An Electrothermally controlled quantum tunneling based microcantilever sensor - A simulation study

Abstract

A novel electrostatic & thermally controlled, bimetal Micro Electromechanical System (MEMS) based platform is simulated which works on the principle of quantum tunnelling. A specific frequency laser strikes the analyte and gets absorbed. The absorbed energy gets released as heat and the accompanying temperature change causes the bimetal microcantilever to bend due to the mismatch in the coefficient of thermal expansion (CTE). This deflection causes a change in quantum tunnelling current between the microcantilever tip and an electrode. The exponential dependence of tunnelling current on the deflection results in milli-Kelvin range temperature variation sensing capability. Microcantilever lengths between $10\mu\mathrm{m}$ to $50\mu\mathrm{m}$, widths between $1\mu\mathrm{m}$ to $5\mu\mathrm{m}$ and thicknesses between 100nm to 300nm are simulated for calculating the average thermal sensitivity over a 10mK range. Also, bimetal combinations of Aluminium-Silver, Aluminium-Chromium and Silver-Nickel are used to calculate the variations in the tunnelling current with change in metal combination for different concentrations of Ammonia. Simulations show that the above scheme can be used for ultra-sensitive thermal sensing, soil spectroscopic and explosive detection applications.