Scanning Tunneling Microscopy Tip Induced Luminescence Of Si(111)-(7×7) Surface And Its Enhancement

It is essential to develop the optoelectronic devices with high information storage density and fast transmission speed to adopt the explosive growth of information.Silicon has great potential in the application of optoelectronic devices.The main difficulty is that silicon,which is an indirect band gap semiconductor,has low luminous efficiency.If the issue that low luminous efficiency of silicon-based light-emitting devices could be effectively solved,the application of ideal and low-cost silicon materials will lead to significant breakthroughs in optoelectronic information technology.In this paper,the highly localized tunneling current excited luminescence of Si(111)-(7×7)surface in the tunnel junction of scanning tunneling microscope(STM)and the enhancement effect of localized surface plasmon of silver metal on luminescence of Si(111)surface were studied.The main contents are as follows:The STM excited luminescence(STML)characteristics of a clean and undamaged Si(111)-(7×7)surface were studied by using a silver tip that with high luminous efficiency,and the luminescence with energy at 1.85 e V was detected,which came from the inherent transition of Si(111)-(7×7)surface,and the STML spectrum shape was independent with the polarity of the excitation voltage.On the damaged Si(111)-(7×7)surface with a defect diameter of about 2 nm,the measured STML spectrum was obviously different from the luminescence spectrum at the undamaged surface,which indicates that the existence of the surface defect will have impact on the optical properties of the surface,showing that the STML is very sensitive to surface conditions.The concept of luminescence enhancement effect of LSP was introduced,and the luminescence characteristics of LSP of different layers of silver islands on the Si(111)3^1/2×3^1/2-Ag surface were studied.Subsequently,two atomic-layer thick silver islands were deposited on a clean Si(111)-(7×7)surface,we found that the LSP of the silver islands have a significant enhancement effect on the luminescence of the Si(111)-(7×7)surface.And the STM excited luminescence(STML)spectrum on Ag island has similar properties to the LSP resonant radiation decay of Ag(111)single crystal.As the excitation voltage increases,the number of peaks on STML spectra increases and then remains unchanged,while the luminescence intensity increased first and then decrease with the voltage increasing.It is the coupling between the LSP of the silver island and the silicon surface that makes the light emission of silicon surface significantly enhanced.