CN113066926A

CN113066926A - A class of room temperature magnetic organic polymer semiconductor materials

Info

Publication number: CN113066926A
Application number: CN202110280213.4A
Authority: CN
Inventors: 刘钢; 薛武红
Original assignee: Shanghai Jiao Tong University
Current assignee: Shanghai Jiao Tong University
Priority date: 2021-03-16
Filing date: 2021-03-16
Publication date: 2021-07-02

Abstract

The invention provides a class of room temperature magnetic organic polymer semiconductor materials, which are nano helical structures and contain C=N double bonds in the helical skeleton; at room temperature, they can also be ferromagnetic. The main source of magnetism is the C=N double bond; and by changing the value of the degree of polymerization, the size of the magnetism can be adjusted, wherein the greater the degree of polymerization, the stronger the magnetism. Therefore, it is expected to be applied to information storage related to magnetic semiconductors, spin transistors, and the like.

Description

Room temperature magnetic organic polymer semiconductor material

Technical Field

The invention relates to the technical field of nanotechnology and information storage, in particular to an organic magnetic random access memory.

Background

Magnetic semiconductors are widely used in magnetic random access memories, sensors, transistors, capacitors, quantum communication, quantum computing, and the like, and for realizing these applications, magnetic semiconductors must satisfy the requirement of stable ferromagnetism at room temperature, i.e., curie temperature is required to reach room temperature or even higher than room temperature. Traditional magnetic semiconductors have Curie temperatures below room temperature and require expensive equipment for fabrication (e.g., molecular beam epitaxy, atomic layer deposition, etc.), and researchers have subsequently discovered means for doping semiconductors with magnetic elements that render them ferromagnetic at room temperature, such magnetic semiconductors being referred to as diluted magnetic semiconductors. However, since the solubility of magnetic elements is low and clusters are easily formed, room-temperature ferromagnetism sometimes observed in semiconductors is actually caused by these magnetic clusters, limiting their integration with mainstream semiconductors and flexible applications. It is therefore very important to develop intrinsic room temperature ferromagnetic semiconductors. Organic semiconductors have the advantage of low cost large area synthesis, which would be of great interest if room temperature ferromagnetism could be achieved in organic semiconductors.

Disclosure of Invention

The invention aims to provide a room-temperature magnetic organic polymer semiconductor material which is low in preparation cost, the Curie temperature is higher than room temperature, and the magnetism can be regulated and controlled by changing the polymerization degree.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows: a room temperature magnetic organic polymer semiconductor material is characterized in that:

the nano-helix structure is provided, and a helix skeleton contains C ═ N double bonds; has a certain degree of polymerization; ferromagnetism at room temperature or above; in the synthetic capacity range, the larger the polymerization degree is, the stronger the ferromagnetism is; has semiconductor characteristics;

the nano spiral structure is based on polyisocyan obtained by polymerization of isocyanic monomers. Including but not limited to one or more of poly (carbazolyl isocyano), poly (tetraphenyl vinyl isocyano) and poly (triphenylamine isocyano).

The polymerization degree is not less than 10 and is not limited to one.

The ferromagnetism is obvious hysteresis loop at room temperature, is not limited to room temperature, and can be any temperature higher than the room temperature.

The semiconductor forbidden band width is larger than 0, is not limited to one forbidden band width, and can be any value meeting the semiconductor forbidden band width.

Preferably, the polymerization degree is higher under the synthetic ability, the better, and stronger ferromagnetism is ensured.

As an implementation, the specific preparation and characterization process of the material is as follows:

(1) preparation of polymeric materials having helical nanostructures and containing C ═ N double bonds in the helical backbone

Dissolving a certain amount of isocyanic monomer in a proper amount of solvent (such as dichloromethane, tetrahydrofuran, chloroform, etc.). Then, 0.01 to 0.1 equivalent of the catalyst was added, and the mixture was stirred at room temperature for 1 to 3 days. After the reaction, the reaction mixture was concentrated and then added dropwise to a stirred poor solvent (e.g., methanol or water) such as methanol (1 to 10mL) to precipitate. Filtering, washing and drying to obtain the polyisocyan polymer.

