- Email: [email protected]
Self-oriented growth of (020) MgSiO3-orthopyroxene and (002) α-Mg2SiO4 films using metal-organic chemical vapor deposition
Ceramics International 45 (2019) 13567–13570
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Short communication
Self-oriented growth of (020) MgSiO3-orthopyroxene and (002) α-Mg2SiO4 films using metal-organic chemical vapor deposition
T
Masakazu Ikai, Akihiko Ito∗ Graduate School of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan
A R T I C LE I N FO
A B S T R A C T
Keywords: Films Surfaces Silicate Mg2SiO4
We demonstrated metal-organic chemical vapor deposition of single-phase MgSiO3-orthopyroxene (-opx) and αMg2SiO4 films, and α-Mg2SiO4–MgO composite films with self-oriented growth on a polycrystalline AlN substrate using Mg acetylacetonate and tetraethyl orthosilicate precursors. We obtained (020)-oriented MgSiO3-opx films, (002)-oriented α-Mg2SiO4 films, and (021)-oriented α-Mg2SiO4–(200) MgO composite films at 22, 46, and 81 mol%MgO, respectively, at a deposition temperature of 1200 K and a total chamber pressure of 0.8 kPa. Maximum deposition rates of 42 and 131 μm h−1 were attained for the (020)-oriented MgSiO3-opx and (002)oriented α-Mg2SiO4 films, respectively.
1. Introduction MgSiO3 and Mg2SiO4 are stoichiometric compounds in a MgO–SiO2 pseudo-binary system. MgSiO3 has several polymorphs, orthopyroxene (opx), clinopyroxene (cpx), protopyroxene (ppx), garnet, ilmenite, and perovskite [1]. Mg2SiO4 exhibits phase transitions under high pressures, and α-Mg2SiO4 transforms into γ-Mg2SiO4 spinel via β-Mg2SiO4 with a modified spinel structure as the pressure increases [2]. MgSiO3opx and α-Mg2SiO4 are the stable phases at room temperature under atmospheric pressure, and are commonly known as enstatite and forsterite, respectively. MgSiO3-opx and α-Mg2SiO4 are promising materials with broad applications in protective, electronic, optical materials, and biomaterials in industrial use. Bulk sintered MgSiO3-opx is used as insulating material in telecommunication and other radio-frequency devices. αMg2SiO4 possesses excellent chemical stability, a low coefficient of thermal expansion, low thermal conductivity, and biocompatibility [3,4]. Additionally, α-Mg2SiO4 powders are used as phosphors [5,6], and single crystals can be used as laser gain media [7]. The vapor deposition of MgSiO3 and Mg2SiO4 coatings has rarely been reported, even though MgSiO3 and Mg2SiO4 thick films would be excellent protective coatings and functional layers for electronic and optical devices, and biocompatible materials. A few studies on the preparation of α- and γ-Mg2SiO4 thin films via magnetron sputtering have been reported in literature [8–10]. Although metal-organic chemical vapor deposition (MOCVD) can produce conformal coatings by controlling their orientation and microstructure [11,12], no study on
∗
the MOCVD of MgSiO3 and Mg2SiO4 films has been reported to date. Herein, we demonstrated the MOCVD of MgSiO3-opx and αMg2SiO4, their self-oriented growth, and discussed their characteristic microstructures in terms of crystallography. 2. Experimental procedure MgSiO3 and Mg2SiO4 films were prepared on a polycrystalline AlN substrate. Mg acetylacetonate (Mg(acac)2) and tetraethyl orthosilicate (TEOS) were heated at 473–543 K and 316–343 K, respectively, and the Mg molar fraction in the vapor was varied from 0 to 100 mol%MgO by changing the vaporization temperatures of each precursor. Ar and O2 were used as the carrier and reactant gases, respectively. The total pressure of the chamber was fixed at 0.8 kPa. A diode laser (wavelength: 1470 nm) was irradiated onto the substrate through a quartz window in the chamber to heat the substrate. The deposition temperature increased from 1000 to 1400 K as the laser power was increased to 170 W. The deposition time was 0.6 ks. The phase composition was investigated using X-ray diffraction (XRD; Bruker D2 Phaser). The microstructures were observed using a scanning electron microscope (SEM; JEOL JCM-6000). The crystal structures were schematically illustrated using the VESTA software package [13]. 3. Results and discussion Amorphous SiO2 films were formed from the TEOS precursor
Corresponding author. E-mail address: [email protected] (A. Ito).
