以表面等离子体为媒介的ZnO薄膜发光增强特性研究

Surface-plasmon-mediated emission enhancement from Ag-capped ZnO thin films

采用两步法制备Si基Ag/ZnO双层结构薄膜,研究了Ag覆盖层的厚度和生长温度T对ZnO近带边发光强度的影响.对于厚度为100nm的ZnO薄膜,发现Ag覆盖层的最佳厚度仅为8nm,此时双层薄膜相对于单层ZnO薄膜的发光增强因子η达到最大值8.1;同时还发现,在最佳Ag层厚度下,生长温度T≥300℃时生长Ag所获Ag/ZnO双层薄膜的ZnO发光强度比生长温度T≤200℃时生长的双层薄膜样品大一倍以上,η≈18.结合对双层薄膜表面形貌的测量,发现高生长温度下得到的双层薄膜样品的高η值可归因于高表面粗糙度导致高的外量子效率.

Ag/ZnO bilayer thin films are fabricated on Si substrates via two-step approach of ＂ZnO sputtering＋ Ag evaporation＂.The enhancement of the near band edge （NBE） emission of the ZnO film is realized through coupling between the surface plasmon resonating energy at Ag/ZnO interface and the photonic energy of ZnO NBE emission.The dependence of the emission enhancement ratio η of ZnO on the thickness and the growth temperature T of Ag cap-layers are investigated.By evaporating Ag（8 nm） cap-layer onto ZnO（100 nm） film at high substrate temperatures （T≥300℃）,the η value reaches about 18,i.e.,η≈18,which is more than twice that of Ag（8 nm）/ZnO（100 nm） bilayer films grown at low temperatures （T≤200℃）.It is found that the realization of the larger η can be ascribed to the bigger surface roughness of Ag/ZnO bilayer samples prepared under higher growth temperatures.