碳化铪针尖的超快laser触发发射
Ultrafast laser-triggered emission from hafnium carbide tips
摘要：
研究了重复频率低于10 fs、150 MHz的钛宝石激光诱导碳化铪（HfC）场发射针尖的电子发射。在低功率下观察到双光子发射，并向尖端施加适度的偏置电场。随着偏置场和/或激光功率的增加，平均电流变得由激光加热引起的热增强场致发射主导：HfC的低热导率和激光的高重复率都可能导致尖端顶点处的温度升高数百开尔文。在两个温度模型的上下文中考虑的时间短于电子-声子耦合时间的热瞬态电流的贡献。在本实验的条件下，从热瞬态的积分电流被证明是可以忽略不计的双光子发射相比。的激光加热和热传导的有限元模型支持这些结论，也被用来比较HfC，钨，和金提示的热效应的性质。
英文摘要：
Electron emission from hafnium carbide (HfC) field emission tips induced by a sub-10 fs, 150 MHz repetition rate Ti:sapphire laser is studied. Two-photon emission is observed at low power with a moderate electric bias field applied to the tips. As the bias field and/or laser power is increased, the average current becomes dominated by thermally-enhanced field emission due to laser heating: both the low thermal conductivity of HfC and the laser's high repetition rate can lead to a temperature rise of several hundred Kelvin at the tip apex. The contribution of current from a thermal transient at times shorter than the electron-phonon coupling time is considered in the context of the two-temperature model. Under the conditions of this experiment, the integrated current from the thermal transient is shown to be negligible in comparison with the two-photon emission. A finite element model of the laser heating and thermal conduction supports these conclusions and is also used to compare the nature of thermal effects in HfC, tungsten, and gold tips.
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