https://doi.org/10.1016/j.ceramint.2019.03.212 Received 3 March 2019; Received in revised form 26 March 2019; Accepted 26 March 2019 Available online 27 March 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
Fig. 3. Phase composition of the obtained films in MgO–Mg2SiO4–MgSiO3–SiO2 system.
Fig. 1. XRD patterns of (a) (020)-oriented MgSiO3-opx film, (b) (002)-oriented α-Mg2SiO4 film, and (c) (021)-oriented α-Mg2SiO4–(200)-oriented MgO composite film. AlN substrate contains YAlO3 and Y3Al5O12 as sintering additives.
without Mg(acac)2 supplication (0 mol%MgO). Randomly oriented MgO films were formed from the Mg(acac)2 precursor without TEOS supplication (100 mol%MgO). Single-phase MgSiO3 films with an orthopyroxene structure (MgSiO3-opx) (Pbca, a = 1.823 nm, b = 0.882 nm, c = 0.518 nm; ICSD No. 17053) were obtained at 1200 K and 22 mol%MgO, with the resultant MgSiO3-opx films possessing a (020) orientation (Fig. 1(a)). The MgO6 octahedral and SiO4 tetrahedral layers were perpendicular to the b-plane in the MgSiO3-opx crystal structure, such that this crystallographic feature might prefer (020)-oriented growth (Fig. 2(a)). Single-phase α-Mg2SiO4 films with an olivine structure (Pbnm, a = 0.476 nm, b = 1.021 nm, c = 0.598 nm; ICSD No. 9685) were prepared at 44 mol%MgO, with the resultant α-Mg2SiO4 films exhibiting a significant-(002) orientation (Fig. 1(b)). The edge-sharing MgO6 octahedra were connected along the b-axis direction in the αMg2SiO4 olivine structure, such that this crystallographic feature might
Fig. 2. Schematic illustrations of crystal structure for (a) (020)-oriented MgSiO3-opx, (b) (002)-oriented α-Mg2SiO4, and (c) (021)-oriented α-Mg2SiO4. 13568
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
Fig. 4. Cross-sectional (a, c, e) and surface (b, d, f) SEM images of (a, b) (020)-oriented MgSiO3-opx film, (c, d) (002)-oriented α-Mg2SiO4 film, and (e, f) (021)oriented α-Mg2SiO4–(200)-oriented MgO composite film.
prefer (002)-oriented growth (Fig. 2(b)). A mixture of (021)-oriented α-Mg2SiO4 and (200)-oriented MgO was obtained at 81 mol%MgO (Fig. 1(c)). A cut-off model of the αMg2SiO4 crystal structure along the (021) plane implies that the pointsharing MgO6 and SiO4 polyhedral network exists parallel to the (021) plane (Fig. 2(c)). Fig. 3 summarizes the phase composition of the prepared films. All of the films were amorphous at 1000K, except for the MgO films prepared at 100 mol%MgO. Amorphous SiO2 films formed at 0–9 mol% MgO and 1200 K. The single-phase MgSiO3-opx film with a (020) orientation and single-phase α-Mg2SiO4 film with a (002) orientation were obtained at 22 and 44 mol%MgO, respectively. Composite films of (021)-oriented α-Mg2SiO4 and (200)-oriented MgO were obtained at 55–81 mol%MgO. The MgO films exhibited no preferred orientation. MgSiO3-opx–α-Mg2SiO4 and α-Mg2SiO4–MgO composite films were obtained at 40–45 mol% and 65–79 mol%MgO, respectively, at 1400 K. Fig. 4 shows the cross-sectional and surface SEM images of the films. The (020)-oriented MgSiO3-opx films had a dense cross-section (Fig. 4(a)), and elongated grains formed on the film surfaces (Fig. 4(b)). The (002)-oriented α-Mg2SiO4 films exhibited columnar growth (Fig. 4(c)), and the film surfaces were covered with a bladed texture (Fig. 4(d)). The (021)-oriented α-Mg2SiO4–(200)-oriented MgO composite films were also composed of a columnar structure that terminated with a pyramidal facet (Fig. 4(e) and (f)). The α-Mg2SiO4 thin films were obtained via magnetron sputtering using a α-Mg2SiO4 target at a deposition rate of 0.1–0.3 μm h−1
Table 1 Literature data on the preparation of Mg2SiO4 and MgSiO3 films. Method
Mg2SiO4 Sputtering Sputtering Sputtering MOCVD MgSiO3 MOCVD
Precursor
Phase
Deposition rate/μm h−1
Ref.
