L10 FePt nanoparticles with distinct perpendicular magnetic anisotropy prepared on Au buffer layers by a micellar method

FePt nanoparticles were self-assembled on a MgO(001) substrate by a micellar method. We introduced an Au buffer layer to control the lattice orientation and the magnetic alignment of FePt nanoparticles. A distinct c-axis preferred orientation of the FePt nanoparticles was achieved during the thermal annealing treatment. The driving force of lattice reorientation is considered to be the result of the stress caused by the lattice misfit between Au and FePt. The degree of c-axis orientation is significantly enhanced with increasing Au thickness, which is attributed to the decrease of the in-plane lattice and the improved crystal quality of the Au layer. Perpendicular magnetic anisotropy was observed for the FePt samples with the Au buffer layer. The out-of-plane coercivity and remanence ratio are3.1 kOe and0.8, respectively, which far exceed the in-plane values.?2011 American Institute of Physics

Effects of silicon incorporation on composition, structure and electric conductivity of cubic boron nitride thin films

We have achieved in-situ Si incorporation into cubic boron nitride (c-BN) thin films during ion beam assisted deposition. The effects of silicon incorporation on the composition, structure and electric conductivity of c-BN thin films were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electrical measurements. The results suggest that the content of the cubic phase remains stable on the whole with the incorporation of Si up to a concentration of 3.3 at.%, and the higher Si concentrations lead to a gradual change from c-BN to hexagonal boron nitride. It is found that the introduced Si atoms only replace B atoms and combine with N atoms to form Si-N bonds, and no evidence of the existence of Si-B bonds is observed. The resistance of the Si-doped c-BN films gradually decreases with increasing Si concentration, and the resistivity of the c-BN film with 3.3 at.% Si is lowered by two orders of magnitude as compared to undoped samples

Ordered FePt Nanoparticle Arrays Prepared by a Micellar Method

We prepared L1(0) phase FePt nanoparticle arrays on Si by a micellar method combined with plasma treatment, in-situ deposition of a Sio(2) overlayer, and a post-annealing. The FePt nanoparticle arrays exhibit a quasi-hexagonal order with tailored inter-particle spacing and particle size. Transformation of L1(0) FePt was achieved for the annealed samples. In addition, the ordering temperature of FePt nanoparticles was reduced by 50 similar to 100 degrees C by Au or Ag doping. The micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media

Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes

n-ZnO/p-GaN heterojunction light-emitting diodes with and without a sandwiched AlN layer were fabricated. The electroluminescence (EL) spectrum acquired from the n-ZnO/p-GaN displays broad emission at 650 nm originating from ZnO and weak emission at 440 nm from GaN, whereas the n-ZnO/AlN/p-GaN exhibits strong violet emission at 405 nm from ZnO without GaN emission. The EL intensity is greatly enhanced by inserting a thin AlN intermediate layer and it can be attributed to the suppressed formation of the GaOx interfacial layer and confinement effect rendered by the AlN potential barrier layer

Effects of Hydrogen Plasma Treatment on the Electrical and Optical Properties of ZnO Films: Identification of Hydrogen Donors in ZnO

Wurtzite ZnO has many potential applications in optoelectronic devices, and the hydrogenated ZnO exhibits excellent photoelectronic properties compared to undoped ZnO; however, the structure of H-related defects is still unclear. In this article, the effects of hydrogen-plasma treatment and subsequent annealing on the electrical and optical properties of ZnO films were investigated by a combination of Hall measurement, Raman scattering, and photoluminescence. It is found that two types of hydrogen-related defects, namely, the interstitial hydrogen located at the bond-centered (H-BC) and the hydrogen trapped at a O vacancy (H-O), are responsible for the n-type background conductivity of ZnO films. Besides introducing two hydrogen-related donor states, the incorporated hydrogen passivates defects at grain boundaries. With increasing annealing temperatures, the unstable H-BC atoms gradually diffuse out of the ZnO films and part of them are converted into H-O, which gives rise to two anomalous Raman peaks at 275 and 510 cm(-1). These results help to clarify the relationship between the hydrogen-related defects in ZnO described in various studies and the free carriers that are produced by the introduction of hydrogen