The Investigation On Deposition And Photoluminescent Characters Of Si/SiO_x Nano Particle-Based Films By Plasma Vapor Deposition

Silicon is one of the most popular semi-conduct materials in the world, and it has ideal optic-electron characters and existing production engineering. While silicon is indirect-gap materials, so the transition probability and luminescent efficiency are low. Si-base photoluminescence is always the most important problem in Si optoelectronic integrated circuit.In 1990, L.T.Canham discovered that porous Silicon would emit violent visible light at room temperature for the first time, which emitting energy was more than band gap in bulk Silicon. However, it is still challenge to explore a new preparation method, Since the investigation on nano Si-based photoluminescent films would be the focus all the time. Since existing preparation methods in chemical solution couldn't satisfy the requirement of IC industry. Nano Si-based photoluminescent films made by plasma enhanced vapor deposition, especially at near-atmosphere, have remarkably better and tailorable characters in photoluminescence. The dissertation primarily aim near-atmosphere plasma vapor synthesis of nano Si-based films with emphasis on the control of morphology, structure and chemical composition and their optical properties of the obtained materials by plasma parameters. We attempt to deposit nanocrystalline silicon embedded in silica films presenting photoluminescence by plasma jet in low pressure. The research work presented can be categorized into three parts:Part I:Characterization of dischargeDuring near atmosphere pressure plasma deposition precesses, plasma parameters are closed to the growth of film. It also has great impact on the morphology, chemical structure composition and their optical properties of nano Si-based films. The discharge characters in Chapter 3 and Chapter 4 are investigated with electrical measurements and numerical simulation. The measured waveforms of applied voltage and discharge current suggest that the discharge show multi-current-peak discharge in near atmosphere by comb-like electrodes, and uniformity of discharge would improve with applied voltage; Plasma jet in low pressure just like glow discharge, and turn-on voltage decreased sharply compared comb-like electrodes, moreover uniformity of discharge increased with RF power. The reaction and dynamic process of monomer in the plasma phase can be easily controlled. Emission spectrum revealed electron temperature was less than leV in comb-shape electrodes and 1.6eV in plasma jet. PIC model was used to simulate electric field and potential distribution when bias voltage was applied. Simulated results indicated the physical parameters were different after and before bias voltage applied, so we could adjust structure and character of films by bias voltage.Part II:Fabrication and manipulation of morphology, structure and chemical composition of nano Si-based filmsNano Si-based films and nanocrystalline silicon embedded in silica films with different morphology, structure and chemical composition were synthesized by a comb-like near atmospheric pressure plasma and a plasma jet in low pressure in Chapter 5. SEM, TEM and FESEM showed the films in near atmospheric pressure were puff and porous, compact in low pressure. FTIR, EDS, LAMAN and XPS revealed that Si-O-Si increased with applied bias voltage in comb-like near atmospheric pressure plasma. In low bias voltage, few Si-Si emerged and Si-H decreased with the increase of bias voltage and duty cycle. Si nanocrystalline appeared in higher RF power and plasma jet.Partâ…¢:Optical properties and luminescence mechanism of nano Si-base photoluminescent filmsPhotoluminescence(PL) and Cathodoluminescence(CL) of nano Si-base photoluminescent films were discussed in Chapter 6. The films deposited by comb-like near atmosphere plasma emitted blue visible light, the PL and CL peaks were invariable in position while increased in intensity. Cathodoluminescence appeared a new peak under high duty cycle of bias voltage. Photoluminescence would blue-shift after annealing. PL of nanocrystalline silicon embedded in silica films also displayed blue-shift, and decreased with RF power in intensity. The analysis of luminescence mechanism in Chapter 7 concluded that Quantum Confinement effect, Quantum Confinement/Luminescence Centers, and H-related Luminescence Groups were explained the reasons of three luminescence peaks, divided from PL.