DEVELOPMENT OF METHODS TO PRODUCE REFINED BEAMS OF NEUTRAL FREE RADICALS FOR SELECTIVE GROWTH OF METASTABLE CONDENSED PHASES

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In order to further evolve quantum-functional nano-devices using metastable condensed phases, it has become indispensable in recent years to ingeniously utilize selective surface reactions of neutral free radicals for the device processing. The problem encountered in the precise experimental study of a chemical reaction between a neutral free-radical species and a well- characterized material surface is how to supply a sufficient-flux purified beam of the momentum-controlled neutral free radicals onto the surface. The continuous supply is all the more difficult, although steady-flux continuous beams are generally more useful for thin-film growth application than pulsed ones. In order to overcome this difficulty the investigator has proposed several experimental approaches to produce steady-flux refined beams of neutral free radicals (RBNR). Two of these approaches are photo-deionization of negative ion beams (PDINIB) and photo-dissociation of energetic compound beams (PDECB).In this st … More udy, firstly, we achieved further enhancement of the rate of neutral free-radical production by improving a trial surface-processing apparatus utilizing RBNR produced by the PDECB and the PDINIB methods. A unique unimolecular-reaction mechanism for the photo- dissociation of the PDECB source compounds was revealed in the course of this study. Furthermore, we realized production of well-collimated hyperthermal beams of various neutral free-radical species.In an application of the PDINIB method to the doping of photo-deionized Cr atoms during the low-temperature epitaxial growth of high-quality (Al, Ga)N by a PDECB-based approach, we found a possibility that the incorporation of the Cr atoms into the growing surface of the diluted magnetic semiconductor (AI, Ga, Cr)N is enhanced by the oblique irradiation. Moreover, we successfully applied the well-collimated neutral beams of atomic Cr to elucidation of the angular- selective surface-reaction mechanism responsible for the epitaxial growth of the desirable metastable condensed phase for spintronics. Less