Nanosecond Laser Ablation of Au@LiNbO3 Core-Shell Nanoparticles in Ethanol: Properties and Application in Optoelectronic Devices

Core/shell nanocomposite is a very interesting structure that exhibits excellent properties such as improved thermal stability and decreased reactivity of the core nanoparticles. Core/shell nanoparticles were synthesized by means of laser ablation in ethanol without using a catalyst. The structural and optical properties of Au@LiNbO3 core/shell nanoparticles as a function of laser fluence are investigated. To fabricate the photodetector, a thin film of Au@LiNbO3 was deposited on a single crystal silicon substrate. X-ray diffraction (XRD) results show that the synthesized nanocomposite is crystalline with a rhombohedral structure and the presence of peaks related to a gold cubic structure, indicating the formation of a core/shell nanocomposite. Transmission electron microscopy (TEM) investigations confirm the formation of core/shell spherical nanoparticles, whose size depends on the laser fluence. The optical properties reveal that the optical energy gap of LiNbO3 was 4.08 eV, while the energy gap of the Au@LiNbO3 core/shell prepared at 1.3, 1.6, 2, and 2.2 J/cm(2) was 3.6, 3.49, 3.4, and 3.8 eV, respectively. The optoelectronic properties of the Au@LiNbO3/Si photodetector fabricated without a buffer layer and an antireflection coating as a function of laser fluence are investigated. The optoelectronic properties show that the maximum responsivity was 0.43 A/W at 400 nm for the Au@LiNbO3/Si photodetector fabricated at 2 J/cm(2). The variation of laser fluence affects the structural, optical, and electrical properties of Au@LiNbO3 core/shell. The best core/shell characteristics and photodetector were obtained at a laser energy of 2 J/cm(2). The energy band diagram confirmed that the presence of Au significantly improved the photoresponse of the photodetector.