A test extraction method for carrier injection barriers in dielectrics

Abstract

The application discloses a method for testing and extracting carrier injection barrier in dielectric, which is based on the relationship between the injection current density and the electric field intensity obtained by the injection charge quantity change rate and the electric field change, and the testing and extraction of the dielectric carrier injection barrier, and comprises the following steps: preparing a dielectric sample; performing electrode unipolar carrier injection test; calculating the conductive current of the carrier migration in the dielectric and the displacement current at the electrode and dielectric interface; calculating the carrier injection current density at the electrode and dielectric interface; correlating the current density and the electric field intensity at the electrode to obtain the carrier injection current density-electric field intensity relationship curve at the electrode interface in the dielectric; performing analysis and fitting to extract the carrier injection barrier. The testing and extraction method can truly reflect the electrical performance parameters of the dielectric under different electric field intensity working states, provides parameters for the charge transport simulation in the dielectric, and has significant scientific and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of dielectric testing, and specifically relates to a method for testing and extracting the carrier injection barrier in a dielectric. Background Technology

[0002] The charge injection barrier in a dielectric is an important electrical performance parameter that affects the amount of charge injected into the dielectric by the electrode, further influencing the electric field distribution and the dielectric's aging characteristics. Existing methods for obtaining the charge injection barrier in a dielectric mainly rely on simulation calculations based on band theory or fitting of conductivity current test results, which have certain limitations.

[0003] In existing technologies, first-principles simulations are used to calculate the injection barrier at the interface between different metal electrodes and dielectrics. However, this method cannot fully consider the influence of the surface states and interface characteristics of the electrode and dielectric on the injection barrier, leading to discrepancies between the simulation results and actual application scenarios. Methods that use dielectric conductivity current and space charge measurements to analyze and fit the injection barrier based on experimental results have the limitation of not effectively distinguishing between positive and negative charge carriers; that is, they cannot separately obtain the injection barriers for electrons and holes injected into the electrode.

[0004] Therefore, it is necessary to propose a method to effectively distinguish between positive and negative polarity charge carriers injected by electrodes, and to further test the injection barrier for extracting positive and negative polarity charge carriers from the dielectric. Summary of the Invention

[0005] The purpose of this invention is to provide a method for testing and extracting the carrier injection barrier in a dielectric. Based on the space charge test results obtained by the electroacoustic pulse method and the structural design of the dielectric sample, the injection barrier of positive and negative polarity charge carriers can be effectively distinguished by changing the polarity of the applied voltage and the positional substitution of the bilayer dielectric.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A method for testing and extracting the carrier injection barrier in a dielectric includes the following steps:

[0008] Step 1: Prepare the medium sample;

[0009] Step 2: Perform electrode unipolar carrier injection test on the sample to obtain space charge test results, and calculate the conduction current of carrier migration in the dielectric and the displacement current at the electrode-dielectric interface based on the test results.

[0010] Step 3: Calculate the carrier injection current density at the electrode-dielectric interface;

[0011] Step 4: Correlate the current density and the electric field strength at the electrode to obtain the relationship curve between the carrier injection current density in the dielectric and the electric field strength at the electrode interface.

[0012] Step 5: Change the polarity of the voltage applied in the space charge test in step 2, repeat steps 3 and 4, and calculate the relationship curve between the injection current density of the other polarity carrier in the dielectric and the electric field strength at the electrode interface.

[0013] Step 6: Analyze and fit the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface to extract the carrier injection barrier.

[0014] In step 1 above, the dielectric sample includes a test dielectric and a barrier layer stacked on top of each other, with an upper electrode and a lower electrode connected to its two sides respectively.

[0015] In step 2 above, the method for electrode unipolar carrier injection testing is to perform space charge testing on the sample at a constant temperature using the electroacoustic pulse method to obtain the space charge test results.

[0016] In step 2 above, the method for calculating the conductivity current of carrier migration in the dielectric is as follows: based on the space charge test results, first calculate the curve Q(t) of the charge carrier accumulation in the dielectric over time, and then calculate the curve dQ(t) / dt of the charge accumulation rate over time to obtain the conductivity current J of carrier migration in the dielectric. c (t)=dQ(t) / dt.

[0017] In step 2 above, the displacement current at the electrode-dielectric interface is calculated based on the space charge test results. First, the curve E of the electric field intensity at the electrode-dielectric interface changing with time is obtained by calculating using the Poisson equation. ele (t), and then calculate the displacement current ε*dE at the electrode-dielectric interface. ele (t) / dt.

