Fabrication of Flat MgO(111) Films on Al<sub>2</sub>O<sub>3</sub>(0001) Substrates by Pulsed Laser Deposition

Susaki, Tomofumi; Kumada, Sho; Katase, Takayoshi; Matsuzaki, Kosuke; Miyakawa, Masashi; Hosono, Hideo

doi:10.1143/apex.2.091403

Cited by 19 publications

(22 citation statements)

References 17 publications

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“…In MgO each cation (Mg 2þ ) layer and anion (O 2À ) layer is alternately stacked along the [111] direction as shown in Fig. 2 [18][19][20][21][22][23][24][25][26] and in LaAlO 3 positively charged (LaO) þ layer and negatively charged (AlO 2 ) À layer is stacked along the [001] direction as shown in Fig. 3.…”

Section: Introductionmentioning

confidence: 99%

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Susaki

Hosono

2013

Jpn. J. Appl. Phys.

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We have studied the work function modulation in pulsed laser deposited nonpolar MgO (100) and polar MgO (100) and LaAlO3 (100) insulating oxide films on Nb:SrTiO3 (100) and (111) substrates using Kelvin probe measurements. The work function modulation in MgO/Nb:SrTiO3 is ∼1 eV, which may be understood by the “electron compression model”, where the leaked-out electrons from Nb:SrTiO3 surface are pushed back by MgO layer, reducing the surface dipole moment. By forming double insulating top layer in LaAlO3/nondoped SrTiO3/Nb:SrTiO3 (100), we have realized the work function as low as ∼2.2 eV, which would be originated in the formation of high-density electrons at the LaAlO3/nondoped SrTiO3 interface and can be very close to the top surface. The present results demonstrate that chemically stable oxides can be used as low work function devices employing heterostructure form.

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Section: Introductionmentioning

confidence: 99%

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Susaki

Hosono

2013

Jpn. J. Appl. Phys.

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“…Such a surface has attracted a great deal of attention from both experimental and theoretical studies. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In spite of the large number of studies made, many features of this process are not yet understood. Therefore, the investigations described herein are aimed at better understanding the microstructural details of MgO(111) films.…”

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confidence: 99%

Heteroepitaxial growth of MgO(111) thin films on Al2O3(0001): Evidence of a wurtzite to rocksalt transformation

et al. 2012

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We report on a growth study of MgO films deposited on Al 2 O 3 (0001) substrates by magnetron sputtering. The films exhibited a preferred rocksalt MgO(111) orientation. Surprisingly, depending on the O 2 gas flow ratio, a structure of graphiticlike wurtzite MgO(0001) has been revealed. The observed Mg-O perpendicular bond length reduction is accompanied by an atomically flat surface morphology for the development of MgO(111) films; the transition to the bulk rocksalt structure occurs in the 3-6 nm coverage range. Previously, relaxation of the electrostatic instability of MgO (111) Nanoscale alkaline earth metal oxides, in particular, MgO, are very promising materials for applications as adsorbents for decontaminating wastewater due to their favorable electrostatic attraction mechanism, and the simplicity of their production from abundant natural minerals.1 Furthermore, the MgO(111) facet, which not only presents the largest number of dangling bonds per atom, but also alternating layers of O 2− and Mg 2+ , and thus, a strong electrostatic field, is obviously anticipated to be more reactive, compared to nonpolar surfaces. In this regard, recent studies on MgO(111) have suggested that the polar oxide surface may be of interest for the catalytic splitting of water and for hydrogen storage. 2On the other hand, there is an increasing interest in the growth of high quality MgO films because of their unique physical properties which allow the fabrication of buffered epitaxial layers of ferroelectric materials and superconductors, as well as wide-band-gap semiconductors for many optoelectronic applications.3 MgO(111) layers are also interesting for the exploitation of spintronic devices. 4 Therefore, it remains a great challenge to develop general methods for the controllable growth of unusual (111) exposed MgO crystal surfaces. Such a surface has attracted a great deal of attention from both experimental and theoretical studies. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In spite of the large number of studies made, many features of this process are not yet understood. Therefore, the investigations described herein are aimed at better understanding the microstructural details of MgO(111) films. To this end, MgO thin films were grown on Al 2 O 3 (0001) ("c-plane sapphire") substrates by sputtering deposition. While bulk MgO has a sixcoordinated rocksalt (B1) crystal structure with a lattice constant a = 0.421 nm, the Al 2 O 3 is rhombohedral (a = 0.476 nm, c = 1.299 nm). As a result, the epitaxy of MgO films on sapphire is not straightforward. There are several experiments showing that (111)-oriented MgO can be accommodated onto sapphire(0001), since it offers the lowest substrate-to-film inplane lattice mismatch (about 8%). One possible mechanism is that growth proceeds by matching domains with a filmto-substrate lattice ratio of 4:5. 20 However, these (111) polar films are intrinsically unstable. Several mechanisms, including vacancy formation, hydroxylation, surface reconstruction, and metallization a...

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“…Since the kinetic energy of ablated species decreases with the oxygen partial pressure, the observed significant roughening at 1 Pa means that the kinetic energy of the ablated species is so small that the growth kinetics is similar to that of MBE, indicating that the high-energy growth process of PLD contributes to the formation of the flat polar surface. MgO(111) (111) substrates with a NiO(111) buffer layer [106]. We have confirmed the atomically flat (111) surface by recording RHEED intensity oscillations during the film growth and by observing the single-step and terrace structure using AFM.…”

Section: Fabrication Of Flat Mgo(111) Films Onmentioning

confidence: 61%

“…Recently, much effort has been spent to grow atomically flat MgO(111) films on Al 2 O 3 (0001) [101,102], GaN(0001) [103], 6H-SiC(0001) [104], and Ag(111) [105] substrates, and successful results were achieved only for Ag (111). In this section, we review our recent growth studies of flat MgO(111) films on Al 2 O 3 (0001) [106] and on YSZ(111) with a NiO(111) buffer [107]. MgO(111) film growth on Al 2 O 3 (0001) is practically important because Al 2 O 3 (0001) is a common commercially available substrate.…”

Section: Introductionmentioning

confidence: 99%

New functionalities in abundant element oxides: ubiquitous element strategy

Hosono

Hayashi

Kamiya

et al. 2011

Science and Technology of Advanced Materials

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While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth's crust), many advanced materials are based on rare elements. A 'rare-element crisis' is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a 'ubiquitous element strategy' for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements.

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Fabrication of Flat MgO(111) Films on Al₂O₃(0001) Substrates by Pulsed Laser Deposition

Cited by 19 publications

References 17 publications

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Heteroepitaxial growth of MgO(111) thin films on Al2O3(0001): Evidence of a wurtzite to rocksalt transformation

New functionalities in abundant element oxides: ubiquitous element strategy

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Fabrication of Flat MgO(111) Films on Al2O3(0001) Substrates by Pulsed Laser Deposition

Cited by 19 publications

References 17 publications

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Control of Surface Work Function by Depositing Insulating Oxide Capping Layers

Heteroepitaxial growth of MgO(111) thin films on Al2O3(0001): Evidence of a wurtzite to rocksalt transformation

New functionalities in abundant element oxides: ubiquitous element strategy

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Fabrication of Flat MgO(111) Films on Al₂O₃(0001) Substrates by Pulsed Laser Deposition