Optoelectronic Enhancement in Nanostructured h‑BN Synthesized Using Pulsed Ultrasonication

This work describes the synthesis of hexagonal boron nitride nanoparticles (h-BN NPs) and their use as a surface-modifying layer to improve the optoelectronic responsivity in the UV region. We have shown by optoelectronic measurements that nano structuring h-BN promotes effective photon interaction, improving the enhancement factor. The synthesized h-BN NPs using the pulsed mode (frequency of 40 kHz) of ultrasonication yield an average size ∼40 nm, as evident from the field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analysis. Devices coated with h-BN NPs synthesized by pulsed ultrasonication exhibit an enhancement ratio (R _OFF/R _ON) of ∼35% higher than those of commercially available light-dependent resistors (LDRs). Detailed structure-property analysis employing Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering, FESEM, and HRTEM supports the role of size, chemical composition, and bonding characteristics of h-BN NPs in improving UV sensitivity. XPS data reveal increased defect concentration in the pulsed and non-pulsed synthesized h-BN NPs due to reduced B-N XPS intensity. Furthermore, O atoms have a greater affinity toward N atoms in pulsed h-BN as compared to non-pulsed h-BN where O atoms bond to B atoms. Raman spectroscopy and XRD also reveal the characteristic peaks of the synthesized h-BN nanostructures. The measured response and decay times of the pulsed h-BN NP-coated devices are ∼4 and ∼121 ms, respectively, which is comparable to commercial LDRs. A detailed comparative analysis of optoelectronic and structural properties of the pulsed h-BN NPs with non-pulsed h-BN NPs and commercially available h-BN was also performed. Variability and reliability analysis of the enhancement ratio in the pulsed h-BN NP-coated LDRs indicate a standard deviation of 0.05 and no appreciable change over a time of more than 15 min, respectively. To conclude, we have developed a unique synthesis technique of nanostructured h-BN for improved optoelectronic performance in the UV region with potential relevance to semiconductor and quantum applications.