Fe-doped ZnO nanocrystals are successfully synthesized and structurally characterized by using x-ray diffraction and transmission electron microscopy. Magnetization measurements on the same system reveal a ferromagnetic to paramagnetic transition temperature above 450 K with a low-temperature... (Read more)

Conduction band electrons in colloidal ZnO quantum dots have been prepared photochemically and examined by electron paramagnetic resonance spectroscopy. Nanocrystals of 4.6 nm diameter containing single S-shell conduction band electrons have g^*=1.962 and a room-temperature... (Read more)

Photoluminescence spectroscopy has been used to study single crystalline ZnO samples systematically annealed in inert, Zn-rich and O-rich atmospheres. A striking correlation is observed between the choice of annealing ambient and the position of the deep band emission (DBE) often detected in ZnO. In... (Read more)

The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from... (Read more)

The self-diffusion coefficient of zinc in ZnO is derived as a function of the chemical potential and Fermi level from first-principles calculations. Density functional calculations in combination with the climbing image-nudged elastic band method are used in order to determine migration barriers for... (Read more)

Photoluminescence spectra are used to characterize high resistivity of In-doped CdZnTe crystal. Shallow level donor-acceptor pair (DAP_s) peak at 1.6014 eV is found due to shallow donor and acceptor compensation related defects, which forms the... (Read more)

Photoluminescence and positron annihilation spectroscopy have been used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The photoluminescence of the samples in the near band edge region has been studied, paying... (Read more)

The discovery of ferromagnetism in Mn-doped GaAs1 has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices2, 3, 4. A major hurdle for realistic applications of Ga_1-XMn_XAs, or other dilute magnetic semiconductors, remains that their ferromagnetic transition temperature is below room temperature. Enhancing ferromagnetism in semiconductors requires us to understand the mechanisms for interaction between magnetic dopants, such as Mn, and identify the circumstances in which ferromagnetic interactions are maximized5. Here we describe an atom-by-atom substitution technique using a scanning tunnelling microscope (STM) and apply it to perform a controlled study at the atomic scale of the interactions between isolated Mn acceptors, which are mediated by holes in GaAs. High-resolution STM measurements are used to visualize the GaAs electronic states that participate in the Mn–Mn interaction and to quantify the interaction strengths as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga_1-XMn_XAs structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples. (Read more)

We calculate the exchange interaction parameters of a classical Heisenberg Hamiltonian for Mn-doped ZnO (Mn concentration between 5% and 20%) by an ab initio Korringa-Kohn-Rostoker coherent-potential-approximation method in the framework of density functional theory. A weak antiferromagnetic... (Read more)

Low temperature wavelength-modulated reflectivity measurements of isotopically engineered ZnO samples have yielded the dependence of their A, B, and C excitonic band gaps on the isotopic masses of Zn and O. The observed dependence is analyzed in terms of the band gap renormalization by zero-point... (Read more)

Experimental studies of Zn_1−xCo_xO as thin films or nanocrystals have found ferromagnetism and Curie temperatures above room temperature and that p- or n-type doping of Zn_1−xCo_xO can change its magnetic... (Read more)

A set of bulk ZnO samples implanted with O and Zn at various densities were investigated by photoluminescence. The implantation concentration of O and Zn is varied between 1×10¹⁷/cm³ and 5×10¹⁹/cm³. The samples were thermally treated in an... (Read more)

Zinc oxide crystals grown by the seeded chemical vapor transport method have been annealed in zinc vapor at 1100 °C for 30 min. These thermochemical reduction treatments produce a deep red coloration in the crystals and increase their n-type electrical conductivity. Electron paramagnetic... (Read more)

ZnMnO nanoclusters were synthesized by the sol–gel method. The structural and magnetic characters were investigated. The XRD spectrum shows ZnMnO nanoclusters are hexagonal wurtzite structures and a small quantity of ZnMn2O4 phase is also present in the spectrum. The percentages of Zn and Mn... (Read more)

Hole burning in and displacements of the magnetic-resonance absorption line of the electron spin of the shallow hydrogen-related donor in ZnO are observed upon resonant irradiation with microwaves at 275 GHz and at 4.5 K in a magnetic field of 10 T. These effects arise from an almost complete... (Read more)

Infrared optical absorption has been used to study OH−impurities into congruent co-doped LiNbO3:Cr3+:ZnO crystals doped with different Zn2+ concentration. The OH− IR absorption spectra present three bands that can be associated with different OH− complex centres available in the... (Read more)

Electric-dipole spin resonance of the deep acceptor Zn_S^- in Si reveals close Γ8 and Γ7 ground states with zero-field separation of only 0.31 meV as compared to the 43 meV of the two valence bands. With Landé's formula for the g factors of a ²T₂ state split by spin-orbit interaction into Γ8 and Γ7 this nearness can be interpreted as strong quenching of the orbital moment. The observed dependence on the Zn isotopic mass indicates a dynamic contribution of the acceptor atom to the electronic state as is expected for a Jahn-Teller effect. (Read more)

The mixed MoO3–ZnO catalyst was expected to reveal the new function as a catalyst. The catalyst was characterized by XRD, ESR, XANES and so on. We found that the MoO3–ZnO catalyst was effective for isomerization and metathesis of 1-butene. The defects with the anion vacancy were formed... (Read more)

A review is given on the diffusion, solubility and electrical activity of 3d transition metals in silicon. Transition elements (especially, Cr, Mn, Fe, Co, Ni, and Cu) diffuse interstitially and stay in the interstitial site in thermal equilibrium at the diffusion temperature. The parameters of the liquidus curves are identical for the Si:Ti — Si:Ni melts, indicating comparable silicon-metal interaction for all these elements. Only Cr, Mn, and Fe could be identified in undisturbed interstitial sites after quenching, the others precipitated or formed complexes. The 3d elements can be divided into two groups according to the respective enthalpy of formation of the solid solution. The distinction can arise from different charge states of these impurities at the diffusion temperature. For the interstitial 3d atoms remaining after quenching, reliable energy levels are established from the literature and compared with recent calculations. (Read more)

The temperature dependence of the spectrum of two trapped hole centers introduced by electron irradiation in ZnO is described. The results firmly establish the identification of these centers as being two slightly inequivalent configurations of the zinc vacancy in its negative charge state. (Read more)

Zinc is a double accepter in silicon and it introduces two levels, E ＋ 0.31 and E ＋ 0.55 eV, into forbidden band [1,2]. The electrical and optical properties of zinc-doped silicon have been investigated by several workers [2-4]. A brief report of the observation of EPR in silicon is given in [5,6]: in these investigations the magnetic field H was perpendicular to the axis of compression of a crystal. Uniaxial compression gave rise to a structure in EPR spectrum of Zn⁶⁷ and this structure was attributed to the hyperfine interaction of an unpaired hole with the magnetic moment of the Zn⁶⁷ nucleus. The present paper describes the result of an investigation of the EPR of the Zn^- state of zinc in p-type silicon doped with zinc in p-type silicon doped with zinc and phosphorus. The investigation was carried out at liquid helium temperature.

Electron irradiated ZnO single crystals show anisotropic ESR spectra corresponding to a spin and a spin 1 hole centers. Tehy are respectively identified as the negative and the neutral charge states of the zinc vacancy. (Read more)

Lines in the EPR spectrum of ZnO crystals irradiated by 3.6 × 1018cm−2 fast neutrons are ascribed to holes on oxygen atoms in the basal plane of O4 tetrahedra which surround Zn vacancies. (Read more)