Search

Publisher Summary Silicon carbide (SiC) is perhaps the oldest semiconductor. Although in the last fifty years considerable use has been made of its abrasive properties, only in the past fifteen years has its potentialities as a semiconductor been exploited. The chapter discusses that Sic devices have distinct properties that lead to specific applications: they are operable up to 500oC, they have enhanced radiation resistance, and certain particular characteristics (example, band gap) lead to specific device applications. Applications in these areas determine the final utilization of Sic devices. The future development of Sic devices probably depends more on engineering perseverence than on semiconductor physics breakthrough.. The sophisticated active devices and integrated circuits now being prepared from silicon will be prepared from Sic when suitable crystals are available and the fabrication techniques are refined.

The metastable, ferromagnetic, tetragonal phase in the Mn-Al system has been obtained by isothermal transformation of a high-temperature phase. Transmission electron micrographs of specimens of this phase so obtained (bulk iHc = 1130 oe) show striations of light (transmitting) and dark (non-transmitting) material. The striations are presumed to arise from stresses induced by the transformation and/or cooling. Transmission electron diffractograms contain individual patterns both with and without superlattice reflections. Respective patterns reveal axial ratios of 0.90 and 0.94, and are correlated with the dark and light areas of the micrographs. From diffraction data it is concluded that the trace of the boundary between the light and dark regions coincides with a projection of the c axis. The possibility of coherency as a mechanism for the high coercive force, analogous to CoPt, is discussed. The type of cooperative atomic interaction as related to the shift in the axial ratio is also discussed.