Enhancement of the emission from TeO₂ nanorods by encapsulation with ZnO

Abstract

TeO 2 -core/ZnO-shell nanorods were synthesized by a two-step process comprising thermal evaporation of Te powders and atomic layer deposition of ZnO. Scanning electron microscopy images exhibit that the core-shell nanorods are 50 -150 nm in diameter and up to a few tens of micrometers in length, respectively. Transmission electron microscopy and X-ray diffraction analysis revealed that the cores and shells of the core-shell nanorods were polycrystalline simple tetragonal TeO 2 and amorphous ZnO with ZnO nanocrystallites locally, respectively. Photoluminescence measurement revealed that the TeO 2 nanorods had a weak broad violet band at approximately 430 nm. The emission band was shifted to a yellowish green region (~540 nm) by encapsulation of the nanorods with a ZnO thin film and the yellowish green emission from the TeO 2 -core/ZnO-shell nanorods was enhanced significantly in intensity by increasing the shell layer thickness. The highest emission was obtained for 125 ALD cycles (ZnO coating layer thickness: ~15 nm) and its intensity was much higher than that of the emission from the uncapsulated TeO 2 nanorods. The origin of the enhancement of the emission by the encapsulation is discussed in detail.

Laser-Assisted Growth of t-Te Nanotubes and their Controlled Photo-induced Unzipping to ultrathin core-Te/sheath-TeO2 Nanowires

“…(ii) The method enables the feasibility of using focused laser beams for selectively inscribing NW/NT patterns of elemental Te and/or TeO 2 on the surface of pre-deposited Te films, thus providing a means of simultaneous growth and integrating the nanostructures into an optoelectronic or photonic device. (iii) Photo-oxidation of t -Te NTs yields ultrathin TeO 2 NWs in contrast to those formed by thermal evaporation232425 whose thickness is in the range of 70–100 nm or larger. Apart from well documented properties of TeO 2 NWs, e.g.…”

“…The first growth of TeO 2 NWs was achieved through heating Te nanostructures, in the presence of oxygen, at high temperature (500°C) for about 20 min22. TeO 2 NWs were found to exhibit room temperature gas sensing properties2324 and enhanced luminescence when covered by a layer of ZnO25. In addition, TeO 2 is a promising optical material that meets several applications in laser devices, optical fibers, and non-linear optics.…”

Atomic layer deposition of ZnO: a review

“…The coating of nanowires, nanotubes or nanorods with ZnO (or coating ZnO nanowires) can offer more possibilities for applications than particles, so there has been considerable research effort to study the use of ZnO in core-shell nanowire systems. Some of the more commonly studied structures include ZnO combined with Si or SiO 2 [185][186][187][188][189][190][191][192][193][194], SnO 2 [195][196][197][198][199], Al 2 O 3 [200][201][202] and carbon nanotubes [203][204][205], but combinations of ZnO with several other materials have also been reported [206][207][208][209][210][211][212][213][214][215][216]. The motivation for these studies has been very application-centered, and the majority of them concentrate on either the photoluminescence or chemiresistive properties of the material system, which have applications in the optoelectronics and gas sensing fields, respectively.…”

Fabrication of Te Micro-Tubes and TeO2 Micro-Wires From Powders by Cold Spray

“…In addition, (Te) can react readily with the other elements to generate many functional materials such as ZnTe, CdTe, Nd 3 Te 4 , and Bi 2 Te 3 .1D tellurium nanocrystals, including Te nanotubes, nanorods, nanowires, and nanobelts, have been synthesized through different routes, such as refluxing process, solvothermal or hydrothermal methods, microwave-assisted method, biomolecule-assisted routes, chemical (physical) vapor deposition, visible-light-assisted technique and thermal evaporation method [2], while the crystal structure of TeO 2 1-D tellurium oxide nanocrystals were tetragonal, Tellurium dioxide (TeO 2 ), a versatile wide band gap semiconductor material, is a significant acousto-optical and electro-optical material with a variety of desirable characteristics including elastic behavior, a high refractive index, and good optical quality [4]. Accordingly, TeO 2 has wide applications in active devices such as deflectors, modulators, dosimeters, optical storage material, laser devices, and gas sensors [5]. TeO 2 nanocrystals have been synthesized by a range of techniques such as thermal evaporation of Te powders, laser ablation of Te, and thermal oxidation of Te in a flow of O 2 with no use of catalyst, Huriet et al [5].…”

“…Accordingly, TeO 2 has wide applications in active devices such as deflectors, modulators, dosimeters, optical storage material, laser devices, and gas sensors [5]. TeO 2 nanocrystals have been synthesized by a range of techniques such as thermal evaporation of Te powders, laser ablation of Te, and thermal oxidation of Te in a flow of O 2 with no use of catalyst, Huriet et al [5].…”