Phase characterization of amorphous tin oxides micro/nanoparticles by Raman spectroscopy

Raman spectroscopy is a valuable technique for elucidating the phase evolution of mixed-phase amorphous tin oxides, which is challenging to characterize due to its complex and low-crystalline structure.In this work, the mixed phase of amorphous tin oxides was synthesized via the electrochemical process.The as-prepared tin oxides were annealed at temperatures ranging from 100 to 500 C in both nitrogen (N 2 ) and air environments.The properties of the tin oxides were investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy.From the results, the XRD patterns exhibited broad and silent peaks, especially at temperatures below 200 C in both environments, which limit the detection of phase evolution.Moreover, XPS mainly provided information on chemical states rather than the amorphous phase.In contrast, the Raman spectroscopy effectively identified vibration modes of the tin oxide phases, providing direct insights into phase transformations, local bonding, and defects, even in low-crystalline systems.The results revealed that under a sufficient ambient oxygen, amorphous SnO 2 /SnO micro/nanoparticles completely transformed to Sn 2 O 3 /Sn 3 O 4 and SnO 2 at 500 C.However, the annealing at 500 C under ambient N 2 resulted in the formation of SnO combined with Sn 2 O 3 , Sn 3 O 4 , and SnO 2 .These findings highlighted that the Raman spectroscopy technique is a crucial procedure for revealing the phase of amorphous tin micro/nanoparticle oxides, providing unique and complementary information on phase evolution and defect structure, which is critical for selecting the appropriate tin oxide phases for p-n junction device applications.