SEMICONDUCTOR STRUCTURE HAVING NANOCRYSTALLINE CORE AND NANOCRYSTALLINE SHELL WITH INSULATOR COATING
Semiconductor structures having a nanocrystalline core and corresponding nanocrystalline shell and insulator coating are described. In an example, a semiconductor structure includes an anisotropic nanocrystalline core composed of a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0. The semiconductor structure also includes a nanocrystalline shell composed of a second, different, semiconductor material at least partially surrounding the anisotropic nanocrystalline core. An insulator layer encapsulates the nanocrystalline shell and anisotropic nanocrystalline core.
1 . A semiconductor structure, comprising:
an anisotropic nanocrystalline core comprising a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0;
a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the anisotropic nanocrystalline core; and
an insulator layer encapsulating the nanocrystalline shell and anisotropic nanocrystalline core.
2 . The semiconductor structure of claim 1 , wherein the insulator layer is bonded directly to the nanocrystalline shell.
3 . The semiconductor structure of claim 2 , wherein the insulator layer passivates an outermost surface of the nanocrystalline shell.
4 . The semiconductor structure of claim 1 , wherein the insulator layer provides a barrier for the nanocrystalline shell and anisotropic nanocrystalline core impermeable to an environment outside of the insulator layer.
5 . The semiconductor structure of claim 1 , wherein the insulator layer encapsulates only a single nanocrystalline shell/anisotropic nanocrystalline core pairing.
6 . The semiconductor structure of claim 1 , wherein the insulator layer comprises a layer of material selected from the group consisting of silica (SiO x ), titanium oxide (TiO x ), zirconium oxide (ZrO x ), alumina (AlO x ), and hafnia (HfO x ).
7 . The semiconductor structure of claim 6 , wherein the layer is a layer of silica having a thickness approximately in the range of 3-30 nanometers.
8 . The semiconductor structure of claim 1 , wherein an outer surface of the insulator layer is ligand-free.
9 . The semiconductor structure of claim 1 , wherein an outer surface of the insulator layer is ligand-functionalized.
10 . The semiconductor structure of claim 1 , wherein the nanocrystalline core has a diameter approximately in the range of 2-5 nanometers, wherein the nanocrystalline shell has a long axis and a short axis, the long axis having a length approximately in the range of 5-40 nanometers, and the short axis having a length approximately in the range of 1-5 nanometers greater than the diameter of the nanocrystalline core, and wherein the insulator layer has a thickness approximately in the range of 1-20 nanometers along an axis co-axial with the long axis and has a thickness approximately in the range of 3-30 nanometers along an axis co-axial with the short axis.
11 . The semiconductor structure of claim 1 , wherein the nanocrystalline shell completely surrounds the nanocrystalline core.
12 . The semiconductor structure of claim 1 , further comprising:
a nanocrystalline outer shell at least partially surrounding the nanocrystalline shell, between the nanocrystalline shell and the insulator layer, the nanocrystalline outer shell comprising a third semiconductor material different from the first and second semiconductor materials.
13 . The semiconductor structure of claim 1 , wherein the anisotropic nanocrystalline core and the nanocrystalline shell form a quantum dot.
14 . The semiconductor structure of claim 13 , wherein the quantum dot has a photoluminescence quantum yield (PLQY) of at least 90%.
15 . The semiconductor structure of claim 13 , wherein emission from the quantum dot is mostly, or entirely, from the anisotropic nanocrystalline core.
16 . The semiconductor structure of claim 15 , wherein emission from the anisotropic nanocrystalline core is at least approximately 75% of the total emission from the quantum dot.
17 . The semiconductor structure of claim 13 , wherein an absorption spectrum and an emission spectrum of the quantum dot are essentially non-overlapping.
18 . The semiconductor structure of claim 13 , wherein an absorbance ratio of the quantum dot for absorbance at 400 nanometers versus absorbance at an exciton peak for the quantum dot is approximately in the range of 5-35.
