In this work, we report a Multi-Walled Carbon Nanotubes (MWCNTs) MIR source for operation with MEMS spectrometers. We designed a miniaturized source that consists of a micro-machined joule heater on a highly doped silicon substrate, where the heater surrounds an active area. The micro heater filament is made of a platinum thin film on top of silicon with a thin titanium layer, which is used as an adhesive layer between the Silicon dioxide (SiO2) and the platinum. After dicing the silicon chips, a multi-layered thin film of solution-based MWCNTs is plotted within the active area using a micro-plotting machine with a layer dimensions of 4x4 mm2 and a layer thickness of about 1μm. Finally, the device is thermally annealed to improve the morphology of the MWCNTs thin film surface. The micro-machined platinum structure is joule heated by means of applying a voltage difference to the designated pads on the chip allowing a uniform surface heating of the active area containing the MWCNTs thin film. In order to measure the emitted radiation, a MEMS MIR FTIR spectrometer is used to measure the emitted power spectral density from the source with and without the plotting of the MWCNTs thin film, in the MIR range from 2.5μm up to 4.8μm while applying different voltages. The recorded results show that the plotting of the MWCNTs over the silicon substrate improved the recorded PSD of the spectrometer for the all applied voltages. The thermal distribution of the active area is also captured by means of infrared camera at different voltages showing maximum temperatures of 251 °C and 296 °C, while applying 25 and 30 Volts, respectively.
Emerging Near-InfraRed (NIR) spectroscopic applications such as biomedical, agrofood, health & beauty and in-line industrial applications require compact and low-cost miniaturized spectrometers. One of the main elements for such devices is the wideband light source, which can be ultimately in the form of an integrated source. In this work, we report a Multi-Walled Carbon Nanotubes (MWCNTs) NIR source for operation with a micro-electro-mechanical system (MEMS) FTIR spectrometer. The source consists of joule micro heater machined on a highly doped silicon substrate, where the heater surrounds an active area. The micro heater is made of a platinum film sputtered on silicon with a thin titanium layer used as an adhesion layer. The chips are singulated then the MWCNTs are plotted in the active area. The SonoPlot® Microplotter II is used to plot a multi-layered 4x4 mm2 MWCNTs thin film with a layer thickness of about 1μm in the active area. A voltage difference is applied to the designated pads on the chip, allowing uniform heating of the square area containing the MWCNTs. The MEMS FTIR spectrometer is used to measure the emitted power spectral density (PSD) from the source with and without the plotting of the MWCNTs thin film. The micro-plotting of the MWCNTs over the silicon substrate improved the PSD recorded by the spectrometer. The reported results show that an engineered light source based on MWCNTs and silicon serves as a good candidate for miniaturized spectrometers.
In this work, lightly-doped black silicon (BSi) is fabricated using cryogenic DRIE in a maskless manner and its transmittance and reflectance are measured using an integrating sphere and a spectrometer in the near infrared (NIR) wavelength range of 1300 nm - 2500 nm. Then, the surface is cleaned and copper (Cu) is deposited on the BSi using the wet deposition technique of electroless plating, enabling high throughput coating. The copper ions are deposited on the BSi surface in a Cu sulphate solution, taking advantage of the conformity of the plating to the nano/micro structures of the BSi targeting lower reflectance and higher absorptivity. The Cu-plated BSi is measured and observed to have a minimum reflectance of 10% compared to 30% in the case of BSi, and a minimum transmittance of 10% compared to 40% in the bare black silicon. Thus, the Cu-plated BSi has a maximum absorptivity of about 80% compared to 30% in the bare BSi. The absorptivity is found to decrease with increasing the wavelength. This enhancement using the electroless Cu plating further qualifies the BSi as a candidate for NIR thermal light sources.