Wide range tunability of surface plasmon resonance of nanostructured Ag deposited by off-axis magnetron sputtering

Abstract

In this work, nanostructured Ag showing size distribution dependent tunable surface plasmon resonance (SPR) are grown on glass substrate using off-axis DC magnetron sputtering at a sputtering power of 74 W. Argon gas pressure is set at 8.0 Pa and the deposition time is varied in the range 5–300 s. The structural, morphological, and optical properties are examined by using X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), and UV–Visible spectrophotometer. XRD patterns of all samples reveal characteristic (111) and (200) peaks of fcc Ag. Broad XRD peaks suggest formation of nanosized Ag crystallites with mean crystallite size of 3 nm. FESEM images depict near spherical Ag grains up to 120 s deposition time and elongated grains with greater substrate coverage with extended deposition time of 300 s. SPR features are well distinct in the optical absorption spectra which are highly sensitive to the deposition time. Within a short deposition time of 5–60 s, nanostructured Ag demonstrates wide range SPR tunability from 438 nm to 530 nm. It is observed that the variations in the size distribution as estimated from FESEM images are crucial to observe systematic red shift of SPR with increasing deposition time. Nanosized Ag produced by off-axis magnetron sputtering may be used as a vital component in plasmonic devices and sensors.