电击穿是电力设备和电子设备中的重要物理现象。最近,AC和DC击穿的机理已初步揭示为电极-电介质界面击穿和体击穿,分别,基于空间电荷动力学,通过数值计算。然而,交流击穿机制仍然缺乏足够的直接实验支持,这限制了对电气结构的进一步理解和设计开发。这里,在这项研究中,将具有33μm至230μm的各种厚度的LDPE薄膜用臭氧表面改性不同的持续时间,以实验研究DC和AC击穿机理。结果表明,羰基(C=O)被引入到薄膜表面,形成浅表面陷阱,导致平均陷阱深度降低,陷阱密度增加。这种表面氧化调制的陷阱分布导致增强的空间电荷注入和体电场畸变,随着氧化持续时间的延长,DC击穿强度降低,在所有薄膜厚度。然而,这种击穿强度的降低仅发生在交流应力下低于55μm的薄膜中,由于在电极-电介质界面处增强的电场畸变更加明显,并且在薄膜中占主导地位。这些实验结果进一步证实了所提出的电介质膜的电极-电介质界面击穿,并提供了对空间电荷调制电击穿的新认识,这符合介电击穿理论,有利于电力设备和电子设备的小型化。
Electrical breakdown is an important physical phenomenon in power equipment and electronic devices. Recently, the mechanism of AC and DC breakdown has been preliminarily revealed as electrode-dielectric interface breakdown and bulk breakdown, respectively, based on space charge dynamics through numerical calculations. However, the AC breakdown mechanism still lacks enough direct experimental support, which restricts further understanding and the design and development of electrical structures. Here, in this study, LDPE films with various thicknesses ranging from 33 μm to 230 μm were surface modified with ozone for different durations to experimentally investigate DC and AC breakdown mechanism. The results indicate that carbonyl groups (C=O) were introduced onto the film surface, forming shallow surface traps and leading to a decreased average trap depth and an increased trap density. Such a surface oxidation modulated trap distribution led to enhanced space charge injection and bulk electrical field distortion, which decreased DC breakdown strength as the oxidation duration went longer, in all film thicknesses. However, such decreases in breakdown strength occurred only in films below 55 μm under AC stresses, as the enhanced electrical field distortion at the electrode-dielectric interface was more obvious and dominating in thin films. These experimental results further confirm the proposed electrode-dielectric interface breakdown of dielectric films and provide new understandings of space charge modulated electrical breakdown, which fulfills dielectric breakdown theory and benefits the miniaturization of power equipment and electronic devices.