Decomposition of amorphous Si2C by thermal annealing

•We investigated the thermal stability of thin films of amorphous Si2C at 1200 °C.•Annealing led to a distinct change of bonding states and of the microstructure.•Two hours of annealing is accompanied with the formation of Si and SiC crystallites.•After 20 h of annealing, the Si decomposes and is transferred to interfaces.•The microstructure of the film changed dramatically.

In the present paper, the decomposition and the crystallization behaviour of amorphous Si2C films, which were deposited by r.f. magnetron co-sputtering on Si wafer substrates, are investigated. For analysis, the following methods were used: x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), grazing incidence x-ray diffractometry (GIXRD), atomic force microscopy and scanning electron microscopy. After deposition, the films exhibited a homogenous amorphous structure with a variety of bonding states reaching from homonuclear silicon-like Si-Si bonds over mixed Si-Si-C bonds to heteronuclear Si-C bonds. Annealing at 1200 °C for 2 h leads to the crystallization of silicon and silicon carbide with grain diameters of several nanometers within the amorphous matrix, as evidenced by GIXRD and TEM. With XPS also a distinct change of the bonding states is detected. After 2 h of annealing, only Si-Si and Si-C bonds are detectable. After prolonged annealing at 1200 °C for 20 h, XPS shows only Si-C bonding states but no more Si-Si bonding. In addition, GIXRD verifies the absence of any polycrystalline silicon in the film. The microstructure of the film changed dramatically towards a jagged and porous structure. The vanishing of silicon during isothermal annealing is explained on base of in situ and ex situ TEM measurements, and a possible model for decomposition is suggested.