Quantum dots of group IV semiconductor materials
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.
1. A quantum dot comprising:
a) a core that is crystalline and including Ge; and
b) a shell that is inorganic and noncrystalline and including GeO n with n between approximately 1.5 and 2, said shell surrounding said core and having a thickness greater than one monolayer of GeO n and up to ten monolayers of GeO n ,
said quantum dot exhibits photoluminescence with a quantum efficiency that is at least 40 percent.
2. The quantum dot of claim 1 , wherein said core has a diameter between approximately 1 nm and 20 nm.
3. The quantum dot of claim 1 , wherein 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 n is between approximately 1.8 and 2.
7. The quantum dot of claim 1 , wherein said shell completely surrounds said core.
8. The quantum dot of claim 1 , wherein said quantum efficiency is at least 50 percent.