19 . The semiconductor structure of claim 13 , wherein the quantum dot is a down-converting quantum dot.
20 . The semiconductor structure of claim 1 , wherein the insulator layer is an amorphous layer.
21 . A semiconductor structure, comprising:
a nanocrystalline core comprising a first semiconductor material;
a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the nanocrystalline core; and
an insulator layer encapsulating the nanocrystalline shell and core, wherein an outer surface of the insulator layer is ligand-functionalized.
22 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer is ligand-functionalized with a ligand selected from the group consisting of a silane comprising one or more hydrolyzable groups and a functional or non-functional bipodal silane.
23 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer is ligand-functionalized with a ligand selected from the group consisting of mono-, di-, or tri-alkoxysilanes with three, two or one inert or organofunctional substituents of the general formula (R 1 O) 3 SiR 2 ; (R 1 O) 2 SiR 2 R 3 ; (R 1 O)SiR 2 R 3 R 4 , where R 1 is methyl, ethyl, propyl, isopropyl, or butyl, R 2 , R 3 and R 4 are identical or different and are H substituents, alkyls, alkenes, alkynes, aryls, halogeno-derivates, alcohols, (mono, di, tri, poly) ethyleneglycols, (secondary, tertiary, quaternary) amines, diamines, polyamines, azides, isocyanates, acrylates, metacrylates, epoxies, ethers, aldehydes, carboxylates, esters, anhydrides, phosphates, phosphines, mercaptos, thiols, sulfonates, and are linear or cyclic, a silane with the general structure (R 1 O) 3 Si—(CH 2 ) n —R—(CH 2 ) n —Si(RO) 3 where R and R 1 is H or an organic substituent selected from the group consisting of alkyls, alkenes, alkynes, aryls, halogeno-derivates, alcohols, (mono, di, tri, poly) ethyleneglycols, (secondary, tertiary, quaternary) amines, diamines, polyamines, azides, isocyanates, acrylates, metacrylates, epoxies, ethers, aldehydes, carboxylates, esters, anhydrides, phosphates, phosphines, mercaptos, thiols, sulfonates, and are linear or cyclic, a chlorosilane, and an azasilane.
24 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer is ligand-functionalized with a ligand selected from the group consisting of organic or inorganic compounds with functionality for bonding to a silica surface by chemical or non-chemical interactions selected from the group consisting of covalent, ionic, H-bonding, and Van der Waals forces.
25 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer is ligand-functionalized with a ligand selected from the group consisting of the methoxy and ethoxy silanes (MeO) 3 SiAllyl, (MeO) 3 SiVinyl, (MeO) 2 SiMeVinyl, (EtO) 3 SiVinyl, EtOSi(Vinyl) 3 , mono-methoxy silanes, chloro-silanes, and 1,2-bis-(triethoxysilyl)ethane.
26 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer is ligand-functionalized to impart solubility, dispersability, heat stability, photo-stability, or a combination thereof, to the semiconductor structure.
27 . The semiconductor structure of claim 21 , wherein the outer surface of the insulator layer comprises OH groups suitable for reaction with an intermediate linker to link small molecules, oligomers, polymers or macromolecules to the outer surface of the insulator layer, the intermediate linker selected from the group consisting of an epoxide, a carbonyldiimidazole, a cyanuric chloride, and an isocyanate.
28 . The semiconductor structure of claim 21 , wherein the insulator layer is bonded directly to the nanocrystalline shell.
29 . The semiconductor structure of claim 28 , wherein the insulator layer passivates an outermost surface of the nanocrystalline shell.
30 . The semiconductor structure of claim 21 , wherein the insulator layer provides a barrier for the nanocrystalline shell and core impermeable to an environment outside of the insulator layer.
31 . The semiconductor structure of claim 21 , wherein the insulator layer encapsulates only a single nanocrystalline shell/nanocrystalline core pairing.
32 . The semiconductor structure of claim 21 , wherein the insulator layer comprises a layer of material selected from the group consisting of silica (SiO x ), titanium oxide (TiO x ), zirconium oxide (ZrO x ), alumina (AlO x ), and hafnia (HfO x ).
