BiI3 nucleation and coalescence onto amorphous substrates

Abstract

BiI3 nucleation and coalescence was performed onto glass substrates. Further film growth onto the bestnucleated layers were then made, with the objective of using these films as detectors for digital imaging.BiI3 was synthesized from Bi2O3CO2.H2O y KI, and then treated with HI to avoid the formation of BiOIby hydrolysis. The material was purified by zone melting followed by two sublimations. Nucleationswere performed by physical vapor deposition (PVD) on 2hx2h glass substrates with an initial pressure of4 x 10-3 Pa. Source and substrate were electrically heated, with temperatures ranging from 150-180 oC and50-150 oC for source and substrate respectively, in order to study supersaturation influence on nucleation.The obtained nuclei were between 0.2 to 0.03 ƒÊm in size. Annealing was performed seeking for nucleicoalescence, heating them at 80-110 oC during 5 days. Coalescence was only observed when annealingthe smallest nuclei (sizes between 0.03 and 0.05 ƒÊm). Optical microscopy shows that nuclei coalescencegiving rounded and highly oriented microcrystals, about 100 times larger in size than the original nuclei.Nuclei coalescence was found to increase with annealing time and temperature. Further growth of BiI3films was performed onto the best nucleated and coalesced layers. These films were characterized byoptical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Resultsare very promising; however, microcrystals do not have a preferred orientation as is desirable for usingthem for the final application they are intended for. Future work will be conducted to improve nucleationand coalescence seeking for uniformity as far as the best orientation for such final application, that means,for ionizing radiation digital imaging.