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from the MSEL Annual Report 1997:  

ADVANCED MATERIALS PROGRAMS:  Thin Film Measurements and Standards

Contact:  Grady S. White (301) 975-5752

Functional ceramics (e.g., ceramics primarily intended for optical, electronic, or thermal management applications) are increasingly being used in film geometries. In response to this growing segment of the ceramics community, the Thin Film Measurements and Standards Program endeavors to provide improved measurement tools and data that are needed to evaluate advanced ceramic films and film systems. Increasingly critical film performance requirements (e.g., reduced dimensions, increased purity, improved interface properties, increased production rates, and tighter control of properties) place stringent demands on film processing control, models, and characterization techniques. However, lack of measurement methods to monitor film processing and accurately characterize film properties as well as limited theoretical understanding of interrelationships between processing conditions and final film properties reduce most film processing to empirical procedures. The activities in this program are designed to address these measurement and modeling issues, both with regard to specific, near term industrial needs as well as to the development of a materials science knowledge base required for use of ceramic films in future applications. Near term and long range goals have been developed based upon both general discussions between Materials Science and Engineering Laboratory staff and representatives of industry and universities at professional meetings and consortia workshops as well as focused, collaborative research projects with specific organizations.

The film characterization techniques in use or under development include electrical, mechanical, optical, thermal, and x-ray measurements. Specific research activities include:

• investigations of the processing and microstructural features that control poling behavior and domain stability in ferroelectric films;

• development and utilization of spectroscopic procedures to evaluate film composition in BaTiO₃ and to detect defects in ferroelectric and semiconductor films;

• development of methods to measure and statistically analyze texture and texture distributions in films and to relate these data to processing conditions;

• development of measurement procedures, models, and standards to permit quantitative evaluation of thermal diffusivity in thin films and to relate thermal diffusivity to film microstructure and morphology;

• application of advanced x-ray measurement capabilities (e.g., EXAFS, DAFS) to the analysis of film structure and composition and the construction of an in-house state-of-the-art x-ray facility.

A critical requirement for the projects cited above is the ability to generate model film systems. To this end, this program includes two film deposition capabilities: metalorganic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD). The MOCVD system is an integral part of the ferroelectric film research projects already listed and, during the past year, has undergone a major upgrade to provide more precise compositional control. In contrast, the PLD facilities, while providing films for investigation, has had additional responsibilities, the development of in situ measurement procedures to monitor the physical and chemical processes involved during the film deposition process and the formation of models to relate the measurements to the film formation.