【摘要】 研究了2 keV电子在直径为800 nm,长度为10μm的聚对苯二甲酸乙二醇酯(polyethylene terephthalate,PET)纳米通道中的输运过程.结果表明,当纳米微通道倾角为0°时,穿透电子的穿透率可达10%,而当倾角大于几何张角时,穿透电子的透射率小于1%.穿透电子角分布中心没有随微孔倾角的变化而移动,因此没有如在正离子的情况下那样观察到绝缘微孔对电子的导向效应.在充电达到稳态时,当微孔倾角小于几何张角时,电子分裂成上下两个电子斑.穿透电子的全角分布的时间演化表明,在充电开始时,穿透电子为单电子斑.随着入射电荷量(充电时间)的累积,穿透电子被上下拉伸,并逐渐分裂成两个电子斑.当纳米微孔的倾角超过几何张角时,穿透电子的分裂趋于消失.对电子造成微孔内壁上的电荷沉积的模拟计算表明,微孔表面被激发出大量空穴,形成正电荷累积;而部分入射电子沉积于表面以下更深处,形成负电荷层,因此不利于产生类似正离子的导向效应.本文还讨论了造成穿透电子角分布上下分裂的可能原因,并据此提出验证电子和离子充电机制不同的新的实验方法.研究结果为利用绝缘微通道控制电子传输技术的发展提供了支撑.更多还原

【Abstract】 The transmission of 2-keV electrons through a polyethylene terephthalate(PET) nanocapillary with a diameter of 800 nm and a length of 10 μm is studied. The transmitted electrons are detected using microchannel plate(MCP) with a phosphor screen. It is found that the transmission rate for the transmitted electrons with the incident energy can reach up to 10 % for an aligned capillary in the beam direction, but drops to less than1% when the tilt angle exceeds the geometrical allowable angle. The transmitted electrons with the incident energy do not move with change of tilt angle, so the incident electrons are not guided in the insulating capillary,which is different from the scenario of positive ions. In the final stage of the transmission, the angular distribution of the transmitted electrons within the geometrical allowable angle splits into two peaks along the observation angle perpendicular to the tilt angle. The time evolution of the transmitted full angular distribution shows that when the beam turns on, the transmission profile forms a single peak. As the incident charge and time accumulate, the transmission profile starts to stretch in the plane perpendicular to the tilt angle and gradually splits into two peaks. When the tilt angle of the nanocapillary exceeds the geometrical allowable angle, this splitting tends to disappear. Simulation of the charge deposition in the capillary directly exposed to the beam indicates the formation of positive charge patches, which are not conducive to guidance, as seen in the case of positive ions. According to the simulation results, we can explain our data. Then, the possible reasons for the splitting the transmission angular profiles are discussed.更多还原