(2) Confirmation of polymerization of isocyano group

The infrared spectrum is used for characterization, and the infrared characteristic peak of the isocyano group is 2120cm^-1About, if the infrared spectrum of the polymer is 2120cm^-1The disappearance of the left and right characteristic peaks proves that the isocyano monomer is polymerized to generate the polyisocyan.

(3) Characterization of the degree of polymerization

The degree of polymerization refers to the number of times repeating units (or segments) appear in succession in the molecular chain of the polymer. The molecular weight of the polymer can be characterized by Gel Permeation Chromatography (GPC), and then the formula weight of the repeating unit is calculated, and the polymerization degree of the polymer can be obtained by the formula polymerization degree (n) as molecular weight/mer.

The number average degree of polymerization of the polymer is roughly calculated in this patent using the number average molecular weight characterized by GPC.

(4) Characterization of semiconductor Properties (any one or more of the following)

1. Testing the size of the characteristic forbidden band width by a cyclic voltammetry;

2. testing and representing the size of forbidden band width through ultraviolet absorption spectrum;

3. judging that the resistor has semiconductor characteristics by testing the variation trend of the resistor along with the temperature;

4. preparing a Hall device and measuring the carrier concentration;

5. and preparing a field effect transistor and testing a transfer curve.

(5) Room temperature magnetic characterization (any one or more of the following)

1. Testing the hysteresis loop of the material at room temperature;

2. preparing a Hall device, testing Hall resistance at room temperature, and confirming room-temperature ferromagnetism if an abnormal Hall effect occurs;

3. the Curie temperature can be judged whether to reach the room temperature or above by testing the variation trend of the magnetic moment along with the temperature.

Compared with the prior art, the invention provides a room-temperature magnetic organic polymer semiconductor material which has the following beneficial effects:

(1) compared with the preparation of inorganic materials, the organic polymer can be synthesized in large batch at low cost;

(2) compared with a diluted magnetic semiconductor realized by a complex doping means, the organic polymer magnetic semiconductor does not need doping, belongs to an intrinsic magnetic semiconductor, and solves the problem of undefined magnetic origin.

(3) The film can be coated on a Si sheet to form a film, and still has room temperature ferromagnetism, which provides necessary precondition for the preparation of a magnetic film device.

Drawings

Fig. 1 is a schematic diagram of a high molecular weight polymer having a nano-helical structure and a helical skeleton including C ═ N double bonds and having a polymerization degree of N (N > 10);

FIG. 2 is a composite roadmap for P (TPE-NC);

FIG. 3 is an infrared spectrum of a monomer TPE-NC and a polymer P (TPE-NC);

FIG. 4 is a gel permeation chromatography spectrum of P (TPE-NC);

FIG. 5 is an atomic microscope topography of P (TPE-NC);

FIG. 6 is a cyclic voltammogram of P (TPE-NC);

FIG. 7 is a room temperature hysteresis loop for P (TPE-NC);

FIG. 8 is a graph of magnetization versus temperature for P (TPE-NC);

FIG. 9 is a hysteresis loop after spin coating the synthesized powder on a Si wafer to form a thin film;

Detailed Description

The invention will be described in further detail below with reference to the embodiments of the drawing, which are intended to facilitate the understanding of the invention and are not intended to limit the invention in any way.

Example 1:

in this embodiment, fig. 2 is a schematic diagram of the synthesis of a P (TPE-NC) material, and the synthesis steps are as follows:

TPE-NC (0.22g, 0.45mmol) was dissolved in anhydrous CH2Cl2(2.25 mL). A solution of NiCl2 · 6H2O (1.066mg, 0.0045mmol) in MeOH (0.1mL) was added via syringe and the mixture was stirred at room temperature for 2 days. The reaction solution was then concentrated to a small volume and then added dropwise to stirred methanol (10 mL). After filtration, the collected dark brown solid was washed several times with methanol and dried under vacuum at 40 ℃ overnight to give 177.5mg of polymer P (TPE-NC).

