CN103033734B - Method for measuring graphene carrier mobility based on non-contact Hall effect - Google Patents

Abstract

The invention belongs to the technical field of semiconductors, and provides a method for measuring graphene carrier mobility based on a non-contact Hall effect. Induced current and Hall current are guided in graphene by adopting an incident electromagnetic wave exciting mode; electromagnetic wave radiated by the Hall current is measured, and is compared with incident electromagnetic wave to obtain the mobility of the graphene; the projection position of excited electromagnetic wave is changed to implement multi-point measurement; and the mobilities of the graphene in different positions are compared to obtain whether the graphene has excellent consistence. The method adopts the non-contact electromagnetic wave to measure the graphene mobility, so that the time spent in measuring the graphene mobility is saved, the influence on properties of the graphene from the traditional method for producing metal probes is avoided, and whether a large amount of prepared graphene has excellent consistence can be judged; and the method has strong practicability and stronger promotion and application benefits.

Description

Method for Measuring Carrier Mobility of Graphene Based on Non-contact Hall Effect

technical field

The invention belongs to the technical field of semiconductors, in particular to a method for measuring graphene carrier mobility based on a non-contact Hall effect.

Background technique

Graphene material is a carbon-based two-dimensional crystal. It is the lightest and thinnest material known so far. The single layer is only atomically thick. It has extremely excellent physical and chemical properties, such as extremely high carrier mobility (theoretical estimation More than 200,000cm ² V ^-1 s ^-1 , hundreds of times that of Si), super mechanical properties (Young's modulus about 1000GP), extremely high specific surface area and excellent gas-sensing properties, extremely high transparency And flexibility, and there is no mismatch between it and the substrate, it can be fully compatible with Si-based device technology, and has outstanding industrial advantages. Therefore, the emergence of graphene has brought dawn to the industry and science and technology circles, and it is the most promising new material to replace Si as the next-generation basic semiconductor material.

In order to improve the consistency of graphene preparation, it is usually necessary to test the mobility of graphene after the preparation is completed. The conventional van der Pauw method has a simple principle and is theoretically suitable for measuring samples of any shape (the material is required to be an approximately two-dimensional material, That is, the thickness is much smaller than the length and width) and the measurement error is small. However, due to the need to make ohmic contacts and metal solder joints, the graphene material is damaged and it is difficult to perform other tests. Moreover, because the thickness of single-layer graphene is too thin, it is difficult to obtain good consistency in the preparation of doped graphene. The work function difference between graphene material and metal material is large, and it is not easy to make a good ohmic contact. The upper electrode is expensive to make, making the van der Pauw method unsuitable for characterizing graphene. Therefore, in order to efficiently characterize graphene and determine whether a large amount of graphene has good consistency, a non-contact method is proposed to measure the mobility.

Contents of the invention

The present invention provides a method for measuring the mobility of graphene carriers based on the non-contact Hall effect, aiming to solve the method for testing the mobility of graphene provided by the prior art, which makes the graphene material damaged and difficult to perform other tests , At the same time, the test cost is high and the operation is complicated.

The object of the present invention is to provide a method for measuring graphene carrier mobility based on the non-contact Hall effect. The method uses incident electromagnetic wave excitation to introduce induced current and Hall current into graphene. The radiated electromagnetic wave is compared with the incident electromagnetic wave to obtain the mobility of graphene, and then the projected position of the excited electromagnetic wave is changed for multi-point measurement.

Further, the specific implementation steps of the method are as follows:

Step 1, place the copper disc on the stage, align it with the electromagnetic wave transmitter, use the test equipment to automatically read the reflected energy of the copper disc, and adjust the equipment parameters with the acquired reflected energy;

Step 2, place the graphene transferred onto the substrate on the stage, and select the built-in response test substrate;

Step 3, apply an anti-phase signal to the balance bridge circuit, and manually adjust the detector to minimize the detected Hall value;

Step 4, under zero magnetic field, measure graphene surface resistance and carrier concentration by reflecting electromagnetic waves, and the measured values will be used for mobility measurement;

Step five, keep the magnetic induction at 5000-10000G, measure the Hall energy radiated by the graphene Hall excitation current, and calculate the graphene mobility from it;

Step six, move the substrate, and measure the mobility of graphene at other positions.

