IFF
Scientific Report 1998/1999

Institute Materials Development:
General Overview

The Institute of Materials Development participates in three Research and Development programs of the research centre:

• GaAs- GaAs defect physics and crystal growth research ("fundamental research for the information technology" program)
• Crystal growth research and sample preparation of intermetallic systems, quasi-crystals and other multicomponent systems ("materials science" program)
• Research on perovskites with high hydrogen solubility and mobility ("high temperature proton conducting materials for fuel cells" program)

High quality research samples are prepared in four service groups:

• Crystal growth, sample preparation and characterisation laboratory (6 staff members). Intermetallic compound crystals (Ni3Al), rare earth chalcogenide crystals (EuO), and large Bi-crystals are three examples of current activities.

• Thin film laboratory (1 staff member, UHV-thin film preparation by sputtering and evaporation methods). Equipment and know-how will be transfered to the new institute of electro-ceramics.

• Thermoanalysis laboratory (1 staff member)

Two important research projects are funded by external research grants:

• GaAs-crystal growth, defect-physics and process chemistry research and development of Tammann/Bridgman-type crystal growth methods for growing large high-quality GaAs-crystals. Industrial technology transfer is based on a contract with the german GaAs production company (see report by Sonnenberg).
• Growth of quasi-crystals for the german quasi-crystal research community. The successful growth methods by the Czochralski and Tammann/Bridgman-technique have been extended to new flux growth methods with large development potential which will improve crystal output rate and crystal quality.

In collaboration with the Institut für Kristallzüchtung in Berlin-Adlershof materials and methods for growthing SiC crystals by gas phase transport have been tested. This expertise has also been used for hydrogen cleaning of SiC wafers for thin film deposition in the Institute of Thin-film and Ion Technology of the Juelich Research
Center (Fattah).

Testing of the GaAs Hot-Wall Czochralski industrial prototype unit (Leybold-IGV-project) has been frequently interrupted by repeated equipment failure due to unreliable components. In principle, this technology would still be interesting for GaAs crystal growth research although its industrial use is hampered by complexity, unreliability and high costs. On the contrary, our Tammann/Bridgman GaAs technology is now well advanced and has demonstrated its superiority for the industrial production of large and high-quality crystals since it is simple, reliable and economical.

Thermodynamic modelling has been used as an important part of the crystal growth research activities. Model and data collections have been developed in cooperation with the Institut für Theoretische Hüttenkunde, RWTH Aachen, and the company Gesellschaft für Thermophysik und Thermochemie in Herzogenrath for the systems Ga-As-B-Si-C-O-H, Si-C-H-O and electro-ceramic materials including charged sublattice defect species together with electronic charge carriers. The results are available in the form of graphical phase diagrams which provide information for those not interested in the thermodynamic details. Thermodynamic properties of selected systems have been measured in collaboration with the Institut für Gesteinshüttenkunde, RWTH Aachen, the Institut für Kristallzüchtung in Berlin and the Bergakademie Freiberg.

The following reports by the leading scientists of the institute provide more detailed insight into selected research results of the year 1998.

H. Wenzl