Carbon Nanotube Thin Film Field Emitting Diode: Understanding the System Response Based on Multiphysics Modeling

TL;DR

This paper presents a multiphysics model of carbon nanotube thin film field emitters, explaining degradation, self-assembly, and current decay, with simulations matching experimental data and exploring parameter effects.

Contribution

It introduces a comprehensive multiphysics modeling framework for CNT thin film emitters, including degradation, self-assembly, and current prediction, advancing understanding of device behavior.

Findings

Model accurately predicts current decay in CNT films.

Degradation involves CNT fragmentation and clustering.

Device geometry significantly affects emission current.

Abstract

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