Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus , 38000 Grenoble, France.
Nanostructures and Synchrotron Radiation Laboratory, Univ. Grenoble Alpes, CEA, INAC-MEM , 38000 Grenoble, France.
ACS Appl Mater Interfaces. 2018 Feb 7;10(5):4794-4800. doi: 10.1021/acsami.7b15649. Epub 2018 Jan 29.
We report a simple and scalable fabrication process of flexible capacitive piezoelectric sensors using vertically aligned gallium nitride (GaN) wires as well as their physical principles of operation. The as-grown N-polar GaN wires obtained by self-catalyst metal-organic vapor phase epitaxy are embedded into a polydimethylsiloxane (PDMS) matrix and directly peeled off from the sapphire substrate before metallic electrode contacting. This geometry provides an efficient control of the wire orientation and an additive contribution of the individual piezoelectric signals. The device output voltage and efficiency are studied by finite element calculations for compression mechanical loading as a function of the wire geometrical growth parameters (length and density). We demonstrate that the voltage output level and sensitivity increases as a function of the wire length and that a conical shape is not mandatory for potential generation as it was the case for horizontally assembled devices. The optimal design to improve the overall device response is also optimized in terms of wire positioning inside PDMS, wire density, and total device thickness. Following the results of these calculations, we have fabricated experimental devices exhibiting outputs of several volts with a very good reliability under cyclic mechanical excitation.
我们报告了一种使用垂直排列的氮化镓（GaN）线制造灵活的电容式压电传感器的简单且可扩展的制造工艺，以及它们的操作物理原理。通过自催化金属有机气相外延获得的生长的 N 极性 GaN 线被嵌入到聚二甲基硅氧烷（PDMS）基质中，并在与金属电极接触之前直接从蓝宝石衬底上剥离。这种几何形状提供了对线材方向的有效控制和各个压电信号的附加贡献。通过有限元计算研究了器件的输出电压和效率作为线材几何生长参数（长度和密度）的压缩机械加载的函数。我们证明，随着线材长度的增加，电压输出水平和灵敏度增加，并且不一定需要锥形形状来产生电势，因为在水平组装的器件中就是这种情况。还优化了线材在 PDMS 内部的定位、线材密度和总器件厚度等方面，以优化整体器件响应的最佳设计。根据这些计算的结果，我们制造了实验器件，在循环机械激励下表现出几伏特的输出，具有非常好的可靠性。
