In this paper, we model the evolution and self-assembly of randomly orientedcarbon nanotubes (CNTs), grown on a metallic substrate in the form of a thinfilm for field emission under diode configuration. Despite high output, thecurrent in such a thin film device often decays drastically. The present paperis focused on understanding this problem. A systematic, multiphysics basedmodelling approach is proposed. First, a nucleation coupled model fordegradation of the CNT thin film is derived, where the CNTs are assumed todecay by fragmentation and formation of clusters. The random orientation of theCNTs and the electromechanical interaction are then modeled to explain theself-assembly. The degraded state of the CNTs and the electromechanical forceare employed to update the orientation of the CNTs. Field emission current atthe device scale is finally obtained by using the Fowler-Nordheim equation andintegration over the computational cell surfaces on the anode side. Thesimulated results are in close agreement with the experimental results. Basedon the developed model, numerical simulations aimed at understanding theeffects of various geometric parameters and their statistical features on thedevice current history are reported.
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