Fe1-xMnx alloy films obtained by rf sputtering technique have been investigated by X-ray diffraction, magnetization and Mossbauer effect measurements. The single bcc phase extends up to about x=0.2, while a bcc-fcc mixed phase appears for x=0.2-0.26. The lattice constants of the bcc phase are about 0.5% larger than those of the bulk specimens. The magnetization decreases monotonically with increasing x in the bcc phase, while it decreases sharply in the bcc-fcc mixed phase. These results are consistent with the Mossbauer spectra of these alloy films. The volume fraction of bcc and fcc phases has been estimated from Mossbauer analyses as well as magnetization measurements.
A high-quality bulk gallium nitride (GaN) substrate, which is suitable for high-quality homoepitaxial growth, is indispensable for realizing high-performance GaN devices. With improvement in the quality of the bulk GaN substrate, the removal of subsurface damage induced during surface polishing has become increasingly necessary. To remove the subsurface damage from the bulk GaN substrate, a chemical finishing method that does not produce further damage is required. We applied plasma chemical vaporization machining (CVM) to remove the subsurface damage from the bulk GaN substrate. In this study, we investigated the etching characteristics of GaN by plasma CVM applying atmospheric pressure Cl 2 /He plasma. The maximum removal rate in the depth direction by plasma CVM was 9100 nm/min, which is seven times greater than that of reactive ion etching (RIE). The activation energy in plasma CVM was estimated to be 2.1 kcal/mol, which is 1.75 times greater than that in RIE. It is supposed that some of the energy required for the removal reaction in RIE is supplied by ion bombardment, but plasma CVM depends on only a chemical reaction without high-energy ion collision. This result suggests that plasma CVM is a finishing method that causes less subsurface damage than RIE.
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