Magnetism and optical properties of nanocrystalline Cu2O and TiO2 powders

Optical properties of oxide magnetic ZnO, Zn0.95Mn0.05O and Cu2O nanopowders

“…The sizes of nanocrystals were determined directly by the transmission electron microscopy (TEM) and by the width of the X-ray diffraction peaks. [4], and it had a distinct shoulder at 4.2 K. The positions of the peak and the shoulder for nanocrystals having the size of 15 nm present a more convicting evidence of the shift of these positions towards higher energies by approximately 15 meV as compared to the excitonic lines for 90 nm nanocrystals.…”

“…Earlier, we had observed the excitonic states in Cu 2 O nanocrystals and part of these results was presented in Ref. [4]. The Cu 2 O monocrystals have the developed system of excitonic states, which are very sensitive to the crystal defects.…”

Native defect-induced multifarious magnetism in nonstoichiometric cuprous oxide: First-principles study of bulk and surface properties ofCu2−δO

“…It has been established experimentally [33][34][35] and theoretically 7,8,14 that the dominant point defects in cuprous oxide under varying oxygen conditions are both neutral and singly negatively charged copper vacancies. As reported, both the electronic and magnetic properties of Cu 2 O is sensitively influenced by its ͑sub-͒stoichiometry and growth conditions, [31][32][33][34] thus reinforcing the need to investigate how deviation from its natural stoichiometry ͑i.e., in the presence of native defects͒ will affect these properties ͑and thus functionality͒ in Cu 2 O. Using the projector-augmented-wave ͑PAW͒ method and the generalized gradient approximation ͑GGA͒, Nolan and Elliott 7 performed density-functional theory ͑DFT͒ calculations, investigating the p-type conduction mechanism in Cu 2 O, and concluded that the p-type semiconducting properties seen in Cu 2 O are attributed to small concentrations of Cu vacancies.…”

“…[25][26][27][28][29][30] This has prompted many researchers to ͑re-͒investigate the fundamental properties of such semiconducting oxides, focusing largely on their deviation from natural stoichiometry and the role of native defects. In relation to Cu 2 O, Yermakov and co-workers 31,32 have found that nanocrystalline powder samples of nonstoichiometric Cu 2 O ͑i.e., Cu 2−␦ O͒ exhibit magnetic hysteresis properties of up to 400 K, suggesting ferromagnetic behavior. These nanoparticles are of 10-100 nm in size and their magnetic properties are reported to be highly dependent on the oxygen concentration during their formation.…”

Optical properties of ZnO, Zn0.99Mn0.01O nanopowders

“…Nanopowder with the size of the nanocrystals of 30 nm were prepared by the method of the gas phase synthesis [7] annealed in air at 400°C during 1 hour. The manganese concentration in nanocrystals Zn 1-x Mn x O before and after the annealing was determined by inductively-coupled plasma mass spectroscopy (iCAP 6000, Thermo) and x=0.01.…”