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15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Partial Pressures of In-Se from Optical Absorbance of the Vapor

The optical absorbance of the vapor phase over various In-Se compositions between 33.3 and 61 atomic percent and 673 and 1418K has been measured and used to obtain the partial pressures of Se2(g) and In2Se(g). The results are in agreement with silica Bourdon gage measurements for compositions between 50 and 61 atomic percent but significantly higher than those from Knudsen cell and simultaneous Torsion-Knudsen cell measurements. The sequiselenide is found to sublime incongruently. Congruent vaporization occurs for the liquid above 1000 K between 50.08 and 56 at. percent Se. The Gibbs energy of formation of the liquid from its pure liquid elements between 1000 and 1300K is essentially independent of temperature and falls between -36 and -38 kJ per gram atomic weight for 50 and 56 percent Se at 1200 and 1300K.

Brebrick, R. F.↗
NASA NTRS2001

Partial Pressures for Several In-Se Compositions from Optical Absorbance of the Vapor

The optical absorbance of the vapor phase over various In-Se compositions between 33.3-60.99 at.% Se and 673-1418 K was measured and used to obtain the partial pressures of Se2(g) and In2Se(g). The results are in agreement with silica Bourdon gauge measurements for compositions between 50-61 at.%, but significantly higher than those from Knudsen cell and simultaneous Knudsen-torsion cell measurements. It is found that 60.99 at.% Se lies outside the sesquiselenide homogeneity range and 59.98 at.% Se lies inside and is the congruently melting composition. The Gibbs energy of formation of the liquid from its pure liquid elements between 1000-1300 K is essentially independent of temperature and falls between -36 to -38 kJ per g atomic weight for 50 and 56% Se at 1200 and 1300 K.

Brebrick, R. F.↗
DOE OSTI2023

Wafer-scale growth of two-dimensional, phase-pure InSe

Two-dimensional (2D) indium monoselenide (InSe) has attracted significant attention as an ultrathin III–VI semiconductor with a combination of favorable attributes that are comparable to those of III–V semiconductors and van der Waals 2D transition-metal dichalcogenides. Nevertheless, there has been no demonstration of large-area synthesis of 2D InSe due to the complexity of the binary In-Se system and the difficulties in promoting lateral growth. Here, we report the polymorph-selective synthesis of epitaxial 2D InSe by metal-organic chemical vapor deposition (MOCVD) over 2-in wafers. We achieve polymorph-selective epitaxial growth of InSe on c-plane sapphire via flow modulation to control the Se/In ratio. The layer-by-layer growth allows thickness control with tunable optical properties comparable to those of bulk crystals. We also demonstrate gate-tunable electrical transport with a field-effect mobility comparable to that of single-crystalline flakes. Importantly, these results indicate that InSe grown by MOCVD could be an effective channel material for back-end-of-line integration in logic transistors.

2D materials↗
NASA NTRS2002

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

The objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the crystals grown by vapor transport as results of buoyance-driven convection and growth interface fluctuations caused by irregular fluid-flows. ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, were grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals were characterized extensively to correlate the grown crystal properties with the growth conditions. The following are the research progress in the past two years. In-situ monitoring of partial pressure by optical absorption technique and visual observation of the growing crystal were performed during vapor growth of ZnSe. Low-temperature photoluminescence (PL) spectra and glow discharge mass spectroscopy (GDMS) were measured on ZnSe starting materials provided by various vendors and on bulk crystals grown from these starting materials by physical vapor transport (PVT) to study the effects of purification and contamination during crystal growth process. Optical characterization was performed on wafers sliced from the grown crystals of ZnSe, ZnTe and ZnSe(1-x),Te(x), (0<x<0.4). Energy band gaps at room temperature were determined from optical transmission measurements and a best fit curve to the band gap vs. composition, x, data gives a bowing parameter of 1.45. Low-temperature photoluminescence (PL) spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for the ZnSe(1-x),Te(x), samples, 0.09<x<0.39. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples. To validate numerical codes, in-situ monitoring during the PVT of HgI2 was designed. Optical absorption spectra of the vapor phase over HgI2 were measured for wavelengths between 200 and 600nm at sample temperatures between 349 and 610K. The Beer's Law constants for 15 wavelengths between 200 and 440 nm were determined. From these constants the vapor pressure of HgI2 was established as a function of temperature for the liquid and the solid Beta-phases To characterize the growth conditions during the PVT growth of In-doped ZnSe the optical absorbance of the vapor phase over the In-Se system were measured and were used to obtain the partial pressures of Se2(g) and In2Se(g).

