CN115074822B

CN115074822B - Two-dimensional quantum dot array and preparation method thereof

Info

Publication number: CN115074822B
Application number: CN202210780274.1A
Authority: CN
Inventors: 卢建臣; 熊玮; 蔡金明
Original assignee: Kunming University of Science and Technology
Current assignee: Kunming University of Science and Technology
Priority date: 2022-07-04
Filing date: 2022-07-04
Publication date: 2023-10-13
Anticipated expiration: 2042-07-04
Also published as: CN115074822A

Abstract

The invention discloses a two-dimensional quantum dot array and a preparation method thereof. In the preparation method, a metal monocrystal is selected as a substrate, and a precursor molecule dibromofluorene is deposited on the surface of the substrate kept at room temperature through a molecular beam epitaxial growth technology, so that a large-scale regular and ordered two-dimensional hexagonal hole structure can be obtained. The hole structure can realize the constraint of free electrons on the surface of the metal substrate so as to form a two-dimensional quantum dot array. The invention provides a method for constructing a high-density quantum dot array on the surface of a metal substrate by using dibromofluorene molecules, which has higher scientific research value and wide application potential.

Description

Two-dimensional quantum dot array and preparation method thereof

Technical Field

The invention relates to the technical field of nano materials, in particular to a large-area two-dimensional porous self-organization structure prepared by dibromofluorene molecules on a metal monocrystalline substrate, which constructs a two-dimensional quantum dot array.

Background

The singular quantum states often drive the development of quantum photovoltaic and fluorescent devices. The organic nanoporous network grown on the noble metal surface is considered as an excellent platform for studying quantum phenomena such as electron scattering. On the surface, porous networks of organic molecules are capable of confining two-dimensional electron gases within the nanopores, so they are commonly referred to as "quantum dot arrays". The bound state in the hole observed by the scanning tunnel microscopy technique is mainly represented by schottky barrier electron state of the metal surface, and energy shift is carried out to a certain extent. This phenomenon is mainly due to repulsive scattering on the walls of the organic molecules and partial quantum confinement within each pore. This may play a vital role in future molecular engineering applications, such as quantum computing or device technology.

Compared with the very time-consuming technology of constructing the quantum fence by utilizing the needle tip manipulation, the supermolecule self-assembly technology can realize the self-repairing process of the sample due to the reversibility of non-covalent interaction, such as hydrogen bond, halogen bond or metal ligand interaction. Thus, a two-dimensional nano porous network with almost no defects and long-range order can be constructed.

The scanning tunnel microscope technology can accurately represent the structure of a sample on an atomic scale, the scanning tunnel differential spectrum technology can represent the energy band structure of the sample and the spatial distribution of a front track, and a good technical platform is provided for researching novel low-dimensional materials with special electronic states. Has a profound impact on the development of molecular electronics and related nanocircuits.

Disclosure of Invention

The invention aims to provide a two-dimensional quantum dot array and a preparation method thereof. Specifically, the invention constructs a two-dimensional porous network on a metal monocrystalline substrate by using dibromofluorene molecules to bind surface two-dimensional electron gas, thereby forming a high-density regular and ordered two-dimensional quantum dot array.

The invention is realized by the following technical scheme: in an ultra-high vacuum environment, dibromofluorene precursor molecules are firstly deposited on an atomically clean metal single crystal substrate kept at room temperature for 60 to 180 seconds, and the deposition time can be changed according to different requirements of sample areas. The morphology and electronic structural features are then characterized by key-resolved scanning tunneling microscopy and scanning tunneling differential spectroscopy and imaging techniques.

Preferably, the method for preparing a quantum dot array according to the present invention further comprises the steps of: the molecular purity of dibromofluorene should be kept above 99%. Before preparing the sample, the impurity removal step should be performed at the deposition temperature for about one hour to ensure that the surface of the sample is free of other impurities.

Preferably, the precursor molecules are kept at the evaporation temperature for 10 minutes before being deposited, so that the molecular beam is stable. After the deposition is finished, the metal monocrystalline substrate is annealed for 10 minutes at room temperature, so that the molecules are fully diffused, arranged and assembled on the substrate.

Preferably, the step of evaporating and depositing the dibromofluorene molecules onto the metal single crystal substrate is evaporating and depositing dibromofluorene molecules onto the metal single crystal substrate by heat-resistant heating.

In certain embodiments of the invention, the dibromofluorene molecules are sublimated at a sublimation temperature of 25 ℃ to 30 ℃. For example, in the case where the sublimation temperature is selected to be 30 ℃, a good deposition effect can be obtained.

In certain embodiments of the invention, the metal single crystal substrate is prepared by a method comprising the steps of: a. performing argon ion sputtering treatment on the metal monocrystal in the ultrahigh vacuum cavity to obtain a metal substrate; b. the metal substrate is heated and maintained at 450 ℃ for 10-30 minutes. c. The metal substrate was slowly cooled to 260 ℃ at an annealing rate of 6 ℃/min, and then allowed to cool naturally.

