002 f (type 2)//220 M reflections to [210] (5°), [310] (16.5°) and [410] (24°) forsterite zones, determined the orientation relationship as (100) f //(1 -1 -1) M , (010) f //(2 -11 -) M and (001) f //(011) M (12 variants), where subscripts f and M refer to forsterite and MgO, respectively [3]. Notable d-spacing matches are d 400 forsterite ~ d 222 MgO and d 004 forsterite ~ d 220 MgO.Possible sources of Si contamination were considered. The SHaRE CM30 always use...

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In-situ formation of MgO2 thin films on MgO single-crystal surfaces at high temperatures

Cited by 31 publications

References 26 publications

Growth and Characterization of Pulsed-Laser-Deposited Ilmenite–Hematite Thin Films

Growth and Characterization of Pulsed-Laser-Deposited Ilmenite–Hematite Thin Films

Evolutionary method for predicting surface reconstructions with variable stoichiometry

Forsterite Formed on MgO Single Crystals During In-Situ Annealing

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