Nanostructural and optical properties of hierarchical ZnO grown via hydrothermal method

A simple hydrothermal method was employed to synthesize 3D hierarchical ZnO nanorods deposited on Si (100) substrate at different growth temperatures (110 and 90oC) within 3 h. The structure, mode and composition of hierarchical ZnO nanorods were investigated by XRD, FESEM and EDX spectroscopy. The polycrystalline ZnO nanostructures products were indexed as hexagonal wurtzite structured, while the morphology was urchin like ZnO nanorods with different aspect ratio of nanorods and stoichiometric. The photoluminescence (PL) properties were studied of as-grown ZnO samples dependent on various growth temperatures. The PL results after UV excitation source were shown a single broad Vis emission peak for both samples with absents of UV emission peak. The emission edge of Vis peak was exhibited blue-shift due to increase temperature growth, and that suggest enhancement in hierarchical ZnO nanorods crystallinity. Oxygen deficiency is evidence on the creation various defects types in hierarchical ZnO nanorods. It is responsible on Vis emission bands. The results demonstrate promising future for the hierarchal ZnO nanostructure which could be applied in optoelectronics and gas sensing

Aluminum doping contents dependent photoluminescence and resistivity of ZnO nanofilms

Using sol-gel spin-coating technique Al-doped ZnO nanofilms (AZONFs) were made on Si(100) substrates and characterized. The obtained nanofilms were annealed at 500 C for 3 h in air. The effects of changing Al doping level (0 to 5 at%) on the structures, morphologies, electrical and photoluminescence characteristics of the nanofilms were evaluated. The XRD patterns of the AZONFs confirmed the formation of wurtzite hexagonal ZnO lattice with preferred growth along (101) lattice plane. In addition, the c-axis orientation of the AZONFs became weaker with the increase in Al doping contents. The surface morphologies, structures, electrical and optical properties of the AZONFs were found to be very sensitive to the Al contents changes. The nanofilm prepared with 1 at% of Al displayed lowest resistivity of 4.238 10-3 O.cm measured by the four-point probe method. The optical band gap energy (increased from 3.22 to 3.304 eV) and carrier mobility of the AZONFs were improved with the increase in Al contents. The proposed AZONFs may be advantageous for various high performance optoelectronic device applications

Structure, morphology and photoluminescence attributes of Al/Ga co-doped ZnO nanofilms: Role of annealing time

The influence of annealing time on the structure, morphology and photoluminescence behavior (Al)/(Ga) co-doped ZnO (AGZO). nanofilms are grown on the p-type Si(100) substrate via combined sol-gel, spin coating annealed in air at 500 °C at 0–3 h. Samples are characterized using XRD, TEM, AFM, FESEM, EDX, (PL) and Raman measurements. XRD pattern confirmed the growth of highly poly-crystalline hexagonal wurtzite structure of ZnO with preferred orientation along (101) direction. At (3 h) is found to cause lattice contraction and strain relaxation. TEM images revealed the nucleation of nanoparticles (NPs) and SAED pattern identified the lattice parameter. Raman spectra of AGZO exhibited optical and acoustic modes. FESEM displayed an increase in the particles size and number of nanoflakes with increasing annealing time. EDX detected right elemental traces. PL revealed an intense emission peak centered at 3.23 eV, which is continuously shifted toward lower frequency with increasing time

The effects of the ambient liquid medium on the ablation efficiency, size and stability of silver nanoparticles prepared by pulse laser ablation in liquid technique

Silver (Ag) nanoparticles (NPs) were synthesized by pulsed laser (Nd:YAG, 1064 nm) ablation of individual target in various solutions. The influence of deionized water (DIW), ethanol and Polyvinylpyrrolidone (PVP) as ambient medium on the fundamental aspects such as ablation efficiency, particle size and stability of Ag NPs was studied. UV-vis spectrophotometer and transmission electron microscopy (TEM) were used to study the optical characterization and morphological analysis of all the synthesized samples, respectively. Preparation in DIW was carried out as a reference sample. The experiments demonstrated that ablation efficiency and stability of NPs in ethanol medium are lowest than those prepared in PVP medium and the reference sample. PVP medium led to higher stability, lower ablation efficiency and finer average particle size compared to reference sample

Gallium contents-dependent improved behavior of sol–gel-grown Al:Ga co-doped ZnO nanostructures

This paper evaluates the improved structural, physical and optical characteristics of aluminum (Al) and gallium (Ga) co-doped ZnO (AGZO) thin film nanostuructures (NSs) synthesized on p-type Si(100) substrate via sol–gel-assisted spin-coating methods. Effects of varying Ga contents (1–5 at.%) on the structure, morphology and photoluminescence (PL) of AGZO films (fixed Al doping of 1 at.%) were determined. Samples were annealed at 500 °C for 3 h and characterized using XRD, FESEM, PL measurements. As-grown NS films revealed hexagonal wurtzite structure with average grain size ranged between 27 and 55 nm. Increase in Ga contents was found to not only reduce the grain size but altered the shape of NSs from nanoparticles (NPs) to nanorods to nanoleaves to nanopeanuts-like morphology. PL spectra displayed a strong UV peak and a broadband in the range of 381–388 nm, attributed to the defect and oxygen vacancy recombination mechanism. The estimated optical band gap of AGZO NSs (3.26–3.20 eV) was lower than pure ZnO films (3.37 eV)