Further, in step 1, the resistance value of the copper disc measured by reflected energy is not greater than 10 ohms.

Further, in step two, the substrate used must be no smaller than 2 inches.

Further, in step six, by comparing the mobility of graphene at different positions, it can be obtained whether the graphene has a good consistency.

The method for measuring the carrier mobility of graphene based on the non-contact Hall effect provided by the present invention adopts the method of incident electromagnetic wave excitation, introduces induced current and Hall current into graphene, and measures the electromagnetic wave radiated by the Hall current , and compared with the incident electromagnetic wave, the mobility of graphene is obtained, and then the projected position of the excited electromagnetic wave is changed to perform multi-point measurement, and by comparing the mobility of graphene at different positions, it can be obtained whether the graphene has good consistency. This method uses non-contact electromagnetic waves to measure the mobility of graphene, which saves the time for measuring the mobility of graphene, avoids the influence of the traditional method of making metal probes on the properties of graphene, and can determine whether a large amount of graphene has good consistency. , strong practicability, and strong promotion and application value.

Description of drawings

Fig. 1 is the implementation flowchart of the method for measuring graphene carrier mobility based on the non-contact Hall effect provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of the principle of the method for measuring the carrier mobility of graphene based on the non-contact Hall effect provided by the embodiment of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the invention.

The object of the present invention is to provide a method for measuring graphene carrier mobility based on the non-contact Hall effect. The method uses incident electromagnetic wave excitation to introduce induced current and Hall current into graphene. The radiated electromagnetic wave is compared with the incident electromagnetic wave to obtain the mobility of graphene, and then the projected position of the excited electromagnetic wave is changed for multi-point measurement.

Fig. 1 shows the implementation process of the method for measuring the carrier mobility of graphene based on the non-contact Hall effect provided by the embodiment of the present invention.

As shown in Figure 1, in the embodiment of the present invention, the specific implementation steps of the method are as follows:

Step 1, place the copper disc on the stage, align it with the electromagnetic wave transmitter, use the test equipment to automatically read the reflected energy of the copper disc, and adjust the equipment parameters with the acquired reflected energy;

Step 2, place the graphene transferred onto the substrate on the stage, and select the built-in response test substrate;

Step 3, apply an anti-phase signal to the balance bridge circuit, and manually adjust the detector to minimize the detected Hall value;

Step 4, under zero magnetic field, measure graphene surface resistance and carrier concentration by reflecting electromagnetic waves, and the measured values will be used for mobility measurement;

Step five, keep the magnetic induction at 5000-10000G, measure the Hall energy radiated by the graphene Hall excitation current, and calculate the graphene mobility from it;

Step six, move the substrate, and measure the mobility of graphene at other positions.

In the embodiment of the present invention, in step 1, the resistance value of the copper disc measured by reflected energy is not greater than 10 ohms.

In the embodiment of the present invention, in the second step, the used substrate must not be smaller than 2 inches.

In the embodiment of the present invention, in step 6, by comparing the mobility of graphene at different positions, it can be obtained whether the graphene has a good consistency.

The application principle of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The purpose of the present invention is to overcome the shortcomings of contact measurement, and provide a non-contact mobility measurement method based on electromagnetic wave excitation, which can eliminate probes and conveniently measure graphene mobility. In addition, its advantage of multi-point measurement can be used to characterize the uniformity of graphene.

