Electrical Processes in Polycrystalline BiFeO3 Film

Abstract

As an oxide with perovskite structure, Bismuth ferrite (BiFeO3, BFO) has been studied from 1970s (Teague, et al. 1970; Kaczmarek, et al. 1975). The structure and magnetic properties of BFO were confirmed before 1970s. As reported, the crystal structure of BFO is perovskite with rhombohedral distortion and the space group is R3c. BFO is G-type antiferromagnetic. It was controversial about whether BFO was ferroelectrics until the hysteresis loop of single crystal BFO was measured in 1970 (Teague, et al. 1970). According to Teague’s results, the single crystal BFO was anisotropy. The remnant polarizations (Pr) along the (100) and (111) direction were 3.5μC/cm2 and 6.1μC/cm2 at the temperature of liquid nitrogen, respectively. However, because of the higher leakage current in the bulk BFO, it was difficult to measure the ferroelectric properties of BFO at room temperature. The problem of higher leakage blocks not only the studies of the electrical properties of BFO, but also the application of BFO in electrical devices. In 2003, the epitaxial BFO films with higher electrical resistivity and higher remnant polarization was fabricated by pulsed laser deposition (PLD) method (J. Wang, 2003). The value of Pr of the epitaxial BFO films is about 50μC/cm2. This value is larger than that of the traditional ferroelectrics such as Pb(Zr,Ti)O3 (PZT), BaTiO3 (BTO). If the BFO film with larger Pr can be used in ferroelectric memory (FeRAM), the size of the storage cell can be reduced and the storage density can be increased (Maruyama, 2007). More studies on BFO films are carried out (Eerenstein, 2005; Zavaliche, 2005; Singh, 2007; Hauser, 2008; Liu, 2008; Yang, 2008). Even though the leakage mechanism in epitaxial BFO film has been studied (Pabst, 2007), the higher leakage current is still an obstacle for the study and application of polycrystalline BFO films. Compared to the epitaxial BFO films grown on perovskite structure substrate, the applications of polycrystalline BFO on silicon wafer are broader in the field of microelectronic devices. In this chapter, polycrystalline BFO films are fabricated by different physical and chemical methods on buffered silicon and perovskite structure substrate. The structural and electrical properties of these polycrystalline BFO films are investigated.