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研究了ZnO薄膜中应力对发光的影响.实验样品为ZnO体单晶、在Si基片上直接生长的ZnO薄膜以及通过SiC过渡层在Si基片上生长的ZnO薄膜.测量了这三种样品的X射线衍射图形、喇曼光谱和光致发光光谱.由X射线衍射图形可以看出,由于SiC过渡层缓解了ZnO与Si之间的晶格失配,使得通过SiC过渡层在Si上生长的ZnO薄膜的结晶质量好于直接在Si上生长的ZnO薄膜的质量.进一步通过喇曼谱测量发现,与ZnO体单晶相比,直接在Si上生长的ZnO薄膜的E2(high)峰红移1.9cm-1,根据喇曼谱峰位移与应力的关系可以推出薄膜中存在0.4GPa的张应力;而通过SiC过渡层在Si上生长的ZnO薄膜的E2(high)峰红移0.9cm-1,对应着0.2GPa的张应力.对照X射线衍射图形的结果可以看出,薄膜中张应力的大小与薄膜的结晶质量密切相关,表明张应力来源于外延层和基片间的晶格失配,晶格失配越大,外延层中产生的张应力越大.有无SiC过渡层的两种薄膜样品的PL光谱中都存在紫外和绿光两种谱带,随样品热处理时氧气分压增加,两种样品都出现绿光增强的相似的变化规律,但有SiC过渡层的样品的变化幅度较小.这一结果说明,绿色发光中心与薄膜的质量,也就是与薄膜中存在的张应力大小有关.在以往研究中得出的非故意掺杂ZnO薄膜的绿色发光中心来源于氧反位缺陷(OZn),文中研究的结果正好可以解释氧反位缺陷形成的原因.由于薄膜中存在张应力,使得样品的能量升高,其结果必然会产生缺陷来释放张应力,以便降低系统能量.而氧离子半径大于锌离子半径,氧替位锌有利于释放张应力,也就是说,在存在张应力的情况下,OZn的形成能降低.这一结果进一步证明Si上生长的ZnO薄膜中的绿色发光中心与氧反位缺陷有关.
The effects of stress on the luminescence of ZnO thin films were studied.The experimental samples were ZnO single crystal, ZnO thin films grown directly on Si substrate and ZnO thin films grown on Si substrate through SiC transition layer.The X Ray diffraction pattern, Raman spectrum, and photoluminescence spectrum. It can be seen from the X-ray diffraction patterns that the SiC transitional layer alleviates the lattice mismatch between ZnO and Si and makes the ZnO thin film grown on Si by the SiC transitional layer Is better than that of ZnO thin films grown directly on Si.According to Raman spectrum measurement, the E2 (high) peak of the ZnO thin film grown directly on Si is redshifted 1.9 cm -1. According to the relationship between the Raman peak shift and the stress, there is a tensile stress of 0.4 GPa in the film. The E2 (high) peak of the ZnO thin film grown on the SiC transition layer redshifts 0.9 cm -1, corresponding to With 0.2GPa tensile stress control X-ray diffraction pattern results can be seen that the size of the film tensile stress and the film is closely related to the quality of the crystal, indicating that the tensile stress derived from the epitaxial layer and the substrate lattice mismatch, crystal The greater the lattice mismatch, the greater the tensile stress in the epitaxial layer There were two bands of UV and green in the PL spectrum of the two kinds of films without SiC transition layer. The oxygen partial pressure increased with the increase of oxygen partial pressure. The results show that the green luminescence center and the film quality, that is, with the size of the tensile stress in the film has been obtained in the previous study unintentionally doped ZnO film green The luminescence center is derived from OZn, and the results of this paper can explain the formation of Oxygen Reverse Defect. Due to the existence of tensile stress in the film, the energy of the sample increases. As a result, defects are inevitable to release Stress in order to reduce the system energy.The oxygen ion radius is greater than the radius of zinc ions, oxygen displacement of zinc is conducive to the release of tensile stress, that is, in the presence of tensile stress, OZn formation can be reduced.This result further proof Si The green luminescent center in the ZnO thin film grown on is related to oxygen anti-defect.