Rapid Selective Ablation and High-Precision Patterning for Micro-Thermoelectric Devices Using Femtosecond Laser Directing Writing

Highly integrated miniature thermoelectric (TE) devices are desirable for applications of chip thermal management and self-powered energy harvesting. Currently, further performance improvement of micro-TE devices is largely limited by micro–nano-patterned processing, which shows the incompatibility with high-performance TE material fabrication or contradiction between machining accuracy and efficiency. This work presents a useful method to flexibly achieve high-precision array patterning for the micro-TE device through the femtosecond laser direct writing technique. By experimentally examining the material ablation process and numerically analyzing the electron-lattice temperature, the laser energy threshold for different materials is determined to obtain the selective removal between TE materials and metallic electrodes. Furthermore, the evaluation criteria are established between the formation quality of microgroove in the array structure and the laser pulse energy distribution, and the shape-control and property-control pattern processing can be realized through the reasonable control of the laser energy. Consequently, the Bi2Te3-based TE pattern with a competitive leg density (496 pairs/cm2) and a high filling factor (55%) is successfully constructed.