Su, Ching-Hua↗
DOE OSTI2020

Materials Data on In2Se3 by Materials Project

In2Se3 crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three In2Se3 sheets oriented in the (0, 0, 1) direction. there are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four Se2- atoms to form distorted corner-sharing InSe4 tetrahedra. There are one shorter (2.49 Å) and three longer (2.76 Å) In–Se bond lengths. In the second In3+ site, In3+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are three shorter (2.70 Å) and three longer (3.42 Å) In–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a single-bond geometry to one In3+ atom. In the second Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent In3+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to six In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In4Se3 by Materials Project

In4Se3 crystallizes in the orthorhombic Pnnm space group. The structure is two-dimensional and consists of two In4Se3 sheets oriented in the (0, 1, 0) direction. there are four inequivalent In+1.50+ sites. In the first In+1.50+ site, In+1.50+ is bonded to five Se2- atoms to form distorted edge-sharing InSe5 square pyramids. There are a spread of In–Se bond distances ranging from 3.01–3.47 Å. In the second In+1.50+ site, In+1.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are two shorter (2.68 Å) and one longer (2.75 Å) In–Se bond lengths. In the third In+1.50+ site, In+1.50+ is bonded in an L-shaped geometry to two equivalent Se2- atoms. Both In–Se bond lengths are 2.84 Å. In the fourth In+1.50+ site, In+1.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.69 Å) and two longer (2.74 Å) In–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three In+1.50+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to five In+1.50+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to five In+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSe by Materials Project

InSe is black P-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of four InSe sheets oriented in the (0, 0, 1) direction. In2+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent Se2- atoms. All In–Se bond lengths are 2.68 Å. Se2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent In2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSe by Materials Project

InSe crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two InSe ribbons oriented in the (0, 1, 0) direction. In2+ is bonded in a distorted T-shaped geometry to three equivalent Se2- atoms. There are two shorter (2.71 Å) and one longer (2.72 Å) In–Se bond lengths. Se2- is bonded in a 3-coordinate geometry to three equivalent In2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSe by Materials Project

InSe is black P-derived structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of six InSe sheets oriented in the (0, 0, 1) direction. In2+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent Se2- atoms. All In–Se bond lengths are 2.68 Å. Se2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent In2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In6Se7 by Materials Project

In6Se7 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are six inequivalent In+2.33+ sites. In the first In+2.33+ site, In+2.33+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of In–Se bond distances ranging from 3.19–3.49 Å. In the second In+2.33+ site, In+2.33+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–3°. There are a spread of In–Se bond distances ranging from 2.70–2.97 Å. In the third In+2.33+ site, In+2.33+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–3°. There are a spread of In–Se bond distances ranging from 2.72–3.01 Å. In the fourth In+2.33+ site, In+2.33+ is bonded to six Se2- atoms to form edge-sharing InSe6 octahedra. There are a spread of In–Se bond distances ranging from 2.77–2.86 Å. In the fifth In+2.33+ site, In+2.33+ is bonded in a 3-coordinate geometry to three Se2- atoms. There are a spread of In–Se bond distances ranging from 2.68–2.75 Å. In the sixth In+2.33+ site, In+2.33+ is bonded in a distorted T-shaped geometry to three Se2- atoms. There are a spread of In–Se bond distances ranging from 2.71–2.78 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to five In+2.33+ atoms. In the second Se2- site, Se2- is bonded to five In+2.33+ atoms to form a mixture of distorted edge and corner-sharing SeIn5 square pyramids. In the third Se2- site, Se2- is bonded to five In+2.33+ atoms to form a mixture of distorted edge and corner-sharing SeIn5 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to five In+2.33+ atoms. In the fifth Se2- site, Se2- is bonded in a distorted T-shaped geometry to three In+2.33+ atoms. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to three In+2.33+ atoms. In the seventh Se2- site, Se2- is bonded to five In+2.33+ atoms to form a mixture of edge and corner-sharing SeIn5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In2Se3 by Materials Project