33 . The semiconductor structure of claim 32 , wherein the layer is a layer of silica having a thickness approximately in the range of 3-30 nanometers.
34 . The semiconductor structure of claim 21 , wherein the nanocrystalline core has a diameter approximately in the range of 2-5 nanometers, wherein the nanocrystalline shell has a long axis and a short axis, the long axis having a length approximately in the range of 5-40 nanometers, and the short axis having a length approximately in the range of 1-5 nanometers greater than the diameter of the nanocrystalline core, and wherein the insulator layer has a thickness approximately in the range of 1-20 nanometers along an axis co-axial with the long axis and has a thickness approximately in the range of 3-30 nanometers along an axis co-axial with the short axis.
35 . The semiconductor structure of claim 21 , wherein the nanocrystalline shell completely surrounds the nanocrystalline core.
36 . The semiconductor structure of claim 21 , further comprising:
a nanocrystalline outer shell at least partially surrounding the nanocrystalline shell, between the nanocrystalline shell and the insulator layer, the nanocrystalline outer shell comprising a third semiconductor material different from the first and second semiconductor materials.
37 . The semiconductor structure of claim 21 , wherein the nanocrystalline core and the nanocrystalline shell form a quantum dot.
38 . The semiconductor structure of claim 37 , wherein the quantum dot has a photoluminescence quantum yield (PLQY) of at least 90%.
39 . The semiconductor structure of claim 37 , wherein emission from the quantum dot is mostly, or entirely, from the nanocrystalline core.
40 . The semiconductor structure of claim 39 , wherein emission from the nanocrystalline core is at least approximately 75% of the total emission from the quantum dot.
41 . The semiconductor structure of claim 37 , wherein an absorption spectrum and an emission spectrum of the quantum dot are essentially non-overlapping.
42 . The semiconductor structure of claim 37 , wherein an absorbance ratio of the quantum dot for absorbance at 400 nanometers versus absorbance at an exciton peak for the quantum dot is approximately in the range of 5-35.
43 . The semiconductor structure of claim 37 , wherein the quantum dot is a down-converting quantum dot.
44 . A lighting apparatus, comprising:
a light emitting diode; and
a plurality of semiconductor structures, each semiconductor structure comprising:
a quantum dot comprising a nanocrystalline core comprising a first semiconductor material and a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the nanocrystalline core, the quantum dot having a photoluminescence quantum yield (PLQY) of at least 90%; and
an insulator layer encapsulating the quantum dot.
45 . The lighting apparatus of claim 44 , wherein emission from each quantum dot is mostly, or entirely, from the nanocrystalline core.
46 . The lighting apparatus of claim 44 , wherein emission from the nanocrystalline core is at least approximately 75% of the total emission from the quantum dot.
47 . The lighting apparatus of claim 44 , wherein an absorption spectrum and an emission spectrum of each quantum dot are essentially non-overlapping.
48 . The lighting apparatus of claim 44 , wherein an absorbance ratio of each quantum dot for absorbance at 400 nanometers versus absorbance at an exciton peak for the quantum dot is approximately in the range of 5-35.
49 . The lighting apparatus of claim 44 , wherein each quantum dot is a down-converting quantum dot.
50 . A method of fabricating a semiconductor structure, the method comprising:
forming an anisotropic nanocrystalline core comprising a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0;
forming a nanocrystalline shell from a second, different, semiconductor material to at least partially surround the anisotropic nanocrystalline core; and
forming an insulator layer encapsulating the nanocrystalline shell and anisotropic nanocrystalline core.
51 . The method of claim 50 , wherein forming the insulator layer comprises bonding the insulator layer directly to the nanocrystalline shell.
52 . The method of claim 51 , wherein bonding the insulator layer directly to the nanocrystalline shell comprises passivating an outermost surface of the nanocrystalline shell.
