Smooth pyroelectric luminescence in LiNbO₃ single crystals

Area of Science:

• Solid-state physics
• Materials science
• Luminescence phenomena

Background:

• Pyroelectric luminescence arises from temperature-induced polarization changes in materials like LiNbO3.
• This light emission is linked to charge carrier recombination processes.
• Atmospheric pressure significantly influences the nature of pyroelectric luminescence.

Purpose of the Study:

• To investigate pyroelectric luminescence in LiNbO3 single crystals under varying atmospheric pressure.
• To elucidate the underlying mechanisms of light emission, including charge carrier recombination.
• To determine deep trap potentials and the nature of electron release mechanisms.

Main Methods:

• Experimental setup exposing LiNbO3 crystals to temperature changes (360-450 K) in high vacuum.
• Simultaneous measurement of surface charge density and emitted light intensity.
• Development and application of a microscopic model for time-dependent luminescence analysis.

Main Results:

• Observed transition from intense gas discharge pulses to smooth pyroelectric luminescence with decreasing pressure.
• Demonstrated that electron release from deep traps follows the Poole-Frenkel effect from a Dirac-well potential.
• Showed disagreement between experimental data and the commonly assumed coulombic trap model.

Conclusions:

• The Poole-Frenkel effect from a Dirac-well potential accurately describes pyroelectric luminescence in LiNbO3.
• The study provides a method for determining deep trap potentials inaccessible via thermal ionization.
• Findings challenge the conventional understanding of trap shapes in pyroelectric materials.