Suppression Technology of Quantum Tunneling Effect in High-Voltage Power Supplies for Electron Microscopes

The high-resolution imaging capability of electron microscopes (hereafter referred to as electron microscopes) relies heavily on the stability and accuracy of the output from high-voltage power supplies. During the operation of an electron microscope, the high-voltage power supply is required to provide an accelerating voltage of 10 kV to 300 kV or even higher for the electron gun, and its output characteristics directly determine the focusing precision and energy consistency of the electron beam. However, the quantum tunneling effect, a typical quantum phenomenon at the microscale, can cause unexpected current leakage inside the high-voltage power supply, leading to voltage drift and increased ripple. This severely restricts the imaging quality and long-term operational reliability of the electron microscope. Therefore, targeted suppression of this effect has become a key technical direction in the design of high-voltage power supplies for electron microscopes.
The manifestation of the quantum tunneling effect in high-voltage power supplies for electron microscopes is clearly scenario-dependent. At the electrode gaps and insulation material interfaces inside the power supply, when the local electric field strength reaches the order of 10^6 V/m, electrons can penetrate the energy barrier in classical physics, forming a tunneling current. This current exhibits random and nonlinear characteristics: in regions with concentrated electric fields at the tips or edges of electrodes, the tunneling probability increases significantly, resulting in current fluctuations ranging from nanoamperes to microamperes. Within the insulating medium, the quantum tunneling effect may also cause degradation of dielectric properties, and long-term accumulation can increase the risk of dielectric breakdown and shorten the service life of the power supply. For transmission electron microscopes pursuing sub-nanometer resolution, a voltage fluctuation of only 0.1% can cause a shift in the wavelength of the electron beam, leading to blurred imaging or contrast distortion. Thus, suppressing the quantum tunneling effect is a core requirement for ensuring the performance of electron microscopes.
Currently, the suppression technologies for the quantum tunneling effect in high-voltage power supplies for electron microscopes mainly focus on three dimensions: electric field regulation, material optimization, and topology improvement. In terms of electric field regulation, the adoption of a gradient-field electrode structure design reduces the concentration coefficient of the edge electric field of traditional planar electrodes from 5~8 to 1.2~1.5. The arc-shaped transition surface disperses the local electric field strength, fundamentally reducing the probability of tunneling. Meanwhile, a nanoscale passivation layer is constructed on the electrode surface to further inhibit the formation of electron tunneling channels by adjusting the height of the interface barrier. In terms of material optimization, traditional insulating materials such as aluminum oxide and silicon nitride are compounded with nanoscale fillers like graphene and carbon nanotubes. By adjusting the filler content, the dielectric constant of the composite material exhibits a gradient distribution, which not only improves the insulation strength but also reduces charge accumulation at the interface. Experimental data show that such modified materials can reduce the tunneling current by 2 to 3 orders of magnitude. In the design of power supply topology, a multi-module series voltage stabilization architecture is adopted, combined with an FPGA-based adaptive feedback control algorithm. This algorithm can real-time detect voltage deviations caused by tunneling current and complete compensation within microseconds, controlling the output voltage ripple within 5 mV and effectively offsetting the dynamic impact of the tunneling effect. In addition, placing the core components of the power supply in a high-vacuum environment above 10^-5 Pa reduces the interference of gas molecules on electron movement, further lowering the fluctuation amplitude of the tunneling current.
The suppression technology of the quantum tunneling effect in high-voltage power supplies for electron microscopes is not only a key support for improving the imaging performance of electron microscopes but also promotes technological breakthroughs of high-voltage power supplies in the field of precision instruments. With the development of materials science and control engineering, the introduction of technologies such as AI predictive control and new two-dimensional insulating materials is expected to realize active prediction and dynamic suppression of the quantum tunneling effect in the future. This will provide core support for the development of electron microscopes toward higher resolution and longer stable operation time, thereby facilitating cutting-edge research breakthroughs in fields such as material characterization and life sciences.