MOCVD法生长SAWF用ZnO/Diamond/Si多层结构

使用等离子体辅助MOCVD系统在金刚石，硅衬底上成功地制备了氧化锌多层薄膜材料，通过两步生长法对薄膜质量进行了优化。XRD测试显示优化后的样品具有c轴的择优取向生长，PL谱测试表明样品经优化后不仅深能级发射峰消失，同时紫外发射峰增强。对优化后的样品的表面测试显示出较低的表面粗糙度。比较氧化锌多层薄膜结构的声表面波频散曲线，ZnO薄膜声表面滤波器受膜厚和衬底材料的影响较大。当ZnO薄膜较薄时，在它上面的传播速度将与衬底上的传播速度接近，与其他衬底上生长的薄膜相比，以金刚石这种快声速材料为衬底的ZnO多层薄膜结构，声表面波滤波器的中心频率将提高1倍左右。

ZnO/Diamond/Si Multi-layer Films Grown by MOCVD for Surface Acoustic Wave (SAW) Devices

Materials with high phase velocity are required to achieve high frequency surface acoustic wave devices. Diamond can be considered as the utmost material when it is coupled with piezoelectric materials such as ZnO. ZnO/diamond/Si structures have exhibited a phase velocity as large as 10 km/s, which enables one to develop a high frequency SAW device without requiring high resolution lithography technologies.In this paper, the piezoelectric characteristic of ZnO multi layer and the potential application for SAW device with ZnO/diamond/Si film are studied. Firstly, ZnO films have been deposited on diamond/Si substrate by plasma assisted metal organic chemical vapour deposition (MOCVD). The characteristic of the films is optimized through two step growth method. X ray diffraction (XRD) spectra show that the as prepared ZnO films are strongly c axis oriented. Photoluminescence (PL) spectra exhibit an intensive ultraviolet emission peak for our samples, while the emission band for deep energy level transition disappears. Scanning probe microscopy (SPM) measurement is also used to analyze the surface roughness of the grown ZnO/diamond/Si films, the sample with lower roughness will reduce the surface influence on SAW device application. To investigate the SAW properties of the ZnO multi layer structure approximatively, the theoretic frequency dispersion curves of SAW for ZnO material on different substrates are studied. The thickness of ZnO film has obvious effect on the working frequency of SAW devices, i.e. , the thinner the ZnO film, the higher the phase velocity of the SAW for our material. And the center frequency of ZnO SAW devices on diamond/Si substrate is about two times of that of ZnO materials on other substrates. So the ZnO/diamond/Si multi layer is promising to fabricate high frequency SAW filter.