Low-power light irradiation based plasmonic photoresponse on quasi-freestanding monolayer/AuNPs hybrid system

This study focuses on plasmonic photoresposne on gold nanoparticles (AuNPs) decorated quasi-freestanding graphene (QFSG) on a vicinal silicon carbide (SiC) substrate in variable intensities light illumination. The key cause of significant photoresponse on AuNPs/QFSG hybrid structure is the mismatched work functions of gold and freestanding graphene resulting the fermi-level alignment. Moreover, the high quality, single crystalline freestanding topmost layer of graphene supported by the underneath multilayer graphene (MLG) on vicinal SiC, provides ample space for AuNPs to create tensile strain upon it, arising from the hexagonal symmetry breaking of carbon rings. Such strain is the source of charge carrier scattering and limits the electron density distribution on hybrid structure. The carrier concentration increases on high-power light irradiation in AuNPs/QFSG structure and mobility decreases due to carrier scattering phenomena and vice-versa. Here, we irradiate our as prepared AuNPs/QFSG device under 365 nm wavelength light with intensities 18 mW/cm², 36 mW/cm² and 60 mW/cm² and observe the photo responsivities 19.9 mA/W, 11.3 mA/W, 7.14 mA/W respectively (At 1 V bias) higher compared to QFSG. Similar trend is observed for 405 nm light irradiation (at 6 mW/cm², 11 mW/cm², and 17 mW/cm²). Therefore, low-intensity illumination shows greater promise for achieving higher photoresponsivity in plasmonic nanoparticle-assisted QFSG/SiC devices. Significant photoresponse at low-bias and low-power light irradiation make our work a novel platform for SiC power-based applications in future.