Effect of post-metallization annealing on the ferroelectric properties of sol-gel derived PZT thin films

A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model.     

The Future of Sol-Gel Science and Technology

This paper addresses the future prospects for sol-gel processing. It includes responses from nearly two dozen leading practitioners of the sol-gel art, who were kind enough to answer a questionnaire about the present state and future directions of the field. Overall, the prospects appear quite bright; but achievement of anything like the full potential of the method will require greatly increased interaction between sol-gel specialists and device technologists.     

Ceramic films for optical applications

Recent progress is reviewed on the wet chemical synthesis of films for optical applications. Specific attention is directed to planar waveguides and to electrooptic, non-linear optical and electrochromic films, including recent results obtained in our laboratories.     

Crystallization of gel-derived glasses

The crystallization behaviors of gels, gel-derived glasses and melted glasses are reviewed, and comparisons are effected among the observed behaviors. These comparisons are related to the behavior expected on the basis of models for the nucleation frequency and crystal growth rate, as well as the anticipated differences in material characteristics among gels and the two types of glasses. Different temperature regimes are identified where different comparisons between melted and gel-derived materials are expected. It is concluded that a need exists for more definitive, detailed data on the crystallization behavior of gel-derived materials.     

Preparation and Characterization of Sol-Gel Derived Y2O3 Thin Films

Sol-gel derived Y2O3 thin films have been prepared on platinum coated silicon wafers and fired to temperatures ranging from 400°C to 750°C. Multiple coats were used to obtain films up to 0.5 m thick with an intermediate firing of 400°C between coatings. Top Pt electrodes were sputtered to form monolithic capacitors. These films exhibited a dielectric constant of 18 and a leakage current of 10–11–10–7 A/cm2, making them attractive candidates for high dielectric constant dielectric films in high density DRAMs.     

Sol-Gel Science and Technology: Current State and Future Prospects

This paper addresses the current state and future prospects of sol-gel processing. It summarizes responses to a questionnaire received from more than four dozen leaders of the sol-gel community. Overall, the respondents remain quite sanguine about the future prospects for the field, and with numerous areas where sol-gel processing can provide unique capabilities and novel materials. The present authors acknowledge this potential, but argue that its achievement will depend upon greatly increased involvement of the sol-gel community with applications, and carrying out a much larger fraction of sol-gel research in the context of applications.     

Ferroelectric Films

The preparation and properties of ferroelectric films are reviewed. Specific attention is directed to ferroelectric films prepared by wet chemical methods. Emphasis is placed on the microstructure and properties of SBT films for memory applications, and their dependence on chemistry and processing, as well as on the effects of chemistry and processing on the properties of piezoelectric and pyroelectric films. Emphasis is placed on recent results obtained in our laboratories, including modeling of the ferroelectric behavior of films and experimental results in each of these areas. Also considered is the use of ferroelectric films in memory, piezoelectric and pyroelectric devices of various types, with specific note made of the recently-announced use of pyroelectric sensors in automobiles.     

Dielectric and Ferroelectric Properties of Sol-Gel Derived YMnO3 Films

There has been considerable interest in ferroelectric (FE) films especially for non-volatile memories and ultra high density DRAM applications. Such FE films typically consist of lead zirconate titanate (PZT) with novel oxide contacts, or layered perovskite such as Sr2Bi2TaO9. Recently, there have been reports of sputtered YMnO3 films which exhibit a single polarization axis and do not contain any volatile species of Pb or Bi. Single crystal YMnO3 exhibits satisfactory polarization (6 C/cm2) and low coercive field (<20 kV/cm). Additionally, the dielectric constant of YMnO3 is quite low (<30) which should facilitate ferroelectric switching. In this study, sol-gel derived YMnO3 films were prepared on platinized Si wafers and their dielectric and ferroelectric properties were characterized. Their electrical properties will be discussed with respect to Y/Mn stoichiometry ratio, hexagonal phase development and processing conditions. The potential of YMnO3 as a material in non-volatile memories is evaluated.