The effect of ALD-grown Al₂O₃on the refractive index sensitivity of CVD gold-coated optical fiber sensors

Abstract

The combined effect of nanoscale dielectric and metallic layers prepared by atomic layer deposition (ALD) and chemical vapor deposition (CVD) on the refractometric properties of tilted optical fiber Bragg gratings (TFBG) is studied. A high index intermediate layer made up of either 50 nm or 100 nm layers of Al2O3 (refractive index near 1.62) was deposited by ALD and followed by thin gold layers (30-65 nm) deposited from a known single-source gold (I) iminopyrrolidinate CVD precursor. The fabricated devices were immersed in different surrounding refractive indices (SRI) and the spectral transmission response of the TFBGs was measured. Preliminary results indicate that the addition of the dielectric Al2O3 pre-coating enhances the SRI sensitivity by up to 75% but this enhancement is highly dependent on the polarization and dielectric thickness. In fact, the sensitivity decreases by up to 50% for certain cases. These effects are discussed with support from TFBG simulations and models, by quantifying the penetration of the evanescently coupled light out of the fiber through the various coating layers. Additional characterization studies have been carried out on these samples to further correlate the optical behaviour of the coated TFBGs with the physical properties of the gold and Al2O3 layers, using atomic force microscopy x-ray photoelectron spectroscopy and an ensemble of other optical and x-ray absorption spectroscopy techniques. The purity, roughness, and morphology of gold thin films deposited by CVD onto the dielectric-TFBG surface are also provided.

Microstructure and mechanical property of high growth rate SiC via continuous hot‐wire CVD

“…Continuous hot‐wire chemical vapor deposition (CVD) is a versatile method for deposition protective coatings (eg, Al 2 O 3 , BN, TiC) and functional films (eg, Au, In 2 O 3 ) onto structural and optical fibers, and widely adopted to fabricate boron, diamond, and SiC monofilaments . Different to the static metallic wires used in commercialized catalytic CVD method, which are mainly used to activate the ambient gas phase, the moving wire acts as both an energy source and the substrate for the growth of deposit during the process of coating and monofilament fabrications.…”

Chemistry of gold(I, III) complexes with organic ligands as potential MOCVD precursors for fabrication of thin metallic films and nanoparticles

“…Gold metal is a highly effective corrosion-resistive material due to its high electrical and thermal conductivity. Thin films and nanomaterials of gold have found some wide range applications such as in optical devices [4,6,8], power sources [151], microelectronic devices [2][3][4][5][6][7][8][9][10] and so on. In the end of last century, Haruta et al [152][153][154] have revealed that gold nanoparticles with diameters less than 10 nm, uniformly dispersed in metal oxides exhibit high catalytic activity in the reaction of CO oxidation at low temperature.…”

“…Thin films deposited onto substrates held at 350°C were confirmed by P-XRD and XPS to be pure gold metal films consisted of densely packed particles less than 50 nm in diameter. Mandia et al [10] have also used the same precursor for the deposition of thin gold films due to its advantages, which include thermal on HSAS was only about 10% at 100 o C. Those processes have influenced the growth rate and purity of metal films prepared from that type of precursors. Compound AuMe 3 PMe 3 was also used in CVD to produce gold nanoparticles with plasmonic properties on amine-terminated surfaces for biosensing applications [38].…”

“…Interest in the chemistry of volatile compounds of gold is associated, primarily, with the growing demand for Metal Organic Chemical Vapor Deposition (MOCVD) precursors used in the process of growing gold thin films and nanoparticles. Due to their low resistivity and high corrosion stability thin films and nanomaterials of gold find numerous valuable applications as in anticorrosion coatings [1], films in optical and microelectronic devices [2][3][4][5][6][7][8][9][10], protective layers for inner surfaces of microwave waveguide resonators [11,12], electrical contacts and interconnects and layers in solar batteries [13]. Furthermore, they find application in electrochemical and biomedical applications [14], in the areas of organic synthesis and catalysis [15,16], photophysics, photochemistry [17][18][19] and in chemotherapy [20].…”

Comprehensive investigation on chalcogenide thin film coated multimode optical fiber: Visible evanescent-wave absorption refractometer

“…Recently, some semiconductor oxide based thin films have been applied intensively to fabricate optical fiber based sensors, for example ZnO [11], In2O3, WO3 [12], Al2O3 [13]. SnO2 coated single mode optical fiber also has also been used to study the LMR effect to measure the relative humidity within near Infra-red region approximately (in the range of 1400-1600), observing the first LMR in 1550 nm and sensitivity of 1.9 nm/%RH [14,15].…”