| Discharge characteristics of DC glow plasma was investigated in this paper and preparation technology of carbon nanotubc was established.We stuch the prepared carbon nanotube with Scanning Electronic Microscope(SEM) as well as Transmission Electron Microscope(TEM) and Raman spectrum, we have study effect of technology condition for growth feature of carbon nanotube.1 Characteristics of dischargeCharacteristics of DC glow discharge at high press were researched, the glow appears at low pressure, the discharge region were composed of four zones with the gas pressure increasing: cathode-glow layer, Faraday dull area, sphere of plasma, and anode-glow layer. Discharge status of each zone was investigated, the cathode-glow layer was the main zone of potential fall, the vest electron with low energy exist in this zone, the gas could not be excited and ionized by electron. In Faraday dull area. the electron energy was low, the elastic collision was dominated among electron and particles, the plasma sphere was the main zone of exciting and ionizing particles, the electrode distant was a great factor to affect the glow state, the plasma sphere disappear when the electrode distant was decreased to certain distance, the longitudinal direction size of plasma sphere increasing with the electrode distant promoting, the across direction size of plasma was invariant. This discharge feature is very important to deposited carbon nanotube.We investigated the relationship between the electrode distant and discharge voltage, discharge voltage take on liner increasing with the electrode distant increasing. When DC discharge current was low at high pressure, the voltage increasing fast with current increasing, but discharge voltage could reach saturation state when discharge current reach to certain value. The gas pressure was more high, the current corresponding to saturation discharge was more low.2 The establishment of preparation technology of carbon nanotube E.lectrode distance was a great factor to affect discharge feature, we utilized this feature to established preparation technology of carbon nanotube at high pressure, the aurum-nickel membrane serve as catalyst, the compound gas of methane and hydrogen were carbon sources gas. The glow was appears at low pressure, the electrode distant was keep to 5mm. no plasma exist in this state. When gas pressure and methane concentration reach to prearrange experimental value, the electrode distant was increasing to 25mm. the plasma sphere appears, the carbon nanotube could be prepared in this state. The preparation technology of parameter range was investigated. We have compared the preparation condition of diamond film with that of carbon nanotube.The growth study of carbon nanotube on multi-species substrate indicated that carbon nanotube can not be deposited on pure nickel membrane. When the thickness of nickel membrane exceed 80nm and aurum membrane exceed 60nm. there was no carbon nanotube deposited on substrate. In the condition of aurum membrane s thickness was 40nm and nickel membrane s thickness was 20nm. 40nm. 60nm respectively. The carbon nanotube could be prepared.3 SEM was employed to analyze the influences of substrate temperature, reaction pressure, components of reaction gases and thickness ratio of Au film to Ni film on the CNTs" growth feature.(1) The effect of substrate temperature for the growth feature of carbon nanotubeCNTs were not obtained at 500°C and 900°C ; a few CNTs of low density were prepared at 600°C; long and dense CNTs with homogenous diameter grew at 700°C;while, at 800°C. it can be seen obviously that the CNTs of bigger diameter and lower density congregated together owning to the high substrate temperature. The temperature range of preparing CNTs was from 600°C to 800°C. 700°C is the best deposited temperature.( 2 ) The effect of reaction pressure for the growth feature of carbon nanotubeThe diameter of CNTs are different at the different gas pressure which was range from 60torr to 90torr. while it is homogenous at 75torr. Further more, at 90torr. thick CNTs are more than thin ones and they twist and transversely connect together.( 3 ) The effect of methane concentration for the growth featureof carbon nanotubeThe CNTs. only a few of which have branches, have homogenous diameter when the methane concentration is 8% and 12%. Yet. the diameter increased obviously when methane concentration was 16%. When methane concentration rose to 20%. it can be seen that thin CNT grew on thick CNT. which is called branch, and the diameter is non-homogenous.(4) The effect of thickness of the catalyst membrane for the growth feature of carbon nanotube.The diameter of CNTs are different corresponding to different thickness of catalyst layer. The diameter increased along with the increasing of the thickness.4, tudy of CNTs by TEMIn the condition of methane concentration variety only, the TEM observation indicated that the carbon nanotube with homoueneous diameter is obtained and it is 20nm when methane concentration was 5%. in the condition of methane concentration was 20%. the diameter of carbon nanotube is 80nm. and the nanotube diameter is non-homogeneous, the diameter of ihin nanotube is 20nm.The diameter of carbon nanotube is 30nm and 50nm when the substrate temperature was600°C , 700°C and 800°C respectively. In the condition of methane concentration is 10% and reaction gas pressure was 70 torr and 90 torn the diameter of carbon nanotube is 30nm and 50nm respectively.The diameter of carbon nanotube become non-homogeneous and the diameter of carbon nanotube increased gradually with the methane concentration increasing as well as substrate temperature and reaction gas pressure increasing.From TEM images, it can be seen that the CNTs with non-homogenous diameter have branch structure and. at the junction, they are Y-shaped. The angles of branches possess both acute angle and obtuse angle, the bamboo-liked carbon nanotube was observed in the TEM images. Compared with other preparation method of carbon nanotube. our method possess the characteristics of simple technology and shorter deposited time.5, Field emission properties of CNTsField emission properties of CNTs deposited with different growth parameters were studied. The results show that the threshold field voltage is about 1.8V/u.m.The craft condition to the threshold field voltage influence little,generally the emission current density approaches mA magnitude. Compare with stands erect array CNTs deposited with the other methed the field emission properties differs a magnitude.When the methane density is 8%. pressure is 70torr. thesubstrate temperature 700°C. field emission properties of CNTs is better.In brief.it is one new way to study the field emission properties of CNTs deposited with DC- PCVD method. The advantage of this method is that CNTs deposit quickly and craft is simple. But CNTs growth is random, not formed the neal array, this affect the field emission propertie of CNTs.if prepares high quality array CNTs. also needs further to optimize the craft.
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