Infrared phonon modes and local structure of amorphous and crystalline LaLuO3 thin films

• Amorphous and crystalline LaLuO3 thin films were grown by PLD.
• The infrared phonon modes are kept in the crystalline thin film but reduced in the amorphous thin film.
• The amorphous thin film has different local structure with crystalline thin film.
• The changes of phonon modes and dielectric constant are closely related to the local structure.

The infrared phonon modes and local structure of amorphous and crystalline LaLuO3 thin films were studied by infrared spectroscopy and X-ray absorption fine structure (XAFS). The infrared spectroscopy shows that the crystalline thin film keeps the main infrared phonon modes and preserves the static dielectric constant as crystal bulk sample. But the infrared phonon modes of amorphous thin film reduce and cause the static dielectric constant to decrease. The result is closely related to the local structure as revealed by XAFS. The crystalline thin film has the similar local structure as crystal bulk sample, while the amorphous thin film presents obvious change. The different local structure of the amorphous thin film results in the change of phonon modes and static dielectric constant.