Ferroelectric films prepared by laser ablation directly on SiC substrates

Because of the common physical properties of silicon carbide (SiC) and lead base ferroelectric films [such as lead zirconate titanate and lead titanate (PZT) and lead titanate (PTO)], it is interesting to investigate ferroelectrics and SiC based integrated devices for potential high radiation environments, high speed, high temperature, and high density memory applications. Here we first report our primary results of depositing lead base ferroelectric films directly onto bare SiC substrates. Ferroelectric films including undoped and doped PZT and PTO were directly deposited on bare 3C-SiC and 4H-SiC substrates. X-ray diffraction analyses indicate that all the PTO films deposited at substrate temperatures from 600 to 650 degrees C are polycrystalline of the pure perovskite phase. PZT films deposited at a substrate temperature of 570 degrees C are dominated by the pyrochlore phase and even at a higher substrate temperature of 650 degrees C both the perovskite and the pyrochlore phases coexist. The pyrochlore phase of the PZT films is able to be converted into the perovskite phase by rapid thermal annealing at 800 degrees C for 30-60 s. The formation of an interfacial layer of a nonferroelectric phase (Pb2Ti2O6), which is caused by interdiffusion, is one of the most serious problems during the fabrication of lead based ferroelectric films directly onto the Si wafer. However, there is no such interdiffusion observed between the ferroelectric films and the SiC substrates. Capacitance versus voltage (C-V) curves of metal/ferroelectric/semiconductor diode structures demonstrate typical C-V hysteresis loops and the capacitance versus temperature measurements further confirm the ferroelectric properties of the films. (C) 1998 American Institute of Physics. [S0021-8979(98)03622-6]