The structural, optical, and magnetic properties of Cu-implanted GaN films have been investigated. No secondary phase was found within the resolution limit of the instrument but the lattice defects such as vacancies were present in the film. Room temperature ferromagnetism was observed with saturation magnetization of 0.3μB/Cu atom. The field-cooled magnetization curves can be well fitted by a Curie-Weiss model and a standard three-dimensional spin-wave model in the low and high temperature ranges, respectively. Our findings indicate that the vacancylike defects should be considered in understanding the observed magnetic properties of the Cu-implanted GaN films.
This paper reports the impact of the Mn incorporation on the structural and magnetic properties of Ga 1-x Mn x N on the metal-organic vapor phase deposition (MOCVD). Crystalline quality and phase purity were determined by high-resolution X-ray diffraction and indicated that no macroscopic second phases are formed during growth. Atomic force microscopy revealed a 2-dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the growth. SQUID measurements showed an apparent ferromagnetic hysteresis behavior. However, none of the requirements for room temperature ferromagnetism in the prevailing mean field DMS theories were found. Therefore, different origins of the ferromagnetic signal are discussed.
The gallium and nitrogen co-doped tin oxide (SnO2 :Ga-N) films have been prepared on α-Al2O3 (0001) substrates at 500°C by metalorganic chemical vapor deposition (MOCVD) method. The relative amount of Ga (Ga/(Ga+Sn) atomic ratio) was 8%. The flow rate of gaseous NH3 injected into the reactor chamber varied from 25sccm to 55sccm. According to the XRD patterns, the film grown at the flow rate of 25sccm has the best crystalline structure. Subsequently, a series of co-doped SnO2 films with the Ga concentration varying from 1% to 12% and the flux of 25sccm for NH3 were fabricated. Post-deposition annealing of the films was carried out at different temperatures for 2 h in nitrogen atmosphere. The structural, electrical and optical transmittance properties of the films have been investigated. For the as-deposited films, except that the film with 12% Ga doping has the amorphous structure, other films have the rutile structures of pure SnO2 with a strong (2 0 0) preferred orientation. After annealing, the structures of all films have changed obviously. Especially, the 12% Ga doping film has the polycrystalline structure also with the (200) preferred orientation. The average transmittances for all the films in the visible range were over 85%. The values of the band gaps varied from 3.3eV to 3.5eV for the as-deposited films and 3.7-3.9eV for the annealed ones. The electrical properties of the as-deposited films varied with the Ga content and were being discussed in detail.
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