Composite Thin Films Of Nano Si-sin_x Light And Nonlinear Optical Properties

The Si-based semiconductor material is one of the most important fundamental materials in electronic technology and information technology areas. Recently, the studies of the photon devices which based on silicon material and even how to achieve the optoelectronics integrated circuit (OEIC) have already become an very important topic concering the development of optoelectronics.In many kind of Si-based semiconductor materials, Silicon nitride is a typical material and its films as passive and insular are widely used in Si devices and integrated circuits. So fabrication of nanocrystal-silicon-embedded silicon nitride(nc-Si/SiNx) thin films composite materials and their optoelectronic properties are important parts of the popular subject in developing Si-based optoelectronic integration.The nc-Si/SiNx composite films were prepared by r. f. magnetron reaction sputtering technique and thermal annealing. The composition,structure,bond formation and optical band gap of the films were characterized by Energy dispersive spectrometer(EDS), Infrared spectroscopy(IR),X-ray diffraction(XRD),Scanning electron microscopy(SEM), Atomic force microscopy(AFM) and Ultraviolet-visible absorption spectroscopy(UV-VIS). The study indicated that the properties of the materials are badly influenced by preparation process.We have studied the photoluminescence (PL) properties of the nc-Si/SiNx composite films. A serial of intense PL bands in 350-900nm range were observed from the films at room temperature, and ascribed to the defects in silicon nitride layers and silicon nanocrystals. To sum up, the energy gap states model and quantum confinement model have priority in explaining the origin and mechanism of PL in nc-Si/SiNx composite films.For the first time ,the nonlinear optical properties of nc-Si/SiNx composite films were investigated by using single beam Z-scan technique with a picosecond pulses laser.At 1064nm and 532nm,the third-order nonlinear optical refractive index and nonlinear absorption coefficient were both enhanced, then theχ(3)were estimated to be on the order of 10-9esu respectively. This was due to the quantum confinement effect.For the first time, we prepared the nc-Si/SiNx composite films on single crystal silicon by radio frequency magnetron reaction sputtering technique and thermal annealing. In the experiment, these samples were inserted as saturable absorber into the resonator, concave-flat cavity was adopted and Nd:YAG was pumped by a xenon lamp,and the Q-switched waveform of 19 ns single pulse width was obtained at repetition rate of 1 HZ . Furthermore , the influence of structural characteristic,pump voltage and cavity length on the properties of laser output was investigated. Then ,these phenomena observed in the experiment was analyzed and discussed which was based on the theory of passively Q-switched. The passive Q-switch characteristic of the films is mainly due to two photon absorption in the nano-silicon-embedded silicon nitride films.