利用胶体小球掩蔽刻蚀技术制备的半导体纳米阵列的场电子发射特性

Electron Field Emission Characteristics from Single-crystal Silicon Nanoarrays Fabricated by Direct Lithography with Nanosphere Mask

利用胶体小球掩蔽刻蚀技术,制备了单晶硅纳米阵列,利用原子力显微镜观察了硅阵列的表面形貌,实验结果表明,硅柱阵列具有高密度和较好的均匀性。同时研究了单晶硅纳米阵列的场电子发射特性。为了提高样品的场发射性能,在所制备的单晶硅有序纳米阵列上生长了一层非晶碳薄膜。与单晶纳米硅柱阵列相比,覆盖有非晶碳膜的样品的场电子发射特性有了明显的改善,表现在场发射的开启电场下降,同时场发射增强因子得到增加。结果表明非晶碳膜确实能够降低电子发射的表面有效势垒,从而增强了场电子发射特性。

The preparation and characteristics of silicon nanoarrays is now an attractive areas of research. At present, most research focused on the optical and electrical properties and applications, and less field emission We present the fabrication of large-scale two dimensional periodic silicon nanoarrays using nanosphere lithography, and the field emission characteristics have been studied. The fabrication process includes following steps： first the crystalline silicon substrate was coated with a monolayer of self polystyrene （PS） spheres of 220 nm in diameter, then the sample was etched by reactive ion etching to produce silicon nanoarrays. AFM images of the nanoarrays show that the tips stand 60-70 nm high and the area density can achieve 6 ×109/cm^2. All field emission measurements were performed at a vacuum of 1.0×10^-4 Pa or better. Expected to improve the field emission characteristics, about 60 nm thickness of a amorphous carbon film was deposited on top of the silicon nanoarrays by plasma-enhanced chemical vapour deposition. Field emission results show that compared to silicon nanoarrays, silicon nanoarrays coated with a thin a-C film effectively lower the threshold fields, approximately 8.1 V/μm, while field enhancement factor increased. When the electric field intensity reached 20 V/μm, the current density can reach about 1.4 mA/cm^2. The improvement of field emission originates from the anisotropie structure of the films, when conductive sp^2 clusters embedded in an insulating sp^3 matrix, the electric field has been enhanced.