Microstructure of non-polar GaN on LiGaO2 grown by plasma-assisted MBE
We have investigated the structure of non-polar GaN, both on the M - and A-plane, grown on LiGaO2 by plasma-assisted molecular beam epitaxy. The epitaxial relationship and the microstructure of the GaN films are investigated by transmission electron microscopy (TEM). The already reported epi-taxial relationship and for M -plane GaN is confirmed. The main defects are threading dislocations and stacking faults in both samples. For the M -plane sample, the density of threading dislocations is around 1 × 1011 cm-2 and the stacking fault density amounts to approximately 2 × 105 cm-1. In the A-plane sample, a threading dislocation density in the same order was found, while the stacking fault density is much lower than in the M -plane sample.
Growth of semipolar {20–21} GaN and {20–2–1} GaN for GaN substrate
In this article, we present a semipolar {20–21} GaN layer and {20–2–1} GaN layer for large GaN substrates. The {20–21} GaN layer was fabricated on {22–43} patterned sapphire substrates (PSSs) by metal‐organic vapor‐phase epitaxy (MOVPE) and hydride vapor‐phase epitaxy (HVPE). We found that the surface roughening and crack generation during the HVPE growth were suppressed by the formation of SiO2‐striped masks parallel to the c‐axis on the MOVPE‐grown {20–21} GaN template. Furthermore, we demonstrated millimeter‐thick crystal growth on a {20–21} GaN layer and a {20–2–1} GaN layer on a GaN substrate using HVPE. The dark‐spot density in the {20–2–1} GaN layer was approximately 9.6 × 106 cm−2 for 960 min growth. The dark‐spot density in the {20–2–1} GaN layer decreased more rapidly than that in the {20–21} GaN layer as growth thickness increased.
Immunization with Brucella melitensis Rev 1 against Brucella ovis infection of rams.
The efficacy of Brucella Melitensis Rev 1 vaccine (Rev 1) for the prophylaxis of Brucella ovis ram epididymitis was evaluated. Twenty-nine 3-month-old rams were vaccinated with 2 X 10(9) Rev 1 and 14 were revaccinated with 5 X 10(8) at 14 months of age. Six rams remained unvaccinated as a control group. All rams were challenged with 5 X 10(8) B. ovis at 21 months of age. Before being slaughtered 8 weeks later, only one vaccinated ram developed epididymitis while four of the six control rams developed testicular alterations. Genital and selected extragenital organs and lymph nodes were removed at slaughter and inoculated on selective media. B. ovis was isolated from 26.6% of the vaccinated rams, 21.4% of the revaccinated rams and 100% of control rams. Portions of epididymis, testes and vesicular glands were also used for pathological studies. More severe lesions were observed in control rams than in vaccinated ones. In conclusion, these results show that vaccination of young lambs, followed or not by revaccination, is a suitable method for the prophylaxis of B. ovis infection of rams.