Understanding the structure of Si nanoclusters in ac-Si:H films using spherical aberration-corrected transmission electron microscopy

摘要

Recent work has shown that the electrical properties of hydrogenated amorphous Si films with nanocrystalline inclusions (ac-Si:H) make this material a promising candidate for applications in solar cells. The present study applies the technique of spherical aberration-corrected high-resolution transmission electron microscopy for the identification and analysis of the crystalline content of an ac-Si:H film. By varying both the spherical aberration of the objective lens and the defocus, regions of crystallinity in the ac-Si:H film can be identified. This study reports the analysis of Si nanoparticles of approximately 1.5 nm in size. Some of these nanoparticles contain planar defects, such as twin defects and stacking faults. All particles observed were the same crystal structure as bulk Si, which agrees with theoretical cluster calculations. Beam damage was observed in the amorphous matrix for long electron-beam exposures.