Semiconductor Structure having Nanocrystalline Core and Nanocrystalline Shell with Insulator Coating

Abstract

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.

What is claimed is: 
     
         1 . A semiconductor structure, comprising:
 a nanocrystalline core comprising a first semiconductor material;   a nanocrystalline shell comprising a second, different, semiconductor material completely surrounding the nanocrystalline core, wherein the nanocrystalline shell has a short axis and a long axis perpendicular to the short axis, and wherein the nanocrystalline core is disposed off-center along the short axis and off-center along the long axis; and   an insulator layer encapsulating the nanocrystalline shell.   
     
     
         2 . The semiconductor structure of  claim 1 , wherein the outer surface of the insulator layer is ligand-functionalized. 
     
     
         3 . The semiconductor structure of  claim 2 , 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 O 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. 
     
     
         4 . The semiconductor structure of  claim 2 , 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. 
     
     
         5 . The semiconductor structure of  claim 2 , 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. 
     
     
         6 . The semiconductor structure of  claim 2 , 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. 
     
     
         7 . The semiconductor structure of  claim 1 , 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. 
     
     
         8 . The semiconductor structure of  claim 1 , wherein the insulator layer is bonded directly to the nanocrystalline shell. 
     
     
         9 . The semiconductor structure of  claim 8 , wherein the insulator layer passivates an outermost surface of the nanocrystalline shell. 
     
     
         10 . The semiconductor structure of  claim 1 , wherein the insulator layer provides a barrier for the nanocrystalline shell and core impermeable to an environment outside of the insulator layer. 
     
     
         11 . The semiconductor structure of  claim 1 , wherein the insulator layer encapsulates only a single nanocrystalline shell/nanocrystalline core pairing. 
     
     
         12 . 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 ). 
     
     
         13 . The semiconductor structure of  claim 12 , wherein the insulator layer is a layer of silica having a thickness approximately in the range of 3-30 nanometers. 
     
     
         14 . 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.   
     
     
         15 . The semiconductor structure of  claim 1 , wherein the nanocrystalline core and the nanocrystalline shell form a quantum dot. 
     
     
         16 . The semiconductor structure of  claim 15 , wherein the quantum dot has a photoluminescence quantum yield (PLQY) of at least 90%. 
     
     
         17 . The semiconductor structure of  claim 15 , wherein emission from the quantum dot is mostly, or entirely, from the nanocrystalline core. 
     
     
         18 . The semiconductor structure of  claim 17 , wherein emission from the nanocrystalline core is at least approximately 75% of the total emission from the quantum dot. 
     
     
         19 . The semiconductor structure of  claim 15 , wherein an absorption spectrum and an emission spectrum of the quantum dot are essentially non-overlapping. 
     
     
         20 . The semiconductor structure of  claim 15 , 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. 
     
     
         21 . The semiconductor structure of  claim 15 , wherein the quantum dot is a down-converting quantum dot. 
     
     
         22 . The semiconductor structure of  claim 2 , 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.