Concentric flower reactor

1. A gas phase nanowire growth apparatus comprising:

a first reaction chamber;

a first input;

a second input;

a catalyst particle inlet configured to provide catalyst particles to the first input or the second input;

a catalyst particle aerosol source fluidly connected to the catalyst particle inlet;

a first metal organic precursor reservoir fluidly connected to the first input and configured to provide the metal organic precursor to grow the nanowires which comprise Group III-V or Group II-VI semiconductor nanowires;

a second inert gas reservoir fluidly connected to the second input; and

a first output and a second output located at an opposite wall of the first reaction chamber from the first and second input and wherein the first output is located concentrically within the second output;

wherein the first input is located concentrically within the second input and the first and second inputs are configured such that a second fluid delivered from the second input provides a sheath between a first fluid delivered from the first input and a wall of the first reaction chamber;

a second reaction chamber fluidly connected to the first reaction chamber, the second reaction chamber having a third input, a fourth input, a third output and a fourth output;

wherein the first output of the first reaction chamber is fluidly connected to the third input of the second reaction chamber and the second output of the first reaction chamber is fluidly connected to the fourth input of the second reaction chamber.

2. The apparatus of claim 1 , wherein the second output further comprises one porous frit or a plurality of porous frits.

3. The apparatus to claim 1 , further comprising one or more heaters configured to heat the first reaction chamber and one or more heaters configured to heat the first input and the second inputs.

4. The apparatus of claim 1 , further comprising at least one lifting mechanism configured to move the first and second inputs, the first and second outputs or both the first and second inputs and the first and second outputs such that a distance between the first and second inputs and the first and second outputs may be increased or decreased.

5. The apparatus of claim 1 , wherein the catalyst particle aerosol source comprises an aerosol generator.

6. The apparatus of claim 1 , further comprising a third reservoir fluidly connected to the first input, wherein the third reservoir comprises a second precursor.

7. The apparatus of claim 6 , wherein the first precursor comprises a group IIIA metal organic compound and the second precursor comprises a group VA compound.

8. The apparatus of claim 1 , wherein the apparatus does not have a deposition substrate in the first reaction chamber.

9. A method of fabricating semiconductor nanowires comprising:

providing a first gas stream to a first reaction chamber, wherein the first gas stream comprises a first precursor for fabricating the semiconductor nanowires;

providing a second gas stream to the first reaction chamber, wherein the second gas stream forms a sheath separating the first gas stream from a wall of the first reaction chamber;

providing nanowire growth catalyst particles from an aerosol in at least one of the first gas stream or the second gas stream;

adding a first dopant gas having a first conductivity type to the first gas stream to grow semiconductor nanowires of the first conductivity type in a gas phase in the first reaction chamber; and

adding a second dopant gas having a second conductivity type after the step of adding the first dopant gas to form a p-n or p-i-n junction in the semiconductor nanowires;

wherein the semiconductor nanowires comprise single crystal Group III-V or Group II-VI semiconductor nanowires;

wherein the first gas stream containing the catalyst particles flows sequentially through one or more reaction zones of the first reaction chamber such that the semiconductor nanowires grow from the catalyst particles and the semiconductor nanowires grown after passage through the reaction zones are carried by the first gas stream surrounded the second gas sheath; and

wherein a flow rate of the first gas stream is higher than a flow rate flow rate of the second gas stream to form an expansion in a diameter of the first gas stream.

10. The method of claim 9 , wherein the step of adding the second dopant gas comprises adding the second dopant gas to the first gas stream to form the p-n or p-i-n junction in the semiconductor nanowires.

11. The method of claim 9 , further comprising:

removing the second gas stream from the first reaction chamber before it reaches a second reaction chamber;

providing the semiconductor nanowires from the first reaction chamber to the second reaction chamber;

providing a third gas stream to the second reaction chamber, wherein the third gas stream comprises a second precursor for fabricating the semiconductor nanowires; and

providing a fourth gas stream to the second reaction chamber, wherein the fourth gas stream forms a sheath separating the third gas stream from a wall of the second reaction chamber;

wherein the step of adding the second dopant gas comprises providing the second dopant gas to the second reaction chamber to form the p-n or p-i-n junction in the semiconductor nanowires in the gas phase in the second reaction chamber.

12. A method of fabricating semiconductor nanowires comprising:

providing a first gas stream to a first reaction chamber, wherein the first gas stream comprises a core flow stream containing a first precursor for fabricating the semiconductor nanowires;

providing a second gas stream to the first reaction chamber, wherein the second gas stream forms a sheath separating the first gas stream from a wall of the first reaction chamber;

providing nanowire growth catalyst particles from an aerosol in at least one of the first gas stream or the second gas stream; and

adding a first dopant gas having a first conductivity type to the first gas stream to grow semiconductor nanowires of the first conductivity type in a gas phase in the first reaction chamber;

removing the second gas stream from the first reaction chamber before it reaches a second reaction chamber;

providing the semiconductor nanowires from the first reaction chamber to the second reaction chamber;

providing a third gas stream to the second reaction chamber, wherein the third gas stream comprises a second precursor for fabricating the semiconductor nanowires;

providing a fourth gas stream to the second reaction chamber, wherein the fourth gas stream forms a sheath separating the third gas stream from a wall of the second reaction chamber;

adding a second dopant gas having a second conductivity type into the second reaction chamber after the step of adding the first dopant gas to grow a p-n or p-i-n junction in the semiconductor nanowires in a gas phase in the second reaction chamber;

wherein a flow rate of the core flow stream is higher than a flow rate flow rate of the second gas stream to form an expansion in a diameter of the core flow stream;

wherein the semiconductor nanowires comprise single crystal Group III-V or Group II-VI semiconductor nanowires; and

wherein the catalyst particles are electrically charged.

13. A method of fabricating semiconductor nanowires comprising:

providing a first gas stream to a first reaction chamber, wherein the first gas stream comprises a first precursor for fabricating the semiconductor nanowires;

providing a second gas stream to the first reaction chamber, wherein the second gas stream forms a sheath separating the first gas stream from a wall of the first reaction chamber;

adding a first dopant gas having a first conductivity type to the first gas stream to grow semiconductor nanowires of the first conductivity type in a gas phase in the first reaction chamber;

adding a second dopant gas having a second conductivity type after the step of adding the first dopant gas to form a p-n or p-i-n junction in the semiconductor nanowires;

monitoring a temperature of the first gas stream in a first input conduit to the first reaction chamber and adjusting the temperature of the first gas stream depending on the monitored temperature;

monitoring a temperature of the second gas stream in a second input conduit to the first reaction chamber and adjusting the temperature of the second gas stream depending on the monitored temperature;

wherein the semiconductor nanowires comprise single crystal Group III-V or Group II-VI semiconductor nanowires; and

wherein the first reaction chamber comprises first and second inputs to input the first and second gas streams to the first reaction chamber and first and second outputs to remove the first and second gas streams from the first reaction chamber and the method further comprises raising or lowering the first and second inputs or the first and second outputs in the first reaction chamber, thereby decreasing or increasing a length of a reaction zone in the first reaction chamber.