Structural characterization of radiofrequency magnetron sputter deposited SiO₂thin films

Abstract

The SiO 2 thin-film structure deposited by radiofrequency (rf) magnetron sputtering was found to depend on whether the native oxide on the Si(111) was removed or not. X-ray reflectivity (XRR) data show that, when deposited on a clean Si(111) surface, the SiO 2 thin film consistently has a two-layer (an overlayer and an interface layer) structure. The interfacial structure depends on the deposition temperature. The film deposited at room temperature has a lower-density interface layer. With increase of the substrate temperature, the density and the thickness of the interface layer also increase. In contrast, when deposited on Si(111) with a native oxide layer, the deposited films have varying structures. At lower temperatures, the XRR data can be fitted with a one-layer model. At higher temperatures, the films consist of two or three layers, including one lower-density top layer, a normal SiO 2 layer and a higher-density interface layer. The layer thickness, surface and interface roughness of the two-group samples were also compared and discussed.

Manganese-Catalyzed Surface Growth of Single-Walled Carbon Nanotubes with High Efficiency

“…But the SiO 2 layer on type 2 substrate was prepared by sputtering technique at room temperature. Brunet-Bruneau et al investigated the properties of evaporated SiO 2 films by using infrared ellipsometry and found that such a deposited SiO 2 film had a complex structure with lower density (even lower than fused silica) and possessed high pore volume fraction. , The newly deposited SiO 2 film also undergoes a loose contact at the interface and exhibits inhomogeneous structure . Therefore, we speculate that the newly deposited SiO 2 film (type 2 substrate) is in some degree similar to the porous catalyst support materials (such as porous SiO 2 , Al 2 O 3 , and MgO) commonly used for bulk growth of SWNTs. ,, Such a loose and porous SiO 2 layer can protect catalyst particles from aggregation and provide more suitable catalyst nanoparticles for SWNT growth. , This point can be confirmed by the AFM results, as shown in parts c and d of Figure .…”

“…25,26 The newly deposited SiO 2 film also undergoes a loose contact at the interface and exhibits inhomogeneous structure. 27 Therefore, we speculate that the newly deposited SiO 2 film (type 2 substrate) is in some degree similar to the porous catalyst support materials (such as porous SiO 2 , Al 2 O 3 , and MgO) commonly used for bulk growth of SWNTs. 3,5,28 Such a loose and porous SiO 2 layer can protect catalyst particles from aggregation and provide more suitable catalyst nanoparticles for SWNT growth.…”