Domain Images and Retention Properties of Pb(Zr,Ti)O 3 Thin Films Observed by Electrostatic Force Microscopy
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ABSTRACT We report results on domain retention in preferentially oriented Pb(ZrTi)0 3 (PZT) thin films on Pt and on LaNiO3 (LNO) electrodes. Effects of bottom electrodes on domain images and retention properties have been explored by detecting an electrostatic force exerted on the biased conductive probe. It was demonstrated that polarization loss of PZT crystallites on LNO appears to be less than that of PZT grains on Pt. Moreover, charge retention was controlled by a reverse-poling protocol during electrostatic force microscopy (EFM) measurements. The surface charge density of the PZT films was observed as a function of time in a selected area where a region is single-poled and another region is reverse-poled. The retention behavior of the regions is very different; the single-poled region shows a declined response and the reverse-poled region reveals a retained characteristic. Decay and retention mechanisms are explained by space-charge redistribution and trapping of defects in the films.
INTRODUCTION Magnetic hard disk is the dominant method for storing data in the microelectronics industry. Its progress has been steered by the ever-growing demand for storage capacity coupled with the continual decrease in price per megabyte. In 1990, state-of-the-art hard disks had an areal density of less than 0.1 Gbit/in 2; currently, disks with areal densities of 5 Gbits/in 2 are being sold. In the near future, it is expected that hard disk drive scaling, and the move to giant magnetoresistive heads, will push areal densities into the upper tens of Gbits/in 2 [1 ]. This growth rate can be described by a 60% cumulative annual increase - at this rate, conventional scaling is expected to run out in 2006. This technological limitation will not stop the need for greater storage capacity in less space. To displace magnetics as the mainstream method for data storage, an emerging technology must offer substantial advantage beyond the incremental advantage of an existing technology. Many approaches have been brought forward; the three most prominent are near339 Mat. Res. Soc. Symp. Proc. Vol. 596 ©2000 Materials Research Society
field recording, magneto-optics, and scanning probe. Table I summaries of the figure-of-merits of the technologies. Development of media seems to be one of the most important factors for realization of the storage system larger than 100 Gbits/in2 . Table I. Atomic force probe technology compared to hard disk, magneto-optics, and near-field recording technology. Characteristic
Near Field
Magneto-optics
Hard Disk
I
II
Atomic Force
Probe
Media Substrate
Aluminum/Glass
Glass/Plastic
Plastic
Si/Sapphire
Recording Surface Tracks defined by
Top Servo Track Writer
Bottom Stamped
Top Stamped or STW
Top Stamped or STW
(STW) Drive
Write/Read
Magnetic Field
Far Field
Near Field
Atomic Force
Technology Writing Process
Coil Switching
Constant Coil (2 Pass)
Coil Switching
DC Conversion
Writing Limit
Induction/Gap
Objective Lens
Solid Immersion
Cantilever
Lens (SIL)
Flying Height
Readi
Data Loading...
