CVD法制备ZnO薄膜生长取向和表面形貌

The Investigation of Growth Orientations of ZnO Films by CVD

利用具有特定温度梯度的CVD设备,以锌粉和氧气为原料,在Si(100)衬底上制备了ZnO薄膜。研究发现,锌粉中加入某些氯化物后可以改变ZnO薄膜的生长取向。用FESEM观察ZnO薄膜的表面形貌,发现Zn和氯化物的量比为1∶1时,生长的ZnO薄膜表面晶粒呈菱形或三角形({101}面),当二者的量比为10∶1时薄膜表面晶粒呈六棱台形({001}面)。XRD分析结果证实,前者只观察到(101)和(202)衍射峰,而后者出现(002)衍射峰且其强度大于(101)衍射峰。改变衬底或温度后得到的结果相同。因此,作者认为氯化物改变薄膜生长取向的现象与衬底和生长温度无关,添加的氯化物起到降低ZnO{101}面表面能的作用,随着氯化物浓度的增加,薄膜从沿[001]方向生长逐渐转向沿[101]方向生长。

ZnO films with unusual surface morphology and growth orientation [ 101 ] were prepared using oxygen gas and zinc powder adding LiCl or NaCl by CVD method. In the CVD growth process, the ZnO films grew at 550 - 650 ℃ for 2 h with adding LiCl and NaCl respectively. The surface morphologies of ZnO films were investigated using FESEM and exhibited rhombus/triangles when the mol ratio of chloride to zinc was 1： 1, and hexagonal pyramids when the ratio was 1： 10. In as-grown wurtize ZnO film, the rhombus and triangle correspond to the {101} faces, while the hexagon corresponds to the {001} face. Authors concluded the added chloride decreased the surface energy of {101} f surface. Meantime, the growth direction was transformed from [002 ] to [ 101 ] with the increasing of chloride concentration as shown in XRD pattern. These results implied that chloride could tune the growth direction of ZnO. This phenomenon could be observed in producing one-dimensional nanostructures but not in films.