Characteristic optimization of MWCNTs using MPCVD system

Microwave Plasma Chemical Vapor Deposition (MPCVD) method can be used to grow various kinds of diamond films and carbon nanotubes at various temperatures. However, it is usually only the hand-on experience that can be relied on to obtain the nearly satisfactory plasma in the MPCVD system. Therefore, this study set up the reflected power sensor as a reference parameter and used a CCD (Charge Coupled Device) to observe the plasma image. Manufacturing parameters, such as gas flow rate, input microwave power, working distance, deposition time, chamber pressure and substrate temperature, were all fixed to grow MWCNTs. The controlled adjustments, as the independent variables, are the positions of E-H tuner along x-axis and y-axis which directly affect the conditions of the plasma. In order to grow multiwalled carbon nanotubes (MWCNTs) of better quality with a self-assembled MPCVD system, the quality indexes of MWCNTs, which are the aspect ratio of MWCNTs and the I_D/I_G intensity ratio of the Raman spectrum of MWCNTs, were analyzed. With the established database, it is found that there exist the optimized positions of E-H tuner along x-axis and y-axis for growing MWCNTs of high quality. Moreover, we used PCA (Principle Component Analysis) method to analysis these data, and a relationship between manufacturing parameters was found.