[0018] The specific process of step 3 above is as follows:

[0019] tt is calculated according to the following formula. transit Carrier injection current density in the dielectric at any given time:

[0020] J inj (tt transit ) = J c (t)+ε*dE ele (tt transit ) / dt

[0021] Where t transit It is the time t required for charge carriers injected from the electrode to migrate to the interface between the dielectric and the barrier layer. transitThe value of is: L / μE=L*Q(t1) / (dQ(t1) / dt), where L is the dielectric thickness, and t1 is determined based on the dQ(t) / dt curve and E. ele (t) The initial time of curve selection.

[0022] The specific content of step 4 above is to select different initial times to obtain a series of carrier injection current density values ​​in the dielectric at different times, thereby constructing a carrier injection current density-time curve in the dielectric, i.e., J inj (t); using time t n Injecting charge carriers into the dielectric at a current density J inj (t n Electric field strength E at the electrode interface ele (t n By correlating the data, the relationship curve between the carrier injection current density in the dielectric and the electric field strength at the electrode interface was obtained.

[0023] In step 1 above, by replacing the positions of the dielectric material under test and the barrier layer material, an injection barrier is obtained for the other electrode to inject charge carriers into the dielectric.

[0024] This invention provides a method for testing and extracting the carrier injection barrier in a dielectric. Through sample structure design and space charge testing, it avoids the problem of bipolar carrier injection. Based on the obtained curve showing the relationship between the carrier injection current density and the electric field strength at the electrode interface, the carrier injection barrier is further extracted through fitting, achieving the goal of accurately reflecting the electrical performance parameters of the dielectric under different electric field strengths. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention;

[0026] Figure 2 This is a schematic diagram of the sample structure of the present invention;

[0027] Figure 3 This is a schematic diagram of the experimental principle of electrode unipolar charge injection in this invention;

[0028] Figure 4 This is a schematic diagram of the space charge measurement system using the electroacoustic pulse method in this invention;

[0029] Figure 5 This is a schematic diagram of the electrode injection current density calculation considering the migration delay of injected charge carriers in this invention. Detailed Implementation

[0030] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] like Figure 1As shown, the present invention provides a method for testing and extracting the carrier injection barrier in a dielectric, comprising the following steps:

[0032] Step 1: Prepare a dielectric sample, which includes a dielectric material to be tested and a barrier layer stacked on top of each other, with its two sides used to connect the upper electrode and the lower electrode, respectively. Figure 2 Taking the contact between the upper electrode and the dielectric being measured as an example, the injection barrier for the upper electrode to inject charge carriers into the dielectric is measured.

[0033] Step 2: Perform electrode unipolar carrier injection test. The test principle is as follows: Figure 3 As shown, Figure 3 Taking the application of a negative polarity voltage and the injection of negative polarity charge carriers as an example, the barrier layer is made of polytetrafluoroethylene. The double-layer sample composed of the barrier layer and the dielectric is placed between the upper and lower electrodes. A DC voltage is applied between the upper and lower electrodes. Under the action of the electric field, the upper electrode injects charge carriers into the dielectric. Under the action of the electric field, the charge carriers in the dielectric migrate and generate electrical current. At the same time, they accumulate in the dielectric and at the interface with the barrier layer. The sample is placed between the upper and lower electrodes. After applying a DC electric field at a constant temperature, the space charge of the sample is tested by the electroacoustic pulse method space charge test system to obtain the space charge test results.

[0034] Based on the space charge test results, the change curve Q(t) of charge carrier accumulation in the dielectric with time is calculated. Further, the change curve dQ(t) / dt of the charge accumulation rate with time is calculated. The conductivity current for carrier migration in the dielectric is J. c (t)=dQ(t) / dt; The curve E of the electric field intensity at the electrode-dielectric interface as a function of time is obtained by calculating using the Poisson equation. ele (t), and further calculations are performed to obtain the displacement current ε*dE at the electrode-dielectric interface. ele (t) / dt;

[0035] Step 3: Calculate tt based on the conduction current and displacement current obtained in Step 2. transit At the moment of electrode-dielectric interface, the carrier injection current density, J inj (tt transit ) = J c (t)+ε*dE ele (tt transit ) / dt;

[0036] Step 4: Since the charge carrier injection current density is closely related to the electric field strength at the electrode, the charge carrier injection current density J is measured at test time t. inj With the electric field strength E at the electrode ele Correlation is used to obtain the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface, such as... Figure 5 As shown;

[0037] Step 5: Change the polarity of the voltage applied in the space charge test in step 2, repeat steps 3 and 4, and calculate the relationship curve between the injection current density of the other polarity carrier in the dielectric and the electric field strength at the electrode interface.

[0038] Step 6: Analyze and fit the relationship curve between carrier injection current density in the dielectric and electric field strength at the electrode interface, and extract the carrier injection barrier. The fitting method includes, but is not limited to, Ohm, Schottky injection, and Fowler-Nordheim injection formula fitting. Analyze the numerical relationship between carrier injection current density in the dielectric and electric field strength at the electrode interface, select the injection formula with the smallest fitting error, and extract the carrier injection barrier.

