MODEL CALCULATION OF FIELD ENHANCEMENT FACTOR OF CNTS HAVING CONICAL TIP TAKING INTO ACCOUNT THE SHIELDING EFFECT

Abstract

This thesis presents a method to compute the field enhancement factor of individual CNT with conical tip and the field enhancement of the same CNT when placed in a cluster of CNTs under any position distribution using mirror method and taking into account the image charge. When the CNT is present in a group of CNTs the shielding effect comes into picture and this shielding effect depends upon length and the spacing between the CNTs.We have derived expressions for field enhancement factor with and without taking into account the screening effect. The variation of the field enhancement factor with the sharpness of the tip is shown. Later we have shown the comparisons with the experimental and theoretical results of the CNTs having hemispherical tip and it was found that the field enhancement factor of the CNTs having conical tip is higher than that of the hemispherical tip, thus offering a better field emission.