Interface-Controlled Carrier Transport in Metal-Lutetium Oxide-Metal Structures Deposited by Electron-Beam Evaporation T
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Interface-Controlled Carrier Transport in Metal-Lutetium Oxide-Metal Structures Deposited by Electron-Beam Evaporation Technique K. Mahmood1, Nadeem Sabir1, 1 Department of Physics, Government College University, Faisalabad, 38100, Pakistan. ABSTRACT Nano-thin films of Lu2O3 with 80nm thickness have been deposited on metal-coated glass substrate in metal-insulator-metal (MIM) geometry by electron-beam evaporation technique. High field and temperature dependent electrical characterization on grown MIM structures have been investigated in symmetric electrode configuration using Al, Cr or Cu metals. The temperature dependent I-T characteristic features have been found to support the conduction mechanism across MIM systems to be an electrode-limited process except for Al-Lu2O3-Al device, which show Poole-Frenkel mechanism in high electric field region. The associated parameters such as activation energy (∆E), coefficient of barrier lowering (β) and effective height of Schottky barrier at zero biasing (Фo) have been evaluated at different values of temperature and electric field to further investigate the dominent conduction mechanism. INTRODUCTION Recently, rare-earth oxide (REO) thin films have been emerged as potential materials for various complex applications in modern electronics (micro/nanoelectronics) and optoelectronics [1-3]. Metal-insulator-metal (MIM) type thin film structures have found applications in miniaturized capacitors; field emission displays (FED) or dynamics random access memories (DRAMs) [4], microcircuit devices and sensors [5]. Moreover, nanocrystals incorporated in dielectrics illustrate high potential to produce a memory with high endurance, low operating voltage, fast write-erase speeds and better immunity to soft errors. Such practical applications provide motivation for the investigation of electrical conduction phenomena in thin insulating films of REOs. Among rareearth oxides, Lu2O3 acquires band gap ~5.3-5.5 eV [6-9] with high refractive index of 1.84 [3] to 2.42, the highest melting point of 2467˚C [3] showing better thermal stability, insulating properties and hygroscopic immunity than other REO thin films. Such unique properties make Lu2O3 as one of the most promising candidates for the next generation gate oxides. The conductivity of rare-earth oxides caused by the excitation of electrons from valence band to conduction band is negligible [10]. Due to their low conductivity amorphous oxides are most suitable for high field conduction studies because they possess negligibly small joule heating at moderate temperatures. The possibility of tunneling or Fowler-Nordheim mechanism [11], space charge limited conduction (SCLC) [12] etc. has been studied in these oxides. Moreover, a complex conduction mechanism based on the field induced lowering of energy barriers due to electron emission from metal cathode i.e. Schottky-Richardson emission [13], or based on libration of electrons from the traps (screened charged intrinsic defects) in the bulk of these oxides i.e. Poole-Frenkel mechanism [14
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