Preparation of novel BC nanostructure/Si photodetectors by laser ablation in liquid.

In this study, boron carbide (BC) nanoparticles (NPs) are synthesized by pulsed laser ablation of boron in ethanol at a laser fluence of 6.36 J cm pulse. The effect of numbers of laser pulses on the structural, optical, and electrical properties of BC NPs was studied. X-ray diffraction (XRD) results revealed that all BC nanoparticles synthesized were polycrystalline in nature with a rhombohedral structure. When the laser pulses increased from 500 to 1500, the optical band gap of BC decreased from 2.45 to 2.38 eV. Fluorescence measurements showed the emission of two emission peaks. The Raman spectra of BC nanoparticles exhibit six vibration modes centered at 270, 480, 533, 722, 820, and 1080 cm. Field emission scanning electron microscope (FESEM) images show the formation of spherical nanoparticles of an average size of 68, 75, and 84 nm for samples prepared at 500, 1000, and 1500 pulses, respectively. The dark I-V characteristics of BC/Si heterojunction photodetectors showed rectification characteristics, and the heterojunction prepared at 500 pulses exhibits the best junction characteristics. The illuminated I-V characteristics of BC/p-Si heterojunction photodetectors exhibited high photosensitivity to white light. The spectral responsivity of the p-BC/p-Si photodetector shows that the maximum responsivity was 0.66 A W at 500 nm for a photodetector prepared at 500 pulses. The highest specific detectivity and quantum efficiency were 2.18 × 10 Jones and 1.64 × 10% at 550 nm, respectively, for a heterojunction photodetector fabricated at 500 pulses, The ON/OFF ratio, rise time, and fall time are measured as a function of the number of laser pulses. The photodetector fabricated at 1500 laser pulses showed roughly rise and fall intervals of 1.5 and 0.8 s, respectively.