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

Abstract

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.

High-Precision and Low-Damage Microchannel Construction via Magnetically Assisted Laser-Induced Plasma Ablation for Micro-Thermoelectric Devices

“…The laser ablation threshold has been measured and fitted by the D 2 method . Assuming a Gaussian beam profile and an ideal threshold behavior of the material, the correlation among the diameter of ablated area D , maximum laser fluence E 0 , and the waist radius of the Gaussian beam ω 0 can be written as where F 0 is the laser peak fluence and F th is the laser ablation threshold. ω 0 is the beam waist radius representing the spot size, which is directly determined by the laser system and the off-focus value.…”

“…The laser ablation threshold has been measured and fitted by the D 2 method 29. Assuming a Gaussian beam profile and an ideal threshold behavior of the material, the correlation among the diameter of ablated area D, maximum laser fluence E 0 , and the waist radius of the Gaussian beam ω 0 can be written as30…”

Active control of focus position of laser beams using thermally induced lensing

“…18,21 High-powered solid-state lasers can be used to manipulate the inner spatial structure of matter in a wide range of materials by repeated passes through their atomic layers. This offers great promise for applications such as rapid patterning and scanning, 22 as well as material processing, 23 and optical coherence tomography. 24 Advances in laser technology have led to new methods for observing thermal lensing, but these advancements must be adapted by researchers and applied to high-power solid-state lasers.…”

Femtosecond Laser‐Induced Periodic Surface Structuring of the Topological Insulator Bismuth Telluride

“…Zhou et al investigated the selective ablation and direct writing of thick films of n-type Bi 2 Te 3 and p-type Sb 2 Te 3 by 290 fs laser pulses at 𝜆 ≈ 343 nm, addressing the fluence threshold and optimal conditions for selective etching to be used in the fabrication of micro-TE devices for chip thermal management and self-powered energy harvesting. [23] Yue et al carried out an analysis of laser-induced photoexcitation of thin film of Bi 2 Te 3 by using 100 fs pulses at 800 nm, inducing a significant change in the refractive index of the material potentially interesting for the elaboration of flat optical devices. [24] Here we report on fs laser irradiation and generation of periodic surface structures on Bi 2 Te 3 , addressing some peculiar features observed in the formation of subwavelength periodic surface structures on this material.…”