Effects of Ag+ ion induced defects on structural, morphological and optical properties of thin VO2 films

• Our work shows that: • Ag + implantation causes structural distortion in VO 2 thin films, shifting XRD and Raman peaks. • Particle size and surface roughness decrease with increasing ion fluence. • XPS reveals shifts of V2p 3/2 and O1s peaks towards lower binding energies. • Optical bandgap decrease tuning is achieved by controlling ion fluence. • Optical band gap reduction is attributed to defect states introduced by implantation. In this study, vanadium dioxide (VO 2 ) films were deposited on silicon substrates by reactive pulsed laser deposition. Post deposition, the films were implanted with 80-keV Ag + -ions to fluences ranging from 0.1x10 16 to 5.0x10 16 ions/cm 2 . The effects of Ag + ion-implantation on the structural, morphological, and optical properties of the films were investigated using various characterization techniques. X-ray diffraction analysis showed a left shift and broadening of the (011) peak with increasing fluence, indicating an expanded lattice and reduced crystallite size along the (0 1 1) direction in VO 2 . Raman spectroscopy revealed a leftward shift in the V-V and V-O Raman bands, suggesting that these bonds were weakened because of implantation. Morphological analysis showed a fluence-dependent decrease in grain size and surface roughness. A shift of V2p 3/2 and O1s peaks towards lower binding energies observed using the X-ray Photoelectron Spectroscopy technique suggested that the electronic structure of VO 2 was altered upon implantation. The obtained results in general showed that Ag + -implantation distorted the monoclinic structure of VO 2 and enhanced infrared absorption in Ag + -implanted films through bandgap reduction, as confirmed by the optical measurements. These changes demonstrated that ion implantation could be used to tune the optical properties of the VO 2 material towards being more suited to infrared sensing applications.