Nitrogen doping of vertically aligned carbon nanotubes for on-chip CMOS-compatible pseudocapacitive supercapacitors

We present a CMOS-compatible, solvent-free nitrogen plasma doping strategy for enhancing the electrochemical performance of vertically aligned carbon nanotube (VACNT) electrode for on-chip supercapacitor applications. By leveraging a hybrid plasma–planar triple spiral antenna (PTSA) system, we decouple plasma density and ion energy to selectively introduce nitrogen species—namely pyrrolic, pyridinic, and quaternary nitrogen—into the VACNT framework. A two-step process comprising Ar plasma defect engineering followed by N 2 plasma doping leads to a substantial improvement in specific capacitance, with optimal conditions (200 W ICP power, − 120 V bias, 10 sccm N 2 ) yielding up to 34.2 mF/cm 2 , nearly double that of pristine VACNTs. Through comprehensive structural and electrochemical analyses, we correlate bonding configurations with pseudocapacitive behavior, demonstrating a pseudocapacitive contribution exceeding 47%. This work offers a scalable and BEOL-compatible route to functionalized carbon nanomaterials, paving the way for high-performance, on-chip energy storage integration. • Demonstrated a CMOS-compatible plasma-based technique for functionalizing vertically aligned carbon nanotubes (VACNTs), enabling high-performance on-chip energy storage integration. • Achieved selective incorporation of electrochemically active nitrogen species including pyrrolic, pyridinic, and quaternary nitrogen by tuning plasma power and substrate bias, highlighting the controllability and adaptability of the two-step Ar/N 2 plasma process. • Observed trends in nitrogen bonding configurations and electrochemical performance aligns with previously reported doping effects in graphene-based systems, supporting the reproducibility and robustness of the proposed methodology.