Fabrication of Polycrystalline Ferroelectric Gate FET Memory with an Intermediate Electrode
We fabricated a new ferroelectric gate field-effect transistor memory (F-FET) with an intermediate electrode inserted between the ferroelectric capacitor (Cf) and the metal-oxide-semiconductor field-effect transistor (MOSFET) for writing data. The structure was a RuO2 top electrode/polycrystalline ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT)/(Pt/RuO2) intermediate electrode/SiO2/Si substrate. The basic operation of the new memory was confirmed by a discrete circuit that the Cf was connected serially with the MOSFET. For data writing, two positive or negative square pulses applied between the top electrode and the intermediate electrode induced the positive (Pr+) and the negative (Pr-) remanent polarizations, respectively, for coding memory states. For data reading, an unipolar square pulse train was applied between the top electrode and the source of the MOSFET, and the drain of the MOSFET was biased by a DC voltage. When the memory state corresponded to the Pr+ or the P-, the drain current (ID) was small or large, respectively. In this study, we used a polycrystalline PZT film to deal with the difficult problems of an epitaxial PZT film such as complicated techniques and high cost of products for commercialization goal.
Improvement of Nondestructive Readout of Ferroelectric Gate FET Memory with an Intermediate Electrode by using New Data Writing and Reading Methods
The nondestructive readout characteristics of the ferroelectric gate field-effect transistor (F-FET) memory with an intermediate electrode for data writing (IF-FET) was investigated by using the conventional and the new writing and reading methods. Normally, for the conventional writing, we use two positive or negative square pulses to induce the positive (Pr<sup>+</sup>) or the negative (Pr<sup>-</sup>) remnant polarizations, respectively. For the conventional reading, unipolar square pulses were applied. Although the difference in output voltages between Pr<sup>+</sup> and Pr<sup>-</sup> is large, the nondestructive readout characteristic for the Pr<sup>-</sup> is poor because the Pr<sup>-</sup> memory state is quickly degraded after each reading due to non-reswitched or nonreturned domains. Therefore, for the new writing, we proposed a new memory state, Pr<sub>0</sub>, instead of Pr<sup>-</sup>. The Pr<sup>0</sup> was induced by a combined pulse with a positive part (V<sub>w</sub> <sup>+</sup>) and a negative part (V<sub>w</sub> <sup>-</sup>). For the new reading, a negative voltage (V<sub>R</sub> <sup>-</sup>) was applied, following a positive voltage (V<sub>R</sub> <sup>+</sup>) to recover the memory state to the initial one. By optimizing the V<sub>w</sub> <sup>-</sup> and the V<sub>R</sub> <sup>-</sup> in the new method, the nondestructive readout is further improved, compared with the conventional method.
Fast seismic data compression based on high-efficiency SPIHT
Based on the set positioning in hierarchical tree (SPIHT) algorithm, fast seismic data compression based on the high-efficiency SPIHT (HESPIHT) algorithm is presented. To verify the validity of the algorithm, 10 seismic cross-sections are selected for the experiment. The result shows that the algorithm can reserve the quality of data better, meanwhile improving the efficiency of encoding and decoding.