film grain size meaning in English

胶片颗粒大小

We also have analyzed the photoluminescence ( pl ) spectra of some zno films , it turns out that the emission of ultraviolet light comes from the radiative recombination of excitons within nano - crystal energy band - gap , and the pl peaks move to smaller wavelength because zn are substituted by fe , co , and cu , which cause the size of the film grains smaller and the effective band - gap bigger . the red emission of zno films is due to , on the one hand , decrease of the film grains size which causes the emission intensity smaller and smaller until it disappears abruptly , on the other hand , the transition of electrons from deep donor level of the oxygen vacancies to the valence band
另外，我们还对薄膜光致发光性质进行了分析和研究，结果表明：纳米结构zno薄膜的紫外发光来源于带间激子的辐射复合发光， pl谱的带边发射峰发生蓝移是由于fe 、 co 、 cu对zn的替代使薄膜粒子的尺寸减小，使薄膜的有效带隙增宽； zno薄膜的红色发光，一方面是zno颗粒尺寸的减少，带间的激子发射峰越来越弱直至猝灭，另一方面主要是与zno晶格中的o空位有关，由深能级复合发光引起红光发射。