Variable range hopping in self-encapsulated carbon features by internal resin direct laser writing carbonization method

The internal resin direct laser writing carbonization (IR-DLWc) method is a technique for in-situ fabrication of self-encapsulated carbon structures inside polyimide via laser. This study investigates the temperature-dependent sheet resistance of IR-DLWc samples of four process conditions and conventional DLWc samples of two process conditions using the three-dimensional variable range hopping (3D-VRH) conduction model. The results show that IR-DLWc samples exhibit significantly higher T₀ values than conventional DLWc samples, indicating more localized electronic states. For the first time, the conductivity decay of both IR-DLWc and conventional DLWc samples was monitored over a 4-year period. The conventional DLWc samples exposed to air showed rapid initial conductivity decay, which slowed over time. In contrast, the IR-DLWc and UV-glue-encapsulated DLWc samples displayed a slower initial decay but continued to decay at a faster rate over time, suggesting complex interactions between air and laser-induced carbon materials. The study also suggests that T₀, an important indicator for assessing hopping barriers and structural disorder affecting electron transport, can serve as a viable metric for characterizing disorder degree in IR-DLWc materials.