This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.

Determining 4H silicon carbide electronic properties through combined use of device simulation and metal-semiconductor field-effect-transistor terminal characteristics

High carbon concentrations at distinct regions at thermally-grown SiO2/6H–SiC(0001) interfaces have been detected by electron energy loss spectroscopy (EELS). The thickness of these C-rich regions is estimated to be 10–15 Å. The oxides were grown on n-type 6H–SiC at 1100 °C in a wet O2 ambient for 4 h immediately after cleaning the substrates with the complete RCA process. In contrast, C-rich regions were not detected from EELS analyses of thermally grown SiO2/Si interfaces nor of chemical vapor deposition deposited SiO2/SiC interfaces. Silicon-rich layers within the SiC substrate adjacent to the thermally grown SiO2/SiC interface were also evident. The interface state density Dit in metal–oxide–SiC diodes (with thermally grown SiO2) was approximately 9×1011 cm−2 eV−1 at E−Ev=2.0 eV, which compares well with reported values for SiC metal–oxide–semiconductor (MOS) diodes that have not received a postoxidation anneal. The C-rich regions and the change in SiC stoichiometry may be associated with the higher than desirable Dit’s and the low channel mobilities in SiC-based MOS field effect transistors.

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Morphological defects and elementary screw dislocations in 4H–SiC were studied by high voltage Ni Schottky diodes. Micropipes were found to severely limit the performance of 4H–SiC power devices, whereas carrot-like defects did not influence the value of breakdown voltage. The screw dislocation density as determined by x-ray topography analysis under the active area of the diode was also found to directly affect the breakdown voltage. Only diodes with low density of screw dislocations and free from micropipes could block 2 kV or higher.