Fabrication and analysis of Cr-doped ZnO nanoparticles from the gas phase

Abstract

High quality Cr-doped ZnO nanoparticles from the gas phase were prepared and investigated with respect to their structural, optical and magnetic properties. The extended x-ray absorption fine structure and the x-ray absorption near edge structure of the particles verify that after nanoparticle preparation Cr is incorporated as Cr3+ ) at least partially on sites with a 4-fold oxygen configuration, most likely on a Zn site, into the wurtzite lattice. Despite the fact that Cr is known to act as an efficient non-radiative loss centre for near band gap emission (NBE), a pronounced NBE is obtained up to room temperature even for a nominal Cr concentration of 10 at.%. Annealing at 1000 degrees C results in a significant improvement of the photoluminescence efficiency and a reduced PL linewidth down to 2.9 meV at low temperatures while the structural and magnetic data indicate the formation of ZnCr2O4 clusters.

Enhanced magnetism in Cr-doped ZnO nanoparticles with nitrogen co-doping synthesized using sol–gel technique

“…However, transition metal doping in DMS materials leads to some problems such as formation of secondary phases or clusters, and the mechanism of ferromagnetism in these materials is still unclear, making them undesirable for device applications. These DMS nanoparticles can be useful in ferrofluid and biomedical applications (Deka et al 2004;Schneider et al 2009). …”

Tailoring magnetic and photoluminescence properties in ZnS/ZnO core/shell nanostructures through Cr doping

“…The disappearance of UV emission band in Cr doped core/shell nanoparticles are due to Cr incorporation in to ZnS/ZnO lattice. It is known that Cr quenches the band edge emission in ZnO [32,33]. Cr doped core/shell NPs show sharp emission peak at 485 nm and the distinct sharp blue emission peak arises from recombination of bound exciton between a shallow Cr 3+ donor level and a recombination centre of intrinsic origin which is probably a V Zn2+ acceptor centre.…”

Band gap tailoring and enhanced visible emission by two-step annealing in Zn0.94Cu0.04Cr0.02O nanocrystals

“…Among these dopant elements, Cu and Cr are important because, (1) Cu is a prominent luminescence activator, which can modify the luminescence of ZnO crystals by creating localized impurity levels [10], (2) trivalent Cr 3? ions exhibit 3d 3 high-spin configuration, which may help to generate large magnetic moments in the host semiconductors [11] and (3) they can change microstructure and optical properties of ZnO system.…”

“…Even though some of the research works have been carried out on Cu or Cr doped ZnO system separately [11,13,[16][17][18][19], comprehensive study of the structural and optical properties of Cu and Mn co-doped ZnO nanocrystals is still scanty. Therefore, in present investigation, Zn 0.94 Cu 0.04 Cr 0.02 O nanocrystals were synthesized by using co-precipitation method.…”