Thermal Chemically Deposited Zno Nanostructures: Influence of Post-Deposition Annealing Temperature on Ph Sensor Performance

Abstract

Zinc oxide (ZnO) nanostructures were synthesized via thermal chemical deposition (TCVD) method and applied as the sensing membrane of an extended-gate field effect transistor (EGFET) pH sensor. The ZnO nanostructures undergone a post-deposition heat treatment with the temperature ranging from 200-500 °C for 15 min in air ambient. The influence of the post-deposition heat treatment on the physical and pH sensing characteristics was investigated. The FESEM images showed that the surface morphology of the samples were dependent on post-annealing treatment. The as-deposited sample showed the biggest grain size and non-uniformed structures. Applying the post-annealing heat treatment caused the surface morphology to become denser and uniform. The most ideal temperature for the heat treatment for EGFET pH sensor application was found at 300 °C resulting in a pH sensitivity of 48.2 mV/pH with 0.9646 linearity.

Fabrication And pH Sensing Characteristics Measurement of Back Gate ZnO Thin Film Planar FET

“…120.97 mA/pH is obtained in the pH range of 3.2 to 11.1 but at higher channel length (L = 12 µm & 15 µm) current sensitivity decreases. Hence, the channel length is an important parameter that affects the current sensitivity as well as [22] 31.81 4-12 not reported ZnO NR based sensor [23] 44.56 4-10 1.7 ZnO film-based sensor [23] 34.82 4-10 not reported ZnO nanostructures [24] 48.2 4-12 not reported ZnO nanowire-based EGFET pH sensor [25] 36.9 4-10 1 EGFET with unpassivated i-ZnO nanorod array [26] 44.01 4-12 0.08 EGFET with passivated i-ZnO nanorod array [26] 49 voltage sensitivity. The maximum current for various channel lengths at different pH is drawn in Fig.…”

“…Young et al [23]. Aimi Bazilah et al reported EGFET based pH sensor in which the sensing layer is fabricated by thermal chemical deposition (TCVD) method and calculated the sensitivity 48.2 mv/pH in the pH range of 4 to 12 [24]. Passivated ZnO film-based sensor and ZnO NR array have higher sensitivity than unpassivated devices because passivation reduces the Fermi level pinning effect [26].…”

“…Average threshold voltage and average current sensitivity at different channel lengths are plotted in Fig. 10 [24]. Passivated ZnO film-based sensor and ZnO NR array have higher sensitivity than unpassivated devices because passivation reduces the Fermi level pinning effect [26].…”