Unveiling molecular vibrations and anisotropy in semiconductor PbCrO4/LAO films using angle-resolved polarized and temperature-dependent Raman spectroscopy

Abstract

The semiconductor ternary compound lead chromate (PbCrO₄) displays promising prospects in pigment and optoelectronic fields. However, previous studies have only focused on its application, neglecting a deep investigation into its molecular vibrational and structural characteristics, such as the influence of interlayer forces. Here, pulse laser deposition was employed for the preparation of highly oriented PbCrO₄/LaAlO₃ thin films. Ultra-low-frequency Raman spectroscopy revealed 16 Raman modes of PbCrO₄. Meanwhile, angle-resolved polarized Raman spectroscopy, an efficient and nondestructive technique, was used to investigate material anisotropy and orientation. The first-order temperature coefficient values (χ) of PbCrO₄ obtained by temperature-dependent Raman spectroscopy were vastly different (from −0.0924 to 0.0053 cm⁻¹ K⁻¹). The small χ value is attributed to the weak interlayer van der Waals forces and electron-phonon interactions, indicating a low level of thermal sensitivity. These findings make PbCrO₄ an ideal material for crafting high-temperature-resistant pigments and orientation-dependent photocatalysts.