53 . The method of claim 50 , wherein forming the insulator layer comprises providing a barrier for the nanocrystalline shell and anisotropic nanocrystalline core impermeable to an environment outside of the insulator layer.
54 . The method of claim 50 , wherein forming the insulator layer comprises encapsulating only a single nanocrystalline shell/anisotropic nanocrystalline core pairing.
55 . The method of claim 54 , wherein forming the insulator layer comprises forming a layer of material selected from the group consisting of silica (SiO x ), titanium oxide (TiO x ), zirconium oxide (ZrO x ), alumina (AlO x ), and hafnia (HfO x ).
56 . The method of claim 55 , wherein forming the layer comprises forming a layer of silica and further comprises using a reverse micelle sol-gel reaction.
57 . The method of claim 56 , wherein using the reverse micelle sol-gel reaction comprises dissolving the nanocrystalline shell/nanocrystalline core pairing in a first non-polar solvent to form a first solution and, subsequently, adding the first solution along with a species selected from the group consisting of 3-aminopropyltrimethoxysilane (APTMS), 3-mercapto-trimethoxysilane, and a silane comprising a phosphonic acid or carboxylic acid functional group, to a second solution comprising a surfactant dissolved in a second non-polar solvent and, subsequently, adding ammonium hydroxide and tetraorthosilicate (TEOS) to the second solution.
58 . The method of claim 57 , wherein the thickness of the insulator layer formed depends on the amount of TEOS added to the second solution.
59 . The method of claim 50 , wherein the first and second non-polar solvents are cyclohexane.
60 . The method of claim 55 , wherein forming the layer comprises forming a layer of silica and further comprises using a combination of dioctyl sodium sulfosuccinate (AOT) and tetraorthosilicate (TEOS).
61 . The method of claim 55 , wherein forming the layer comprises forming a layer of silica and further comprises using a combination of polyoxyethylene (5) nonylphenylether and tetraorthosilicate (TEOS).
62 . The method of claim 50 , wherein forming the insulator layer comprises forming the insulator layer to have a ligand-free outer surface.
63 . The method of claim 50 , further comprising:
ligand-functionalizing an outer surface of the insulator layer.
64 . The method of claim 63 , wherein ligand-functionalizing the outer surface of the insulator layer comprises treating the semiconductor structure with a ligand selected from the group consisting of mono-, di-, or tri-alkoxysilanes with three, two or one inert or organofunctional substituents of the general formula (R 1 O) 3 SiR 2 ; (R 1 O) 2 SiR 2 R 3 ; (R 1 O)SiR 2 R 3 R 4 , where R 1 is methyl, ethyl, propyl, isopropyl, or butyl, R 2 , R 3 and R 4 are identical or different and are H substituents, alkyls, alkenes, alkynes, aryls, halogeno-derivates, alcohols, (mono, di, tri, poly) ethyleneglycols, (secondary, tertiary, quaternary) amines, diamines, polyamines, azides, isocyanates, acrylates, metacrylates, epoxies, ethers, aldehydes, carboxylates, esters, anhydrides, phosphates, phosphines, mercaptos, thiols, sulfonates, and are linear or cyclic, a silane with the general structure (R 1 O) 3 Si—(CH 2 ) n —R—(CH 2 ) n —Si(RO) 3 where R and R 1 is H or an organic substituent selected from the group consisting of alkyls, alkenes, alkynes, aryls, halogeno-derivates, alcohols, (mono, di, tri, poly) ethyleneglycols, (secondary, tertiary, quaternary) amines, diamines, polyamines, azides, isocyanates, acrylates, metacrylates, epoxies, ethers, aldehydes, carboxylates, esters, anhydrides, phosphates, phosphines, mercaptos, thiols, sulfonates, and are linear or cyclic, a chlorosilane, and an azasilane.
65 . The method of claim 63 , wherein ligand-functionalizing the outer surface of the insulator layer comprises imparting solubility, dispersability, heat stability, photo-stability, or a combination thereof, to the semiconductor structure.