Integration of ZnO nanorods with MOS capacitor for self-powered force sensors and nanogenerators

Yulin Geng,Peter Lomax,Muhammad Mubasher Saleem,Karina Jeronimo,Rebecca Cheung,Muhammad Ammar Bin Che Mahzan,Enrico Mastropaolo

doi:10.1088/1361-6528/ac19d7

Abstract

In this work, we present a novel force-sensing device with zinc oxide nanorods (ZnO NRs) integrated with a metal-oxide-semiconductor (MOS) capacitor and encapsulated with Kapton tape. The details of the fabrication process and working principle of the integrated ZnO NRs-MOS capacitor as a force sensor and nanogenerator have been discussed. The fabricated ZnO-MOS device is tested for both the open-circuit and resistor-connected mode. For an input force in the range of 1–32 N, the open-circuit output voltage of the device is measured to be in the range of 60–100 mV for different device configurations. In the resistor-connected mode, the maximum output power of 0.6 pW is obtained with a 1 MΩ external resistor and input force of 8 N. In addition, the influence of different seed layers (Ag and ZnO) and the patterning geometry of the ZnO nanorods on the output voltage of ZnO-MOS device have been investigated by experiments. An equivalent circuit model of the device has been developed to study the influence of the geometry of ZnO NRs and Kapton tape on the ZnO-MOS device voltage output. This study could be an example of integrating piezoelectric nanomaterials on traditional electronic devices and could inspire novel designs and fabrication methods for nanoscale self-powered force sensors and nanogenerators.

Highlights

After a certain time (∼150 s), the voltage output became less stable, which is probably related to the strain-stress hysteresis due to the existence of the Kapton tape and the unstable mechanical coupling between Kapton tape and zinc oxide nanorods (ZnO NRs)
The bottom side of ZnO NRs has been connected with the top metal contact of the MOS capacitor; the top-side of ZnO NRs is floated and encapsulated with the Kapton tape
For the non-patterned Ag seeded ZnO NRs, the voltage output of the MOS capacitor has been found to be 60–100 mV when the applied force is in the range 1–32 N. and up to 0.6 pW maximum power have been observed when the device is connected with a 1 MΩ resistor

Summary

Introduction

Since the initial work on the application of piezoelectric zinc oxide nanorods (ZnO NRs) for the conversion of mechanical energy into electrical energy in 2006 [1], the nanostructurebased piezoelectric devices have drawn a lot of interest in energy harvesting [1,2,3] and self-powered strain/stress sensing applications [4,5,6,7]. The working principle of these devices is based on the piezoelectric effect: the input mechanical stress results in induced polarization charges or electric field between the two terminals of piezoelectric materials [8]. The device based on the piezoelectric material can be self-powered and can work without an external power supply, which has attracted much attention in future cost-saving sensing applications [9, 10]. The piezoelectric polarization can be used to modulate the SB between the piezoelectric semiconductor and metal, which provides more possibility for novel sensing microsystems [4, 11,12,13,14]

Objectives

Methods

Results

Conclusion