US-12625099-B2 - Method for characterizing energy level of core/shell nanoparticle

Abstract

In a method for determining an energy level of a core/shell according to an example, a valence band energy level of a shell and a core-level energy level of a core in a core/shell nanoparticle are measured together, and by using a valence band energy level and a core-level of a core nanoparticle including only a core, a reliable energy level in a core/shell structure may be determined.

Inventors

• Jeong Won KIM
• Jiyoung YOON

Assignees

• KOREA RESEARCH INSTITUTE OF STANDARDS AND SCIENCE

Dates

Publication Date

20260512

Application Date

20220421

Priority Date

20200129

Claims (8)

1. 1 . A method for characterizing an energy level of a core/shell nanoparticle including a core and a shell surrounding the core, the method comprising: measuring a core-level binding energy E B Core (core-level) and a valence band maximum energy E VBM (core) of a core in a core nanoparticle having only the core using photoelectron spectroscopy; measuring a core-level binding energy E B Core-Shell (core-level) of the core in the core/shell nanoparticle and a valence band maximum energy E VBM (shell) of the shell in the core/shell nanoparticle using photoelectron spectroscopy; and calculating a valence band maximum energy E′ VBM (core) of a material forming the core in the core/shell nanoparticle, wherein the valence band maximum energy E′ VBM (core) of the material forming the core in the core/shell nanoparticle is given as follows: E VBM ′ ( core ) = E VBM ( core ) + E B Core - Shell ( core - level ) - E B Core ( core - level ) .
2. 2 . The method as set forth in claim 1 , wherein the core is InP, the shell is ZnSe, and the core-level is 3d 5/2 of In.
3. 3 . The method as set forth in claim 1 , further comprising: calculating a conduction band minimum energy E′ CBM (core) of the core in the core/shell nanoparticle, wherein a core energy bandgap BG(core) in the core/shell nanoparticle is measured using photoluminescence spectroscopy, wherein the core energy bandgap BG (core) is a difference between the conduction band minimum energy E′ CBM (core) of the core and valence band maximum energy E′ VBM (core) in the core/shell nanoparticle, and wherein the conduction band minimum energy E′ CBM (core) of the core in the core/shell nanoparticle is given as follows: E CBM ′ ( core ) = E VBM ′ ( core ) + BG ⁡ ( core ) .
4. 4 . The method as set forth in claim 1 , further comprising: calculating conduction band minimum energy E CBM (shell) of the shell in the core/shell nanoparticle, wherein the conduction band minimum energy E CBM (shell) of the shell is given as follows: E CBM ( shell ) = E VBM ( shell ) + BG ( shell ) , and wherein a shell energy bandgap BG(shell), which is a difference between the conduction band minimum energy E CBM (shell) and the valence band maximum energy E VBM (shell) of the shell in the core/shell nanoparticle, is a value measured in a bulk state.
5. 5 . The method as set forth in claim 1 , wherein core-level binding energies E B Core (core) and E B Core-Shell (core-level) are measured using X-ray, and wherein valence band maximum energies E VBM (core) and E VBM (Shell) are measured using ultraviolet (UV) light or X-ray.
6. 6 . The method as set forth in claim 1 , wherein the core in each of the core nanoparticle and the core/shell nanoparticle is a first II-VI, IV-VI, or III-V semiconductor, and the shell is a second II-VI, IV-VI, or III-V semiconductor different from the first II-VI, IV-VI, or III-V semiconductor.
7. 7 . The method as set forth in claim 6 , wherein the first II-VI, IV-VI, or III-V semiconductor is InP.
8. 8 . The method as set forth in claim 1 , wherein the photoelectron spectroscopy when measuring each of the core-level binding energy E B Core (core-level) of the core in the core nanoparticle and the core-level binding energy E B Core-Shell (core-level) of the core in the core/shell nanoparticle comprises X-ray photoelectron spectroscopy.