Electron tomography analysis of 3D interfacial nanostructures appearing in annealed Si rich SiC films
The optical and electrical properties of Si rich SiC (SRSC) solar cell absorber layers will strongly depend on interfacial layers between the Si and the SiC matrix and in this work, we analyze hitherto undiscovered interfacial layers. The SRSC thin films were deposited using plasma-enhanced chemical vapor deposition (PECVD) technique and annealed in Nitrogen environment at 1100 °C. The thermal treatment leads to metastable SRSC films spinodally decomposed into a Si-SiC nanocomposite. After the thermal treatment, the coexistence of crystalline Si and SiC nanostructures was analysed by high resolution transmission electron microscopy (HRTEM) and electron diffraction. From the quantitative extraction of the different plasmons signals from electron energy-loss spectra, an additional structure, amorphous SiC (a-SiC) was found. Quantitative spectroscopic electron tomography was developed to obtain three dimensional (3D) plasmonic maps. In these 3D spectroscopic maps, Si regions appear as network structure inside the SiC matrix where the a-SiC appears as an interfacial layer separating matrix and Si network. The presence of the a-SiC interface can be explained in the framework of the nucleation and growth model.