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
Fusion TEM holder tip
Image courtesy of Thin Solid Films

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.