The technical key to realize the purpose of the present invention is: adopt the mode of incident electromagnetic wave excitation, introduce induction current and Hall current in graphene, measure the electromagnetic wave that Hall current radiates, and compare with incident electromagnetic wave, obtain the migration of graphene Rate. Change the projected position of the excited electromagnetic wave to perform multi-point measurement. Its implementation steps include the following:

(1) Place the copper disc on the stage and align it with the electromagnetic wave transmitter. The test equipment automatically reads the reflected energy of the copper disc, so as to adjust the equipment parameters and compensate for the energy fluctuations that may occur during the test. The resistance value of the copper disc measured by reflected energy is not greater than 10ohms;

(2) Place the graphene transferred onto the substrate on the stage, and select the corresponding test substrate built into the software, and the substrate used must not be smaller than 2 inches;

(3) The system applies an anti-phase signal to the balance bridge circuit, and manually adjusts the detector to minimize the detected Hall value and cancel the noise as much as possible;

(4) Under zero magnetic field, the surface resistance and carrier concentration of graphene are measured by reflecting electromagnetic waves, and the measured values will be used for the measurement of mobility;

(5) Keep the magnetic induction at 5000-10000G, measure the Hall energy radiated by the graphene Hall excitation current, and calculate the graphene mobility from this;

(6) Move the substrate, measure the mobility of graphene at other positions, and compare different positions to find out whether the material is uniform.

Using the above method to measure the mobility of graphene is characterized in that the measurement of the mobility does not need to be contacted with a metal probe, which is convenient for measuring the mobility of different positions of the material.

The present invention has the following advantages:

1. Due to the use of non-contact electromagnetic waves to measure the mobility of graphene, the fabrication of probes is omitted and material damage is avoided.

2. Due to the use of non-contact electromagnetic waves to measure the mobility of graphene, it is convenient to measure the mobility of different positions and characterize the uniformity of graphene preparation.

With reference to Fig. 1, the present invention provides following embodiment:

Example 1:

The realization steps of the present invention are as follows:

Step 1, use the copper disc to adjust the equipment parameters.

Place the copper disc on the stage and align it with the electromagnetic wave transmitter. The test equipment automatically reads the reflected energy of the copper disc. The resistance value of the copper disc measured by the reflected energy is not greater than 10ohms.

Step 2, adjust the reflection Hall value.

Transfer the graphene to a 4-inch Si substrate, place it on the stage, align the electromagnetic wave emitter, and adjust the reflection Hall value to the minimum.

Step 3, measuring graphene surface resistance and carrier concentration.

Under zero magnetic field, graphene surface resistance and carrier concentration were measured by reflecting electromagnetic waves.

Step 4, measuring graphene mobility.

Keep the magnetic induction at 5000G, measure the Hall energy radiated by the graphene Hall excitation current, and the system automatically calculates the graphene mobility.

Step 5, move the substrate, and measure the mobility at other positions.

Example 2:

The realization steps of the present invention are as follows:

Step A, using the copper disc to adjust the device parameters.

Place the copper disc on the stage and align it with the electromagnetic wave transmitter. The test equipment automatically reads the reflected energy of the copper disc. The resistance value of the copper disc measured by the reflected energy is not greater than 10ohms.

Step B, adjusting the reflective Hall value.

Transfer the graphene to a 3-inch SiO ₂ substrate, place it on the stage, align the electromagnetic wave emitter, and adjust the reflection Hall value to the minimum.

Step C, measuring graphene surface resistance and carrier concentration.

Under zero magnetic field, graphene surface resistance and carrier concentration were measured by reflecting electromagnetic waves.

Step D, measuring graphene mobility.

Keep the magnetic induction at 7000G, measure the Hall energy radiated by the graphene Hall excitation current, and the system automatically calculates the graphene mobility.

Step E, moving the substrate, and measuring mobility at other positions.

Example 3:

The realization steps of the present invention are as follows:

Step 1, use the copper disc to adjust the equipment parameters.

Place the copper disc on the stage and align it with the electromagnetic wave transmitter. The test equipment automatically reads the reflected energy of the copper disc. The resistance value of the copper disc measured by the reflected energy is not greater than 10ohms.

Step 2, adjust the reflection Hall value.

Transfer the graphene to a 2-inch GaN substrate, place it on the stage, align the electromagnetic wave emitter, and adjust the reflection Hall value to the minimum.

