Effect of bimaterial microcantilever physical dimensions on photothermal sensing characteristics

•The role of physical dimensions of bimaterial microcantilevers (BMCs) on their photothermal response is investigated.•Sensitivity of BMCs increases with decreasing width by length ratio (W/L) but at the cost of deterioration in response time.•These results are explained on the basis of decrease in effective stiffness and thermal conductance of MCs with reducing W/L.•Figures of merit such as absorbed power, incident flux and temperature sensitivities of BMCs were estimated and reported.•Noise equivalent power of BMCs was found to be at an optimum value (566 pW/Hz) for W/L ratio ~ 0.3. [Display omitted] In the present work, the role of bimaterial microcantilever (MC) physical dimensions on its photothermal sensitivity, response time and noise characteristics are studied. Laser induced deflection in Al/Si MCs with varying Width/Length (W/L) ratio between 0.07 and 0.6 (at a constant thickness of ~2 µm) was studied using an AFM head, by sequentially exposing them to a UV laser source (wavelength ~406 nm) at a constant incident laser power of 2.5 mW. While the absorbed power and incident flux sensitivities were found to decrease with increasing W/L ratio, response time was found to improve. These results are explained on the basis of simultaneous decrease in effective stiffness and thermal conductance of MCs with reducing W/L ratio. Noise equivalent power, counter intuitively, did not improve with reducing dimensions, instead it was found to be at its optimum value (566 pW/Hz) for W/L ratio ~0.3 and is explained on the basis of variation in MC stiffness and Q-factor with MC dimensions.