Preparation and Molecular Dynamics Evaluation of Super Hard BN Film by Ion-Beam-Assisted Deposition

采用离子混合-气相沉积(IVD)技术，在氮离子的同时照射下沉积B蒸气制备了BN薄膜。考察了工艺参数对薄膜的形貌、成分、化学键、晶体结构、努氏硬度和体积电阻的影响。选择了传输比B/N、N离子加速能、束流角度、微晶取向和衬底温度等工艺参数，寻找了形成立方氮化硼的最佳条件。MR分析表明，在较低的加速电压和较高的输运比下，形成了具有很高诺氏硬度的CBN和hBN的混合相，并用牛顿环法估算了BN薄膜的压缩内应力。用配备迈克尔逊干涉仪的光学显微镜测量了牛顿环。结果表明，在较低的加速电压和较高的传输比B/N下，存在较高的压应力，这与cBN的形成条件相对应。根据从头计算得到的BN晶体的电子分布，B原子和N原子之间的相互作用表现出角度依赖性。因此，在本研究中应用了经验的多体势--Albe势。计算结果表明，CBN结构是由hBN或RBN的晶体结构转变而成。此外，在转变过程中，通过N离子的穿透和SP3键的形成来测量体积的增加。因此，CBN薄膜的高内压应力是由晶体结构转变过程中形成的SP3键引起的

BN films were prepared by depositing B vapor under simultaneous irradiation of N ions, that is ion mixing and vapor deposition (IVD) technique. The effect of processing parameters on morphology, composition, chemical bonding, crystal structure, Knoop hardness and volume resistance are evaluated. For the processing parameters, transport ratio B/N, acceleration energy of N ions, beam angle, crystallite orientation and temperature of substrate are selected and the optimum condition for the formation of cubic BN is searched. From MR analysis, it is revealed that the mixture phase of cBN and hBN, which shows very high Knoop hardness, is formed at low acceleration voltage and high transport ratio.The compressive internal stress of BN films were estimated using the Newton ring method. The New-ton rings were measured with the optical microscope which was equipped with a Michelson interferometer. As a result, high compressive stress is measured at low acceleration voltage and high transport ratio B/N, which corresponded to the condition for formation of cBN.The molecular dynamics analysis was applied to investigate the generation mechanism of internal stress. According to the electron distribution of BN crystal obtained by ab-initio calculation, interaction between B and N atom shows angle dependence. Therefore, Albe potential, an empirical many-body potential, is applied in this study. Numerical results suggested that cBN structure is generated by transition of crystal structure from hBN or rBN. Besides, increase of volume was measured by the penetration of N ions and formation of sp3 bonds during transition. Therefore, it is concluded that the high internal compressive stress of cBN film is caused by formation of sp3 bonds during transition of crystal structure