Investigation of nanoscratch anisotropy of C-plane sapphire wafer using friction force microscope
Investigation of nanoscratch anisotropy of C-plane sapphire wafer using friction force microscope
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DOI：
10.1016/j.precisioneng.2021.08.011
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发表时间：
2022
影响因子：
3.6
通讯作者：
Wangpiao Lin;J. Shimizu;Li-bo Zhou;T. Onuki;Hirotaka Ojima
中科院分区：
文献类型：
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作者：
Wangpiao Lin;J. Shimizu;Li-bo Zhou;T. Onuki;Hirotaka Ojima
在本研究中，在（0001）平面蓝宝石晶圆衬底上，采用三角形锥体单晶金刚石尖端的摩擦显微镜进行了侧面多次扫描纳米划伤实验，以阐明其韧性加工机制及其各向异性。通过摩擦力显微镜观察蓝宝石c面各划痕方向的划痕力、深度、比划痕能等特征，比划痕能呈现出三重对称的趋势。随后，通过扫描选择显微镜验证了附着在金刚石针尖上的切削屑呈现出塑性变形特征。基于蓝宝石的滑移/孪晶体系，利用合力计算了各个划痕方向上的施密德因子，在菱形面上计算的施密德因子最高。在此基础上，利用简单的切屑形成模型计算了菱形面上沿孪晶方向的分解剪应力，结果表明，这些剪应力比菱形面孪晶的临界分解剪应力大几倍。结果发现，当设置划痕方向，使金刚石刀尖的三个面中有一个面接近平行于其中一个菱形面时，菱形面作为切屑剪切面，可以使比划痕/切割能量最小化。划伤亚表面的透射电镜横截面图像也清楚地显示出亚表面损伤的存在，包括与菱形面相关的孪晶和层错。
In this study, nanoscratch experiments using side-forward multiple scans by friction force microscope with triangular pyramidal monocrystalline diamond tip were conducted on a (0001) plane sapphire wafer substrate to clarify the ductile-regime machining mechanism including its anisotropy. Various characteristics, such as scratch force, depth and specific energy for each scratch direction on C-plane of sapphire, were manifested by a friction force microscope, and the specific scratch energy showed a trend of three-fold symmetry. Subsequently, cutting chips which adhere to the diamond tip exhibited plastic deformations features were testified by a scanning election microscope. Based on slip/twinning systems of sapphire, Schmid factor was calculated for each scratch direction using the resultant force, and the calculated Schmid factors on the rhombohedral planes became the highest. Following the results, the resolved shear stresses along the twinning directions on the rhombohedral planes were calculated using a simple chip formation model, and they were several times larger than the critical resolved shear stress for rhombohedral twinning. As a result, it was found that when the scratch direction is set so that one of the three faces of the diamond tip is close to parallel to one of the rhombohedral planes, the rhombohedral plane acts as the chip shear plane and the specific scratch/cutting energy can be minimized. The cross-sectional transmission electron microscope images of scratched sub-surface also distinctly displayed the existence of subsurface damages consisting of twins and stacking faults relating rhombohedral planes.