α-Mg2SiO4 target α-Mg2SiO4 target Mg target Mg(acac)2 and TEOS
α α γ α
0.12 0.18–0.27 0.14 28–131
[9] [8] [10] Present study
Mg(acac)2 and TEOS
opx
(Table 1) [8,9]. Kang et al. reported on the reactive sputtering of a Mg metal target and (100) Si substrate, with epitaxial growth of the γMg2SiO4 thin film with a spinel structure on (100) Si substrate achieved [10]. No study has reported on the preparation of MgSiO3 films. Herein, we demonstrated the first MOCVD of MgSiO3-opx and αMg2SiO4 films with self-oriented growth at high deposition rates. The single-phase MgSiO3-opx and α-Mg2SiO4 films exhibited significant (020) and (002) orientations, respectively. The deposition rates of the CVD-films were 140–1300 times higher than those of the sputtered films. 4. Conclusions The metal-organic chemical vapor deposition of single-phase MgSiO3-opx and α-Mg2SiO4 films and α-Mg2SiO4–MgO composite films were demonstrated using Mg(acac)2 and TEOS precursors. The singlephase MgSiO3-opx film with a (020) orientation was obtained at 22 mol %MgO, whereas the single-phase α-Mg2SiO4 film with a (002) orientation was prepared at 46 mol%MgO. The (021)-oriented αMg2SiO4–(200) MgO composite films formed at 81 mol%MgO. The oriented MgSiO3-opx and α-Mg2SiO4 films had columnar structures in cross-section and exhibited blade-like textures on the film surfaces. The preferred orientation of the films was associated with the crystallographic features of each phase. The deposition rates of the (020)-oriented MgSiO3-opx and (002)-oriented α-Mg2SiO4 films were 42 and 131 μm h−1, respectively, which were 140–1300 times higher than those prepared via the sputtering method. Acknowledgements This study was supported in part by JSPS KAKENHI Grant Number JP17H03426. This work was performed under the Cooperative Research Program of “Network Joint Research Center for Materials and Devices”. This study was also supported in part by Instrumental Analysis Center, Yokohama National University. Appendix A. Supplementary data
42
Present study
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2019.03.212. 13569
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
References [1] M. Matsui, G.D. Price, Computer simulation of the MgSiO3 polymorphs, Phys. Chem. Miner. 18 (1992) 365–372, https://doi.org/10.1007/BF00199417. [2] T. Katsura, E. Ito, The system Mg2SiO4–Fe2SiO4 at high pressures and temperatures: precise determination of stabilities of olivine, modified spinel, and spinel, J. Geophys. Res. Solid Earth. 94 (1989) 15663–15670, https://doi.org/10.1029/ JB094iB11p15663. [3] S. Ni, L. Chou, J. Chang, Preparation and characterization of forsterite (Mg2SiO4) bioceramics, Ceram. Int. 33 (2007) 83–88, https://doi.org/10.1016/j.ceramint. 2005.07.021. [4] R. Choudhary, P. Manohar, J. Vecstaudza, M.J. Yáñez-Gascón, H.P. Sánchez, R. Nachimuthu, J. Locs, S. Swamiappan, Preparation of nanocrystalline forsterite by combustion of different fuels and their comparative in-vitro bioactivity, dissolution behaviour and antibacterial studies, Mater. Sci. Eng. C 77 (2017) 811–822, https:// doi.org/10.1016/j.msec.2017.03.308. [5] S.A. Hassanzadeh-Tabrizi, E. Taheri-Nassaj, Polyacrylamide gel synthesis and sintering of Mg2SiO4:Eu3+ nanopowder, Ceram. Int. 39 (2013) 6313–6317, https:// doi.org/10.1016/j.ceramint.2013.01.056. [6] K. Mondal, P. Kumari, J. Manam, Influence of doping and annealing temperature on the structural and optical properties of Mg2SiO4:Eu3+ synthesized by combustion method, Curr. Appl. Phys. 16 (2016) 707–719, https://doi.org/10.1016/j.cap.2016. 04.001.
