Cortelli Giorgio, Patruno Luca, Cramer Tobias, Murgia Mauro, Fraboni Beatrice, de Miranda Stefano
Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Viale del Risorgimento 2, 40136 Bologna, Italy.
Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy.
ACS Appl Nano Mater. 2021 Aug 27;4(8):8376-8382. doi: 10.1021/acsanm.1c01590. Epub 2021 Jul 20.
The nanomechanical properties of ultrathin and nanostructured films of rigid electronic materials on soft substrates are of crucial relevance to realize materials and devices for stretchable electronics. Of particular interest are bending deformations in buckled nanometer-thick films or patterned networks of rigid materials as they can be exploited to compensate for the missing tensile elasticity. Here, we perform atomic force microscopy indentation experiments and electrical measurements to characterize the nanomechanics of ultrathin gold films on a polydimethylsiloxane (PDMS) elastomer. The measured force-indentation data can be analyzed in terms of a simple analytical model describing a bending plate on a semi-infinite soft substrate. The resulting method enables us to quantify the local Young's modulus of elasticity of the nanometer-thick film. Systematic variation of the gold layer thickness reveals the presence of a diffuse interface between the metal film and the elastomer substrate that does not contribute to the bending stiffness. The effect is associated with gold clusters that penetrate the silicone and are not directly connected to the ultrathin film. Only above a critical layer thickness, percolation of the metallic thin film happens, causing a linear increase in bending stiffness and electrical conductivity.
刚性电子材料在柔软衬底上的超薄和纳米结构薄膜的纳米力学性能对于实现可拉伸电子学的材料和器件至关重要。特别令人感兴趣的是屈曲的纳米厚薄膜或刚性材料的图案化网络中的弯曲变形，因为它们可被用于补偿缺失的拉伸弹性。在此，我们进行原子力显微镜压痕实验和电学测量，以表征聚二甲基硅氧烷（PDMS）弹性体上超薄金薄膜的纳米力学性能。所测得的力-压痕数据可以根据描述半无限柔软衬底上弯曲板的简单解析模型进行分析。由此产生的方法使我们能够量化纳米厚薄膜的局部杨氏弹性模量。金层厚度的系统变化揭示了金属薄膜与弹性体衬底之间存在一个扩散界面，该界面不影响弯曲刚度。这种效应与穿透硅树脂且未直接连接到超薄薄膜的金簇有关。只有在临界层厚度以上，金属薄膜才会发生渗流，导致弯曲刚度和电导率呈线性增加。
