| AVS 57th International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF1-TuM |
| Session: | ALD: Dielectrics for Semiconductors |
| Presenter: | F. Zhang, University of California, Los Angeles |
| Authors: | F. Zhang, University of California, Los Angeles T.E. Quickel, University of California, Los Angeles Y.-C. Perng, University of California, Los Angeles S. Tolbert, University of California, Los Angeles J.P. Chang, University of California, Los Angeles |
| Correspondent: | Click to Email |
Atomic layer deposition (ALD) of complex oxides is a viable method to tailor the composition and microstructure of the resulting thin films, thereby generating multi-functionality that is needed in various device applications. Another desirable feature of ALD is its ability to uniformly and conformally coat complex surface structures of high aspect ratios, making it possible to interface distinct materials to form composite materials that may show exciting properties, such as multiferroic behavior.
In this work, lead zirconium titanate (PZT) films were synthesized by depositing PbO, ZrO2 and TiO2 ALD layers with a sequence of (Pb-O)-(Ti-O)-(Pb-O)-(Zr-O). The deposition rate for PZT was approximately 0.7nm/cycle-sequence. The as-deposited materials were amorphous but crystallized into perovskite structure upon annealing to 950oC. The polarization properties found in the P-V measurements including remanent polarization (Pr), saturation polarization (Ps), and coercive field (Ec) are promising and are strongly affected by the ALD sequence which dictates the composition and structuring of the resulting thin film.
One example of the advantages of ALD produced PZT can be seen in our work on composite multiferroic materials, which can be created by coupling together nanoscale ferroelectric and ferromagnetic materials. In this work, mesoporous cobalt ferrite (CFO) thin films formed by block-copolymer templating methods with pores 14 nm in diameter were used as the ferromagnetic framework. Ultra-thin ALD PZT films were used to create a uniform and conformal coating over and on all CFO pore spaces and generate a nano-structured PZT-CFO hybrid material, as confirmed by scanning electron microscope (SEM), transmission electron microscope (TEM), and ultraviolet photoelectron spectroscopy (UPS) measurements. Superconducting quantum interference device (SQUID) magnetometry is underway to assess the multiferroic properties of this PZT/CFO composite, including both in-plane and out-of-plane saturation magnetization measurements after electrical poling and polarization voltage (P-V) measurements.