Abstract
Electro-chromic materials (EC) are a new class of electronically reconfigurable thin films that have the ability to reversibly change optical properties by electric charge insertion/extraction. Since their discovery by Deb, they have been employed in applications related to display technology, such as smart windows and mirrors and active optical filters. In this sense, a variety of studies related to the tuneable optical characteristics of EC materials have recently been reported, however, their microwave tuneable dielectric characteristics have been left somewhat unexplored. In 2016 Bulja showed that dc bias voltage induced modulation of the optical characteristics of an inorganic Conductor/WO3/LiNbO3/NiO/Conductor EC cell isaccompanied by the modulation of its high frequency (1–20 GHz) dielectric characteristics. In general, according to the state of the art, cells of different material compositions are needed to produce devices of tailor made characteristics. Here, we report the discovery that the microwave dielectric and the optical characteristics of an EC cell can be engineered to suit a variety of applications without changing their material composition. The obtained results indicate the potential for producing novel, tuneable and tailor-engineered materials that can be used to create next generation agile microwave-optical devices.
Highlights
The property of a change, evocation or bleaching of colour influenced by either an electron-transfer process or by a sufficient electrochemical potential, referred to as electrochromism, is exhibited by several organic and inorganic materials[1,2,3,4,5,6,7,8,9,10,11,12,13,14]
The applied dc bias voltage was increased in steps of 1 V and the cells were kept at this dc bias voltage for 6 minutes, while their responses were monitored
We have demonstrated that the extent of tunability of dielectric and optical properties of Electro-chromic materials (EC) materials with electrochromical complementary Conductor/WO3/LiNbO3/NiO/Conductor structure can be varied without changing their material composition
Summary
The two broadband impedance transformers act as transitions from the anode to the coplanar waveguide (CPW), needed for on-wafer measurements. This improved version of the measurement device, considers the experiences related to the conductor thickness and electrodes shape from our preceding work[19]. With a height of 600 μm is an n-doped Si wafer with a surface resistivity of 10 Ω.cm and dielectric constant of εrSi = 11.9 On top of this layer, a thin dielectric layer of SiO2 with a height of htrench = 300 nm is deposited so as to separate the conductive Si layer from the deposited gold ground plane. Ellipsometry and interferometry were used to determine the refractive indices and the thicknesses of the individual WO3, NiO and LiNbO3 layers prior to actual device fabrication.
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