Then, the structure, the degree of polymerization, the conductivity type and the magnetism of the alloy are characterized:

(1) the infrared spectra of the monomer TPE-NC and the high molecular polymer P (TPE-NC) are shown in FIG. 3, 1495cm-¹The peak of (A) is attributed to C ═ C skeleton vibration of aromatic hydrocarbon, 1750cm^-1The characteristic peak is attributed to stretching vibration of the carbonyl group. 2121cm belonging to isocyano stretching vibration in infrared spectrum^-1The peak disappeared in the infrared absorption spectrum of P (TPE-NC), which indicates that the N.ident.C group undergoes polymerization reaction to form polyisocyan.

(2) The polymer P (TPA-NC) was subjected to gel permeation chromatography, and as shown in FIG. 4, the number average molecular weight (Mn), weight average molecular weight (Mw) and Z average molecular weight (Mz +1) were found to be 207167, 310685 and 751880, respectively. The polydispersity was measured as 1.499682, indicating a relatively uniform molecular weight distribution. The formula weight of the mer is 477, which is calculated to give a number average degree of polymerization of about 434.

(3) The morphology of P (TPA-NC) was characterized by atomic force microscopy, and as shown in FIG. 5, the P (TPA-NC) macromolecule chain exhibited a right-handed helical conformation.

(4) The electrical properties of P (TPE-NC) were tested using cyclic voltammetry, based on a three-electrode working system, in which the Pt electrode was the working electrode, the platinum wire electrode was the counter electrode, and the Ag/AgCl electrode was the reference electrode. As can be seen in FIG. 6, the first oxidation peak and reduction peak of P (TPE-NC) versus Ag/AgCl are +1.39V and-0.95V, respectively. According to the following equation

HOMO/LUMO＝-[E_onset-E_{ox.(ferrocene)}]-4.8ev

The HOMO and LUMO energy levels of P (TPE-NC) were calculated to be-5.81 eV and-3.47 eV, respectively, and the electrochemical bandgap of P (TPE-NC) was further calculated to be 2.34 eV.

(5) Room temperature hysteresis loops and magnetic moment variation curves (fig. 7 and 8) of the synthesized powder with temperature are measured by using a superconducting quantum interferometer, and the powder is known to have very strong room temperature ferromagnetism, the saturated magnetic moment can reach 75uemu/mg, and the curie temperature is higher than room temperature.

Example 2:

in this example, the synthesized powder was first dissolved using a solvent and then spin-coated on a Si wafer by a spin coater, and then a room temperature hysteresis loop was tested (fig. 9). The test method was exactly the same as (5) in example 1.

Comparative example 1:

this example further illustrates that the film made of the synthesized material still has room temperature ferromagnetism, which lays a foundation for the preparation of magnetic electronic devices.

The above embodiments are provided to explain the technical solutions of the present invention in a detailed manner, and it should be understood that the above examples are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modification, addition or equivalent substitution made within the scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A room temperature magnetic organic polymer semiconductor material is characterized in that:

the nano-helix structure is provided, and a helix skeleton contains C ═ N double bonds;

has a certain degree of polymerization;

has ferromagnetism;

has semiconductor characteristics.

2. A class of room temperature magnetic organic polymer semiconductor materials as claimed in claim 1, wherein: the nano-helical structure is a polymer based on an isocyanic monomer.

3. A class of room temperature magnetic organic polymer semiconductor materials as claimed in claim 1, wherein: the degree of polymerization is not less than 10.

4. A class of room temperature magnetic organic polymer semiconductor materials as claimed in claim 1, wherein: the ferromagnetism means that the material still has ferromagnetism at room temperature or above.

5. A class of room temperature magnetic organic polymer semiconductor materials as claimed in claim 1, wherein: the semiconductor is a semiconductor with a forbidden band width of more than 0.