Structural and Electrical Characteristics of Ternary Oxide SmGdO 3 for Logic and Memory Devices
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Structural and Electrical Characteristics of Ternary Oxide SmGdO3 for Logic and Memory Devices Yogesh Sharma, Pankaj Misra and Ram S. Katiyar Department of Physics, University of Puerto Rico, PR-00936-8377, USA ABSTRACT We report on the structural and electrical characteristics of bulk and thin film of ternary oxide SmGdO3. Bulk sample of SmGdO3 was prepared by pelletizing and sintering the calcined mixture of predetermined amount of Sm2O3 and Gd2O3 powders. The crystalline structure of the sample was studied by X-ray diffraction measurements and Raman spectroscopy. Capacitance and leakage current measurements on bulk sample revealed a high and linear dielectric constant of ~ 19 with low dielectric loss and leakage current which is suitable for gate dielectric application in CMOS logic devices and high-k MIM capacitors. In addition, the non-volatile resistive memory switching phenomenon was studied in thin films of SmGdO3 which were deposited by pulsed laser deposition using sintered pellet of SmGdO3 as target. Commercially available Pt/TiO2/SiO2/(100) Si was used as substrate and top Pt electrode of lateral dimension 40×40μm2 were deposited by sputtering to construct Pt/SmGdO3/Pt MIM devices. After initial forming process which occurred at comparatively higher voltage, the Pt/SmGdO3/Pt devices showed repeatable unipolar switching between high and low resistance states with low and well defined switching voltages. These properties indicate suitability of this material for the emerging logic and memory device applications. INTRODUCTON The lanthanide sesquioxides (Ln2O3) have been widely investigated because of their interesting optical, electronic and magnetic properties [1]. Among these, some of the Ln2O3 compounds have also emerged as potential high-k gate dielectric material for Metal-Oxide-Semiconductor (MOS) and Resistive Random Access Memory (ReRAM) device applications [2,3]. Most of the sesquioxides which exhibit high dielectric constant show high hygroscopic nature which deteriorates their ability in terms of high-k gate dielectric applications [4]. One of the Ln2O3 compounds, Lanthanum oxides (La2O3) which has high dielectric constant of ~ 27, is not stable in air and very hygroscopic to form hydroxide [4]. Interlanthanide oxides, also called as ternary oxides could be used to prevent the aforementioned problems of sesquioxides. The ternary oxides of La2O3 such as LaGdO3 and LaErO3 have been shown to exhibit excellent properties as compared to their constituent sesquioxides [5, 6]. However, it has been seen that because of very hygroscopic nature of Lanthanum oxides (La2O3), even ternary oxides encounter stability issue in gate-dielectric applications [5]. Therefore, it is imperative to investigate the Lanthanum free ternary high-k dielectric materials to overcome the hygroscopic issue in terms of gate-dielectric and ReRAM applications. In this report we synthesised a Lanthanum-free novel high-k ternary oxide SmGdO3 (SGO) and explored its structural and electrical properties in bulk and thin film forms, for
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