Growth of bismuth tri‐iodide platelets by the physical vapor deposition method

Abstract

The work reports the growth of single BI 3 crystals with platelets habit. Platelets were grown by physical vapor deposition (PVD) in a high vacuum atmosphere and with argon, polymer or iodine as additives. Crystals grew in the zone of maximum temperature gradient, perpendicular to the ampoule wall. Crystals grown with argon as additive show a very shining surface, have hexagonal (0 0 l) faces, sizes up to 20 x 10 mm 2 and thicknesses up to 100 µm. They were characterized by optical microscopy and scanning electron microscopy (SEM). Dendritic-like structures were found to be their main surface defect. SEM indicates that they grow from the staking of hexagonal unities. Electrical properties of the crystals grown under different growth conditions were determined. Resistivities up to 2 x 10 12 Ωcm (the best reported value for monocrystals of this material) were obtained. X-ray response was measured by irradiation of the platelets with a 241 Am source of 3.5 mR/h. A comparison of results according to the growth conditions was made. Properties of the crystals grown by this method are compared with the ones measured for others previously grown from the melt. Also, results for bismuth tri-iodide platelets are compared with the ones obtained for mercuric and lead iodide platelets.

Correlation between growth orientation and growth temperature for bismuth tri‐iodide films

“…This possibility was not studied yet. The similarity between the behavior of bismuth tri-iodide and lead iodide when growing their films, confirms that these two form a sub-group of the heavy metal iodides, with properties quite different than the mercuric iodide`s ones [16]. The obtained bismuth tri-iodide films have thicknesses in the range 20 to 33 µm, smaller than the suitable values for 99% stopping of X-rays used for medical radiography.…”

“…They have high densities and atomic absorption coefficients (which determine that thicknesses of 70-80 µm are enough for 99% of absorption of 20 keV radiation), wide energy band gaps (1.7 -2.5 eV at RT), therefore they give a lower dark current through the detector without any cooling, and a relative low energy necessary for the creation of an electron-hole pair (4 -5 eV), then, they may give a higher signal to noise response [16].…”

Crystal and Electronic Structures of Complex Bismuth Iodides A3Bi2I9 (A = K, Rb, Cs) Related to Perovskite: Aiding the Rational Design of Photovoltaics

“…In comparison, the optoelectronic properties of bismuth halides have been the focus of many fewer studies. The simple iodide BiI 3 has been investigated for applications such as hard radiation detection, 6-9 Xray imaging, [10][11][12] and for solar cells as hole transport material. 13 Recently, some of us have demostrated that BiI 3 can be used as the active layer in photovoltaic devices.…”

Bismuth tri-iodide nanoparticles synthesized from octadecene suspension

“…Also it has a wide band gap of 1.72 eV which determines that the detectors made with this material be suitable for room temperature operation [2][3][4]. These properties have led to several reports about BiI 3 application on detectors for counting and spectrometry [2,3,[5][6][7] as far as for X-ray imaging application, depositing the material as photoconductor onto readout matrixes [8][9][10].…”