[0039] In step 1, by replacing the positions of the dielectric material under test and the barrier layer material, the injection barrier for the lower electrode to inject charge carriers into the dielectric can be obtained. For solid dielectrics, the solid dielectric and the barrier layer material are hot-pressed to eliminate the air gap between the two layers, thus eliminating the influence of the air gap on the test results. For liquid dielectrics, in order to reduce the influence of liquid flow on the stability of the sample, the liquid dielectric is brought into contact with the lower electrode, and a barrier layer is placed on top of the liquid dielectric to realize the test extraction of the injection barrier for the lower electrode to inject charge carriers into the liquid dielectric. By changing the polarity of the applied voltage, the injection barriers for the lower electrode material to inject negative and positive charge carriers into the liquid dielectric can be obtained.

[0040] In step 2, the testing system is as follows: Figure 4 As shown, it includes an electrode system, a high-voltage DC power supply 1, a high-voltage DC power supply 2, a nanosecond pulse source, an oil bath circulation system, an oscilloscope, and a computer, wherein:

[0041] The electrode system includes a current-limiting resistor R1, a coupling capacitor C, a matching resistor R2, an upper electrode, a lower electrode, a piezoelectric sensor, an absorption layer, and an amplifier;

[0042] The high-voltage DC power supply 1 is used to provide a DC electric field. The high-voltage DC power supply 1 is connected to the upper electrode through a current-limiting resistor R1 to prevent damage to the equipment from a large current when the insulating material sample breaks down.

[0043] The high voltage DC power supply 2 is used to provide voltage to the nanosecond pulse source. The nanosecond pulse source is connected to the upper electrode through the coupling capacitor C to block the DC high voltage of the high voltage DC power supply 1 from entering the nanosecond pulse source circuit. A matching resistor R2 is connected between the coupling capacitor C and the electrode shell.

[0044] The oil bath circulation system includes a high-temperature circulating oil bath and a low-temperature circulating oil bath, used for temperature control during testing;

[0045] The piezoelectric sensor, absorption layer, and amplifier are placed sequentially below the lower electrode to achieve the conversion and amplification of acoustic signals;

[0046] The oscilloscope and computer are used for signal acquisition and processing, and the amplifier, oscilloscope and computer are connected in sequence.

[0047] The carrier injection current density-electrode interface electric field intensity relationship curve in the dielectric is obtained through the following steps: First, based on the dQ(t) / dt curve and E... ele (t) curve, choose the initial time t1 for calculation, since it takes time t for the injected charge carriers to migrate to the interface between the dielectric and the barrier layer. transit Therefore, the conductivity current J of the carrier migration injected into the electrode at time t1 is... c (t1) = dQ(t2) / dt is obtained at time t2, where t2 = t1 + t transit , t transit ≈L / μE=L*Q(t1) / (dQ(t1) / dt), where L is the dielectric thickness. Therefore, the electrode injection current density at time t1 is J. inj (t1)=dQ(t2) / dt+ε*dE ele (t1) / dt.

[0048] Furthermore, at time t2, the injected carriers at the electrode undergo t... transit ≈L*Q(t2) / (dQ(t2) / dt) migrates to the interface between the dielectric and the barrier layer, and its electrical conduction current J c (t2) = dQ(t3) / dt is obtained at time t3, therefore, the electrode injection current density at time t2 is J. inj (t2)=dQ(t3) / dt+ε*dE ele (t2) / dt.

[0049] And so on, t n-1 At time J, the electrode injection current density is inj (t n-1 )=dQ(t n ) / dt+ε*dE ele (t n-1 ) / dt. Where t n =t n-1 +t transit ≈t n-1 +L*Q(t n-1 ) / (dQ(t n-1 ) / dt).

[0050] By selecting different initial times t1, a series of electrode injection current density values ​​at different times can be obtained, which ultimately constitute the carrier injection current density-time curve in the dielectric, i.e., J inj(t).

[0051] Furthermore, using time t n Injecting charge carriers into the dielectric at a current density J inj (t n Electric field strength E at the electrode interface ele (t n Correlation is used to obtain the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface, such as... Figure 5 As shown.

[0052] Figure 5 The diagram shows a schematic of the electrode injection current density calculation considering the migration delay of injected charge carriers. The electric current dQ(t) / dt and the electric field strength E at the electrode-dielectric interface are also considered. ele (t) Select time t1 on the curve, and use the formula t n =t n-1 +t transit ≈t n-1 +L*Q(t n-1 ) / (dQ(t n-1 Calculate the other times t2, t3, t4, and t5 using ) / dt. Then, calculate the electric field intensity E at the electrode-dielectric interface corresponding to each time point. ele (t n The value is used as the x-axis, and the formula J is used. inj (t n-1 )=dQ(t n ) / dt+ε*dE ele (t n-1 The carrier injection current density at each time point is obtained by calculating t / dt, and used as the ordinate. The corresponding discrete points are plotted in the above coordinate system. By changing the initial time t1, a series of different discrete points can be obtained, and the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface can be obtained.