Drawings

Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 shows a two-dimensional porous nano-network scanning tunneling microscope image formed by self-assembly of dibromofluorene molecules in accordance with an embodiment of the present invention;

FIG. 2 illustrates a scanning tunneling microscope key resolution image and a primitive structure in accordance with an embodiment of the present invention;

FIG. 3 shows an optimized structure calculated by density functional theory and weak interactions and primitive cell structures between molecules according to an embodiment of the present invention;

fig. 4 shows a spectral characterization of a scanned tunnel differential spectrum according to an embodiment of the invention.

FIG. 5 illustrates standing wave phenomena in a quantum dot array exhibited by a scanned tunnel differential image in accordance with an embodiment of the invention;

Detailed Description

The invention will now be described in further detail with reference to the following specific embodiments, which are given by way of illustration only and are not intended to limit the scope of the invention.

Test instrument and apparatus:

cryogenic scanning tunneling microscope: purchased from omacron, germany.

K-cell molecular evaporation source: purchased from omacron, germany.

Argon ion gun: purchased from omacron, germany.

Raw materials:

dibromofluorene molecules: purchased from chemoson, 99% purity.

Metal single crystal substrate (gold, silver, copper): purchased from MaTecK with 99.999% purity.

Examples

Preparation of metal monocrystalline substrate

And carrying out argon ion sputtering treatment on the metal monocrystalline substrate in the ultrahigh vacuum cavity by using an argon ion gun to obtain the metal substrate, heating the metal substrate and maintaining the temperature at 450 ℃ for 10-30 minutes to obtain a clean and flat metal monocrystalline substrate.

After the metal single crystal substrate is prepared, dibromofluorene molecules are sublimated and deposited on the surface of the metal single crystal substrate kept at room temperature at a sublimation temperature of 30 ℃ by utilizing a thermal resistance type K-cell molecular evaporation source in an ultra-high vacuum environment. The deposition time of dibromofluorene molecules was 60 seconds. After the deposition was completed, dibromofluorene molecules on the metal single crystal substrate were maintained at an annealing temperature of 30 ℃ for 10 minutes. The purpose is to allow for adequate diffusion, alignment and assembly of the molecules.

Fig. 1 shows a scanning tunnel microscope image of a preparation method according to an embodiment of the present invention, a diagram is a two-dimensional porous network structure with large area defect-free long range order, b diagram is a two-dimensional porous network enlarged diagram marked by white square frames, in which a primitive cell structure can be observed, and the distance between adjacent holes is 30.3±0.1 a, and the two layers of molecules are spaced apart. Fig. 2 shows a two-dimensional porous network structure characterized by a bond resolution scanning tunneling microscope technique, wherein the single pore spacing is 26.5±0.1 a, each pore is composed of six dibromofluorene molecules, the molecular armchair boundaries face to the pore centers, and weak interaction forces inside self-assembly can be resolved by the scanning pattern. Fig. 3 shows a structural model optimized by density functional theory calculation, and marks the corresponding primitive cell structure and weak interaction force, which are better matched with the experiment. Fig. 4 shows the electronic structure of a two-dimensional porous network obtained by scanning tunnel differential spectroscopy according to an embodiment of the invention, the spectral information obtained from the pores shows a distinct peak at-230 and mV, with an energy shift of 270 mV relative to the schottky barrier (-500 mV) of a pure gold substrate, which is caused by the binding effect of the two-dimensional pores on the two-dimensional electron gas of the substrate. Fig. 5 shows a scanned tunnel differential image taken at-230 mV, where bright electronic state features in the aperture can be observed. The phenomenon is a standing wave phenomenon caused by scattering of surface electron states on the wall of dibromofluorene molecules. Each bright spot is a bound quantum dot, and the extended large-area quantum dots form a regular high-density quantum dot array.

Claims

1. A preparation method of a two-dimensional quantum dot array is characterized by comprising the following steps: the method comprises the steps of firstly depositing precursor molecular dibromofluorene on the surface of a metal monocrystalline substrate through a molecular beam epitaxy technology, and further obtaining a sample, wherein the sample can obtain a large-area long-range ordered porous two-dimensional network nano structure after room temperature annealing, and the two-dimensional network nano structure can bind free electrons on the surface of the metal to form a high-density regular ordered two-dimensional quantum dot array.

2. The method of manufacturing according to claim 1, characterized in that: the sublimation temperature of the precursor molecule dibromofluorene is 30 ℃.

3. The method of manufacturing according to claim 1, characterized in that: the deposition time of the precursor molecule dibromofluorene is 60 to 180 seconds.

4. The method of manufacturing according to claim 1, characterized in that: the metal monocrystalline substrate is gold, silver or copper.

5. The method of manufacturing according to claim 1, characterized in that: the sample annealing temperature ranges from 25 ℃ to 100 ℃.

6. The method of manufacturing according to claim 1, characterized in that: the size of the large-area long-range ordered two-dimensional quantum dot array exceeds 1000 square nanometers.