Murray Richard, O'Neill Orla, Vaughan Eoghan, Iacopino Daniela, Blake Alan, Lyons Colin, O'Connell Dan, O'Brien Joe, Quinn Aidan J
Tyndall National Institute, University College Cork, Dyke Parade, Cork, T12R5CP, Ireland.
Nanotechnology. 2022 Jul 14;33(40). doi: 10.1088/1361-6528/ac7c7b.
We report a simple, scalable two-step method for direct-write laser fabrication of 3D, porous graphene-like carbon electrodes from polyimide films with integrated contact plugs to underlying metal layers (Au or Ni). Irradiation at high average COlaser power (30 W) and low scan speed (∼18 mm s)leads to formation of 'keyhole' contact plugs through local ablation of polyimide (initial thickness 17m) and graphitization of the plug perimeter wall. Top-surface laser-induced graphene (LIG) electrodes are then formed and connected to the plug by raster patterning at lower laser power (3.7 W) and higher scan speed (200 mm s). Sheet resistance data (71 ± 15 Ω sq.)indicates formation of high-quality surface LIG, consistent with Raman data which yield sharp first- and second-order peaks. We have also demonstrated that high-quality LIG requires a minimum initial polyimide thickness. Capacitance data measured between surface LIG electrodes and the buried metal film indicate a polyimide layer of thickness ∼7m remaining following laser processing. By contrast, laser graphitization of polyimide of initial thickness ∼8m yielded devices with large sheet resistance (>1 kΩ sq.). Raman data also indicated significant disorder. Plug contact resistance values were calculated from analysis of transfer line measurement data for single- and multi-plug test structures. Contacts to buried nickel layers yielded lower plug resistances (1-plug: 158 ± 7 Ω , 4-plug: 31 ± 14 Ω) compared to contacts to buried gold (1-plug: 346 ± 37 Ω , 4-plug: 52 ± 3 Ω). Further reductions are expected for multi-plug structures with increased areal density. Proof-of-concept mm-scale LIG electrochemical devices with local contact plugs yielded rapid electron transfer kinetics (rate constant ∼ 0.017 cm s), comparable to values measured for exposed Au films ( ∼0.023 cm s). Our results highlight the potential for integration of LIG-based sensor electrodes with semiconductor or roll-to-roll manufacturing.
我们报告了一种简单、可扩展的两步法，用于从具有与底层金属层（金或镍）集成接触插塞的聚酰亚胺薄膜直接写入激光制造三维多孔类石墨烯碳电极。在高平均二氧化碳激光功率（30瓦）和低扫描速度（约18毫米/秒）下进行辐照，通过局部烧蚀聚酰亚胺（初始厚度17微米）和插塞周边壁的石墨化，形成“锁孔”接触插塞。然后通过在较低激光功率（3.7瓦）和较高扫描速度（200毫米/秒）下进行光栅图案化，形成顶表面激光诱导石墨烯（LIG）电极并将其连接到插塞上。薄层电阻数据（71±15Ω/sq.）表明形成了高质量的表面LIG，这与产生尖锐一阶和二阶峰的拉曼数据一致。我们还证明，高质量的LIG需要最小的初始聚酰亚胺厚度。在表面LIG电极和埋入金属膜之间测量的电容数据表明，激光加工后剩余的聚酰亚胺层厚度约为7微米。相比之下，初始厚度约为8微米的聚酰亚胺的激光石墨化产生的器件具有较大的薄层电阻（>1kΩ/sq.）。拉曼数据也表明存在明显的无序。通过对单插塞和多插塞测试结构的传输线测量数据进行分析，计算出插塞接触电阻值。与埋入金的接触相比，与埋入镍层的接触产生的插塞电阻更低（单插塞：158±7Ω，四插塞：31±14Ω），而与埋入金的接触（单插塞：346±37Ω，四插塞：52±3Ω）。对于具有增加面密度的多插塞结构，预计会有进一步的降低。具有局部接触插塞的毫米级LIG电化学器件的概念验证产生了快速的电子转移动力学（速率常数约为0.017厘米/秒），与暴露的金膜测量值（约0.023厘米/秒）相当。我们的结果突出了基于LIG的传感器电极与半导体或卷对卷制造集成的潜力。
