Sputtered PdO Decorated TiO2 Sensing Layer for a Hydrogen Gas Sensor

Jeong Hoon Lee,Kyu Hyoung Lee,Jin-Hyung Lee,Tae Hoon Lee,Jinseok Kim,Inho Kim,Young-Seok Shim,Seungmin Kwak,Yong Kyoung Yoo

doi:10.1155/2018/8678519

Abstract

We report a sputtered PdO decorated TiO2 sensing layer by radiofrequency (RF) sputtering methods and demonstrated gas sensing performance for H2 gas. We prepared sputtered anatase TiO2 sensing films with 200 nm thickness and deposited a Pd layer on top of the TiO2 films with a thickness ranging from 3 nm to 13 nm. Using an in situ TiO2/Pd multilayer annealing process at 550°C for 1 hour, we observed that Pd turns into PdO by Auger electron spectroscopy (AES) depth profile and confirmed decorated PdO on TiO2 sensing layer from scanning electron microscope (SEM) and atomic-force microscope (AFM). We also observed a positive sensing signal for 3, 4.5, and 6.5 nm PdO decorated TiO2 sensor while we observed negative output signal for a 13.5 nm PdO decorated one. Using a microheater platform, we acquired fast response time as ~11 sec and sensitivity as 6 μV/ppm for 3 nm PdO under 33 mW power.

Highlights

Hydrogen gas (H2) is considered a promising future energy source and has numerous applications in industry, such as chemical production, automobiles, and fuel cells
Many attempts have been made to develop gas sensor devices based on ceramic-based metal-oxide sensors, two-dimensional (2D) material-based sensors, mixed composite structures, structures decorated with second-phase particles, and metal-oxide–graphene based gas sensors [2]
We calculated the average grain size of the TiO2 using X-ray diffraction (XRD) peak broadening based on the Scherrer formula [16]

Summary

Introduction

Hydrogen gas (H2) is considered a promising future energy source and has numerous applications in industry, such as chemical production, automobiles, and fuel cells. The general techniques of H2 gas sensing, such as gas chromatography and mass spectroscopy, have several limitations such as slow response, large system size, low portability, and high cost. To detect H2 gas, the sensing system requires a small size, rapid response, and high portability, sensitivity, and selectivity. While the nano-material-based hydrogen gas sensor possesses a great sensing performance, the metal-oxide sensors are good candidates for commercializing sensors since it is compatible with the commercial CMOS (complementary metal-oxide semiconductor) process. One could realize small/portable sensors with signal processing. N-type semiconductors for metal-oxide gas sensors, such as SnO, ZnO, TiO2, and WO3, have been used under normal atmospheric conditions and typical working temperatures in the 200–400∘C range [3, 4].

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Results

Conclusion