Spinel ZnGa2O4 has received significant attention from researchers due to its wide bandgap and high chemical and thermal stability; hence, paving the way for it to have potential in various applications. This review focuses on its physical, optical, mechanical and electrical properties, contributing to the better understanding of this material. The recent trends for growth techniques and processing in the research and development of ZnGa2O4 from bulk crystal growth to thin films are discussed in detail for device performance. This material has excellent properties and is investigated widely in deep-ultraviolet photodetectors, gas sensors and phosphors. In this article, effects of substrate temperature, annealing temperature, oxygen partial pressure and zinc/gallium ratio are discussed for device processing and fabrication. In addition, research progress and future outlooks are also identified.

No abstract

No abstract

In this study, a sol-gel titanium dioxide (TiO 2 ) was spin-coated on indium tin oxide (ITO) substrate as a sensing membrane for the extended-gate field-effect transistor (EGFET). To improve its sensing properties, the resultant films were thermal annealed at various temperatures. It shows that, as TiO 2 was post-annealed at T a =200 o C for 30 min, a highest pH sensitivity of 79.9 ȝA/pH was derived. As T a > 500 o C, the pH sensitivity was declined substantial to 70.1 ȝA/pH. The sensitivity would further deteriorate to 61.8 ȝA/pH as the annealing time extended to 90 min under identical T a . These phenomena could be attributed to the less surface hydroxyl sites of TiO 2 thin film at elevated T a . X-ray diffractograms indicates that an amorphous titania resides as T a < 200 o C which presents more surface hydroxyl sites than those of crystalline structures at elevated T a . It reveals that the pH sensitivity of EGFET was relied on the density of the surface hydroxyl structures. To employ to the portable sensing devices with desirable pH sensitivity, the post annealing of the asdeposited TiO 2 film is a crucial process.

This study investigates the effects of damp heat stability on the optoelectronic properties of ZnO:Al (AZO) and ZnO:Ga(GZO) films with respect to thin-film solar cells. The lowest resistivities of AZO and GZO thin films are 8.2621×10-4 Ω-cm and 2.8561×10-4 Ω-cm, respectively. After damp heat testing for 999h, the resistivities of AZO and GZO thin film increase by 39.72% and 11.97%, respectively. XPS binding energy analysis shows that the AZO thin film has a higher O 1s spectrum than the GZO thin film. Thus, the carrier concentration of films decreases, as a higher binding energy is attributed to the chemisorbed oxygen atoms (O-). Experimental results show that after expousre to a damp heat test at 85°C and 85% relative humidity for electrical, optical, structural, and morphological analysis, GZO films are more stable than AZO films.