Synthesis and characterization of Mn-doped ZnO nanorods grown in an ordered periodic honeycomb pattern using nanosphere lithography

We report a study of the structural, optical and magnetic properties of undoped and Mn-doped ZnO nanorods grown by chemical bath deposition in a periodic honeycomb lattice formation. Mn-doping is accomplished by a diffusion process at a constant time of 8 h for different temperatures of 500, 600 and 700 °C. Undoped and Mn-doped ZnO nanorods had a hexagonal wurtzite structure with a (002) preferred orientation. From SEM results, it was seen that Mn-doped ZnO nanorods grew vertically in the honeycomb lattice with lengths of 0.8 μm. XPS results showed that Mn3+ ions was successfully incorporated in the ZnO matrix by substituting for Zn2+ ions and that Mn-doping increased the number of oxygen vacancies in ZnO compared to undoped ZnO. This result was also supported by photoluminescence data at 10 K. Magnetic data showed that all the samples exhibited ferromagnetic character. Although the origin of undoped ZnO is related to oxygen vacancy-induced d0 ferromagnetism, bound magnetic polarons are responsible from the ferromagnetism of Mn-doped ZnO samples which have Tc values above the room temperature

Defect-induced room temperature ferromagnetism in B-doped ZnO

ZnO microrods were grown on glass substrates by the spray pyrolysis method and boron was doped into the ZnO microrods by diffusion. X-ray diffraction results confirmed that the incorporation of B leads to a slight reduction in the deposit texture. Scanning electron microscopy measurements showed that the morphology of the ZnO samples changed from a microrod to nanocrystalline structure with B-doping. Photoluminescence data indicate that B-doping leads to a relative increase of the unstructured green band intensity. Magnetic measurements revealed that B-doped ZnO samples exhibited room temperature ferromagnetism related to defects, in agreement with first principles theoretical calculations

Structural, optical and magnetic properties of Ni-doped ZnO micro-rods grown by the spray pyrolysis method

Undoped and Ni-doped ZnO micro-rod arrays were successfully synthesized by the spray pyrolysis method on glass substrates. Analysis of the samples with x-ray diffraction and scanning electron microscopy showed that these micro-rod arrays had a polycrystalline wurtzite structure with a highly c-axis preferred orientation. Photoluminescence studies at both 300 K and 10 K show that the incorporation of nickel leads to a relative increase in the visible blue light band intensity. Magnetic measurements indicated that Ni-doped ZnO samples exhibit ferromagnetic behavior at room temperature, which is possibly related to the presence of point defects

Defect-mediated ferromagnetism in ZnO:Mn nanorods

In this work, the structural, chemical and magnetic properties of ZnO:Mn nanorods were investigated. Firstly, well-aligned ZnO nanorods with their long axis parallel to the crystalline c-axis were successfully grown by the vapor phase transport technique on Si substrates coated with a ZnO buffer layer. Mn metal was then diffused into these nanorods at different temperatures in vacuum. From SEM results, ZnO:Mn nanorods were observed to have diameters of ~100 nm and lengths of 4 µm. XPS analysis showed that the Mn dopant substituted into the ZnO matrix with a valence state of +2. Magnetic measurements performed at room temperature revealed that undoped ZnO nanorods exhibit ferromagnetic behavior which may be related to oxygen vacancy defect-mediated d0 ferromagnetism. ZnO:Mn samples were seen to show an excess room temperature ferromagnetism that is attributed to the presence of oxygen vacancy defects forming bound magnetic polarons involving Mn

CZTS layers formed under sulfur-limited conditions at above atmospheric pressure

In this study CZTS thin films were grown by a two-stage process that involved sequential sputter deposition of metallic Cu, Zn, and Sn layers on Mo coated glass substrates followed by RTP annealing in a sulfur atmosphere at background gas pressures in the range of 1–2 atm. Sulfurization was carried out in a mini reaction volume that provided a relatively S-limited environment. Reacted films were characterized using XRD, EDX, SEM, photoluminescence and Raman spectroscopy. It was found that, under the S-limited regime provided in these experiments the Cu-S secondary phase formation was most extreme in the sample grown at 1.5 atm, whereas films grown at lower and higher pressures showed much smaller degree of phase separation. Reaction at 2 atm yielded a compound film that was the closest to the initial precursor in terms of its composition. SEM micrographs showed rough morphology and polycrystalline structure that changed with the sulfurization pressure. The optical band gap of the films as determined by photoluminescence was found to be about 1.37 eV. These experiments demonstrated the importance of the sulfurization pressure as well as the size of the reactor internal volume in determining secondary phase formation in two-stage processed CZTS layers. © 2018 Elsevier Lt

