Spectroscopic Study On The Interactions Between Pulsed-Laser-ablation-produced Plasma And ECR Plasma

The subject investigated in this thesis is the plasma produced from pulsed laser ablation of solid target and the plasma produced from electron cyclotron resonance discharge in gases.The characteristics,including the temporal and spatial evolution behaviors,of the two types of plasmas and their interactions were studied by means of optical emission spectroscopy.The work includes two parts:ECR nitrogen plasma and PLA-produced aluminum plasma and their interactions;ECR nitrogen plasma and PLA-produced boron-carbon plasma and their interactions.Recently,pulsed laser ablation has achieved many successful applications,such as pulsed laser deposition(PLD),element analysis and micro-manufacturing.The PLD methods have already been successfully applied in the fabrication of varies kinds of functional thin films such as semiconductor films,high-T_c superconductor films, ferroelectrics films and piezoelectric films.Plasmas with high degree of ionization and high purity can be produced by Electron cyclotron resonance microwave discharge at low working pressures.The hybrid plasma produced from simultaneous ECR and PLA processes combines the characteristics of both ECR plasma and PLA plasma,which could achieve unique effects in thin film deposition.For example,ECR plasma aided PLD is a promising technique for preparing thin films,which has many successful applications.In this thesis,the components,temporal and spatial evolution of the hybrid plasma during the ECR-PLD process for fabricating AlN and BCN thin films were spectroscopicly studied.The excitation processes between those two types of plasmas and the mechanism responsible for the successful film deposition were discussed.By means of the ECR-PLD method with pulsed laser ablation of an aluminum target in the environment of ECR nitrogen plasma,we have prepared high-quality AlN thin films.In this thesis,optical emission spectra and their temporal and spatial evolution of the laser-ablation produced Al plume from an aluminum target and the ECR nitrogen plasma were studied.By comparing the differences in the evolution behaviors of the emission lines from Al atoms,Al ions,nitrogen molecules and nitrogen molecular ions in vacuum,N₂ and ECR N₂ environment,we attempted to understand the interactions and excitation processes between PLA plasma and ECR plasma and the mechanism responsible for the high-quality film preparation by ECR-PLD technique.We found that the optical spectra from the ECR nitrogen plasma are abundant in emissions from nitrogen molecules and nitrogen molecular ions.In vacuum,Al atoms and Al ions share the same single-peak temporal behaviors but the velocity of Al ions is faster.In nitrogen,the temporal behaviors of Al atoms and Al ions and the intensity of the emission lines from Al atoms have no significant change but the intensity of Al ions lines decreases.The introduction of the ECR microwave discharge has no obvious effect on Al ions but it enhances the emissions from Al atoms as well as changes the temporal behavior of Al atoms from single-peak to double-peak.Otherwise,the species in the background environment have also been influenced by the Al plume.We observed the similar temporal characteristics between the Al ions lines and the emissions from nitrogen molecular ions when the Al plume expanded through the nitrogen gas.In ECR plasma,the intensity of the emission lines from nitrogen molecular ions increases and their temporal characteristic turns to be double-peak,while the first peak coincides with the single peak of Al ions lines and the second one coincides with the behaviors of the second peak of Al atoms in ECR nitrogen environment.The results above show the existence of plentiful processes of energy exchange between the two types of plasmas when the PLA Al plasma expands though the ECR nitrogen plasma,which make the Al ions recombined,and the Al atoms excited.At the same time,the species in background environment becomes more active due to the collisions between the plume and the background gas or ECR plasma.In conclusion,we consider in the hybrid plasma the existence of the active particles,such as Al atoms,Al ions,nitrogen molecules and nitrogen molecular ions, as the key factor for the successful preparation of AlN thin films by ECR-PLD method.In this thesis,we also presented spectroscopic study on the ECR-PLD process of BCN films deposition.The temporal and spatial evolution of the optical emission spectrum of the hybrid plasma when the PLA boron-carbon plasma expands through the ECR nitrogen plasma has been investigated.The temporal and spatial behaviors of the emission lines from boron atoms,boron ions,carbon atoms and nitrogen molecular ions in vacuum,N₂ and ECR N₂ environment have been discussed.We found that the ECR microwave discharge had no obvious effect on both boron and carbon atoms and ions emission lines.At the same time,the emission bands from nitrogen molecular ions excited by the PLA boron-carbon plasma in nitrogen gas or ECR nitrogen plasma environment have been observed.Although the intensity of N₂⁺ emission lines in ECR N₂ environment is close to the one in N₂ environment,its duration time has been extended,which means the existence of PLA plume provides a more active environment and facilitates the reaction of carbon atoms and boron atoms with nitrogen molecules during the film deposition process.It could be the reason why high-quality BCN films have been prepared by ECR-PLD method.