雷射燒結矽奈/微米顆粒於柔性基板之機制及其熱電元件應用

Abstract

矽基材料在半導體中佔有舉足輕重的地位。近年來，隨著穿戴式電子裝置的興起，如何將半導體材料整合至可撓式基板，成為柔性電子技術發展中的重要課題。然而，傳統矽薄膜製程多需倚賴高溫與高真空環境，不利於應用在柔性基板之中。本研究中採用波長532 nm之奈秒脈衝雷射將矽顆粒燒結於柔性基板上，提供一個於大氣環境下快速加工且可圖形化的低溫製程方式，並探討樣品的燒結品質以及應用。 於PET基板上分別燒結P型矽奈米顆粒、P型矽奈/微米顆粒以及N型矽奈米顆粒，針對不同材料與雷射參數，分別評估其表面形貌、厚度、電阻率與熱電性質。比較P型矽奈米顆粒與P型矽奈/微米混合顆粒之薄膜，經雷射燒結後，P型奈/微米混合顆粒薄膜展現良好連續性與結晶性，最低電阻率為4.8 Ω-cm，明顯優於P型矽奈米顆粒薄膜的11.9 Ω-cm。我們進一步提出二次沉積與燒結於P型矽/奈微米顆粒薄膜，欲提升薄膜中大顆粒間的連結性以及改善薄膜厚度均勻性。最終使薄膜電阻率下降至2.2 Ω-cm，厚度均勻性亦改善，厚度標準差由1.0 μm降至0.4 μm。 在熱電性能方面，一次燒結之P型矽奈/微米混合顆粒薄膜於330 K下測得的席貝克係數為71.2 μV/K，明顯高於僅含奈米顆粒之P型薄膜，顯示混合顆粒結構有助於提升熱電表現。最後，製作出結合P型與N型矽薄膜之柔性PN接面熱電元件，並進行彎曲測試。該元件於330 K下之最大席貝克係數可達145.0 μV/K，優於P型、N型薄膜個別絕對值相加結果，且經彎曲測試後仍保有良好的元件性能，證實其可撓性。 本研究展示以雷射燒結技術於柔性基板上製備矽奈/微米混合顆粒薄膜之可行性，並證實二次燒結製程有助於提升薄膜品質。此技術兼具低成本、短製程時間及常壓環境操作等優勢，對於未來應用於可撓式熱電元件與穿戴式能源回收系統具有良好潛力。

Silicon-based materials play a pivotal role in the semiconductor industry. With the recent rise of wearable electronic devices, integrating semiconductor materials onto flexible substrates has become a critical challenge in the advancement of flexible electronics. However, conventional silicon thin-film fabrication often relies on high-temperature and high-vacuum environments, which are unsuitable for flexible substrates. In this study, we employed a 532 nm nanosecond pulsed laser to sinter silicon particles onto flexible substrates, offering a rapid, patternable, and low-temperature processing approach under ambient conditions. The quality of the sintered films and their application potential were thoroughly investigated. P-type silicon nanoparticles (P-SiNPs), P-type silicon nano/microparticles (P-Si NPs/MPs), and N-type silicon nanoparticles (N-SiNPs) were respectively sintered on PET substrates. Based on material type and laser parameters, we evaluated their surface morphology, thickness, resistivity, and thermoelectric properties. Compared to the P SiNPs films, the P-Si NPs/MPs films exhibited superior continuity and crystallinity after laser sintering, achieving a minimum resistivity of 4.8 Ω-cm, which is significantly lower than the 11.9 Ω-cm observed in the nanoparticle-only films. To further enhance interparticle connectivity and improve thickness uniformity, a secondary deposition and sintering process was applied. This method successfully reduced the resistivity to 2.2 Ω cm and improved thickness uniformity, decreasing the standard deviation from 1.0 μm to 0.4 μm. In terms of thermoelectric performance, the once-sintered P-Si NPs/MPs film exhibited a Seebeck coefficient of 71.2 μV/K at 330 K, which is notably higher than that of the nanoparticle-only film, demonstrating the positive impact of the mixed-particle structure in reducing porosity and carrier scattering.A flexible PN junction thermoelectric device was subsequently fabricated by combining the secondary-sintered P-Si NPs/MPs film with an N-SiNPs film. At 330 K, the device achieved a maximum Seebeck coefficient of 145.0 μV/K, which exceeded the sum of the absolute Seebeck coefficients of the individual P-type and N-type films. Bending tests further validated the device’s flexibility, with performance retained after mechanical deformation. This work demonstrates the feasibility of using laser sintering to fabricate silicon nano/microparticles films on flexible substrates and confirms that secondary sintering can effectively improve film quality. The proposed method offers advantages such as low cost, short processing time, and operation in ambient conditions, showing strong potential for future applications in flexible thermoelectric devices and wearable energy harvesting systems.