Use of CdTe quantum dots for high temperature thermal sensing

Abstract

An optical-thermal experimental system, in which CdTe quantum dots (QDs) were used as thermal sensors, is developed for micro-electromechanical system (MEMS) temperature measurements in the high temperature range (>70 °C). Laboratory-prepared CdTe QDs with suitably controlled synthesis conditions show excellent temperature sensitivity. For orange emitting CdTe QDs, calibration from a type A micro-heater yields a linear relation between the spectral peak shift and the temperature over the temperature range of 27 °C to 170 °C, the last being the highest temperature of the heater achieved in our current optical-thermal experimental setup. This linear relation is consistent with the predictions for semiconductor quantum systems from the principle of thermo-quantum mechanics for the temperature above the Debye point. Analysis of the experimental data indicates that the orange emitting QDs possess a thermally-induced spectral-shift sensitivity of 0.34 nm °C⁻¹, which is approximately about 2–3 times better than reported. The excellent repeatability and accuracy of the calibrated orange emitting CdTe QDs as thermal sensors are further demonstrated by applying them in monitoring electric thermal characteristics of type B MEMS structures. While calibration is for up to 170 °C, the temperature of up to 212 °C for the type B MEMS heater was measured with a satisfactory accuracy using the CdTe QDs, further demonstrating the stability of the thermal-spectral properties of the QDs. The existence of a unique “burnout” spectrum in the temperature dependent PL spectra also suggests that optical-thermally sensitive QDs can be applied in both monitoring the temperature development and diagnosing circuit breakout due to over-heating.