Intrinsic Stress and Grain Alignment in Diamond Films

在许多衬底上CVD沉积金刚石的一个问题是，金刚石薄膜中的固有应力大于薄膜/衬底热膨胀不匹配引起的应力，这导致金刚石薄膜脱落或衬底弯曲。沉积后退火不能消除这些本征应力。PI小组最近的工作已经确定，中间退火步骤，在明显的晶粒撞击之后，但在形成致密薄膜之前，可以最小化金刚石薄膜中的固有应力，并减少剥落。中间退火步骤以这样的方式改变了薄膜的微观结构，以减少后续金刚石薄膜生长过程中的应力演化。初步的电镜研究（非原位SEM和原位TEM热阶段实验）表明，接触的金刚石晶粒在退火过程中发生了旋转。对观察到的应力降低的合理解释是，晶粒旋转导致相邻晶粒之间更好的晶体排列。随后在这些晶粒上的生长可以形成更稳定的晶界结构，不易受到引起内在拉应力的松弛机制的影响。本研究将研究这一现象的基本原理，以优化和控制金刚石和其他薄膜中的应力水平。该研究将由一个由PI （CVD/薄膜）和2名co-PI（透射电子显微镜/晶体学家和物理学家/拉曼光谱学家）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，金刚石薄膜中的固有应力大于薄膜/衬底热膨胀不匹配引起的应力，从而导致金刚石薄膜脱落或衬底弯曲。沉积后退火不能消除这些本征应力。PI小组最近的工作已经确定，中间退火步骤，在明显的晶粒撞击之后，但在形成致密薄膜之前，可以最小化金刚石薄膜中的固有应力，并减少剥落。本研究将研究这一现象的基本原理，以优化和控制金刚石和其他薄膜中的应力水平。该研究将由一个由PI （CVD/薄膜）和2名co-PI（透射电子显微镜/晶体学家和物理学家/拉曼光谱学家）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). ***