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of and claims priority to PCT/KR2020/018298 filed on Dec. 15, 2020, which claims priority to Korea Patent Application No. KR 10-2020-0010502 filed on Jan. 29, 2020, the entireties of which are both hereby incorporated by reference. TECHNICAL FIELD The present disclosure relates to a method for characterizing an energy level of a nanoparticle having a core/shell structure and, more particularly, to a method for characterizing an energy level of a nanoparticle having a core/shell structure using photoelectron spectroscopy. BACKGROUND Even when materials are the same, a band gap and an energy level may be changed depending on a diameter of a core and a thickness of a shell in a core/shell nanostructure due to a quantum confinement effect. A core/shell semiconductor nanostructure has characteristics in which an energy level is changed, as compared with a structure having only a core. For example, a conduction band energy level and a valence band energy level of core nanoparticles having only a core are not the same as a conduction band energy level and a valence band energy level of a core in a core/shell structure. In nanoparticles having a core/shell structure, a conduction band energy level and a valence band energy level of a core and a conduction band energy level and a valence band energy level of a shell are required to be precisely measured. SUMMARY An aspect of the present disclosure is to provide a method for determining an energy level of nanoparticles having a core/shell structure using photoelectron spectroscopy. A valence band energy level and a conduction band energy level of a core and a valence band energy level and a conduction band energy level of a shell may determine physical and chemical properties of nanoparticles having a core/shell structure. A core/shell nanoparticle according to an example embodiment includes a core and a shell surrounding the core. A method for characterizing an energy level of the core/shell nanoparticle includes: measuring core-level binding energy EBCore(core-level) and valence band maximum energy EVBM(core) of a core in a core nanoparticle having only the core using photoelectron spectroscopy; measuring core-level binding energy EBCore-Shell(core-level) of the core and valence band maximum energy EVBM(shell) of the shell in the core/shell nanoparticle including the core and a shell surrounding the core using photoelectron spectroscopy; and calculating valence band maximum energy E′VBM(core) of a material forming the core in the core/shell nanoparticle using the core-level binding energy EBCore(core-level) of the core and the valence band maximum energy EVBM(core) of the core in the core nanoparticle and the core-level binding energy EBCore-Shell(core-level) of the core and the valence band maximum energy EVBM(shell) of the shell in the core/shell nanoparticle. In an example embodiment, the core may be InP, the shell may be ZnSe, and the core-level may be 3d5/2 of In. In an example embodiment, the valence band maximum E′VBM(core) in the core/shell nanoparticle is given as follows: EVBM′(core)=EVBM(core)+EBCore-Shell(core-level)-EBCore(core-level) in an example embodiment, the method may further include calculating a conduction band minimum energy E′CBM(core) of the core in the core/shell nanoparticle. A core energy bandgap BG(core) in the core/shell nanoparticle may be measured using photoluminescence spectroscopy. The core energy bandgap BG(core) may be a difference between the conduction band minimum energy E′CBM(core) of the core and valence band maximum energy E′VBM(core) in the core/shell nanoparticle. Accordingly, the conduction band minimum energy E′CBM(core) of the core in the core/shell nanoparticle may be given as follows: ECBM′(core)=EVBM′(core)+BG⁡(core) In an example embodiment, the method may further include calculating conduction band minimum energy ECBM(shell) of the shell in the core/shell nanoparticle. The conduction band minimum energy ECBM(shell) of the shell may be given as follows: ECBM(shell)=EVBM(hell)+BG(shell), and a shell energy bandgap BG(shell), which is a difference between the conduction band minimum energy ECBM(shell) and the valence band maximum energy EVBM(shell) of the shell in the core/shell nanoparticle, may be a value measured in a bulk state. In an example embodiment, core-level binding energies EBCore (core) and EBCore-Shell (core-level) may be measured using X-ray, and valence band maximum energies EVBM(core) and EVBM(Shell) may be measured using ultraviolet (UV) light or X-ray. BRIEF DESCRIPTION OF DRAWINGS The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings. FIG. 1 is a diagram illustrating a band diagram of a core/shell nanoparticle according to an example embodiment of the present disclosure. FIG