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.
Interaction of PbTiO3 Films with Si Substrate
An investigation was made of the reasons why ferroelectric PbTiO3 films are hard to grow on single-crystal Si substrates. PbTiO3 films were formed on Si(100) and MgO(100) single-crystal substrates, and X-ray photoelectron spectroscopy (XPS) was used to analyze the composition, chemical structure and oxidation state at the interface between the substrate and the film. It was found that lead, oxygen and silicon diffused markedly at the interface and that the PbTiO3 film experienced both a lead deficiency and Si diffusion. These phenomena are thought to be the reasons why it is difficult to form good PbTiO3 films on silicon substrates by chemical vapor deposition (CVD). It was observed that the addition of TiO2 and ZrO2 films at the interface with the silicon substrate reduced the diffusion of Si to the PbTiO3 film.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.