[7] A.V. Gaister, E.V. Zharikov, V.F. Lebedev, A.S. Podstavkin, S.Y. Tenyakov, A.V. Shestakov, I.A. Shcherbakov, Pulsed and cw lasing in a new Cr3+, Li:Mg2SiO4 laser crystal, Quant. Electron. 34 (2004) 693, https://doi.org/10.1070/ QE2004v034n08ABEH002748. [8] C.S. Han, B.C. Mohanty, C.Y. Kang, Y.S. Cho, Sputter-deposited low loss Mg2SiO4 thin films for multilayer hybrids, Thin Solid Films 527 (2013) 250–254, https://doi. org/10.1016/j.tsf.2012.11.143. [9] C.S. Han, B.C. Mohanty, H.R. Choi, Y.S. Cho, Surface scaling evolution and dielectric properties of sputter-deposited low loss Mg2SiO4 thin films, Surf. Coating. Technol. 231 (2013) 229–233, https://doi.org/10.1016/j.surfcoat.2012.07.071. [10] L. Kang, J. Gao, H.R. Xu, S.Q. Zhao, H. Chen, P.H. Wu, Epitaxial Mg2SiO4 thin films with a spinel structure grown on Si substrates, J. Cryst. Growth 297 (2006) 100–104, https://doi.org/10.1016/j.jcrysgro.2006.09.036. [11] P. Zhao, A. Ito, R. Tu, T. Goto, Preparation of highly (100)-oriented CeO2 films on polycrystalline Al2O3 substrates by laser chemical vapor deposition, Surf. Coating. Technol. 204 (2010) 3619–3622, https://doi.org/10.1016/j.surfcoat.2010.04.037. [12] D. Guo, A. Ito, R. Tu, T. Goto, Microstructure and dielectric response of (111)oriented tetragonal BaTiO3 thick films prepared by laser chemical vapor deposition, J. Asian Ceram. Soc. 1 (2013) 197–201, https://doi.org/10.1016/j.jascer.2013.05. 007. [13] K. Momma, F. Izumi, VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data, J. Appl. Crystallogr. 44 (2011) 1272–1276, https:// doi.org/10.1107/S0021889811038970.
13570
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Short communication
Self-oriented growth of (020) MgSiO3-orthopyroxene and (002) α-Mg2SiO4 films using metal-organic chemical vapor deposition
T
Masakazu Ikai, Akihiko Ito∗ Graduate School of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan
A R T I C LE I N FO
A B S T R A C T
Keywords: Films Surfaces Silicate Mg2SiO4
We demonstrated metal-organic chemical vapor deposition of single-phase MgSiO3-orthopyroxene (-opx) and αMg2SiO4 films, and α-Mg2SiO4–MgO composite films with self-oriented growth on a polycrystalline AlN substrate using Mg acetylacetonate and tetraethyl orthosilicate precursors. We obtained (020)-oriented MgSiO3-opx films, (002)-oriented α-Mg2SiO4 films, and (021)-oriented α-Mg2SiO4–(200) MgO composite films at 22, 46, and 81 mol%MgO, respectively, at a deposition temperature of 1200 K and a total chamber pressure of 0.8 kPa. Maximum deposition rates of 42 and 131 μm h−1 were attained for the (020)-oriented MgSiO3-opx and (002)oriented α-Mg2SiO4 films, respectively.
