Focal plane detector optical readout Gallo, G; Bonanno, D L; Bongiovanni, D G ...
Journal of physics. Conference series,
07/2018, Letnik:
1056, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A preliminary study of an alternative solution for the optical detection and tracking of the ions in the MAGNEX focal plane detector for the NUMEN project is presented. The tracks of the ions are ...sampled by means of the light that they produce through a scintillating gas, which is collected by arrays of Silicon Photo Multiplier suitably arranged. A complete Geant4 simulation is under development in order to correlate detector geometry, characteristics of the gas and light collection efficiency. Fast timing performance could be achieved through a completely digital (on-off) read-out system of the light sensors and a position reconstruction algorithm.
In this paper, we studied the effect of temperature and mask margin size on optical emission and growth rate enhancement (GRE) of InGaN grown by metal organic chemical vapor deposition (MOCVD) and ...nano-selective-area growth (NSAG) on AlN-buffered Si(111). For all mask geometries and temperatures, NSAG produced 90% single-crystal InGaN nanopyramids with smooth facets, perfect selectivity, and 1.2 times the indium composition enhancement (23% and 33% for 800 degreesC and 780 degreesC NSAG, respectively) as found in non-NSAG planar growth at the same conditions. The vapor phase diffusion model was found to be insufficient to predict NSAG GRE, and we propose an explanation combining mechanisms from the vapor phase diffusion with surface migration models. A two-peak emission was noted for all NSAG. The total and relative intensities of the two peaks was found to be strongly dependent upon both temperature and local indium precursor concentration during growth, the latter of which varies based on mask margin size. In NSAG grown at lower temperature and with higher local indium precursor concentration, the bluer of the two peaks was more dominant and the overall emission intensity was higher. InGaN nanopyramids were chemically uniform, ruling out phase separation as origin of the double-peak. We propose an explanation based on the sudden transition from strained to relaxed growth moderated by temperature and local indium precursor concentration.
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