Correlation of surface processes with characteristic sensing responses of PdO thin films to ethanol

I. Kai Cheng, Jeng Han Wang, Cheng Yu Tsai, Yi Sheng Chen, Fu Ming Pan

Research output: Contribution to journalArticle

Abstract

Gas sensing characteristics of PdO nanoflake thin films exposed to ethanol (EtOH) at temperatures below 250 °C was studied. The PdO thin film responses distinctly to 0.15 ppm EtOH in dry air at temperatures above 100 °C. A characteristic valley-shaped response feature develops in the early stage of the exposure to EtOH at 150 °C and above. Formation of the valley feature is a result of the combined effects of two types of surface processes, which successively modify the sensor conductance in the opposite way. Dehydrogenation of adsorbed EtOH induces reduction of preadsorbed oxygen anions and the PdO substrate, resulting in the drop of the conductance. On the other hand, subsequent adsorption of EtOH and oxygen on newly growing Pd nanoclusters, which develop due to the reduction of the PdO substrate, causes the increase in the conductance. The Pd nanoclusters can be later reoxidized in the EtOH gas mixture, thereby modifying the sensing behavior of the PdO sensor. X-ray photoelectron spectroscopy (XPS), diffusive reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) were used to study adspecies and gaseous species formed in the EtOH gas sensing reactions. On the basis of the characteristic electrical response and chemical characterizations, we proposed the formation mechanism for the characteristic response feature.

Original languageEnglish
Pages (from-to)589-596
Number of pages8
JournalApplied Surface Science
Volume473
DOIs
Publication statusPublished - 2019 Apr 15

Fingerprint

Ethanol
Thin films
Nanoclusters
Gases
Oxygen
Sensors
Substrates
Dehydrogenation
Temperature programmed desorption
Gas mixtures
Fourier transform infrared spectroscopy
Anions
Negative ions
X ray photoelectron spectroscopy
Adsorption
Temperature
Air

Keywords

  • Dehydrogenation
  • Ethanol
  • MOS gas sensor
  • Pd nanoclusters
  • PdO
  • Reduction

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

Cite this

Correlation of surface processes with characteristic sensing responses of PdO thin films to ethanol. / Cheng, I. Kai; Wang, Jeng Han; Tsai, Cheng Yu; Chen, Yi Sheng; Pan, Fu Ming.

In: Applied Surface Science, Vol. 473, 15.04.2019, p. 589-596.

Research output: Contribution to journalArticle

Cheng, I. Kai ; Wang, Jeng Han ; Tsai, Cheng Yu ; Chen, Yi Sheng ; Pan, Fu Ming. / Correlation of surface processes with characteristic sensing responses of PdO thin films to ethanol. In: Applied Surface Science. 2019 ; Vol. 473. pp. 589-596.
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