Quantum dots of Group IV semiconductor materials

Abstract

The invention relates to a quantum dot. The quantum dot comprises a core including a semiconductor material Y selected from the group consisting of Si and Ge. The quantum dot also comprises a shell surrounding the core. The quantum dot is substantially defect free such that the quantum dot exhibits photoluminescence with a quantum efficiency that is greater than 10 percent.

What is claimed is:  
     
         1 . A quantum dot comprising: 
 a) a core including a semiconductor material Y selected from the group consisting of Si and Ge; and    b) a shell surrounding said core,    said quantum dot being substantially defect free such that said quantum dot exhibits photoluminescence with a quantum efficiency that is greater than 10 percent.    
     
     
         2 . The quantum dot of  claim 1 , wherein Y is Si, and said core has a diameter between approximately 1 nm and 20 nm.  
     
     
         3 . The quantum dot of  claim 1 , wherein Y is Ge, and said core has a diameter between approximately 1 nm and 50 nm.  
     
     
         4 . The quantum dot of  claim 1 , wherein said core has, a diameter between approximately 1 nm and 10 nm.  
     
     
         5 . The quantum dot of  claim 1 , wherein said core is substantially spherical with an aspect ratio between approximately 0.8 and 1.2.  
     
     
         6 . The quantum dot of  claim 1 , wherein said shell has a thickness between approximately 0.1 nm and 5 nm.  
     
     
         7 . The quantum dot of  claim 1 , wherein said shell includes an oxide.  
     
     
         8 . The quantum dot of  claim 1 , wherein said shell includes an oxide YO n  with n being between approximately 0 and 2.  
     
     
         9 . The quantum dot of  claim 8 , wherein n is between approximately 1.8 and 2.  
     
     
         10 . The quantum dot of  claim 1 , wherein said shell completely surrounds said core.  
     
     
         11 . The quantum dot of  claim 1 , wherein said quantum dot exhibits photoluminescence with a quantum efficiency that is at least 20 percent.  
     
     
         12 . The quantum dot of  claim 1 , wherein said quantum dot exhibits photoluminescence with a quantum efficiency that is at least 50 percent.  
     
     
         13 . The quantum dot of  claim 1 , further comprising at least one surface ligand coupled to said shell.  
     
     
         14 . The quantum dot of  claim 1 , further comprising a plurality of surface ligands coupled to said shell to provide a surface coverage between approximately 50 percent and 100 percent.  
     
     
         15 . A quantum dot comprising: 
 a) a core including a semiconductor material Y selected from the group consisting of Si and Ge; and    b) a ligand layer surrounding said core, said ligand layer including a plurality of surface ligands,    said quantum dot exhibiting photoluminescence with a quantum efficiency that is greater than 10 percent.    
     
     
         16 . The quantum dot of  claim 15 , wherein said plurality of surface ligands are coupled to said core to provide a surface coverage between approximately 50 percent and 100 percent.  
     
     
         17 . The quantum dot of  claim 15 , wherein said plurality of surface ligands are coupled to said core to provide a surface coverage between approximately 80 percent and 100 percent.  
     
     
         18 . The quantum dot of  claim 15 , wherein a surface ligand of said plurality of surface ligands contains an atom selected from the group consisting of C, O, S, Si, N, P, and Se, and said core forms a covalent bond with said atom.  
     
     
         19 . The quantum dot of  claim 15 , wherein a surface ligand of said plurality of surface ligands is selected from the group consisting of alkyls, alkenyls, alkynyls, aromatics, aromatic heterocycles, conjugated aromatics, polyenes, cyanides, hydroxys, alkoxys, carboxylates, phenoxys, siloxys, cyanates, thioalkyls, thioaryls, thiocyanates, silylthios, substituted silyl groups, amino groups, mono-substituted amines, di-substituted amines, imino groups, and silylaminos.  
     
     
         20 . The quantum dot of  claim 15 , wherein said, quantum dot exhibits photoluminescence with a quantum efficiency that is at least 20 percent.  
     
     
         21 . The quantum dot of  claim 15 , further comprising a shell positioned between said core and said ligand layer and surrounding said core, said shell including an oxide YO n  with n being between approximately 0 and 2.