[0053] Finally, the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface was analyzed and fitted to extract the carrier injection barrier.

[0054] In summary, this invention provides a method for testing and extracting the carrier injection barrier in a dielectric. This method, based on the rate of change of injected charge and the change of electric field, obtains the relationship between the injected current density and the electric field strength, and then tests and extracts the carrier injection barrier. The method includes the following steps: preparing a dielectric sample; performing unipolar carrier injection tests at the electrodes; calculating the conductivity current for carrier migration in the dielectric and the displacement current at the electrode-dielectric interface; calculating the carrier injection current density at the electrode-dielectric interface; correlating the current density with the electric field strength at the electrode to obtain a curve showing the relationship between the carrier injection current density in the dielectric and the electric field strength at the electrode interface; and performing analysis and fitting to extract the carrier injection barrier. This testing and extraction method provides electrical performance parameters that accurately reflect the dielectric under different electric field strengths, providing parameters for charge transport simulation in dielectrics, and offering a theoretical basis for dielectric structure design and modification, thus possessing significant scientific and economic benefits.

[0055] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for testing and extracting the carrier injection barrier in a dielectric, characterized in that... Includes the following steps: Step 1: Prepare the medium sample; Step 2: Perform electrode unipolar carrier injection test on the sample to obtain space charge test results, and calculate the conduction current of carrier migration in the dielectric and the displacement current at the electrode-dielectric interface based on the test results. Step 3: Calculate the carrier injection current density at the electrode-dielectric interface; Step 4: Correlate the current density and the electric field strength at the electrode to obtain the relationship curve between the carrier injection current density in the dielectric and the electric field strength at the electrode interface. Step 5: Change the polarity of the voltage applied in the space charge test in step 2, repeat steps 3 and 4, and calculate the relationship curve between the injection current density of the other polarity carrier in the dielectric and the electric field strength at the electrode interface. Step 6: Analyze and fit the relationship curve between carrier injection current density in the dielectric and electric field intensity at the electrode interface, and extract the carrier injection barrier. In step 1, the double-layer dielectric sample includes a test dielectric and a barrier layer stacked on top of each other, with an upper electrode and a lower electrode connected to its two sides, respectively. The specific content of step 4 is to select different initial times to obtain a series of carrier injection current density values ​​in the dielectric at different times, thereby constructing a carrier injection current density-time curve in the dielectric, i.e., J inj (t); using time t n Injecting charge carriers into the dielectric at a current density J inj (t n Electric field strength E at the electrode interface ele (t n By correlating the data, the relationship curve between the carrier injection current density in the dielectric and the electric field strength at the electrode interface was obtained.

2. The method as described in claim 1, characterized in that: In step 2, the method for electrode unipolar carrier injection testing is to perform space charge testing on the sample at a constant temperature using the electroacoustic pulse method to obtain the space charge test results.

3. The method as described in claim 1, characterized in that: In step 2, the method for calculating the conductivity current of carrier migration in the dielectric is as follows: based on the space charge test results, first calculate the curve Q(t) of the charge carrier accumulation in the dielectric over time, and then calculate the curve dQ(t) / dt of the charge accumulation rate over time to obtain the conductivity current J of carrier migration in the dielectric. c (t) = dQ(t) / dt.

4. The method as described in claim 1, characterized in that: In step 2, the displacement current at the electrode-dielectric interface is calculated based on the space charge test results. First, the curve E of the electric field intensity at the electrode-dielectric interface over time is calculated using the Poisson equation. ele (t), and then calculate the displacement current ε*dE at the electrode-dielectric interface. ele (t) / dt.

5. The method as described in claim 1, characterized in that: The specific process of step 3 is as follows: tt is calculated according to the following formula. transit Carrier injection current density in the dielectric at any given time: J inj (t-t transit )= J c (t)+ ε*dE ele (t-t transit ) / dt Among them, t transit It is the time t required for charge carriers injected from the electrode to migrate to the interface between the dielectric and the barrier layer. transit The value of is: L / μE=L*Q(t1) / (dQ(t1) / dt), where L is the dielectric thickness, and t1 is determined based on the dQ(t) / dt curve and E. ele (t) The initial time of curve selection.

6. The method as described in claim 1, characterized in that: In step 1, by replacing the positions of the dielectric material under test and the barrier layer material, an injection barrier is obtained for another electrode to inject charge carriers into the dielectric.

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