Enhanced field emission from nanosecond laser based surface micro-structured stainless steel

This paper presents results of field emission study of laser based surface micro-structured stainless steel (SS). Surface micro-structuring of SS samples has been performed by direct irradiation of sample surface with a frequency doubled Nd:YAG nanosecond (ns) laser in atmospheric ambience. Laser treated samples have been characterized in terms of their surface morphology, elemental composition and field emission properties. Our results reveal formation of micro-protrusions of varying height and tip diameter depending on incident laser fluence. Within the laser irradiated spot, regions near periphery showed formation of micro-protrusions with number density as high as 4.5 × 107 protrusions/cm2. Such laser micro-structured samples have shown much lower turn on electric field (7.5 V/μm) in comparison to untreated SS samples. Macroscopic field enhancement factor (γc) and macroscopic pre-exponential correction factor which is a provisional measure of area efficiency of emission of the laser modified sample surface were estimated to be 585 and 2.72 × 10−10, respectively. Emission current stability measurements for a preset level of 4 μA showed good performance when tested over a period ∼140 min.