Intrinsic Stress and Grain Alignment in Diamond Films

9619520谢尔登在许多衬底上CVD沉积金刚石的一个问题是，金刚石薄膜中的本征应力大于薄膜/衬底热膨胀失配造成的应力，这会导致金刚石薄膜剥落或衬底弯曲。沉积后的退火不会消除这些本征应力。PI的小组最近的工作已经确定，在显著的颗粒撞击之后，但在致密的薄膜形成之前的中间退火步骤，可以最小化金刚石薄膜中的内应力，并减少层裂。中间退火步骤改变了薄膜的微结构，从而减少了随后金刚石薄膜生长过程中的应力演化。初步的电子显微镜研究(非原位扫描电子显微镜和原位电子显微镜热台实验)表明，接触的金刚石颗粒在退火过程中发生旋转。对观察到的应力降低的合理解释是，颗粒旋转导致相邻颗粒之间更好的晶体排列。随后在这些颗粒顶部的生长可以形成更稳定的晶界配置，这些晶界配置不太容易受到松弛机制的影响，这种松弛机制可能会产生内在的拉应力。拟议的研究将研究这种现象的基本原理，以优化和控制钻石和其他薄膜中的应力水平。这项研究将由一个由PI(化学气相沉积/薄膜)和2个共同PI(一名透射式电子显微镜/结晶学家和一名物理学家/拉曼光谱仪)组成的重点研究小组进行。在许多衬底上CVD沉积金刚石的一个问题是，金刚石薄膜中的本征应力大于薄膜/衬底热膨胀失配造成的应力，这会导致金刚石薄膜剥落或衬底弯曲。沉积后的退火不会消除这些本征应力。PI的小组最近的工作已经确定，在显著的颗粒撞击之后，但在致密的薄膜形成之前的中间退火步骤，可以最小化金刚石薄膜中的内应力，并减少层裂。拟议的研究将研究这种现象的基本原理，以优化和控制钻石和其他薄膜中的应力水平。这项研究将由一个由PI(化学气相沉积/薄膜)和2个共同PI(一名透射式电子显微镜/结晶学家和一名物理学家/拉曼光谱仪)组成的重点研究小组进行。***

9619520 Sheldon One problem with CVD deposition of diamond on many substrates is that the intrinsic stresses in the diamond film are larger than the stresses caused by the film/substrate thermal expansion mismatch, which causes the diamond film to spall off or the substrate to bow. Post- deposition annealing does not remove these intrinsic stresses. Recent work by the PI's group has determined that an intermediate annealing step, after significant grain impingement, but before a dense film was formed, can minimize intrinsic stress in the diamond film, and reduce the spallation. The intermediate annealing step alters the film microstructure in such a way to reduce stress evolution during subsequent diamond film growth. Preliminary electron microscopy studies (ex situ SEM and in situ TEM hot-stage experiments) indicate that contacting diamond grains rotate during annealing. A reasonable explanation for the observed stress reduction is that grain rotation results in better crystallographic alignment between adjacent grains. Subsequent growth on top of these grains can then form more stable grain boundary configurations that are less susceptible to the relaxation mechanisms that can induce intrinsic tensile stress. The proposed research would study the fundamentals of this phenomenon in order to optimize and control stress levels in diamond and other thin films. The research will be performed by a Focused Research Group consisting of the PI (CVD/thin films), and 2 co-PIs (a transmission electron microscopist/crystallographer and a physicist/Raman spectroscopist). %%% One problem with CVD deposition of diamond on many substrates is that the intrinsic stresses in the diamond film are larger than the stresses caused by the film/substrate thermal expansion mismatch, which causes the diamond film to spall off or the substrate to bow. Post- deposition annealing does not remove these intrinsic stresses. Recent work by the PI's group has determined that an intermediate annealing step, after significant grain impingement, but before a dense film was formed, can minimize intrinsic stress in the diamond film, and reduce the spallation. The proposed research would study the fundamentals of this phenomenon in order to optimize and control stress levels in diamond and other thin films. The research will be performed by a Focused Research Group consisting of the PI (CVD/thin films), and 2 co-PIs (a transmission electron microscopist/crystallographer and a physicist/Raman spectroscopist). ***