| Plasma technology has been widely used to modify the characteristics of materials asit can produce chemically active radicals. By means of plasma technology, materials withunique structures and surface characteristics can be fabricated, which can not be achievedby any other commercial technology. Plasma processing technology plays an extremelyimportant role in the world’s leading manufacturing industries. Application of lowtemperature plasmas has become one of the important scientific projects with globalinfluence, and has a huge impact on the development of high-tech economy as well as thetransformation of traditional industries.The low temperature plasma discharges used in industry are mostly produced by theelectromagnetic field excitation, such as Radio frequency (RF) discharge, microwavedischarge, etc. RF plasma discharges (frequency of1-500MHz) have the advantages overDC discharges of being able to work under low pressure (The plasma impedance decreaseswith the increase of frequency), effective ionization mechanism (The electrons can gainenergy in the whole cycle) and uniform spatial distribution. Meanwhile, RF plasmadischarges have the advantage over microwave discharges of possessing a cheap RF powersupply with a large power. The above characteristics make RF plasma become the mostpopular choice in industrial applications.In this thesis, depending on the existing plasma discharge systems, novel RF plasmadischarge system has been analyzed, designed and constructed. Meanwhile, relevantdischarge systems have been developed. The design concept has been realized and theexpected objectives have been achieved mainly in the following areas.(1) We have constructed and studied the Helicon Wave Plasma (HWP) dischargesystem with moderate magnetic fields (6300G), by which continuous and steady HWP discharge has been realized. The research of plasma characteristics has been carried outthrough diagnostic analysis, and further promotes the development of a novel plasmadiagnostic technique (magnetically insulated baffled probe). Preliminary experimentalresults have been obtained. Based on these researches, the discharge scheme on EAST withstrong magnetic field has been proposed, and the wall cleaning experiment on EAST hasbeen successfully carried out. Our research can provide valuable scientific reference forTokamak wall treatment with independent intellectual property rights.(2) For the first time, we have constructed and studied the multi-frequencycapacitively-combined inductively-coupled plasmas (ICP/CCP) discharge system, bywhich the ion energy, ionic flux and uniformity of the plasma can be manipulatedindependently. Parameters of dynamic balance in etching/deposition have been acquiredthrough research on fluorocarbon plasma etching/deposition on SiC, thus providingreference for the development of controllable etching/deposition techniques insemiconductors.Research on interactions between RF plasma and materials has been carried out, byselecting the materials corresponding to different discharge systems according to thecharacteristics of different discharge systems as well as particular requirements of materialprocessing. A series of research results has been obtained.1) Research on plasma discharge and material processing of novel magnetization RFplasmas has been carried out. Cleaning experiments aimed at wall materials graphite IVgroup has been conducted. The results show that the sruface of the samples withoutplasma treatment is of porous structure, large average size, and is adsorbed by a largenumber of small granular impurities. However, the sruface of the samples with HWPtreatment is of compact and tight structure, smaller average size, and is obvious inelimination of adsorbed granular impurities.The RF power supply, vacuum electrodes, matching network and antenna have beensuccessfully connected on EAST in Institute of Plasma Physics, Chinese Academy ofSciences. HWP discharge experiment has been carried out with antennas in various shapesand sizes, under different frequencies, powers, magnetic field and discharge pressures. Parameters of HWP have been diagnostic analyzed by Langmuir probe measurementsystem. The results show that the discharge threshold power is very low (<50W), andreflection power is zero. The plasmas excited by antenna5is of higher brightness anduniformity than the plasmas excited by other antennas. Moreover, the plasmas arrive thewall along the lines of magnetic force more easily after adding the poloidal field.2) Well-aligned Cr/Cu doped ZnO nanorod arrays were synthesized by the RF plasmadeposition method. The Zn0.94Cr0.06O nanorod arrays were aligned perpendicular to the Sisubstrate. The PL and O K-edge XANES analyses indicate the existence of numerous Znvacancies. No secondary phase in the sample is found within the XANES and HRTEMdetection limits. The saturated magnetization is1.16μBper Cr ion at650oC and decreaseswith decreasing substrate temperature. The Zn0.94Cr0.06O nanorod arrays exhibit obviousstable RT ferromagnetic ordering, which is believed to originate from the Zn vacancymediated BMP model. From first-principles calculations, we conclude that the Zn vacancycan be controlled to tune the ferromagnetism of the Zn0.94Cr0.06O nanorod arrays.The experimental results indicate the existence of numerous O vacancies and provideevidence for absence of any secondary phase or nanoclusters in Zn0.92Cu0.08O nanorods.The saturated magnetization was0.12μB/Cu at600oC and de-creases with decreasing thesubstrate temperature. Our results revealed that the interactions between substitutionalCuZnin a divalent charge and oxygen vacacy played an important role in the ferromagneticorigin of Zn0.92Cu0.08O nanorods.3) ICP/CCP nitrogen (N) plasma discharges were investigated to nitridize ultrathinHfO2films for leakage improvement. In terms of the plasma chemical and surfaceprocesses, nitridation samples show great improvements in surface structure and theleakage current property (it decreases from4.6×104to2.1×107A cm2), while theleakage current is independent of the morphology. By modulating the EEPFs depending onthe power levels of CCP and ICP, the radical concentration of the N atom increases by theelectron–neutrals collision dependence on the high-energy electron, resulting in more Natoms incorporated in HfO2films. The lower effective electron temperature and ion energywere obtained with ICP power, causing less film surface damage. Therefore, N atoms possess intrinsic effects that drastically reduce the electron leakage current through HfO2dielectrics by deactivating the oxygen vacancy related gap states.C4F8-based ICP/CCP was used to process6H-SiC substrates. By modulating themulti-frequency powers, the concentrations of F and fluorocarbon radicals are increased bythe collisions of electron-neutrals, which depend on high-energy electrons, resulting in ahigh Si selectively etching rate and a low fluorocarbon film deposition rate. The effects ofplasma parameters on the chemical compositions, and surface morphology properties ofSiC substrates are discussed in detail.4) Transparent conductive AZO films are prepared on quartz substrates bydual-ion-beam sputtering deposition at room temperature. The structural, electrical andoptical properties of AZO films are closely related to the assisting-ion beam energy. Withincreasing assisting-ion beam bombardment, AZO films have a strong improved crystallinequality and increased radiation damage such as oxygen vacancies and zinc interstitials. Thelowest resistivity of4.9×103Ω cm and highest transmittance of above85%in the visibleregion were obtained under the assisting-ion beam energy200eV.High-quality Hf1-xZrxO1-yNygate dielectric thin films are deposited by ion beamassisted deposition. The chemical compositions, thermal stability, surface morphology andoptical properties of Hf1-xZrxO1-yNyfilms are discussed in detail. EDS analyses confirmthat nitrogen is incorporated into Hf1-xZrxO1-yNyfilms effectively, the crystallizationtemperature of Hf1-xZrxO1-yNyfilms is above1100oC. |
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