• PDF / 419,846 Bytes
• 8 Pages / 612 x 792 pts (letter) Page_size
• 1 Downloads / 203 Views

DOWNLOAD

REPORT

---

Materials Characterization Heterostructure

and

Device

Performance

of

a

CMR-Ferroelectric

S. R. Surthi, S. Kotru, and R. K. Pandey Department of Electrical and Computer Engineering The University of Alabama, Tuscaloosa, AL 35487-0286, U.S.A. ABSTRACT The films of colossal magnetoresistive La0.67Ca0.33MnO3 (LCMO) and ferroelectric SbSI were grown by pulsed laser deposition method for fabricating their heterostructures. By varying the processing conditions during film growth and controlling subsequently the annealing conditions, the resistivity transport properties of the LCMO films could be greatly modified. Preliminary tests on the ferroelectric field effect transistor (FeFET) based on LCMO-SbSI heterostructure showed that the device behaves like a nonvolatile memory element. The FeFET showed a maximum channel modulation of ~10% at room temperature, and the switching voltage was less than 2 V.

INTRODUCTION Since the discovery of colossal magnetoresistance (CMR) in the early 1990s, the Mn-based perovskite oxides of the form R1-xBxMnO3 (R = rare earth, B = divalent cations like Ca, Sr, Ba) have experienced a huge resurgence [1-3]. This has triggered intense studies on the fundamental physics and the future industrial applications of these materials. Under a certain range of doping, these oxides exhibit simultaneous electronic and magnetic transitions, where the magnetic Curie temperature (TCM) marks a transition from a high temperature paramagnetic insulator (or semiconductor) to a low temperature ferromagnetic metal. Additionally, the magnetic and transport properties of CMR materials are very sensitive to the oxygen content and doping and can be changed by varying the materials processing conditions. A measurable field effect, i.e. field induced modulation of resistance, has also been reported in the CMR manganates [4]. This effect is independent of field-direction and occurs above TCM, where the temperature dependence of resistivity is semiconductor-like (i.e. activated resistivity transport). This makes the CMR oxides a likely candidate for use as semiconductors in novel field effect transistors with ferroelectric gate. These devices can be interrogated by reading the resistance (or conductance) of the CMR-based channel. Unlike ferroelectric capacitive memory elements, the act of reading does not affect the state of the device and hence the memory readout is nondestructive. Even though the ferroelectric field effect transistors (FeFETs) have been studied since the 1950s [5-8] an acceptable nonvolatile memory element with adequate retention and write-erase speed has not been demonstrated. This is mainly due to the difficulty in controlling the interface between the ferroelectric and semiconductor [9]. Recently, researchers have proposed the use of all-perovskite ferroelectric/semiconductor heteroepitaxial structures to improve upon the quality of the interface [10]. Most of the heterostructure devices reported so far are based on ferroelectric Pb-Zr-Ti-oxide (PZT) or related perovskite oxides [9-12]. In this