Fabrication and characterization of silver nanoparticles on nickel silicide nanowire-based schottky diode for DNA sensing / Nur Fatin Farhanah Nazarudin

Nur Fatin Farhanah , Nazarudin (2023) Fabrication and characterization of silver nanoparticles on nickel silicide nanowire-based schottky diode for DNA sensing / Nur Fatin Farhanah Nazarudin. PhD thesis, Universiti Malaya.

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Abstract

In this work, nickel silicide nanowires (NiSi NWs) were grown using chemical vapour deposition and subsequently decorated with silver nanoparticles (Ag NPs) using thermal evaporation in the same vacuum deposition system via a two-step processes. The main objective was to fabricate hybrid heterostructured nanowires for a Schottky-diode-based DNA sensor. The first part of the experiment focused on the growth of NiSi NWs and Ag-NP-decorated NiSi NWs (Ag NPs-NiSi NWs) at different substrate temperatures (ranging from 400 to 520 ºC). From this study, it was found that the physical properties, such as surface morphology and crystal structure, of the hybrid Ag NPs-NiSi NWs were strongly dependent on substrate temperature. The Ag NPs-NiSi NWs produced at substrate temperature of 470 ºC had the highest growth rate and area density of 52.6 ± 16.7 Å/s and 12,713.2 ± 230.8 counts/cm2, respectively, with a high density of assembled Ag NPs (~13.7 ± 1.5 nm in diameter) on the NWs’ surface. It is worth noting that the hybrid heterostructured Ag NPs-NiSi NWs demonstrated a significant enhancement in their localised surface plasmon resonance, with a strong absorption band in the optical region at around 420 nm and enhanced electrical conductivity. In the second part, Schottky diodes based on the sandwiched structure of deoxyribonucleic acid with metal, which was DNA/NiSi NWs and DNA/Ag NPs-NiSi NWs, were fabricated. Currentvoltage (I-V) measurements with response times from 0.08 to 40 minutes at room temperature were performed on the two diodes to investigate their electrical and sensing properties. The grafting and hybridisation of DNA on the NiSi NWs and the Ag NPs-NiSi NWs were investigated as well by studying their surface morphology and optical properties via FESEM analysis, Raman spectroscopy and UV-Vis-NIR spectroscopy. The obtained results show that the DNA significantly changed the morphologies of the NiSi NWs and the Ag NPs-NiSi NWs. Furthermore, the utilisation of Ag NPs decorated on the NiSi NWs yielded a significant enhancement factor of 103 for the DNA signal in Raman scattering spectra. This enhancement was attributed to the LSPR effect in the visible region at around 396 nm. The electronic properties of the Schottky diodes based on the DNA/NiSi NWs and the DNA/Ag NPs-NiSi NWs demonstrated a rectifying behaviour. Based on the I-V profiles, the diode based on the hybrid heterostructured Ag NPs-NiSi NWs, with turn-on voltage of 0.3 V, ideality factor of 1.4, reverse saturation current of 3.14 × 10-18 A/cm2, series resistance of 22.47 kΩ, and a high rectification ratio of 789013.30, showed higher sensitivity towards DNA compared with the diode based on the DNA/NiSi NWs.

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