研究了CVD法定向生长的多壁碳纳米管薄膜的在高电压条件下场发射特性 .我们发现在固定电压条件下发射电流和时间的关系按指数规律减弱 .另一个值得关注的现象是碳纳米管的发射性能的不可恢复性损坏 .电流电压关系也由幂次关系I =aVb 改变为幂次关系I =a(V -V0 ) b′,其中 ,b和b′的值均为 2～ 3.最后讨论了电流减弱的原因 The field emission characteristics of multi-walled carbon nanotube films grown by CVD method under high voltage were investigated. We found that the relationship between emission current and time decreases exponentially with a fixed voltage. Another interesting phenomenon is that carbon nanotubes , The current-voltage relationship is also changed from the power relation I = aVb to the power relation I = a (V-V0) b ’, where b and b’ are both 2 to 3. Finally, the reason for the current weakening is discussed