Step 3, measuring graphene surface resistance and carrier concentration.

Under zero magnetic field, graphene surface resistance and carrier concentration were measured by reflecting electromagnetic waves.

Step 4, measuring graphene mobility.

Keep the magnetic induction at 10000G, measure the Hall energy radiated by the graphene Hall excitation current, and the system automatically calculates the graphene mobility.

Step 5, move the substrate, and measure the mobility at other positions.

The invention discloses a non-contact Hall effect-based graphene carrier mobility measurement method, which mainly solves the problem of non-contact measurement of graphene mobility. The measurement steps are: (1) Place the Cu disc on the stage and align it with the electromagnetic wave transmitter. The test equipment automatically reads the reflected energy of the copper sheet, so as to adjust the equipment parameters and compensate for the energy that may occur during the test. fluctuation. The resistance value of the Cu disc measured by the reflected energy is not greater than 10ohms; (2) Place the graphene transferred to the substrate on the stage, select the corresponding test substrate built into the software, and the used substrate must not be less than 2 Inch; (3) The system applies an anti-phase signal to the balance bridge circuit, and manually adjusts the detector to minimize the detected Hall value and offset the noise as much as possible; (4) Measure the graphene surface by reflecting electromagnetic waves under 0 magnetic field Resistance and carrier concentration, the measured value will be used to measure the mobility; (5) Keep the magnetic induction at 100-1000G, measure the Hall energy of the graphene Hall excitation current radiation, and calculate the graphene mobility from this; (6 ) to move the substrate, measure the graphene mobility at other positions, and compare different positions to find out whether the material is uniform. The invention saves the time for measuring the mobility of graphene and avoids the influence of making metal probes on the properties of graphene.

The method for measuring the carrier mobility of graphene based on the non-contact Hall effect provided by the embodiment of the present invention adopts the method of incident electromagnetic wave excitation to introduce induced current and Hall current into graphene, and radiate out by measuring the Hall current. The electromagnetic wave, and compared with the incident electromagnetic wave, the mobility of graphene is obtained, and then the projected position of the excited electromagnetic wave is changed, and multi-point measurement is performed, and by comparing the mobility of graphene at different positions, it can be obtained whether the graphene has a good consistency. This method uses non-contact electromagnetic waves to measure the mobility of graphene, which saves the time for measuring the mobility of graphene, avoids the influence of the traditional method of making metal probes on the properties of graphene, and can determine whether large-scale preparation of graphene has good properties. Consistency, strong practicability, and strong promotion and application value.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (1)

1. the method for graphene carrier mobility is measured based on contactless Hall effect, it is characterized in that, the mode that the method adopts incident electromagnetic wave to excite, induction current and Hall current is introduced in Graphene, by measuring the electromagnetic wave that Hall current gives off, and compared with incident electromagnetic wave, draw the mobility of Graphene, change again and excite electromagnetic launching position, carry out multimetering;

The specific implementation step of the method is as follows:

Step one, is placed on copper coin sheet on objective table, aims at electromagnetic wave transmitter, utilizes testing apparatus automatically to read the reflected energy of copper sheet, and the reflected energy adjustment device parameter obtained;

Step 2, is placed on the Graphene transferred on substrate on objective table, selects built-in response test substrate;

Step 3, apply inversion signal to balanced bridge circuit, manual adjustments detector, makes the Hall value detected reach minimum;

Step 4, under zero magnetic field, by reflected electromagnetic wave measurement Graphene surface resistance and carrier concentration, measured value will be used for the measurement of mobility;

Step 5, keeps magnetic induction density at 5000-10000G, measures the Hall energy of Graphene Hall excitation current radiation, and calculates Graphene mobility thus;

Step 6, moving substrate, measures other position Graphene mobilities;

In step one, the copper coin sheet resistance values measured by reflected energy is not more than 10ohms;

In step 2, use substrate must be not less than 2 inches;

In step 6, by comparing diverse location Graphene mobility, Graphene can be obtained whether there is good consistance.