Group i-iii-vi material nano-crystalline core and group i-iii-vi material nano-crystalline shell pairing

Abstract

Nano-crystalline core and nano-crystalline shell pairings having group I-III-VI material nano-crystalline cores, and methods of fabricating nano-crystalline core and nano-crystalline shell pairings having group I-III-VI material nano-crystalline cores, are described. In an example, a semiconductor structure includes a nano-crystalline core composed of a group I-III-VI semiconductor material. A nano-crystalline shell composed of a second, different, group I-III-VI semiconductor material at least partially surrounds the nano-crystalline core.

What is claimed is: 
     
         1 . A semiconductor structure, comprising:
 a nano-crystalline core comprising a first group I-III-VI semiconductor material; and   a nano-crystalline shell comprising a second, different, group I-III-VI semiconductor material at least partially surrounding the nano-crystalline core.   
     
     
         2 . The semiconductor structure of  claim 1 , wherein the first group I-III-VI semiconductor material is silver gallium sulfide having a stoichiometry of approximately AgGaS 2 . 
     
     
         3 . The semiconductor structure of  claim 2 , wherein the nano-crystalline core has a peak emission approximately in the range of 475-575 nanometers. 
     
     
         4 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core is an emitter having a direct, bulk band gap approximately in the range of 1-2.5 eV. 
     
     
         5 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core and nano-crystalline shell have a lattice mismatch of less than approximately 4%. 
     
     
         6 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core/nano-crystalline shell pairing is a pairing selected from the group consisting of copper indium sulfide (CIS)/silver gallium sulfide (AgGaS 2 ), copper indium selenide (CISe)/AgGaS 2 , copper gallium selenide (CuGaSe 2 )/copper gallium sulfide (CuGaS 2 ), and CuGaSe 2 /AgGaS 2 . 
     
     
         7 . The semiconductor structure of  claim 1 , further comprising:
 a nano-crystalline outer shell comprising a third, different, semiconductor material at least partially surrounding the nano-crystalline shell.   
     
     
         8 . The semiconductor structure of  claim 7 , wherein the third semiconductor material is zinc sulfide (ZnS). 
     
     
         9 . The semiconductor structure of  claim 7 , further comprising:
 a compositional transition layer disposed between, and in contact with, the nano-crystalline core and nano-crystalline shell, the compositional transition layer having a composition intermediate to the first group I-III-VI semiconductor material and the second group I-III-VI semiconductor material.   
     
     
         10 . The semiconductor structure of  claim 9 , wherein the compositional transition layer is an alloyed layer comprising a mixture of the first group I-III-VI semiconductor material and the second group I-III-VI semiconductor material. 
     
     
         11 . The semiconductor structure of  claim 9 , wherein the compositional transition layer is a graded layer comprising a compositional gradient of the first group I-III-VI semiconductor material proximate to the nano-crystalline core through to the second group I-III-VI semiconductor material proximate to the nano-crystalline shell. 
     
     
         12 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core is anisotropic nano-crystalline core having an aspect ratio between, but not including, 1.0 and 2.0. 
     
     
         13 . The semiconductor structure of  claim 1 , wherein the nano-crystalline shell is an anisotropic nano-crystalline shell having an aspect ratio approximately in the range of 2-6. 
     
     
         14 . The semiconductor structure of  claim 13 , further comprising:
 an insulator coating surrounding and encapsulating the nano-crystalline core/nano-crystalline shell pairing.   
     
     
         15 . The semiconductor structure of  claim 14 , wherein the insulator coating comprises an amorphous 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 ). 
     
     
         16 . The semiconductor structure of  claim 1 , wherein the nano-crystalline shell completely surrounds the nano-crystalline core. 
     
     
         17 . The semiconductor structure of  claim 1 , wherein the nano-crystalline shell only partially surrounds the nano-crystalline core, exposing a portion of the nano-crystalline core. 
     
     
         18 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core is disposed in an asymmetric orientation with respect to the nano-crystalline shell. 
     
     
         19 . The semiconductor structure of  claim 1 , wherein the nano-crystalline core and nano-crystalline shell form a quantum dot. 
     
     
         20 . The semiconductor structure of  claim 19 , wherein the quantum dot is a down-converting quantum dot. 
     
     
         21 . A composite, comprising:
 a matrix material; and   a plurality of semiconductor structures embedded in the matrix material, each semiconductor structure comprising:
 a nano-crystalline core comprising a first group I-III-VI semiconductor material; 
 a nano-crystalline shell comprising a second, different, group I-III-VI semiconductor material at least partially surrounding the nano-crystalline core; and 
 an amorphous insulator coating surrounding and encapsulating the nano-crystalline core/nano-crystalline shell pairing. 
   
     
     
         22 . The composite of  claim 21 , wherein each of the plurality of semiconductor structures is cross-linked with, polarity bound by, or tethered to the matrix material. 
     
     
         23 . The composite of  claim 21 , wherein each of the plurality of semiconductor structures is bound to the matrix material by a covalent, dative, or ionic bond. 
     
     
         24 . The composite of  claim 21 , wherein one or more of the semiconductor structures further comprises a coupling agent covalently bonded to an outer surface of the amorphous insulator coating. 
     
     
         25 . The composite of  claim 21 , wherein, fro each of the plurality of semiconductor structures, the first group I-III-VI semiconductor material is silver gallium sulfide having a stoichiometry of approximately AgGaS 2 . 
     
     
         26 . The composite of  claim 25 , wherein, for each of the plurality of semiconductor structures, the nano-crystalline core has a peak emission approximately in the range of 475-575 nanometers. 
     
     
         27 . The composite of  claim 21 , wherein, for each of the plurality of semiconductor structures, the nano-crystalline core/nano-crystalline shell pairing is a pairing selected from the group consisting of copper indium sulfide (CIS)/silver gallium sulfide (AgGaS 2 ), copper indium selenide (CISe)/AgGaS 2 , copper gallium selenide (CuGaSe 2 )/copper gallium sulfide (CuGaS 2 ), and CuGaSe 2 /AgGaS 2 . 
     
     
         28 . A method of fabricating a semiconductor structure, the method comprising:
 forming a first solution comprising a gallium (Ga) source and a silver (Ag) source;   adding sulfur (S) to the first solution to form a second solution comprising the Ga source, the Ag source, and the sulfur; and   heating the second solution to form a plurality of silver gallium sulfide (AGS) nano-particles.   
     
     
         29 . The method of  claim 28 , wherein forming the first solution comprises dissolving gallium acetylacetonate (ACAC) and silver nitrate (AgNO 3 ) in dodecanethiol (DDT) in the presence of a mixture of carboxylic acids. 
     
     
         30 . The method of  claim 29 , further comprising:
 degassing the first solution while heating the first solution at a temperature of approximately 100 degrees Celsius.   
     
     
         31 . The method of  claim 30 , further comprising:
 subsequent to the degassing, heating the first solution to a temperature of approximately 150 degrees Celsius under an atmosphere of argon (Ar).   
     
     
         32 . The method of  claim 28 , wherein forming the second solution comprises rapidly injecting the sulfur into the first solution. 
     
     
         33 . The method of  claim 28 , further comprising:
 heating the second solution to a temperature of approximately 250 degrees Celsius.   
     
     
         34 . The method of  claim 28 , wherein forming the plurality of AGS nano-particles comprises forming a plurality of particles of stoichiometry approximately AgGaS 2 . 
     
     
         35 . The method of  claim 28 , wherein forming the first solution comprises using a Ga source to Ag source ratio of at least approximately 1:2.