Optical and gas-sensing properties, and electronic structure of the mixed-phase CaCu 3 Ti 4 O 12 /CaTiO 3 composites

Abstract

Optical and gas-sensing properties, and electronic structure of the mixed-phase CaCu3Ti4O12/CaTiO3 composites, Materials Research Bulletinhttp://dx. Graphical abstract A) B)Highlights  CCTO/CTO composites were synthesized by a solid-state reaction using various milling durations; These composites have a broad PL emission band located at 450 nm; CCTO/CTO material was deposited onto an alumina substrate using a screen-printing technique, and hence, could be structured for gas-sensing applications;  Our theoretical findings may further elucidate the electronic structure associated with the interfacial band alignment (type I-straddling gap); Combined experimental and theoretical investigations were conducted on the electronic structure, as well as the optical and gas-sensing properties of mixedphase CaCu3Ti4O12/CaTiO3 (CCTO/CTO) composites, which were synthesized by a solid-state reaction using various milling durations. Our results revealed that these CCTO/CTO composites have a broad photoluminescence (PL) emission band located at 450 nm, which is strongly influenced by the milling process duration. Scanning electron microscopy images confirmed that the use of longer milling durations favored the formation of pores and increased the active surface area of the CCTO/CTO thick films. The thick films were prepared using the screenprinting technique, and hence, could be structured for gas-sensing applications. Our theoretical findings may further elucidate the electronic structure associated with the interfacial band alignment (type I-straddling gap) of the CCTO/CTO composite systems.

Controlling the Electronic, Structural, and Optical Properties of Novel MgTiO3/LaNiO3 Nanostructured Films for Enhanced Optoelectronic Devices

“…It is wellknown that during the excitation process of such nanostructured films, the trapping of the electron-hole pairs occurs in the structural defects. In other words, the process is characterized by the involvement of numerous states within the band gap of the system as a result of the relaxation, and an intense emission of the photon also occurs [26,[33][34][35][36][37][38]. Our results revealed that the PL emission behavior of these novel high-quality functional materials is, in turn, actively controlled by their interface features.…”

“…As a consequence, these findings are commonly consistent with our XRD results for MTO/Si films. Generally, this can attributed to the chemical nature of the reactive species involved, and itis also strongly dependent on the experimental conditions used during the growth of such films [34][35][36][37]. Therefore, these results suggest that the structural changes promoted particularly at the LNO/Si interface, in principle, reduce the polarization, which is capable of populating stable excited electronic states [38,39].…”

“…Clearly, the abovementioned important underlying physical behavior can be easily explained from a structural perspective. Thus, the different intrinsic (hence the bulk-surface) and extrinsic (hence the contact interface) defect distributions play a crucial role in streamlining the behavior of the PL emissions at the nanoscale [33][34][35]38]. To clarify the small structural changes that occur mainly at the contact interface of these nanostructured films, we elucidate the cluster-to-cluster charge transfer processes (CCCT) based on the cluster complex notation of such systems [36], as follows:…”

“…Remarkably, the first effect can be attributed to the intrinsic defects in the Si, LNO, or MTO materials, i.e., the defects derived from the material constituted by the oxygen vacancies in three different charge states ( from the interface features between these complex clusters, which produce extrinsic defects by combining and interacting, which in turn decrease or increase the band gap, and hence can either allow the PL emission or not. Moreover, before the photon arrival, the short-and medium-range structural defects, in particular, generate localized states within the band gap and a non-homogeneous charge distribution in the unit cell [26,[34][35][36][37][38]. After the photon arrival, the lattice configuration changes.…”

“…Moreover, all of the deposited films had a dense microstructure with excellent contact interfaces (see cross-section views in Figure 4 (a-c)), which is promising for developing various interesting technological applications. It is important to note that a deeper understanding of the interface features is crucial when designing novel functional materials with tuned properties [30][31][32][33][34]. In this context, PL emission measurements combined with high-level DFT calculations are often employed to probe the effect of small changes in a crystalline structure.…”