| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 103 === The electron beam (e-beam) was utilized to direct-writing nano-scale Cu patterns on a surface with a thin aqueous layer of CuSO4 solution, through the reaction of Cu2+ + 2e- → Cu.
A transmission electron microscopy (TEM, model: JEOL JEM 2010) served as the e-beam source. The TEM not only provided highly convergent and controllable e-beam but also in-situ and high-resolution imaging after writing process. Thin aqueous layer facilitated the formation of Cu patterns and helped to confine the writing on the surface. For this demonstration, liquid sample holder (K-kit) for TEM was employed to form a sealed space in a TEM. The aqueous CuSO4 solution inside the sample holder was allowed to partially dry-off until a thin aqueous layer was left on the surface. E-beam was thus manipulated with pre-designed path to reduce the Cu ion in the solution and form the desired patterns.
The influence of gap of K-kit (the spacing between upper and lower Si3N4 film), e-beam exposure time, and concentration of CuSO4(aq) was studied to find the optimized condition for direct-writing of Cu patterns. It was found that the gap of K-kit would impact the thickness of CuSO4(aq) solution thin film, and K-kit with 2 um gap could create a suitable thickness to facilitate the reaction. When it comes to the influence of e-beam exposure time, it was found that the thickness of reduced Cu increased with the increase of exposure time. At an insufficient CuSO4(aq) concentration, the Cu patterns would become discontinuous and only Cu nanoparticles were left on the e-beam moving path. On the other hand, Cu nanoparticles would freely nucleate near Cu patterns at an excessive CuSO4(aq) concentration.
Finally, an optimized condition was used for nano-scale Cu patterns direct-writing successfully. This method shows significant potential for the application on patterned metal fabrication and worth further detailed study and development.
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