Infrared sensitive mixed phase of V₇O₁₆ and V₂O₅ thin-films

Area of Science:

• Materials Science
• Thin Film Technology
• Semiconductor Physics

Background:

• Vanadium oxides (V_xO_y) exhibit diverse electrical and optical properties.
• Controlling the phase and defect chemistry is crucial for tailoring their functionality.
• Low-temperature deposition methods are desirable for flexible substrate compatibility.

Purpose of the Study:

• To investigate the formation and properties of mixed V7O16 and V2O5 thin films.
• To understand the influence of annealing temperature on phase composition and material characteristics.
• To elucidate the mechanisms behind the infrared sensitivity and optical-electrical property correlations.

Main Methods:

• Cathodic vacuum arc-deposition for thin film growth.
• Post-annealing treatments at various temperatures (300-450 °C).
• Raman spectroscopy, optical transmission, photoluminescence (PL), and time-resolved photoluminescence (TRPL) measurements.

Main Results:

• Stabilization of a mixed V7O16 and V2O5 phase achieved via post-annealing between 300-400 °C.
• Complete conversion to V2O5 observed at higher annealing temperatures (~450 °C).
• Increased V2O5 content correlated with higher optical transmission, lower electrical conductivity, and reduced optical bandgap.
• Defect roles (oxygen vacancies) identified through PL and TRPL, explaining property variations.
• Infrared sensitivity attributed to plasmonic absorption in the V7O16 degenerate semiconductor phase.

Conclusions:

• Mixed V7O16 and V2O5 thin films can be controllably synthesized at low temperatures.
• Annealing provides a route to tune the phase composition and optical-electrical properties.
• The observed IR sensitivity is linked to the plasmonic behavior of the V7O16 phase, suggesting potential for IR detector applications.