A Dual-Material Phononic-Chimney Architecture for Zero-TCE Frequency Stabilization in Piezoresistive NEMS Resonators

Next-generation Nanoelectromechanical Systems (NEMS) utilizing Thermal-Piezoresistive Resonators (TPRs) are fundamentally limited by parasitic frequency drift induced by internal Joule heating. Current stabilization methods relying on external phase-locked loops negate the footprint advantage of nanoscale sensors. Furthermore, internal structural compensation such as SiO2 composite cladding or Phononic Crystal (PnC) thermal drains suffers from severe thermal insulation and nanoscale surface boundary scattering, respectively. In this paper, we propose and computationally verify a "Phononic-Chimney" architecture. By isolating an active monocrystalline silicon resonant core with a PnC mechanical bandgap, and bypassing horizontal phonon scattering via Z-axis high-K metallic (gold) thermal vents, we demonstrate substantially reduced Temperature Coefficient of Elasticity (TCE) drift without external circuitry. Fully coupled, temperature-dependent finite element multiphysics simulations confirm that peak core self-heating is clamped to ΔT ≈ 1.40 K under full Joule load, and that the resulting resonant frequency drift is reduced to the kHz scale (≈1.8 kHz at the nominal design point) — roughly one to two orders of magnitude below an uncompensated PnC anchor under comparable heating. No Q-factor figure is reported; the methodological limitation and path forward are described in Section 4.7 and Section 7.