ZnS Covering of ZnO Nanorods for Enhancing UV Emission from ZnO

Abstract

Enhancing the ultraviolet (UV) emission from zinc oxide (ZnO) is of special significance for fabricating ZnO-based short-wavelength light-emitting devices. Herein, we report the enhancement of the UV near-band-edge (NBE) emission of ZnO by covering the surface of ZnO nanorods with a thin ZnS coating. The ZnO nanorods were grown via hydrothermal reactions, and the ZnS covering was realized by pulsed laser deposition. The prepared samples were characterized for morphology and structure by field emission scanning electron microscopy, transmission electron microscopy, Raman scattering spectroscopy, and Fourier-transform infrared spectroscopy measurements. Photoluminescence of the samples was measured at room temperature and reduced temperatures for a systematic examination of the effect of the ZnS covering on the NBE emission of ZnO. The bare ZnO NRs without ZnS covering can emit a strong UV NBE emission at room temperature along with a very weak visible emission ascribed to deep level defects. After being covered with a 4 nm thick ZnS coating, the ZnO NBE emission was enhanced about 2.5 times at room temperature. The ZnO NBE emission of the bare and ZnS-covered ZnO nanorods increases as the temperature decreases, with the ZnO NBE emission of the latter increasing more evidently. At a low temperature of 100 K, an about 4-fold enhancement in the UV ZnO NBE emission is obtained for the 4 nm thick ZnS-coverd ZnO nanorods compared with the bare ZnO nanorods.

Interaction of an Ultrathin Zinc Surface Passivation Layer with a Room Temperature-Deposited Al-Doped ZnO Film Leading to Highly Improved Electrical Transport Properties

“…36-1541). 24 The broadness of the (002) peak indicates poor crystallinity of the film owing to the deposition process at RT. However, a gradual increase in the intensity of the (100) peak, a simultaneous decrease of the (002) peak, and gradual appearance of the (110) peak intensity have been observed as the Zn overlayer thickness is increased, suggesting a change in the orientation of the crystallites.…”

Single‐electron spodium bonds: Substituent effects

“…It was also previously demonstrated that the H 3 C radical can engage in single‐electron hydrogen, lithium, sodium, halogen, chalcogen, pnicogen, tetrel, and triel bonds. [ 38–44 ] Their interaction energies at the MP2/aug‐cc‐pVTZ level are respectively 6.39 kJ/mol in H 3 C⋯HCN, [ 36 ] 10.36 kJ/mol in H 3 C⋯ICN, [ 61 ] 15.47 kJ/mol in H 3 C⋯SeHF, [ 41 ] 9.8 kJ/mol in H 3 C⋯PH 2 F, [ 42 ] 8.73 kJ/mol in H 3 C⋯SnH 3 F, [ 43 ] and 70.85 kJ/mol in H 3 C⋯Al (CN) 3. [ 44 ] The interaction energy of the SpF 2 complexes is larger in magnitude than 16 kJ/mol, and the electron‐withdrawing ability of the F atom is less than that of the CN group; thus, the H 3 C radical seems to have a greater affinity for the Sp atom than for the main group atoms.…”

“…This substitution effect was also found in the single‐electron hydrogen, halogen, chalcogen, pnicogen, tetrel, and triel bonds. [ 38–44 ] The CH 3 group in Sp (CH 3 ) 2 weakens the single‐electron spodium bond, whereas the CH 3 group strengthens the single‐electron halogen bond, which becomes stronger in the order: H 3 C radical < ethyl radical < iso‐propyl radical < tert‐butyl radical. [ 62 ] The halogen substitution in SpX 2 has an interesting effect on the strength of the single‐electron spodium bond.…”

“…For the main group atom, its most positive MEP increases for the heavier main group atom, and the corresponding interaction energy also increases. [ 38–44 ] That is, for the single‐electron hydrogen, halogen, chalcogen, pnicogen, tetrel, and triel bonds with the H 3 C radical as the electron donor, the electrostatic interaction is dominant. But for the single‐electron spodium bond, besides the electrostatic interaction, the contribution made by polarization is also very important.…”

“…[ 36 ] Although single‐electron hydrogen‐bonded complexes exhibit the same spectral properties as those formed by neutral molecules, they have a different topological profile. [ 27 ] In addition, the H 3 C radical can interact as an electron donor to bind with halogen, lithium, chalcogen, sodium, pnicogen, tetrel, and triel atoms, thus forming single‐electron lithium, [ 38 ] sodium, [ 39 ] halogen, [ 40 ] chalcogen, [ 41 ] pnicogen, [ 42 ] tetrel, [ 43 ] and triel bonds, [ 44 ] respectively. Ab initio studies of hydrogen, lithium and halogen single‐electron bonds were carried out using HBe, H 2 B, and H 3 C radicals as electron donors, and the results showed that the interactions between hydrogen, lithium, and halogen bonds are enhanced in the order H 3 C < HBe < H 2 B.…”