雙光子吸收是一種非線性光學現象，可以用高尖峰強度的緊聚焦光束來實現。相互作用區域局限於極其局部的焦點體積。本研究旨在探討負型光阻SU8的雙光子聚合。利用波長740 nm的鈦寶石雷射為能量源引發雙光子吸收，進而導致SU8的聚合。SU8的雙光子聚合本質上是累積效應，因為體素會隨著曝光時間的增加變大。SU8結構線寬對掃描速度和雷射功率呈現對數性的依賴關係。解析度取決於雷射功率和掃描速度，這很大程度上取決於光起始劑的效率。本研究達到了80 nm的最小線寬。結構的附著力受到圖案設計的影響。沒有足夠的機械支撐，這些結構在顯影階段無法承受沖洗力。
本研究使用SU8和銅前驅物，包括硝酸銅和氯化銅，來開發複合材料。由於良好的導電性和成本效益，銅被選擇為填充材料。合成的複合溶液是藍色且均勻的，可將其旋塗在基材上以形成均勻的薄膜。飛秒雷射的照射引發雙光子吸收，導致SU8的聚合，銅離子的還原和銅顆粒的燒結。掃描速度會影響表面形態，因為掃描速度太慢會導致熱能積累和燒蝕。複合結構的線寬取決於雷射功率。隨著掃描速度增加，複合結構的電阻降低，直到達到最佳掃描速度。另一方面，隨著激光功率的增加，線寬增加而電阻減小。本研究達到的導電率為365.50 S/m，遠高於導電率為10-14 S/m的純SU8。

Two-photon absorption is a nonlinear optical phenomenon which can be realized with a tightly focused beam with high peak intensity. The interaction region is limited to an extremely localized focal volume. In this study, two-photon polymerization of negative tone photoresist, SU8 is investigated. Titanium sapphire femtosecond laser at 740 nm is used as energy source to induce two-photon absorption which in turn leads to polymerization of SU8. Two-photon polymerization of SU8 is accumulative in nature, as bigger voxel is obtained with increased exposure time. Line width of SU8 structures demonstrate logarithmic dependence on scanning speed and laser power. Resolution is determined by laser power and scanning speed, which is greatly dependent on efficiency of photoinitiator. A minimum line width of 80 nm is achieved in this study. Adhesion of structures is influenced by pattern design. Without sufficient mechanical support, these structures are unable to withstand rinsing forces during development stage.
Composite material is developed using SU8 and copper precursors, particularly copper (II) nitrate tyihydrate and copper (II) chloride dihydrate. Copper is selected as filler material due to excellent electrical conductivity and cost effectiveness. Blue, homogenous composite solution is synthesized, which can be spin coated on substrate to create a uniform thin film. Irradiation of femtosecond laser induces two-photon absorption that leads to polymerization of SU8, reduction of copper ions and sintering of copper particles. Surface morphology is affected by scanning speed, as low scanning speed subsequently leads to accumulation of heat energy and ablation. Line width of composite structure is determined by laser power. Electrical resistance of the composite structures decreases with scanning speed until optimum scanning speed is achieved. On the other hand, as laser power increases, line width increases while resistance decrease. Electrical conductivity of 365.50 S/m is achieved, which is a leap of advancement as compared to pure SU8 with conductivity of 10-14 S/m.

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