Preparation and characterization of silica coating with embedded germanium particles for infrared band-pass filter application

Abstract

Composite systems based on micro or nanoparticles of low bandgap semiconductors in the dielectric media offer unique properties. These systems can control the electromagnetic waves propagation through surface plasmon resonance. These systems find their application in solar cells, communications, sensors and many more. Germanium microparticles in the silica matrix form the composite which falls into the category of surface plasmon resonance systems. The research was aimed to develop theses spectral sensitive composite coatings onto the surface of gradient heat flux sensors.

In order to develop these germanium embedded silica coatings, the sol-gel synthesis route for silica formation and spin coating for deposition on the sensor was adopted. The experimental procedure was designed to achieve uniform crack-free coating over the sensor surface. Germanium particles were also introduced in the coating and the coating was tried to optimize for a variety of surfaces including silicon wafer, and sensors based on silicon-aluminum and nickel-steel systems.

The morphology of coatings was tested through scanning electron microscopy, X-ray diffraction. The sol-gel process was monitored and designed with the help of FTIR while spectral properties were tested through diffuse reflectance measurement by UV-Vis spectrometry. Crack free coatings up to 1µm were achieved for most case by the use of a binder.