X.M. Wu

Electric and magnetic properties of Cr-doped SiC films grown by dual ion beam sputtering deposition

Cr-doped SiC thin films have been fabricated on Al2O3 and Si substrates by using dual ion beam sputtering deposition at room temperature. The films have been characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy (XPS). XRD and TEM results show that the films are amorphous. The XPS studies confirm that the Cr3+ ion occupies the Si site in amorphous SiC (a-SiC). The temperature dependence of resistivity measurements reveals that Cr doping does not change the semiconducting property of the a-SiC films. The magnetic measurements reveal that the Cr-doped a-SiC thin films are ferromagnetic with Curie temperature Tc above room temperature. The carriers mediate the interaction of the magnetic ions, resulting in this ferromagnetic behaviour.

Tunable ferromagnetic behavior in Cr doped ZnO nanorod arrays through defect engineering

Zn vacancy (VZn) effects on the microstructure and ferromagnetism (FM) of Zn0.94Cr0.06O nanorod arrays have been investigated using a combination of experimental measurements and first-principles calculations. The well-aligned Zn0.94Cr0.06O nanorod arrays were synthesized by radio frequency magnetron sputtering deposition at different substrate temperatures. The Cr K-edge X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy results revealed that the Cr3+ ions were located at the substitutional Zn sites. Moreover, the O K-edge XANES analysis and resonance Raman scattering indicated the existence of numerous VZn. The stable FM observed at room temperature was an intrinsic property of Zn0.94Cr0.06O nanorod arrays. With increasing substrate temperature, improved crystallinity along with the increase in VZn was observed in Zn0.94Cr0.06O nanorod arrays, and an enhancement of magnetic moment in the samples came forth. First-principles calculations revealed that the enhanced magnetism mainly comes from the unsaturated 2p orbitals of the surrounding O atoms, which is caused by the presence of the Zn vacancy. This research represents a novel promising route for tuning the magnetic behavior of nano-dilute magnetic semiconductor systems via VZn changes.

Effect of Multiple Frequency H 2 /Ar Plasma Treatment on the Optical, Electrical, and Structural Properties of AZO Films

Transparent conductive Al-doped zinc oxide thin films for film solar cells were prepared on Si and quartz substrates by radio frequency magnetron sputtering at room temperature. Then, these films were treated by high-density H2/Ar plasma, which was capacitively coupled plasma combined with inductively coupled plasma modes. The density of hydrogen atoms was characterized by optical emission spectroscopy equipped in the system. The structural, electrical, and optical properties of the films were investigated in terms of spectrophotometry, Hall effect measurements, X-ray diffraction, scanning electron microscope, and atomic force microscopy. The effects of low-frequency power on the optical, electrical, and structural properties were discussed.

The suppression mechanism of the electron emission from a molybdenum grid coated with carbon or hafnium film

In our experiments, carbon and hafnium films were deposited onto molybdenum substrates by dual ion beam sputtering and radio-frequency magnetron sputtering technology, respectively, and then the BaO layer was deposited on C/Mo and Hf/Mo substrates by a chemical method in order to simulate the working conditions of the grids contaminated by active electron-emission substances from the cathode. The composition and phase change of the samples were investigated after annealing from 600 to 950 °C. The results show that the carbon or hafnium film can effectively reduce accumulation of the cathode emitting substance BaO on the grid surface. The suppression mechanism of the electron emission from the grid is discussed.