Research On Structure And Property Of Si-Based Films Using Magnetron Sputtering

Silicon-based films can emit visible light and exhibit novel optoelectronic properties and special structure.It shows high potential on light-emitting devices,photodetector, optoelectronic devices and sensor.If the silicon-based films have a favorable luminescence properties in visible light,this important semiconductor will be the basic material in the next generation of the electronics.The aim of this paper is to study the surface topography, microstructure and PL characterization of silicon-based films.The result is available not only preparing the certain silicon-based films,but also for studying the luminescence mechanism further.On the basis of reviewing the development of silicon-based films,different types of Ge/Si nanomultilayers,Si/SiO₂ superlattices,Sn embedded in SiO₂ film have been successfully prepared by magnetron sputtering and subsequently thermal annealed in an Ar atmosphere at a temperature of more than 500℃.The surface topography and microstructure of the nanomultilayers are characterized by X-ray diffraction,Raman spectrometry,SEM.When the substrate is at room temperature,the as-deposited Ge/Si nanomultilayers are amorphous.However,the amorphous phase transforms to crystalline phase when the deposition temperature is 300℃.The surface of the as-deposited nanomultilayers is compact and smooth when the sputtering power is 100 W.The distribution of the grain size is uniform,and the grain size is estimated to be 25 nm.When the annealing temperature is 500℃,the Ge/Si nanomultilayers transform into GeSi alloy.For the sample annealed at 800℃,nanocrystals consisted of pure Ge and pure Si without Ge-Si alloying is present. The as-deposited Si/SiO₂ superlattices show the features of amorphous silicon.The surface of the as-deposited Si/SiO₂ superlattices is compact and smooth,and the distribution of grain size estimated to be 20 nm is uniform.For Si/SiO₂ superlattices annealed at 1100℃,the Si sublayer sandwiched between potential barriers SiO₂ is crystalline structure.The visible PL peak accompanying to a blueshifl with the decrease of Si sublayer thickness has been observed,and the intensity of this peak enhances with the increase of annealing temperature.The visible luminescence properties of Si/SiO₂ multilayers can be ascribed to quantum confinement of electron-hole pairs.in quantum wells with grain size lower than 4.5 nm.In Si/SiO₂ superlattices,not only quantum confinement but also Si-SiO₂ interface states play an important role in the optical transition. The PL peak located 779 nm is independent of the thickness of Si sublayer,so it may be ascribed to interface mediated transition.Typical Si dangling bonds defect could be a dominating obstacle to high luminescence efficiencies.Sn nanocrystals embedded into SiO₂ matrix have been prepared by magnetron co-sputtering of Sn-Si,SiO₂ targets.The results of Raman spectra and XRD show that crystallization has taken place in the composite films after annealing and a part of amorphous Sn has been changed intoβ-Sn,which may nucleate into Sn nanocrystals embedded in SiO₂ matrix.It have been demonstrated the presence ofβ-Sn and SnO phases in the sample,which indicates Sn was partially oxidized during co-sputtering process forming SnO shells around the large Sn nanocrystals.Also,the SEM images also indicated the size of Sn nanocrystals increased with increasing annealing temperature.Two intense PL peaks at about 336nm and 440nm were observed.The PL peak located at 440nm was mainly caused by the quantum confinement,which has a blue-shift as the annealing temperature increases.It is also found that the PL peak located at about 336nm was originated from luminescence centers related to Sn-O defect level.