Study Of High Gas Pressure DC Glow Discharge And Characteristics And Applications Of Thick Diamond Films Synthesized By Plasma CVD

Diamond films with high quality were synthesized by high gas pressure andhigh electric current DC glow discharge plasma chemical vapor deposition.Diamond films with this method have high growth rate. There are great differencesbetween DC glow discharge at high gas pressure and at low gas pressure. Thecharacteristics of DC glow discharge at high pressure were researched in this thesis.The technics of DC glow discharge at high pressure were optimized. Growthcharacteristics of diamond films and technology of making diamond film tools werestudied. Growth techniques of diamond films with high thermal conductivity andhigh abrasiveness ratio were set up. The followings are the main contents of thisthese: 1. Characteristics of discharge Characteristics of DC glow discharge at high gas pressure were researched.There are four parts in the region of discharge: cathode-glow, Faraday dull area,sphere of plasma and anode-glow. The situation of different discharge parts wasstudied: original electrons come from thermal electron emission and γ process. A lotof electrons appear when original electrons and gas particles collide, and at thesame time gas was ionized. Cathode-glow covers cathode, and its area increaseswith discharge current increasing or gas pressure decreasing. Energy of electrons inthe Faraday dull area is low. Most collisions between electrons and other particlesare elastic, and energy of electrons increases gradually in the course of moving tothe anode. Thickness of Faraday dull area is correlative with the category ofdischarge gas. Sphere of plasma is main region of gas excitation and ionization. Itscolor, size and shape depend on gas category, gas density, gas pressure anddischarge current, size proportion and space between cathode and anode. We haveacquired the relations of various discharge parameters that discharge voltageincreases with gas pressure increasing as well as space between cathode and anode.Voltage saturation appears in the course of electric current increasing. Resistancebetween two electrodes decreases with the current increasing. It indicates that thenumber of the electrification particles increases as current increases. The factors, which can predominate the stability of high gas pressure DC glowdischarge such as cathode and power supply, were investigated in this paper.According to the principle of capacitance- inductance transformer, we developedpower supply which is suited for high pressure DC glow discharge. The powersupply can accord with the requirement of high gas pressure DC glow discharge. 1282. The growth characteristics of thick diamond films Growth rate of diamond films, surface figure, crystal boundary, quality,distribution of thickness, micro-crack and split have been researched in this paper. Discharge current and gas flux have a great impact on growth rate of diamondfilms. Diamond films were deposited by employing methane, acetone, ethanol aswell as the compounds of methane and methanol, and growth rate of diamond filmswas studied. The growth rate of diamond films increases when carbon-source gasincreases. Diamond phase is restrained because of graphite phase being depositedheavily on the diamond surface when carbon-source gas reached to a curtainamount. Meanwhile, graphite is etched rapidly, leading to the decreasing of thegrowth rate of diamond films. And growth rate maximum, which depends on thecategories of carbon-source gas, appears with flow rate increasing. The maximumof growth rate will increase if we have appended oxygenous carbon-source gasproperly, but the growth rate will decrease obviously when oxygen flow rate excess.The maximum of growth rate appears with discharge current increasing as well ascarbonaceous gas flow rate increasing. The growth rate will increase with gaspressure increasing. Substrate temperature influences the growth rate evidently. It isbeneficial to increase the growth rate of di...