Exploration of New Properties of Oxides by the Growth Control Using Pulsed Laser Epitaxy
- PDF / 1,910,387 Bytes
- 12 Pages / 391.5 x 607.5 pts Page_size
- 103 Downloads / 157 Views
STRACT Metal oxides exhibit a wide variety of properties originating mainly from strong electron correlation. Electronic properties of oxides had been utilized mostly in the bulk form till recently and people frequently observed significant changes in such properties when these materials were converted into thin films. For the electronic application in recent years, hybridization and integration of materials in thin film forms are becoming more and more important. In view of our recent studies on high-Tc superconducting junctions and ZnO light emitting devices, this paper is devoted to stimulate the exploration of oxides as new innovative electronic materials by discussing the control of epitaxial thin film growth.
1. INTRODUCTION Electrofunctional oxides are generally composed of more elements including volatile oxygen than currently used semiconductors to give versatile crystal phases which can be interchanged by external energies. Because of this structural complexity, the well developed thin film technology in semiconductors cannot be simply applied to oxides. When we try to fully extract the potential ability of oxides in thin films and devices, we must pay a lot of
329 Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research Society
attention to structural sensitivity in the fabrication method and process parameters. Since our first success in the fabrication of high-Tc superconducting La2 .-SrxCuO 4 _-thin films by an off-axis sputtering method[l], we have been elucidating key factors for high quality epitaxial thin film growth of complex oxides[21. In this paper, these key factors are discussed in relation to their significance for device application and exploration of new structures and properties of oxide materials. 2. FUNCTIONAL PRORERTIES OF OXIDES Electronic properties of semiconductors are almost exclusively dominated by charge carriers, whereas those of metal oxides depends on spin and quantized energy states of phonons and photons as well. Correlation among charge, orbital, spin, phonon and photon can produce a wide variety of properties in metal oxides and are put together in Tablel. Recent topics include intrinsic Josephson effect in high Tc cuprates[3], colossal magnetoresistance (CMR) in (La,Sr)MnO3[4], quantum paraelectricity in SrTiO 3 [5], and excitonic UV lasing at room temperature in ZnO[6]. Atomically controlled epitaxial film growth is important for exerting these properties in plane films and multilayer devices, and also for constructing artificially designed lattices and superlattices that may exhibit novel physical properties. Table 1 Functional properties of oxides Phonon
Spin
NCharge
Charge conductivity electromagnetism e, h, ion couper pai superconductivity high power magnet Spin
Phonon
Photon
CMR Hall effect
para-, ferromagnetism Meissner effect
piezo-, pyromagnetic phase electricity transition Seebeck effect superconductivity photonconductivity magnet-optic photovoltaic effect disk
330
dielectlicity piezoelectricity
Photon light emitting devices Kerr effect Josep
Data Loading...
