Pillar Height Dependence of Field-Emission Properties in an Array of Carbon Nanotube Pillars

Carbon nanotube pillars with optimal field-emission properties, including a high field enhancement factor $\beta$ of 5384 and a low turn-on field $E_{\text{to}}$ of 0.84 V/μm, have been achieved when the ratio of interpillar spacing to pillar height is 2. However, when this ratio exceeds 2, the field enhancement factor increases with increasing pillar height since the field can be enhanced by increasing the aspect ratio. When the ratio is smaller than 2, the field enhancement factor decreases with increasing pillar height owing to the increased field-screening effect. A simulation has been performed to verify the experimental results.