Quantum Structures Laboratory, Department of Electrical and Computer Engineering, University of California, Riverside, CA, 92521, USA.
Irvine Materials Research Institute University of California, Irvine, CA, 92697-2800, USA.
Sci Rep. 2017 Jun 22;7(1):4087. doi: 10.1038/s41598-017-04297-1.
One of the low-dimensional Boron Nitride (BN) forms, namely, cubic-BN (c-BN) nanodots (NDs), offers a variety of novel opportunities in battery, biology, deep ultraviolet light emitting diodes, sensors, filters, and other optoelectronic applications. To date, the attempts towards producing c-BN NDs were mainly performed under extreme high-temperature/high-pressure conditions and resulted in c-BN NDs with micrometer sizes, mixture of different BN phases, and containing process-related impurities/contaminants. To enhance device performance for those applications by taking advantage of size effect, pure, sub-100 nm c-BN NDs are necessary. In this paper, we report self-assembled growth of c-BN NDs on cobalt and nickel substrates by plasma-assisted molecular beam epitaxy. It is found that the nucleation, formation, and morphological properties of c-BN NDs can be closely correlated with the nature of substrate including catalysis effect, lattice-mismatch-induced strain, and roughness, and growth conditions, in particular, growth time and growth temperature. The mean lateral size of c-BN NDs on cobalt scales from 175 nm to 77 nm with the growth time. The growth mechanism of c-BN NDs on metal substrates is concluded to be Volmer-Weber (VW) mode. A simplified two-dimensional numerical modeling shows that the elastic strain energy plays a key role in determining the total formation energy of c-BN NDs on metals.
一种低维氮化硼 (BN) 形式，即立方 BN (c-BN) 纳米点 (NDs)，为电池、生物学、深紫外发光二极管、传感器、滤波器和其他光电子应用提供了多种新的机会。迄今为止，制备 c-BN NDs 的尝试主要是在极端高温/高压条件下进行的，得到的 c-BN NDs 具有微米级尺寸、不同 BN 相的混合物，并含有与工艺相关的杂质/污染物。为了通过利用尺寸效应来提高这些应用的器件性能，需要纯净的、亚 100nm 的 c-BN NDs。在本文中，我们报告了通过等离子体辅助分子束外延在钴和镍衬底上自组装生长 c-BN NDs。研究发现，c-BN NDs 的成核、形成和形态特性可以与衬底的性质密切相关，包括催化作用、晶格失配引起的应变和粗糙度，以及生长条件，特别是生长时间和生长温度。c-BN NDs 在钴上的平均横向尺寸随生长时间从 175nm 增加到 77nm。c-BN NDs 在金属衬底上的生长机制被归结为 Volmer-Weber (VW) 模式。简化的二维数值模型表明，弹性应变能在决定 c-BN NDs 在金属上的总形成能方面起着关键作用。
