多孔硅可见光发射研究

用常规电化学方法制备了发射高效可见光的多孔硅样品。对样品进行了光谱研究。用非化学方法从样品表面得到了粉末状荧光物质(非多孔硅膜研磨产物),光谱测定证实它的光致发光光谱与原多孔硅样品光致发光光谱相同,粉末进一步研磨后仍能发出同样的可见光。多孔硅样品还可以实现阴极射线激发发出同样的高效可见光,但易因电子束的轰击而发光强度较快减弱。用扫描电镜(SEM)对多孔硅样品的形貌、结构、荧光粉末的形状、尺寸、多孔硅样品阴极荧光发射区域进行了系统的研究。实验结果表明多孔硅样品一般可分为三层结构:表面层、多孔层和单晶硅衬底,样品荧光是来源于其表面层的。对样品表层组分的x射线光电子谱(XPS)分析表明,此时的多孔硅表层有大量非硅元素存在,如:C、O、F(没考虑H),硅元素的原子个数比只占30％～50％。用同样的电化学方法在单晶硅未抛光面上和多晶硅未抛光面上制得了均匀发射可见光样品。上述实验结果说明,多孔硅的高效可见光发射是来源于样品制备过程中在其表面层中形成的粉末状荧光物质。

Study of the Visible Light from Porous Silicon

The porous silicon emitting visible light is made by the standard method of anodic oxidation. The sample is studied using photoluminescence (PL). A kind of powder—like fluorescent material is nonchemically obtained from the surface of the sample. The fluorescent powder shows the same PL spectrum as that of the porous silicon and it still emits the same efficient light after further grinding. The porous silicon can also emit the same efficient visible light with the excitation of electron beam. But the intensity of cathodeluminescence (CL) will fade away with the excitation of the electron beam. The morphology and microstructure of porous silicon, the powder morphology and size of fluorescent powder and the source of the CL from porous silicon were studied by scanning electron microscopy (SEM). The experiments show that the porous silicon is composed of three separate layers: surface layer, porous layer arid single crystalline silicon substrate. The fluorescence is exactly from surface layer. The x-ray photoelectron spectroscopy (XPS) shows that the surface layer is composed of many kinds of elements, such as Si, C, O, F and so on. The Si content is only 30％～50％ (H is not counted in). The homogeneous visible light emitting samples are also fabricated on the unpolished surfaces of single crystalline silicon and polycrystalline silicon. All the results above-mentioned suggest that the efficient visible light of porous silicon is from the powder-like fluorescent material produced in the process of anodization.