Influence of pre-annealing Cu-Sn on the structural properties of CZTSe thin films grown by a two-stage process

In this study CZTSe thin film were synthesized by a two-stage process that included sequential sputter deposition of Cu and Sn layers forming a Cu/Sn structure, pre-annealing the Cu/Sn structure at 200–380 °C for some of the samples, sputtering of additional Zn and Cu over the Cu/Sn structure, evaporation of a Se cap forming a Cu/Sn/Zn/Cu/Se precursor film, and exposing the precursor film to high temperature annealing treatment at 550 °C for 15 min to form the compound. The results of the characterization carried out on the compound layers revealed that the phase content, composition and microstructure of these layers changed noticeably depending on whether or not a pre-annealing step was utilized. Although XRD studies suggested presence of secondary phases, especially in the non-pre-annealed samples, the data was dominated by kesterite CZTSe phase reflections. Raman spectra of the films verified the formation of kesterite CZTSe structure and some other phases, which were determined to be SnSe 2 and possibly ZnSe. SEM micrographs showed denser structure in the pre-annealed samples. © 2018 Elsevier Lt

Growth and characterization of Cu2SnS3 (CTS), Cu2SnSe3 (CTSe), and Cu2Sn(S,Se)3 (CTSSe) thin films using dip-coated Cu–Sn precursor

Ternary compounds Cu2SnS3, Cu2SnSe3 and Cu2Sn(S,Se)3 thin films used in thin film solar cell applications were prepared at the first time by such a two-stage process that includes dip-coating of Cu–Sn precursors as distinct from vacuum-based fabrication methods followed by sulfurization/selenization of prepared precursors via rapid thermal processing at 550 °C. All prepared thin films revealed Cu-poor composition. X-ray diffraction and Raman spectra of the samples showed that Cu2SnS3 and Cu2SnSe3 thin films had a monoclinic structure as a dominant phase and additionally some secondary phases such as tetragonal Cu2SnS3 and orthorhombic Cu3SnS4. However, the tetragonal and orthorhombic phases had more impact on Cu2Sn(SSe)3 thin film. Compact, dense, and small grained surface morphologies were obtained for the Cu2SnS3 and Cu2Sn(SSe)3 thin films, while the surface morphology of the Cu2SnSe3 thin film had larger grained surface morphology. The Cu2SnS3 thin film demonstrated higher transmittance (~ 65%) and two different absorption edges that indicates formation of two band gap energy. Band gap values of Cu2SnS3, Cu2Sn(SSe)3 and Cu2SnSe3 thin films were found 0.97 eV (and 1.51 eV), 1.25 eV and 0.78 eV, respectively. The lowest resistivity (2.48 × 10-1 ? cm) and the highest carrier concentration (1.64 × 1019 cm-3) values were observed for Cu2Sn(SSe)3 thin film. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Recep Tayyip Erdogan ÜniversitesiThis work was supported by the research fund of Recep Tayyip Erdogan University, Rize, Turkey, under Contract No. FDK-2018-96

Effects Of Cu Diffusion-Doping On Structural, Optical, And Magnetic Properties Of Zno Nanorod Arrays Grown By Vapor Phase Transport Method

Well-aligned ZnO nanorods were prepared by the vapor phase transport method on Si covered with a ZnO buffer layer. After the nanostructure growth, Cu was doped into the ZnO nanorods by diffusion at three different temperatures and for different times. Undoped and Cu diffusion-doped ZnO samples are highly textured, with the c axis of the wurtzite structure along the growth direction. The incorporation of Cu caused some slight changes in the nanorod alignment, although the wurtzite crystal structure was maintained. X-ray photoelectron spectroscopy measurements revealed that Cu ions were in a divalent state and substituted for the Zn2+ ions of the ZnO matrix. Photoluminescence results at 10K indicate that the incorporation of copper leads to a relative increase of Cu-related structured green band deep level intensity. Magnetic measurements revealed that both undoped and Cu diffusion-doped ZnO samples exhibited room temperature ferromagnetism. It was also found that bound magnetic polarons play an important role in the appearance of room temperature ferromagnetism in Cu diffusion-doped ZnO nanorods. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673861]Wo