藍寶石晶體缺陷之X 光位像術研究

X-ray topographic study of defects in sapphire crystals

劉鴻霖(Hong-Lin Liou)

指導教授 ： 張石麟

國立清華大學/理學院/物理學系/碩士(2012年)

摘要

X 光位像術是一種非常有用且是非破壞性的單晶品質探測方法，其實驗基礎建
立於X 光繞射。利用二維的X 光位像對比與強度分佈可以了解晶體內的各種缺陷與
繞射現象。本實驗在國家同步輻射中心BL07A 光束線架設多晶體X 光位像術，利用
雙晶矽單光儀(DCM)挑選X 光能量19keV，再藉由矽(115)的非對稱性繞射放大X 光
照射面積並使其平行度更高，之後利用此X 光照射樣品於穿透式的X 光繞射幾何之
下，並收集X 光位像影像。同時我們也利用8.4keV 的X 光，藉由矽(113)非對稱繞
射後的X 光觀察高吸收下的穿透式X 光繞射。
實驗的影像利用電荷耦合元件(charge couple device)攝影機收集影像，結果
顯示矽的繞射影像沒有產生對比，為完美晶體。藍寶石晶體的繞射影像有許多錯位
對比產生，不同生長方式與等級的藍寶石晶體有著不同的錯位密度，且利用反射搖
擺曲線觀察半高寬的結果與錯位密度互相比較。利用高吸收的X 光繞射，吾人觀察
到動力繞射影像與X 光單擺效應。更詳細的結果將於本論文呈現。

關鍵字

X光位像術 ； 晶體缺陷 ； X光繞射 ； 藍寶石

並列摘要

X-ray topography is a useful and non-destructive way to reveal the quality of single crystals, and X-ray topography experiment is built on X-ray diffraction. Lattice defects
and X-ray diffraction phenomenon can be observed from the contrast and distribution of diffraction intensity of 2D topographic images. We have set up an X-ray topographic
arrangement at the NSRRC BL07A by following a multiple crystals technique. The monochromatic X-ray beam from Si double-crystal monochromator (DCM) is enlarged
and collimated by a third Si crystal at 19keV via the (115) asymmetric reflection, then the specimens are illuminated in a Laue diffraction geometry and the diffraction images are
recorded. Also, we have observed high absorption contrast X-ray diffraction topographs by using low energy (8.4keV) X-rays via the Si (115) asymmetric reflection.
A charge couple device (CCD) is used as the detector for image recording. The results show no image contrasts of Si crystals, indicating that Si crystals are perfect. It is
found that there are many dislocation lines on sapphire (Al2O3) topographic images, and the dislocation density is different for different crystal growth method or grade. We can also relate dislocation density with the FWHM of rocking curve. In the end, the dynamical diffraction contrasts and Pendell sung effect have been observed in the high
absorption contrast diffraction imaging. Detailed experimental results will be presented.

參考文獻

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