1. Introduction MgSiO3 and Mg2SiO4 are stoichiometric compounds in a MgO–SiO2 pseudo-binary system. MgSiO3 has several polymorphs, orthopyroxene (opx), clinopyroxene (cpx), protopyroxene (ppx), garnet, ilmenite, and perovskite [1]. Mg2SiO4 exhibits phase transitions under high pressures, and α-Mg2SiO4 transforms into γ-Mg2SiO4 spinel via β-Mg2SiO4 with a modified spinel structure as the pressure increases [2]. MgSiO3opx and α-Mg2SiO4 are the stable phases at room temperature under atmospheric pressure, and are commonly known as enstatite and forsterite, respectively. MgSiO3-opx and α-Mg2SiO4 are promising materials with broad applications in protective, electronic, optical materials, and biomaterials in industrial use. Bulk sintered MgSiO3-opx is used as insulating material in telecommunication and other radio-frequency devices. αMg2SiO4 possesses excellent chemical stability, a low coefficient of thermal expansion, low thermal conductivity, and biocompatibility [3,4]. Additionally, α-Mg2SiO4 powders are used as phosphors [5,6], and single crystals can be used as laser gain media [7]. The vapor deposition of MgSiO3 and Mg2SiO4 coatings has rarely been reported, even though MgSiO3 and Mg2SiO4 thick films would be excellent protective coatings and functional layers for electronic and optical devices, and biocompatible materials. A few studies on the preparation of α- and γ-Mg2SiO4 thin films via magnetron sputtering have been reported in literature [8–10]. Although metal-organic chemical vapor deposition (MOCVD) can produce conformal coatings by controlling their orientation and microstructure [11,12], no study on
∗
the MOCVD of MgSiO3 and Mg2SiO4 films has been reported to date. Herein, we demonstrated the MOCVD of MgSiO3-opx and αMg2SiO4, their self-oriented growth, and discussed their characteristic microstructures in terms of crystallography. 2. Experimental procedure MgSiO3 and Mg2SiO4 films were prepared on a polycrystalline AlN substrate. Mg acetylacetonate (Mg(acac)2) and tetraethyl orthosilicate (TEOS) were heated at 473–543 K and 316–343 K, respectively, and the Mg molar fraction in the vapor was varied from 0 to 100 mol%MgO by changing the vaporization temperatures of each precursor. Ar and O2 were used as the carrier and reactant gases, respectively. The total pressure of the chamber was fixed at 0.8 kPa. A diode laser (wavelength: 1470 nm) was irradiated onto the substrate through a quartz window in the chamber to heat the substrate. The deposition temperature increased from 1000 to 1400 K as the laser power was increased to 170 W. The deposition time was 0.6 ks. The phase composition was investigated using X-ray diffraction (XRD; Bruker D2 Phaser). The microstructures were observed using a scanning electron microscope (SEM; JEOL JCM-6000). The crystal structures were schematically illustrated using the VESTA software package [13]. 3. Results and discussion Amorphous SiO2 films were formed from the TEOS precursor
Corresponding author. E-mail address: [email protected] (A. Ito).
https://doi.org/10.1016/j.ceramint.2019.03.212 Received 3 March 2019; Received in revised form 26 March 2019; Accepted 26 March 2019 Available online 27 March 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
Fig. 3. Phase composition of the obtained films in MgO–Mg2SiO4–MgSiO3–SiO2 system.
