Our colleague Dr. sc. Nikša Krstulović, in collaboration with colleagues from the Ruđer Bošković Institute and colleagues from Spain and the Czech Republic, published a paper in the journal Sensors and Actuators B: Chemical in which he deals with the study of ZnO thin films as gas-sensitive sensors.

The role of the pulsed laser deposition in different growth atmospheres on the gas-sensing properties of ZnO films

Kamran Syed, Nikša Krstulović, Juan Casanova-Cháfer, Eduard Llobet, Frank Güell, Paulina R. Martínez-Alanis, Marijan Marciuš, Ekaterina Shagieva, Davor Ristić, Hrvoje Gebavi, Nikola Baran, Mile Ivanda, Sensors and Actuators B: Chemical 382, 133454 (2023)

DOI:  10.1016/j.snb.2023.133454

ZnO films were fabricated at Institute of Physics by pulsed laser deposition of ZnO using two different background atmospheres (argon/vacuum). The gas-sensing properties of both the vacuum and the argon-grown ZnO films against reducing and oxidizing gases were examined. Gas-sensing properties were investigated in details for nitrogen dioxide (NO₂) at different operating temperatures and concentrations. NO₂ gas is one of the key air pollutants and causes climate change and health problems. Although both types of ZnO films have shown a good response towards NO₂ at ppb levels, the films prepared under vacuum conditions showed higher responses. This was attributed to differences in crystallinity, microstructure, and the type of defects present in these materials.

Figure 1. a) PLD chamber at Institute of Physics, b) PLD sheme

Figure 2. XRD diffractograms of ZnO films fabricated by Pulse laser deposition on silicon substrate using two different background atmospheres (Argon/Vacuum)

Figure 3. Sensor resistance changes using the PLD ZnO films grown under vacuum (a) and argon (b) exposed to repeated exposure and recovery cycles to five increasing concentrations of NO₂. Sensors are operated at their optimal working temperatures (200 ◦C)

Figure 4. a) NO₂ sensing results obtained for vacuum-grown ZnO, b) and argon-grown ZnO at three different working temperatures

Highlights

• ZnO films were grown by pulsed laser deposition under two different atmospheres (vacuum or argon) at room temperature.
• The microstructure, crystalline phase, chemical composition and optical properties of the films have been studied.
• Films grown under vacuum conditions show good properties for detecting NO₂ at ppb level.
• The superior gas sensing performance of vacuum-grown ZnO films is attributed to their higher number of oxygen vacancies.