Ammonium phosphomolybdate: a material for dielectric crossover and resistive switching performance

Area of Science:

• Materials Science
• Solid State Physics
• Inorganic Chemistry

Background:

• Yellow ammonium phosphomolybdate [(NH4)3PMo12O40] (YAPM) is a versatile inorganic compound with established applications.
• Dielectric materials and memory devices are crucial components in modern electronics.

Purpose of the Study:

• To investigate YAPM as a novel dielectric material for memory device fabrication.
• To explore the effects of UV irradiation and pressure on YAPM's electrical properties.
• To characterize the charge transport mechanisms and memory behavior of YAPM-based devices.

Main Methods:

• Synthesis and characterization of YAPM.
• UV irradiation (∼365 nm) and pressure application experiments.
• Dielectric spectroscopy and AC conductivity measurements.
• Electron Paramagnetic Resonance (EPR) spectroscopy.
• Fabrication and electrical testing of Au‖YAPM‖Au memory devices on flexible substrates.

Main Results:

• YAPM exhibits UV-tunable dielectric performance and AC conductivity, attributed to electron accumulation forming green APM (GAPM).
• UV exposure induces a transition from YAPM to GAPM, altering dielectric constant and loss.
• Pressure induces Mo(vi) to Mo(v) reduction, similar to UV-exposed GAPM, confirmed by EPR.
• AC conductivity shows a crossover from quantum mechanical tunneling to hopping conduction under UV.
• The fabricated device demonstrates resistive memory behavior with Schottky-type emission (OFF state) and Poole-Frenkel (ON state) transport.
• A stable ON-OFF current ratio of 2 × 10^2 was achieved.
• UV exposure leads to a complete shift to a stable ON-state conductivity.

Conclusions:

• YAPM is a promising novel dielectric and memory material with UV-tunable properties.
• The observed memory effect is linked to UV-induced phase transition and charge transport mechanisms.
• The flexible paper-based memory device shows potential for applications in flexible electronics.