Fig. 1. XRD patterns of (a) (020)-oriented MgSiO3-opx film, (b) (002)-oriented α-Mg2SiO4 film, and (c) (021)-oriented α-Mg2SiO4–(200)-oriented MgO composite film. AlN substrate contains YAlO3 and Y3Al5O12 as sintering additives.
without Mg(acac)2 supplication (0 mol%MgO). Randomly oriented MgO films were formed from the Mg(acac)2 precursor without TEOS supplication (100 mol%MgO). Single-phase MgSiO3 films with an orthopyroxene structure (MgSiO3-opx) (Pbca, a = 1.823 nm, b = 0.882 nm, c = 0.518 nm; ICSD No. 17053) were obtained at 1200 K and 22 mol%MgO, with the resultant MgSiO3-opx films possessing a (020) orientation (Fig. 1(a)). The MgO6 octahedral and SiO4 tetrahedral layers were perpendicular to the b-plane in the MgSiO3-opx crystal structure, such that this crystallographic feature might prefer (020)-oriented growth (Fig. 2(a)). Single-phase α-Mg2SiO4 films with an olivine structure (Pbnm, a = 0.476 nm, b = 1.021 nm, c = 0.598 nm; ICSD No. 9685) were prepared at 44 mol%MgO, with the resultant α-Mg2SiO4 films exhibiting a significant-(002) orientation (Fig. 1(b)). The edge-sharing MgO6 octahedra were connected along the b-axis direction in the αMg2SiO4 olivine structure, such that this crystallographic feature might
Fig. 2. Schematic illustrations of crystal structure for (a) (020)-oriented MgSiO3-opx, (b) (002)-oriented α-Mg2SiO4, and (c) (021)-oriented α-Mg2SiO4. 13568
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
Fig. 4. Cross-sectional (a, c, e) and surface (b, d, f) SEM images of (a, b) (020)-oriented MgSiO3-opx film, (c, d) (002)-oriented α-Mg2SiO4 film, and (e, f) (021)oriented α-Mg2SiO4–(200)-oriented MgO composite film.
prefer (002)-oriented growth (Fig. 2(b)). A mixture of (021)-oriented α-Mg2SiO4 and (200)-oriented MgO was obtained at 81 mol%MgO (Fig. 1(c)). A cut-off model of the αMg2SiO4 crystal structure along the (021) plane implies that the pointsharing MgO6 and SiO4 polyhedral network exists parallel to the (021) plane (Fig. 2(c)). Fig. 3 summarizes the phase composition of the prepared films. All of the films were amorphous at 1000K, except for the MgO films prepared at 100 mol%MgO. Amorphous SiO2 films formed at 0–9 mol% MgO and 1200 K. The single-phase MgSiO3-opx film with a (020) orientation and single-phase α-Mg2SiO4 film with a (002) orientation were obtained at 22 and 44 mol%MgO, respectively. Composite films of (021)-oriented α-Mg2SiO4 and (200)-oriented MgO were obtained at 55–81 mol%MgO. The MgO films exhibited no preferred orientation. MgSiO3-opx–α-Mg2SiO4 and α-Mg2SiO4–MgO composite films were obtained at 40–45 mol% and 65–79 mol%MgO, respectively, at 1400 K. Fig. 4 shows the cross-sectional and surface SEM images of the films. The (020)-oriented MgSiO3-opx films had a dense cross-section (Fig. 4(a)), and elongated grains formed on the film surfaces (Fig. 4(b)). The (002)-oriented α-Mg2SiO4 films exhibited columnar growth (Fig. 4(c)), and the film surfaces were covered with a bladed texture (Fig. 4(d)). The (021)-oriented α-Mg2SiO4–(200)-oriented MgO composite films were also composed of a columnar structure that terminated with a pyramidal facet (Fig. 4(e) and (f)). The α-Mg2SiO4 thin films were obtained via magnetron sputtering using a α-Mg2SiO4 target at a deposition rate of 0.1–0.3 μm h−1
Table 1 Literature data on the preparation of Mg2SiO4 and MgSiO3 films. Method
Mg2SiO4 Sputtering Sputtering Sputtering MOCVD MgSiO3 MOCVD
Precursor
Phase
Deposition rate/μm h−1
Ref.
