Ag-BaO薄膜在垂直表面电场作用下的光吸收增强

Enhanced Photoabsorption of Ag-BaO Thin Films with Applied Vertical Electric Field on the Surface

Ag BaO薄膜是金属纳米微粒埋藏于半导体介质中的功能复合薄膜 ,它具有超快的光电时间响应 ,可以检测超短激光脉冲 ,在Ag BaO薄膜表面加入垂直电场 ,可以提高薄膜的光电发射效率 ,在垂直表面电场作用下近紫外波段光吸收有较明显增强现象 ,在波长λ =3 0 3nm处 1 5V电压作用下光吸收增强 6 5% ,3 0V电压作用下增强 1 8%。这种光吸收增强是由于在电场作用下 ,薄膜的能带结构发生倾斜 ,以及在强电场下能级分裂。光吸收涉及被激发电子在倾斜能带间隧穿几率的增加 ,和被激发电子在这些分裂能级间的跃迁。

The Ag BaO are composite thin films in which metallic nanoparticles are embedded in semiconductor matrixes.It has an ultrafast response time of photoemission and can be used for detecting ultrashort duration laser pulses.After applying a vertical electric field on the surface of thin films,the efficiency of photoemission can be increased.The Ag BaO thin films were prepared by vacuum evaporation.The total thickness of thin film was 200～300nm,but the thickness of the Ag BaO thin films was 100～140nm which got rid of the thickness of the above and bottom electrodes.The thin films presented obvious enhanced photoabsorption in the near ultraviolet region when a vertical electric field was applied to the surface of the thin films.The photoabsorption at wavelength λ =303nm was increased by 6 5% and 18% stimulated by vertical voltage 15V and 30V on the surface,respectively.The reason of enhanced photoabsorption is that the energy band of thin film becomes oblique and split under the application of a strong electric field.Through absorbing the energy of photons,excited electrons trend to increase the probability for tunneling in oblique energy band and for transition between split energy levels.