Improvement of luminescence degradation in pure water of nanocrystalline silicon particles covered by a hydrogenated amorphous carbon layer

Abstract

The stability of luminescence in pure water of surface-modified nanocrystalline silicon (nc-Si) particles has been studied. The surfaces of nc-Si particles were modified with more stable silicon-oxygen (Si-O) and silicon-carbon (Si-C) bonds by the formation of a thin native oxide layer and a hydrogenated amorphous carbon (a-C:H) layer consisting of both disordered regions and graphite bands. The peak position of luminescence in pure water of the sample with the a-C:H layer was similar to that in the sample without the a-C:H layer. Moreover, the degradation rate of the luminescence intensity of the sample with the a-C:H layer was less than that of the sample without the a-C:H layer, for immersion in pure water above 100 h. The luminescence in pure water of the a-C:H coated sample could be seen with the naked eye even after aging for 200 h. The degradation of the luminescence in pure water can be improved remarkably by the formation of Si-O and Si-C bonds with strong bond strengths on the surfaces of the nc-Si particles.