α-Mg2SiO4 target α-Mg2SiO4 target Mg target Mg(acac)2 and TEOS
α α γ α
0.12 0.18–0.27 0.14 28–131
[9] [8] [10] Present study
Mg(acac)2 and TEOS
opx
(Table 1) [8,9]. Kang et al. reported on the reactive sputtering of a Mg metal target and (100) Si substrate, with epitaxial growth of the γMg2SiO4 thin film with a spinel structure on (100) Si substrate achieved [10]. No study has reported on the preparation of MgSiO3 films. Herein, we demonstrated the first MOCVD of MgSiO3-opx and αMg2SiO4 films with self-oriented growth at high deposition rates. The single-phase MgSiO3-opx and α-Mg2SiO4 films exhibited significant (020) and (002) orientations, respectively. The deposition rates of the CVD-films were 140–1300 times higher than those of the sputtered films. 4. Conclusions The metal-organic chemical vapor deposition of single-phase MgSiO3-opx and α-Mg2SiO4 films and α-Mg2SiO4–MgO composite films were demonstrated using Mg(acac)2 and TEOS precursors. The singlephase MgSiO3-opx film with a (020) orientation was obtained at 22 mol %MgO, whereas the single-phase α-Mg2SiO4 film with a (002) orientation was prepared at 46 mol%MgO. The (021)-oriented αMg2SiO4–(200) MgO composite films formed at 81 mol%MgO. The oriented MgSiO3-opx and α-Mg2SiO4 films had columnar structures in cross-section and exhibited blade-like textures on the film surfaces. The preferred orientation of the films was associated with the crystallographic features of each phase. The deposition rates of the (020)-oriented MgSiO3-opx and (002)-oriented α-Mg2SiO4 films were 42 and 131 μm h−1, respectively, which were 140–1300 times higher than those prepared via the sputtering method. Acknowledgements This study was supported in part by JSPS KAKENHI Grant Number JP17H03426. This work was performed under the Cooperative Research Program of “Network Joint Research Center for Materials and Devices”. This study was also supported in part by Instrumental Analysis Center, Yokohama National University. Appendix A. Supplementary data
42
Present study
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2019.03.212. 13569
Ceramics International 45 (2019) 13567–13570
M. Ikai and A. Ito
References [1] M. Matsui, G.D. Price, Computer simulation of the MgSiO3 polymorphs, Phys. Chem. Miner. 18 (1992) 365–372, https://doi.org/10.1007/BF00199417. [2] T. Katsura, E. Ito, The system Mg2SiO4–Fe2SiO4 at high pressures and temperatures: precise determination of stabilities of olivine, modified spinel, and spinel, J. Geophys. Res. Solid Earth. 94 (1989) 15663–15670, https://doi.org/10.1029/ JB094iB11p15663. [3] S. Ni, L. Chou, J. Chang, Preparation and characterization of forsterite (Mg2SiO4) bioceramics, Ceram. Int. 33 (2007) 83–88, https://doi.org/10.1016/j.ceramint. 2005.07.021. [4] R. Choudhary, P. Manohar, J. Vecstaudza, M.J. Yáñez-Gascón, H.P. Sánchez, R. Nachimuthu, J. Locs, S. Swamiappan, Preparation of nanocrystalline forsterite by combustion of different fuels and their comparative in-vitro bioactivity, dissolution behaviour and antibacterial studies, Mater. Sci. Eng. C 77 (2017) 811–822, https:// doi.org/10.1016/j.msec.2017.03.308. [5] S.A. Hassanzadeh-Tabrizi, E. Taheri-Nassaj, Polyacrylamide gel synthesis and sintering of Mg2SiO4:Eu3+ nanopowder, Ceram. Int. 39 (2013) 6313–6317, https:// doi.org/10.1016/j.ceramint.2013.01.056. [6] K. Mondal, P. Kumari, J. Manam, Influence of doping and annealing temperature on the structural and optical properties of Mg2SiO4:Eu3+ synthesized by combustion method, Curr. Appl. Phys. 16 (2016) 707–719, https://doi.org/10.1016/j.cap.2016. 04.001.
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