Correlation of resistance switching behaviors with dielectric functions of manganite films: A study by spectroscopic ell
- PDF / 248,353 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 100 Downloads / 198 Views
Correlation of resistance switching behaviors with dielectric functions of manganite films: A study by spectroscopic ellipsometry Masaki Yamada1, Toshihiro Nakamura2, and Osamu Sakai1 1 Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan 2 Department of Engineering Science, Osaka Electro-Communication University, 18-8 Hatsucho, Neyagawa, Osaka 572-8530, Japan
ABSTRACT Pr0.5Ca0.5MnO3 (PCMO) films were deposited on LaAlO3 (100) substrates under pressure from 1.33 to 5.33 Pa by RF magnetron sputtering. Resistance switching and dielectric functions of PCMO films were studied by DC current-voltage characteristic measurements and spectroscopic ellipsometry (SE) measurements. Resistance switching was observed in the devices composed of PCMO films deposited under low pressures of 1.33 and 2.67 Pa. SE measurements revealed that dielectric functions also depended on deposition pressure. PCMO films deposited under lower pressure had larger high-frequency dielectric constant, larger oscillator strength of the electric dipole charge transitions in MnO6 octahedral complexes, and lower oscillator strength of d-d transitions in Mn3+ and Mn4+ ions. SE measurements suggested that oxygen vacancies and MnO6 octahedral complexes play an important role in resistance switching in PCMO films. INTRODUCTION Recently, next-generation nonvolatile memories have been intensively researched and developed as future replacements for volatile memories such as dynamic random access memory in the application to IT equipment. Electric-pulse-induced resistance switching observed in metal oxides such as Pr1-xCaxMnO3 provides a possibility of one of next-generation nonvolatile memories, called resistance random access memory (ReRAM) [1-8]. ReRAM has the advantage of low power consumption, small bit cell size, and fast switching speed. The ReRAM devices composed of Pr1-xCaxMnO3 films show bipolar resistance switching behavior. Impedance spectroscopic studies suggested that resistance switching was mainly due to the resistance change in the interface between the Pr1-xCaxMnO3 films and the electrode [4,5]. Moreover, the transport of oxygen ions between the interfacial oxide layer of electrode materials and oxygen vacancies by the electric field was proposed as a model of the resistance switching [6,7]. On the other hands, resistance switching behaviors are affected by the crystal structure of Pr1-xCaxMnO3 films [8]. The crystal structure of Pr1-xCaxMnO3 films might affect the behavior of oxygen ions migrating between the Pr1-xCaxMnO3 films and the interfacial oxide layer. Considering that the crystal structure has a significant influence on optical properties in films, spectroscopic ellipsometry (SE) is one of the useful methods for studying optical properties of various materials including perovskite manganese oxide [9,10]. In SE, the optical properties of thin films
117
can be analyzed on the basis of dielectric functions. The dielectric function in the visible light region gives
Data Loading...
