Abstract
In this work, we propose a novel approach for wafer-scale integration of 2D materials on CMOS photonic chip utilising methods of synthetic chemistry and microfluidics technology. We have successfully demonstrated that this approach can be used for integration of any fluid-dispersed 2D nano-objects on silicon-on-insulator photonics platform. We demonstrate for the first time that the design of an optofluidic waveguide system can be optimised to enable simultaneous in-situ Raman spectroscopy monitoring of 2D dispersed flakes during the device operation. Moreover, for the first time, we have successfully demonstrated the possibility of label-free 2D flake detection via selective enhancement of the Stokes Raman signal at specific wavelengths. We discovered an ultra-high signal sensitivity to the xyz alignment of 2D flakes within the optofluidic waveguide. This in turn enables precise in-situ alignment detection, for the first practicable realisation of 3D photonic microstructure shaping based on 2D-fluid composites and CMOS photonics platform, while also representing a useful technological tool for the control of liquid phase deposition of 2D materials.
Highlights
Fourier Transform Infrared Spectroscopy (FTIR)[30] are not suitable for studies of fluid nanocomposites with relatively low concentrations of nanoparticles dispersed
To optimise the optofluidic waveguide design for facilitating strong confinement of light on chip and to significantly enhance the Raman back-scattered signal of the individual incorporated 2D nanoplatelets, we model the variation in the intensity of the Raman bands of dispersed nanoparticles while varying parameters that can be experimentally controlled, such as: the waveguide width, w, and the buffer oxide (BOX) layer thickness, Figure 3. (a) SEM image of the chip used for Raman measurements, before infiltration with the nanocomposite. (b) Polarised microscopy image of the structure infiltrated with a composite of MLC 6608 and graphene oxide
We consider the specific case of the D and G bands of 2D carbon-based materials (Fig. 2)- such as graphene and graphene oxide (GO)- dispersed in a nematic liquid crystal (LC) host, the proposed methodology can be utilised for any fluid-dispersed material
Summary
Fourier Transform Infrared Spectroscopy (FTIR)[30] are not suitable for studies of fluid nanocomposites with relatively low concentrations of nanoparticles dispersed. We propose an in-situ micro-Raman characterisation approach, whereby the Raman signal of 2D dispersed nanoparticles is selectively enhanced through the design of optofluidic waveguide geometry on silicon-on-insulator (SOI) platform.
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