Decomposition of Amorphous Si2C by Thermal Annealing

Gustus, René, Wolfgang Gruber, Lienhard Wegewitz, Udo Geckle, Robby Prang, Christian Kübel, Wolfgang Maus- Friedrichs, et al., 2014

Abstract

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.

Impact Statement

The observation of amorphous Si2C films’ crystallization after being deposited from RF magnetron co-sputtering on Si wafer substrates. The crystallization is a result of annealing at 1200° C at 2 hours. After 20 hours, the polycrystalline silicon vanishes from the film. Its dematerialization is demonstrated through in situ and ex situ TEM measurements, suggesting a possible decomposition model.