A STUDY ON SENSITIZATION OF INFRARED EMISSION FROM Yb AND Er CO-DOPED NANOCRYSTALLINE Si THIN FILMS

本文研究了Er~(2+)&lt；~(3+)&Gt~(2+)离子4f壳层内跃迁对1.54μm光致发光的敏化。采用激光烧蚀法制备了掺Yb纳米晶Si(nc-Si：Yb)、掺Er纳米晶Si(nc-Si：Er)以及掺Yb和Er共掺纳米晶Si(nc-Si：YbEr)薄膜。在Ar激光(488 Nm)激发下，测量了这些样品的光致发光。在Nc-Si：Yb薄膜中观察到了0.980μm(Yb^&lt；5/2&gt；到^2F_&lt；7/2&gt；跃迁)的尖锐发射。在Nc-Si：Er薄膜中检测到了0.984μm发射(Er~(3+)~(3+))和1.535μm发射(~^4I~~(13/2)~^4I~~(15/2))。结果表明，Yb^&lt；3+&gt；离子和Er^&lt；3+&gt；离子由于光致载流子的作用通过能量传递过程被激发，并且^4F_&lt；5/2&gt；能级位于比^4I_&lt；13/2&gt；能级高约5 meV的能级。因此，在nc-Si：YbEr薄膜中，由于作为Yb^4i&lt；15/2&gt；3+&gt；2μ^4i&lt；13/2&gt；2→^4i&lt；13/2&gt；2→^4i&lt；15/2&gt；→^4i&lt；13/2&gt；3+&gt；离子级联去激过程的最后一步，预期与Er有关的1.54 Tm发射会得到增强。在nc-Si：YbEr薄膜中观察到约3倍的Er相关1.54μm发射强度的敏化。为了获得最佳的敏化效果，需要对系统的Yb掺杂水平进行详细的研究。

A sensitization of photoluminescence at 1.54 μm originating from the intra-4f shell transition in Er^<3+> ions has been investigated in this research. Yb doped nanocrystalline Si (nc-Si:Yb), Er doped nanocrystalline Si (nc-Si:Er), and Yb and Er co-doped nanocrystalline Si (nc-Si:YbEr) thin films have been fabricated on Si substrate using laser ablation. The photoluminescence from these samples, was measured under the host excitation of Ar laser line (488 nm). Sharp emission at 0.980 μm (^2F_<5/2> to ^2F_<7/2> transition in Yb^<3+> ions) was observed in nc-Si:Yb thin films. The 0.984 μm emission (^4I_<11/2> to ^4I_<15/2> transition in Er^<3+> ions) and 1.535 μm emission (^4I_<13/2> to ^4I_<15/2> transition in Er^<3+> ions) were detected in nc-Si:Er thin films. This result indicates that the Yb^<3+> ions and Er^<3+> ions are excited through an energy transfer process due to the photo-induced carriers in the host nc-Si thin films, and the ^4F_<5/2> level is in located higher energy side by about 5 meV than ^4I_<13/2> level. Therefore, it is expected in nc-Si:YbEr thin films that Er-related 1.54 μm emission as the last step of cascaded de-excitation process of the ^2F_<5/2> → ^4I_<11/2> → ^4I_<13/2>2 → ^4I_<15/2> transitions is enhanced due to playing as the sensitizer of the Yb^<3+> ions introduced. Indeed, about 3 times sensitization on the Er-related 1.54 μm emission intensity was observed in nc-Si:YbEr thin films. Details of the I investigation on the systematical Yb doping level are required for the optimum sensitization.