Static and Ultrafast Dynamics of Defects of SrTiO3 in LaAlO3/SrTiO3 Heterostructures

TL;DR

This study maps defect energy levels in LaAlO3/SrTiO3 heterostructures, revealing ultrafast defect dynamics and relaxation processes using femtosecond laser spectroscopy, highlighting oxygen defects' role in the substrate.

Contribution

It provides a detailed defect energy level map and identifies ultrafast relaxation processes in LaAlO3/SrTiO3 heterostructures, advancing understanding of defect dynamics.

Findings

Ultrafast relaxation of 2-3 ps from conduction band to defect level

Slower relaxation of 70-92 ps within defect levels

Oxygen defects dominate the defect landscape in SrTiO3

Abstract

A detailed defect energy level map was investigated for heterostructures of 26 unit cells of LaAlO3 on SrTiO3 prepared at a low oxygen partial pressure of 10-6 mbar. The origin is attributed to the presence of dominating oxygen defects in SrTiO3 substrate. Using femtosecond laser spectroscopy, the transient absorption and relaxation times for various transitions were determined. An ultrafast relaxation process of 2-3 picosecond from the conduction band to the closest defect level and a slower process of 70-92 picosecond from conduction band to intra-band defect level were observed. The results are discussed on the basis of propose defect-band diagram.