Excitation band-gap tuning of dopant based quantum dots with core-inner shell-outer shell

• US 7,687,800 B1
• Filed: 11/21/2008
• Issued: 03/30/2010
• Est. Priority Date: 11/23/2007
• Status: Expired due to Fees

• Current Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Original Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Santra, Swadeshmukul, Kar, Soumitra
• Primary Examiner(s): Smith; Bradley K
• Assistant Examiner(s): Valentine; Jami M
• Application Number:
  US12/275,269
• Time in Patent Office: 494 Days
• Field of Search: 257/14, 257/E29.071, 438/962, 977773-774
• US Class Current: 257/14
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: H01L 29/127 Quantum box structures
• CPC Class Codes: H01L 29/22 including, apart from doping materials or other impurities, only AIIBVI compounds
• CPC Class Codes: H01L 29/225 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: Y10S 438/962 Quantum dots and lines
• CPC Class Codes: Y10S 977/773 Nanoparticle, i.e. structure having three dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/774 Exhibiting three-dimensional carrier confinement, e.g. quantum dots

Abstract

A composition and method for fabricating and tuning a dopant based core-shell semiconductor having a quantum dot core with an excitation band-gap are provided. A quantum dot core composed of an alloy of cadmium sulfide (CdS) and zinc sulfide (ZnS) as semi-conductor materials include a dopant of manganese (Mn) added to the core and an outer shell of zinc sulfide (ZnS). The dopant based core/shell quantum dot semiconductor of the present invention allows the fine tuning of an excitation band-gap, covering a wide range (from 2.4 eV to ˜4 eV). When doped with Mn, these alloy Qdots emit bright yellow/orange light. Tuning of the excitation band is accomplished by changing the alloy composition of the core. Based on photophysical studies a new core/shell/shell model is provided, in place of the traditional core/shell model. Due to the interfacial diffusion of the cations from the core and shell an intermediate alloy layer is formed providing an inner shell; this inner shell layer is the real host of the dopant ions.

Claims

1. A dopant based core/shell/shell semiconductor having a quantum dot core with a tunable excitation band-gap comprising:

an alloy of cadmium sulfide (CdS) and zinc sulfide (ZnS) semiconductor materials to form a core;

a concentric layer composed of in-situ formed Cd_xZn_(1-x)S alloy embedded with the dopant manganese (Mn) forming an inner shell surrounding the core; and

an outer shell of zinc sulfide (ZnS).

2. The dopant based core/shell/shell quantum dot core of claim 1, wherein the alloy of CdS and ZnS varies from an approximately 100% ZnS core to an approximately 100% CdS core, when the alloy is approximately 100% of ZnS and approximately 100% CdS, there is interfacial diffusion of Cd and Zn atoms forming an additional interfacial alloy.

3. The dopant based core/shell/shell quantum dot core of claim 1, wherein the alloy of CdS and ZnS and the dopant of Mn have a composition selected from at least one of the following:

ZnS;

Mn,

Zn_0.75Cd_0.25S;

Mn,

Zn_0.50Cd_0.50S;

Mn,

Zn_0.25Cd_0.75S;

Mn, and

CdS;

Mn.

4. The dopant based core/shell/shell quantum dot semiconductor of claim 1, wherein the core dopant is only manganese (Mn) and the shell is only zinc sulfide (ZnS).

5. The dopant based core/shell/shell semiconductor with quantum dot core of claim 1, wherein the core/shell/shell particle size is between approximately 3.0 nanometers (nm) to approximately 3.5 nanometers (nm) in diameter with a core approximately 2.0 nanometers (nm) to approximately 2.7 nanometers (nm) in diameter.

6. The dopant based core/shell/shell semiconductor with quantum dot core of claim 1, wherein the excitation spectrum is in a wavelength range from approximately 275 nm to approximately 490 nm.

7. The dopant based core/shell/shell semiconductor with quantum dot core of claim 6, wherein the excitation spectrum is efficient for capturing a broad spectrum of solar light.

8. The dopant based core/shell/shell semiconductor with quantum dot core of claim 1, wherein the tuning of the excitation band is accomplished by changing the alloy composition of the core.

9. The dopant based core/shell/shell semiconductor with quantum dot core of claim 2, wherein the core is an alloy and the composition of the interfacial alloy layer varies depending on the percentage of Cd and Zn inside the core.