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- 1. Phys. Rev. B 75, 144404 (2007) , “Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory”, Debjani Karmakar, S. K. Mandal, R. M. Kadam, P. L. Paulose, A. K. Rajarajan, T. K. Nath, A. K. Das, I. Dasgupta, and G. P. DasFe-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)
- 2. Phys. Rev. Lett. 98, 186804 (2007) , “Room-Temperature Electron Spin Dynamics in Free-Standing ZnO Quantum Dots”, William K. Liu, Kelly M. Whitaker, Alyssa L. Smith, Kevin R. Kittilstved, Bruce H. Robinson, and Daniel R. GamelinConduction 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)
- 3. Appl. Phys. Lett. 89, 262112 (2006) , “Identification of oxygen and zinc vacancy optical signals in ZnO”, T. Moe Børseth, B. G. Svensson, A. Yu. Kuznetsov, P. Klason, Q. X. Zhao, and M. WillanderPhotoluminescence 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)
- 4. Appl. Phys. Lett. 89, 112124 (2006) , “Electric conductivity of boron nitride thin films enhanced by in situ doping of zinc”, K. Nose, H. Oba, and T. YoshidaThe 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)
- 5. Appl. Phys. Lett. 88, 201918 (2006) , “Diffusion of zinc vacancies and interstitials in zinc oxide”, Paul Erhart and Karsten AlbeThe 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)
- 6. J. Appl. Phys. 100, 013518 (2006) , “Photoluminescence analysis on the indium doped Cd0.9Zn0.1Te crystal”, Qiang Li, Wanqi Jie, Li Fu, Ge Yang, Gangqiang Zha, Tao Wang, and Dongmei ZengPhotoluminescence spectra are used to characterize high resistivity of In-doped CdZnTe crystal. Shallow level donor-acceptor pair (DAPs) peak at 1.6014 eV is found due to shallow donor and acceptor compensation related defects, which forms the... (Read more)
- 7. J. Appl. Phys. 99, 053516 (2006) , “Correlation between Zn vacancies and photoluminescence emission in ZnO films”, A. Zubiaga, J. A. García, F. Plazaola, F. Tuomisto, K. Saarinen, J. Zuñiga Pérez, and V. Muñoz-SanjoséPhotoluminescence 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)
- 8. Nature 442, 436 (2006) , “Atom-by-atom substitution of Mn in GaAs and visualization of their hole-mediated interactions”, D. Kitchen, A. Richardella, J. -M. Tang, M. E. Flatt, A. YazdaniThe 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 Ga1-XMnXAs, 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 Ga1-XMnXAs structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples. (Read more)
- 9. Phys. Rev. B 74, 235208 (2006) , “Theoretical study of the magnetism of Mn-doped ZnO with and without defects”, D. Iuan, B. Sanyal, and O. ErikssonWe 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)
- 10. Phys. Rev. B 74, 165203 (2006) , “Isotopic-mass dependence of the A, B, and C excitonic band gaps in ZnO at low temperatures”, S. Tsoi, X. Lu, A. K. Ramdas, H. Alawadhi, M. Grimsditch, M. Cardona, and R. LauckLow 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)
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