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采用射频磁控溅射方法制备单层AlN,Si3N4薄膜和不同调制周期的AlN/Si3N4纳米多层膜.采用X射线衍射仪、高分辨透射电子显微镜和纳米压痕仪对薄膜进行表征.结果发现,多层膜中Si3N4层的晶体结构和多层膜的硬度依赖于Si3N4层的厚度.当AlN层厚度为4.0nm、Si3N4层厚度为0.4nm时,AlN和Si3N4层共格外延生长,多层膜形成穿过若干个调制周期的柱状晶结构,产生硬度升高的超硬效应.随着Si3N4层厚的增加,Si3N4层逐步形成非晶并阻断了多层膜的共格外延生长,多层膜的硬度迅速降低,超硬效应消失.采用材料热力学和弹性力学计算了Si3N4层由晶态向非晶转变的临界厚度.探讨了AlN/Si3N4纳米多层膜出现超硬效应的机理.
Single-layer AlN, Si3N4 thin films and AlN / Si3N4 multilayer films with different modulation periods were prepared by RF magnetron sputtering.The films were characterized by X-ray diffraction, high resolution transmission electron microscopy and nanoindentation. , The crystal structure of the Si3N4 layer and the hardness of the multilayer film in the multilayer film depend on the thickness of the Si3N4 layer.When the AlN layer thickness is 4.0 nm and the Si3N4 layer thickness is 0.4 nm, The film formation through the columnar crystal structure of several modulation cycles, resulting in a superhard effect of increasing the hardness.With the Si3N4 layer thickness increases, Si3N4 layer gradually amorphous and block the multilayer epitaxial growth, and more The hardness of the film decreases rapidly and the superhard effect disappears.The critical thickness of the Si3N4 layer from amorphous to amorphous is calculated by means of material thermodynamics and elastic mechanics.The mechanism of superhardness of AlN / Si3N4 multilayer is discussed.