225nm UV light emitting BN at the room temperature prepared by laser-plasma synergetic deposition

(1)我们开展了一种新型BN的研究，这是NIMS首次发现并于1999年报道的SP^3键合的5H-BN。这种BN是用等离子体和激光协同沉积的方法制备的，既有粉末，也有薄膜。这种BN在225 nm处表现出强烈的紫外光发射，在300 nm处表现出宽泛的紫外光发射。前一条带最多地出现在粉末样品中，可能是由于粉末样品的结晶度较高所致。另一方面，薄膜样品只显示了300 nm的宽带。值得注意的是，这两个波段在室温下都是兴奋的。为了实现将这些样品应用于紫外光发射器件的最终目标，了解其生长机理以及结构特征与紫外光性能之间的关系是非常重要的。(2)由于结构特性来源于生长动力学，我们发明了一种利用样品…的光致发光(PL)来原位观察薄膜生长速率的新方法更激动人心的是加工中的准分子激光。扫描电子显微镜观察发现，在生长过程的中期，生长模式发生了从纤维生长到微锥生长的转变，相应的生长速率也发生了相应的变化。(3)对于粉末样品的生长，我们观察到了不同生长阶段对应的透射电子显微镜图像。在此基础上，我们得出结论：存在一种最有可能处于BN超临界流体状态的前驱体。我们用二维非线性动力学系统的数学方法建立了一个生长模型，在该模型中我们展示了等离子体和激光的协同效应，从而诱导了sp3键合的5H-BN的非平衡相的形成。(4)对于薄膜的生长机制，根据实验观察，我们可以证明这是一种由等离子体提供前驱体自由基的光化学激活生长。我们建立了一个模型，其中强迫振荡光化学反应与前驱体自由基的表面扩散竞争。通过该模型，我们可以解释在Si(100)衬底上观察到的微锥分布随温度变化的均匀-分形转变，以及观察到的分形形貌的来源。(5)紫外光发射的寿命足够短，表明该材料是一种直接跃迁半导体，适用于未来的固态紫外光LED。较少

(1)We have carried out the research on a new type of BN, namely, sp^3-bonded 5H-BN, which was originally found at the NIMS for the first time and reported in 1999. This BN is prepared in the forms of powder as well as films by synergetic deposition methods using plasma and laser. This BN shows a UV emission sharply at 225nm and broadly at 300nm. The former band is observed only in the powder samples most, probably due to the high crystallinity. On the other hand, film samples show only the 300 nm broad band. It is noteworthy that both bands are excited at room temperatures. To achieve the final goal of application of these samples to UV light emission devices, it is important to understand the growth mechanism and the relationship between the structural characteristics and the UV properties.(2)Since the structural properties originate from the growth dynamics, we invented a new in-situ observation method of the growth rates of films by utilizing photoluminescence (PL) from the samples … More excited by the processing excimer laser. We could find the transition of the growth mode from initial fibrous growth to the micro-cone formation at the mid stage by scanning electron microscopy and the corresponding change of the growth rate was clearly seen in the in-situ PL observation.(3)As for the growth of powder samples, we observed transmission electron microscopic (TEM) images corresponding to some different stages of the growth. Based on them, we concluded the existence of a precursor which is most likely in the supercritical fluid state of BN. We built a growth model using the mathematics of 2-dimensional nonlinear dynamical system, and by which we showed a synergetic effect of plasma and laser to induce the nonequilibrium phase formation of sp^3-bonded 5H-BN.(4)As for the film growth mechanism, based on experimental observations, we could demonstrate that it was a photochemically-activated growth where precursor radicals were supplied from a plasma. We build a model where forced-oscillatory photochemical reactions compete with surface diffusion of the precursor radicals. By the model, we could explain the temperature-dependent uniform-fractal transition of the micro-cone distribution observed on Si(100) substrates, and the origin of the observed fractal morphology.(5)The lifetime of the UV emission was short enough to indicate that this material is a direct-transition semiconductor and applicable to future solid state UV LED. Less