We demonstrate voltage-triggered self-sustained relaxation oscillation (SSRO) in two-terminal devices based on highly oriented vanadium dioxide (VO2) grown on silicon substrates with aluminum nitride (AlN) buffer layers. Cross-sectional TEM and XRD confirm high-quality VO2/AlN/Si heteroepitaxy, while SEM reveals uniform morphology. The films exhibit sharp insulator-to-metal transitions with resistance changes of > 104 and electrical resistivities of ∼1.49 × 10–1 and ∼1.31 × 10–5 Ω·m at 300 and 390 K, respectively. Statistical analysis of 100 devices shows consistent switching voltages near 6.3 V, demonstrating reproducibility. The AlN buffer enables lattice-matched growth, acts as a diffusion barrier, and induces tensile strain, increasing the transition temperature (Tc ≅ 350 K) and broadening the operational window. Voltage oscillations measured across 2–10 kΩ resistors show frequency modulation, while temperature-dependent and time-resolved tests confirm robust stability. In a simple series circuit with a 6 kΩ resistor, the oscillation frequency can be controlled by voltage from ∼296 to ∼1076 kHz, with a tuning sensitivity of ∼260 kHz/V. This frequency tuning range can be extended using external capacitors. These VO2/AlN/Si heterostructures provide a compact, CMOS-compatible, low-power platform for oscillatory devices, offering large resistance modulation, thermal robustness, and reproducible performance for neuromorphic circuits and spiking networks.
Seo et al. (Sat,) studied this question.