Studies on Ferroelectric Properties of Sol-Gel Derived Pb(Zr[sub 0.53]Ti[sub 0.47])O[sub 3] Using Ba[sub 0.5]Sr[sub 0.5]RuO[sub 3] as the Conductive Electrodes

Abstract

Pb͑Zr 0.53 Ti 0.47 )O 3 ͑PZT͒ thin films with a ͑110͒ preferred orientation were prepared on Ba 0.5 Sr 0.5 RuO 3 (BSR͒/Ru/SiO 2 /Si substrates using a sol-gel method. The oxide bottom electrode, BSR, was fabricated at various temperatures on Ru/SiO 2 /Si substrates by rf sputtering. The annealed PZT films on BSR/Ru/SiO 2 /Si substrates exhibited improved crystallinity. The electrical properties of PZT films, such as the electric field ͑E͒ induced variations of the leakage current density, the dielectric constant, and the polarization were strongly dependent on the processing temperatures of the PZT films as well as the bottom oxide electrode. A typical PZT thin film annealed at 650°C on the BSR electrode, which was deposited at 450°C on the Ru/SiO 2 /Si substrate by a sputtering technique, has a leakage current of 2.7 ϫ 10 Ϫ7 A/cm 2 at an applied electric field of 500 kV/cm and a dielectric constant of 968. From the polarization-electric field characteristics, the remanent polarization and coercive field of the PZT were found to be 38.9 C/cm 2 and 59.6 kV/cm, respectively, at an applied voltage of 5 V. The PZT films exhibited fatigue-free characteristics up to ϳ1.0 ϫ 10 12 switching cycles under 5 V bipolar pulses. Pb͑Zr,Ti͒O 3 ͑PZT͒ thin films have attracted attention because of the excellent ferroelectric properties, which can be exploited for applications in nonvolatile random access memories ͑NVRAMs͒ and dynamic random access memories ͑DRAMs͒. 1-4 However, many reports have indicated that the PZT thin films have serious fatigue problems when deposited on metal electrodes because of the degradation of the film/electrode interface, which results in a relatively shorter number of switching cycles. 5-7 The conductive metallic oxide electrodes, such as RuO 2 , 8 IrO 2 , 9 (La 0.5 ,Sr 0.5 )CoO 3 , 10 BaRuO 3 ͑BRO͒, 11 SrRuO 3 ͑SRO͒, 12 and Ba x Sr 1Ϫx RuO 3 ͑BSR͒, 13 have been found to improve the fatigue properties of the PZT capacitors. The polarization fatigue, which arises out of repeated switching cycles, gets suppressed at a ferroelectric film/oxide electrode heterostructure as the oxide electrodes act as sinks for the oxygen vacancies. The selection of electrode materials will also affect the microstructure and the electrical properties of the thin films. Moreover, the perovskite oxide electrodes should have similar lattice parameter and crystal structure with PZT thin films as these characteristics decide the formation of the chemically and thermally stable PZT/ perovskite oxide electrode interface, which eventually enhance the ferroelectric characteristics of PZT films. 14 However, it is very difficult to deposit preferentially oriented PZT or BSR films on silicon substrates. In most of the studies on epitaxial PZT or BSR thin films, the films were deposited on SrTiO 3 ͑STO͒ or LaAlO 3 ͑LAO͒ substrates. [15][16][17] In our earlier study, 18 the ͑110͒-oriented SRO oxide electrodes were deposited on an Ru/SiO 2 /Si substrate at a low temperature, subsequently ͑110͒-oriented PZTs were grown on SRO(110)/Ru/SiO...

Electrical properties of resistance switching V-doped SrZrO3 films on textured LaNiO3 bottom electrodes

“…The requirements for a high performance NVM are that it should have the properties of reversible switching, non-destructive readout, low operation voltage, long retention time, high endurance, high operation speed, low power consumption, small size and low cost [1]. Many new devices have been proposed for NVM applications [1][2][3][4][5]. Resistive random access memory (RRAM) is one of the promising candidates for the next generation NVM.…”