痞客jaher

要給老闆的作業，大概拖了將近ㄧ各星期吧=.=a

我真的不是故意的，中翻英後從２頁內容縮成不到１頁那也不是我願意的

你就將就點吧　ｍ（＿。＿）ｍ

Substrate preparation

In order to obtain reproducible high-quality epilayer substrate preparation should deserve the most attention. The as-receivedγ-LAO substrates were thus only degreased sequentially in acetone (3 min) and methanol (3 min) in an ultrasonic bath. Finally, the substrate was puffed by pure nitrogen gas speedy. The γ-LAO substrate was then fixed to a Mo holder. Prior to growth, the substrate was outgassed in the chamber for 20 min at 700℃.

Growth processes

   The adsorption experiments were performed in the Veeco Applied-EPI 930 radio frequency plasma assisted molecular-beam epitaxy chamber equipped with a standard effusion cell for Ga evaporation. The chamber also contains Veeco Applied EPI uni-bulb RF-plasma cell to provide active nitrogen for GaN growth processes. The growth processes and conditions are as follows. Before depositing buffer layers, theγ-LAO substrate were exposed to a N₂- plasma flux for nitridation at 200℃ for 10 min, the N2-plasma power was 500W and the N₂ flow rate is preserved in 1.00 sccm. After that, about 10 nm LT GaN buffer layer were grown. Then, HT GaN film was grown on the buffer layer. During the growth of the GaN films, the N₂-plasma power was 500W and the N₂ flow rate varied from 0.63 to 0.75 sccm, while the N/Ga flux ratio was varied from about 15 to 39 as measured by a flux monitor. The growth temperature was in the range from 500 to 600℃ and the growth rate was about 0.4 μm/h. The total thickness of the GaN film was varied from 1.6 to 1.9 μm. In situ RHEED observations were carried out throughout the growth and the cooling processes without nitrogen flux. In order to characterize the GaN film quality, XRD and SEM measurements were carried out.