In the present work a positive secondary ion emission from a silicon produced by Au m Ϫ projectiles (m ϭ 1-3) with energies of E 0 ϭ 9 and 18 keV and by Al m Ϫ projectiles (m ϭ 1,2) with energies of E 0 ϭ 6, 9, 12, and 18 keV have been studied. Anomalous high nonadditivity of sputtering as large cluster Si n ϩ ions (n Ͼ 4) under molecular Au m Ϫ ion bombardment has been found. As compared with heavy (Au m Ϫ ) projectiles, the light (Al m Ϫ ) projectiles are not effective for sputtering of large cluster ions. For molecular Al m Ϫ ion bombardment nonadditivity of sputtering of small cluster Si n ϩ ions (n Յ 4) increases with decreasing of the energy E 0 from 9 to 6 keV/atom. This effect shows that the efficiency of nonadditive sputtering strongly depends on the penetration depth of molecular projectile and, hence, on the energy density deposited by molecular projectile into subsurface layers of the target from which the cluster ion emission occurs. (Int J Mass Spectrom 209 (2001) 141-152)
Three series of 1 µm thick Ga 1−x Mn x As films with different Mn composition have been characterized using high-resolution x-ray diffraction (HRXRD). The results show that they are highly-crystalline and the growth is reproducible. The Mn compositions have also been measured by other popular methods: in situ ion gauge, x-ray fluorescence (XRF), electron probe microanalysis (EPMA) and secondary ion mass spectrometry (SIMS). The results show that the Mn concentrations measured by different methods are different and the difference between them becomes smaller with increasing Mn content.
For the first time, GaN pn-junctions were fabricated by hydride vapor phase epitaxy. GaN pn-structures were grown directly on 6H-SiC substrates without any buffer layer. Undoped GaN layers were n-type with Nd-Na concentration ranged from 1×1017 to 5×1018 cm−3. Magnesium was used as an acceptor to grow p-type GaN layers. Mg atomic concentration determined by secondary ion mass spectroscopy ranged from 5×1019 to 5×1020 cm−3. As-grown GaN layers doped with Mg were p-type, and p-type conductivity was improved by post-growth anneal. Mesa diodes with a vertical current flow geometry were formed by reactive ion etching. The position of the GaN pn-junction was determined by the electron beam induced current method. The electrical characteristics of the pn diodes were studied. Electroluminescence from the pn diodes was measured.
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