Synthesis of Si3N4 nanoparticles via pulsed laser ablation of silicon in nitrogen-rich NH4Cl solution for photodetection applications

In this work, we synthesized Silicon nitride (Si₃N₄) nanoparticles for the first time using a facile, room-temperature pulsed-laser ablation in liquid method by irradiating a silicon wafer target in an aqueous NH₄Cl solution under nitrogen-rich conditions. The ablation was carried out with a 532 nm Nd: YAG laser at fluences of 55, 65, and 75 J/cm 2 for 300 pulses, where NH 4 Cl served as an in-situ nitrogen source to form Si N bonds. The structural analysis confirmed that Si 3 N 4 nanostructures had been formed, where the crystallite size decreased with increasing fluence from 39.9 to 20.0 nm when increasing the fluence from 55 to 75 J/cm 2 , respectively The Scanning electron microscope (SEM) results showed that the size of the particles increased in a fluence-dependent manner, from 37.8 nm to 80 nm median particle sizes. Energy-Dispersive X-ray (EDX) analysis showed that the degree of nitridation increases at 75 J/cm 2 , with a Si/N ratio up to 0.718, and the oxygen content reduces to around 28%. Optical measurements indicated a blue shift of the absorption edge from 215 to 220 nm to 205–210 nm, accompanied by an increase of about 5.64 to 5.90–5.97 eV in the optical band-gap energy. The Al/Si 3 N 4 /Si MIS photodetector fabricated at laser fluence of 65 J/cm 2 exhibited excellent photodetection performance: responsivity of 0.57 A/W and external quantum efficiency of 1.58 × 10 2 % at λ = 450 nm and rise and fall times of 0.14868 and 0.15668 s, respectively.