单根准直碳纳米纤维的场发射特性

采用等离子体增强热灯丝化学气相沉积方法，以甲烷和氢气为反应气体，在钨丝衬底上制备出准直的碳纳米纤维(CNFs)，其生长密度小于10.6cm-2，长度为6—30μm，直径为60—100nm.并采用自制的双探针扫描电子显微镜系统，对所生长的单根CNF作了场发射特性研究.结果表明，其场发射开启电压约为5V/μm，相应的发射电流达到20μA/cm2，同时，对不同长度的CNFs及单根CNF不同位置的场发射研究表明，场发射电流的大小不仅与材料本身的功函数、外电场场强、材料的微观结构以及宏观的几何结构有关，而且电子在输运过程中所受到的散射也是决定场发射电流大小的关键因素. 关键词： 碳纳米纤维 化学气相沉积 场发射 扫描电子显微镜

Field emission from individual vertically carbon nanofibers

Individual high-aspectratio carbon nanofibers(CNFs) were grown on W wire by plasma-enhanced hot filament chemical vapor deposition method, using a gas mixture of methane and hydrogen. The average diameter and length of carbon nanofibers are 60—100 nm and 6—30 μm, respectively, and the density of carbon nanofibers is less than 10.6cm-2. The field emission properties from individual carbon nanofibers have been measured using a movable W probe with a low-curvature radius. The results indicated that the CNFs showed a turn on field of about 5 V/μm and the field-emission current density of 20μA/cm2 at 5 V/μm.The experimental data also indicated that the length of CNFs and the position of a CNF are responsible for the properties of field emission related to the parameters such as the work function of materials, applied field and the field amplification factor. Furthermore, the electron scattering induced by defects in CNFs is also a key factor on the field-emission current.