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

为了进一步发展使用亚稳凝聚相的量子功能纳米器件，近年来巧妙地利用中性自由基的选择性表面反应来加工器件是必不可少的。在对中性自由基与材料表面之间的化学反应进行精确实验研究时，遇到的问题是如何在表面上提供足够通量的动量控制的中性自由基光束。尽管稳定通量连续光束通常比脉冲光束更适用于薄膜生长应用，但持续的供应更加困难。为了克服这一困难，研究者提出了几种实验方法来产生稳定通量的中性自由基（RBNR）精束。其中两种方法是负离子束的光去电离（PDINIB）和高能复合束的光解离（PDECB）。在本研究中，首先，我们利用PDECB和PDINIB方法产生的RBNR改进了实验表面处理装置，进一步提高了中性自由基的产生速度。本研究揭示了PDECB源化合物光解离的一个独特的单分子反应机制。此外，我们还实现了各种中性自由基的准直超热光束的产生。将PDINIB方法应用于高质量（Al, Ga）N的pdecb低温外延生长过程中光去离子化Cr原子的掺杂，我们发现斜向辐照可能会增强Cr原子在稀释磁性半导体（A1, Ga, Cr） N生长表面的掺入。此外，我们成功地应用原子Cr的良好准直中性光束来阐明自旋电子学中理想的亚稳凝聚相外延生长的角选择性表面反应机制。少

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 stu … More dy, 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 (A1, 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