In2Se3 crystallizes in the hexagonal P6_1 space group. The structure is three-dimensional. there are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four Se2- atoms to form InSe4 tetrahedra that share corners with two equivalent InSe4 tetrahedra, corners with four equivalent InSe5 trigonal bipyramids, and an edgeedge with one InSe5 trigonal bipyramid. There are a spread of In–Se bond distances ranging from 2.60–2.68 Å. In the second In3+ site, In3+ is bonded to five Se2- atoms to form InSe5 trigonal bipyramids that share corners with four equivalent InSe4 tetrahedra, an edgeedge with one InSe4 tetrahedra, and edges with two equivalent InSe5 trigonal bipyramids. There are a spread of In–Se bond distances ranging from 2.64–2.97 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three In3+ atoms. In the second Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three In3+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In2Se by Materials Project

In2Se crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. there are four inequivalent In1+ sites. In the first In1+ site, In1+ is bonded in an L-shaped geometry to two equivalent Se2- atoms. Both In–Se bond lengths are 2.97 Å. In the second In1+ site, In1+ is bonded in a distorted T-shaped geometry to three Se2- atoms. There are one shorter (2.81 Å) and two longer (2.99 Å) In–Se bond lengths. In the third In1+ site, In1+ is bonded in a distorted T-shaped geometry to three Se2- atoms. There are one shorter (2.83 Å) and two longer (2.88 Å) In–Se bond lengths. In the fourth In1+ site, In1+ is bonded in a T-shaped geometry to three Se2- atoms. There are a spread of In–Se bond distances ranging from 2.90–3.05 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to six In1+ atoms to form SeIn6 octahedra that share corners with two equivalent SeIn5 trigonal bipyramids, edges with two equivalent SeIn6 octahedra, and edges with two equivalent SeIn5 trigonal bipyramids. In the second Se2- site, Se2- is bonded to five In1+ atoms to form SeIn5 trigonal bipyramids that share corners with two equivalent SeIn6 octahedra, corners with two equivalent SeIn5 trigonal bipyramids, edges with two equivalent SeIn6 octahedra, and an edgeedge with one SeIn5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 14–74°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In2Se3 by Materials Project

In2Se3 crystallizes in the hexagonal P6_5 space group. The structure is three-dimensional. there are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded in a 3-coordinate geometry to three Se2- atoms. There are a spread of In–Se bond distances ranging from 2.95–3.25 Å. In the second In3+ site, In3+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of In–Se bond distances ranging from 2.51–2.96 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to three In3+ atoms. In the second Se2- site, Se2- is bonded in a 1-coordinate geometry to one In3+ and one Se2- atom. The Se–Se bond length is 2.44 Å. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to three In3+ and one Se2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In2Se3 by Materials Project

In2Se3 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one In2Se3 sheet oriented in the (0, 0, 1) direction. In3+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.68 Å) and three longer (2.99 Å) In–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to six equivalent In3+ atoms to form edge-sharing SeIn6 octahedra. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on In3Se by Materials Project

In3Se is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. In is bonded to eight equivalent In and four equivalent Se atoms to form distorted InIn8Se4 cuboctahedra that share corners with twelve equivalent InIn8Se4 cuboctahedra, edges with eight equivalent SeIn12 cuboctahedra, edges with sixteen equivalent InIn8Se4 cuboctahedra, faces with four equivalent SeIn12 cuboctahedra, and faces with fourteen equivalent InIn8Se4 cuboctahedra. All In–In bond lengths are 3.40 Å. All In–Se bond lengths are 3.40 Å. Se is bonded to twelve equivalent In atoms to form distorted SeIn12 cuboctahedra that share corners with twelve equivalent SeIn12 cuboctahedra, edges with twenty-four equivalent InIn8Se4 cuboctahedra, faces with six equivalent SeIn12 cuboctahedra, and faces with twelve equivalent InIn8Se4 cuboctahedra.

36 MATERIALS SCIENCE↗