Ultrahigh carrier mobility in an amorphous-carbon-adsorbed diamond conductive channel

Hydrogen-terminated diamond (H-diamond) has emerged as a promising dopant-free p-type semiconductor owing to its distinctive surface conductivity. However, the development of H-diamond-based electronic devices remain constrained by their limited carrier mobility and poor environmental stability. In this work, we developed an innovative approach through conformal deposition of an amorphous carbon (a-C) layer on H-diamond surfaces via microwave plasma chemical vapor deposition. This engineered interface establishes a highly conductive channel exhibiting an unprecedented hole mobility exceeding 1470 cm²V⁻¹ s⁻¹, while maintaining optimal carrier density (∼10¹² cm⁻²) and remarkably low sheet resistance (2300 Ω/□). The modified surface demonstrates exceptional environmental stability, retaining its electrical properties for over two months under ambient conditions while maintaining excellent conductivity at elevated temperatures up to 575 K. Comprehensive characterization through photoluminescence spectroscopy, ultraviolet photoelectron spectroscopy, and comparative vacuum/ambient Hall measurements reveals a charge transfer doping mechanism predominantly mediated by the adsorbed a-C layer, with secondary contributions from ambient molecular species. This breakthrough provides critical insights for designing stable, high-performance H-diamond-based electronic systems for advanced applications in extreme environments.