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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on TlGaSe2 by Materials Project

TlGaSe2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.28–3.69 Å. In the second Tl1+ site, Tl1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.30–3.79 Å. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are three shorter (2.45 Å) and one longer (2.46 Å) Ga–Se bond lengths. In the second Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.43–2.46 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two Ga3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to three Tl1+ and two Ga3+ atoms. In the third Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two equivalent Ga3+ atoms. In the fourth Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two equivalent Ga3+ atoms. In the fifth Se2- site, Se2- is bonded in a 5-coordinate geometry to three Tl1+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlGaSe2 by Materials Project

TlGaSe2 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.42–3.96 Å. In the second Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.32–4.03 Å. In the third Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.40–3.99 Å. In the fourth Tl1+ site, Tl1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Tl–Se bond distances ranging from 3.38–3.99 Å. There are four inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.43–2.45 Å. In the second Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are two shorter (2.44 Å) and two longer (2.45 Å) Ga–Se bond lengths. In the third Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are one shorter (2.43 Å) and three longer (2.45 Å) Ga–Se bond lengths. In the fourth Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are three shorter (2.44 Å) and one longer (2.45 Å) Ga–Se bond lengths. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two Ga3+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two Ga3+ atoms. In the third Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two Ga3+ atoms. In the fourth Se2- site, Se2- is bonded in a distorted water-like geometry to four Tl1+ and two Ga3+ atoms. In the fifth Se2- site, Se2- is bonded in a distorted water-like geometry to four Tl1+ and two Ga3+ atoms. In the sixth Se2- site, Se2- is bonded in a distorted water-like geometry to four Tl1+ and two Ga3+ atoms. In the seventh Se2- site, Se2- is bonded in a 2-coordinate geometry to four Tl1+ and two Ga3+ atoms. In the eighth Se2- site, Se2- is bonded in a distorted water-like geometry to four Tl1+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlGaSe2 by Materials Project

TlGaSe2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Tl1+ is bonded in a 10-coordinate geometry to two equivalent Tl1+ and eight equivalent Se2- atoms. Both Tl–Tl bond lengths are 3.27 Å. All Tl–Se bond lengths are 3.50 Å. Ga3+ is bonded to four equivalent Se2- atoms to form edge-sharing GaSe4 tetrahedra. All Ga–Se bond lengths are 2.47 Å. Se2- is bonded in a distorted L-shaped geometry to four equivalent Tl1+ and two equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2017

Design of Multifunctional Materials: Chalcogenides and Chalcopyrites

There is a strong need for developing multifunctional materials to reduce the cost of applied material without compromising the performance of the detectors, devices and sensors. The materials design, processing, growth and fabrication of bulk and nanocrystals and fabrication into devices and sensors involve huge cost and resources including a multidisciplinary team of experts. Because of this reason, prediction of multifunctionality of materials before design and development should be evaluated. Chalcogenides and chalcopyrites are a very exciting class of materials for developing multifunctionality. Materials such as Gallium selenide GaSe and zinc selenide ZnSe have been proven to be excellent examples. GaSe is a layered material and very difficult to grow in large crystal. However, it's ternary and quaternary analogs such as thallium gallium selenide TlGaSe2, thallium gallium selenide sulfide TlGaSe2-xSs, thallium arsenic selenide Tl3AsSe3, silver gallium selenide AgGaGe3Se8, AgGaGe5Se12 and several others have shown great promise for multifunctionality. Several of these materials have shown good efficiency for frequency conversion (nonlinear optical NLO), electro-optic modulation, and acousto-optic tunable filters and imagers suitable for the visible, near-infrared wavelength, mid wave infrared (MWIR), long wave infrared (LWIR) and even up to Tera hertz wavelength (THW) regions. In addition, this class of materials have demonstrated low absorption coefficients and power handling capability in the systems. Also, these crystals do not require post growth annealing, show very large transparency range and fabricability.

Singh, N. B.↗
NASA NTRS2016

Design and Growth of Novel Compounds for Radiation Sensors: Multinary Chalcogenides

Increasing threats of radiological weapons have revitalized the researches for low cost large volume -ray and neutron ray sensors In the past few years we have designed and grown ternary and quaternary lead and thallium chalcogenides and lead selenoiodides for detectors to meet these challenges. These materials are congruent, can be tailored to enhance the parameters required for radiation sensors. In addition, this class of compounds can be grown by Bridgman method which promises for large volume productions. We have single crystals of several compounds from the melt including Tl3AsSe3, Tl3AsSe3-xSx, TlGaSe2, AgGaGe3Se8, AgxLi1-xAgGaGe3Se8 and PbTlI5-x Sex compounds. Experimental studies indicate that these have very low absorption coefficient, low defect density and can be fabricated in any shape and sizes. These crystals do not require post growth annealing and do not show any second phase precipitates when processed for electrode bonding and other fabrication steps. In this paper we report purification, growth and fabrication of large Tl3AsSe3 (TAS) crystals. We observed that TAS crystals grown by using further purification of as supplied high purity source materials followed by directionally solidified charge showed higher resistivity than previously reported values. TAS also showed constant value as the function of voltage. A low thermal gradient and high purity source material were used to reduce thermal stresses in large crystals. By improving the purification of the as supplied source materials very high quality thallium, selenium and arsenic was achieved for preparing stoichiometric Tl3AsSe3 compound. Low gradient (<20K/cm) and slow growth rate (1-2 cm/day) produced crystals with reduced stress. Crystals did not show any micro cracking during fabrication of crystals grown with high purity and at low thermal gradient. Since thallium is a major component and very sensitive to surface oxidation, removal of surface and bulk oxides is very important. Intentional increase in the growth rate from 1cm/day to higher speed (>5cm/day) showed very different morphologies on the surface of the crystals. Electrical resistivity was one order of magnitude higher than previously reported value and it was observed to be constant as the function of frequency.

Singh, N. B.↗
DOE OSTI2024

Colloidal AInSe 2 (A = K, Rb, Cs) Nanocrystals with Tunable Crystal and Band Structures

Wide band gap AInSe 2 (A = K, Rb, Cs) is an important interlayer material for improving the efficiency of Cu(In,Ga)(S,Se) 2 (CIGS) solar cells. Compared to high-vacuum deposition and solid-state synthesis, a less energyintensive method is of interest for its fabrication. Herein, we present the rapid, low-temperature colloidal synthesis of AInSe 2 nanocrystals that opens a pathway for convenient solution processing. The crystal structures and electronic band structures of the nanocrystals were studied, and their particle morphology was found to be dependent on the choice of alkali metal and selenium precursors. Homogeneous solid solution (K,Rb,Cs)InSe 2 nanocrystals were synthesized using a mixture of alkali metal precursors. Their compositions, lattice parameters, and band gaps were easily tuned based on the K:Rb:Cs precursor ratio, providing potential for interface engineering of CIGS nanocrystal-based solar cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