ZnO图形化阵列制备及其场致发射性能研究

Preparation of ZnO Patterned Array and Its Field Emission Performance

针对传统图形化工艺复杂且图形未经精细设计,导致电场分布不均匀的问题,通过ANSYS Maxwell 16.0仿真软件研究电子运动轨迹规律,提出图形化发射体阵列有效发射尺寸和最佳阵列间距阴极结构的新思路,改善场发射性能。仿真结果表明,当阵列间距为200μm时,图形化阵列中心区域的电场分布平坦,阵列四周突变上升。这是由于阵列边缘部分相比于阵列中心区域部分更表现出针尖的特性,当阵列间距越小时,单元阵列之间的边缘区域场强叠加,出现场强叠加区。当阵列间距逐渐增大时,场强边缘叠加效应削弱,同时电场屏蔽效应也削弱。因此,阵列边长越大,为400μm时,阴极表面场强趋于平坦,场强边缘叠加效应和电场屏蔽效应达到平衡。而阵列间距增大到600μm时,会导致单元阵列平面中心位置相对较远,单元阵列场发射相对独立,电子发射出现空档区域。因此,阵列间距选取适中数值时,阵列边缘场强叠加效应削弱,四周电场也不会出现盲区,电场基本达到均匀分布。根据仿真结果,通过喷墨打印图形化种子层实现图案化发射体阵列精准定位,再水热生长ZnO纳米棒阴极阵列。场致发射实验结果表明,随着间距的增加,开启场强E_(on)从200μm时的2.95 V/μm降低到400μm时的0.57 V/μm,并进一步变为600μm时的2.26 V/μm;而场增强因子β随阵列间距从200μm增加到600μm,先增大后减小。这与仿真结果吻合,即在ZnO阴极阵列有效发射尺寸为200μm情况下,当阵列间距为400μm时,场发射性能最优,其开启场强为0.57 V/μm,场发射增强因子为32179。通过调控图形化阵列电子发射轨迹,从而减小场叠加和场屏蔽效应可以改善场发射性能。结合图形化设计和喷墨打印的高效性,有望实现高性能场致发射电子源。

The field emission electron source has a wide range of application value in the field of vacuum electronics,and the realization of the uniformity and patterning of the in-situ growth of the emitter material is the key technology.The traditional patterning process is complicated and the pattern has not been carefully designed,resulting in uneven electric field distribution.This paper uses ANSYS Maxwell 16.0simulation software to study the law of electron motion trajectory,and proposes a new idea of the effective emission size of the graphical emitter array and the cathode structure of the optimal array spacing to improve the field emission performance.The simulation results show that when the array spacing d is 200μm,the electric field distribution in the central area of the patterned array is flat,and the surrounding area of the array rises abruptly.This is mainly due to the fact that the edge part of the array exhibits the characteristics of a needle tip more than the central part of the array.When d is smaller,the field strength of the edge area between the unit arrays is superimposed,and a field strength superimposition area appears.When d slowly increases,the edge superposition effect of the field strength is weakened,and the electric field shielding effect is also weakened.Therefore,when d is larger(400μm),the field strength of the cathode surface tends to be flat,because the edge superposition effect of the field strength and the electric field shielding effect are balanced.However,as d increases to a certain extent,when the array spacing is 600μm,the center position of the cell array plane can be relatively far away,the field emission of the cell array is relatively independent,and the electron emission has a neutral area.It can be seen that when d is selected at a moderate value,the superposition effect of the field strength at the edge of the array is weakened,and there will be no blind areas in the surrounding electric field,and the electric field basically achieves a uniform distribution.Subsequently,according to the simulation results,the patterned seed layer is accurately positioned by inkjet printing,and then the ZnO nanorod array is hydrothermally grown.Field emission test results show that as d increases,the turn-on field strength E_(on) decreases from 2.95 V/μm at200μm to 0.57 V/μm at 400μm,and further changes to 2.26 V/μm at 600μm.The enhancement factor b increases first and then decreases as d increases from 200μm to 600μm.This is consistent with the simulation results,that is,when the effective emission size of the ZnO cathode array is 200μm,when d is400μm,the field emission performance is optimal,and its turn-on field is 0.57 V/μm,and the field emission enhancement factor is 32179.Combining the high efficiency of graphic design and inkjet printing,it is expected to realize a high-performance field emission electron source.