A method for transferring FIB samples to substrates for transport measurements at mesoscopic scale

Abstract

The present invention discloses a method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic size, comprising the following steps: an etching step: polishing a single crystal sample to be etched to a smooth and flat surface, adhering the polished single crystal sample to the stage of a FIB double beam system through conductive carbon glue, and obtaining a target sample thin slice S in the order of depositing a protective layer, digging grooves up and down, rough cutting, cutting U-shaped grooves, fine trimming, and cutting amorphous; a sampling step: removing the single crystal sample on the stage of the FIB double beam system, adhering the sample to a three-axis sampling stage through carbon glue, and covering the surface of the single crystal sample with a layer of PDMS gel, then lowering a probe, squeezing the thin slice sample S to naturally break the connection at its side, and naturally adsorbing it on the PDMS gel; a transfer step of transferring the thin slice sample to a standard electrode substrate; and a deposition step. The present invention can quickly and accurately prepare excellent target samples for subsequent research.

Description

Technical Field

[0001] The present invention relates to the field of sample preparation and transport measurement of single crystal samples at mesoscopic size, and in particular to a method for transferring a FIB sample at mesoscopic size to a substrate for transport measurement. Background Art

[0002] The FIB sample (focused ion beam sample preparation) preparation methods are currently mainly concentrated on focused ion beam-robot transfer and Karp ring electrostatic adsorption method to achieve sample transfer. The former has more stringent requirements on samples and a low success rate, while the latter also has disadvantages such as high cost, low success rate, and damage to samples.

[0003] The shortcomings of the current existing technologies mainly focus on the limitations on the conditions of the samples themselves, the damage that may be caused to the samples during the preparation process, the high cost of preparing the samples, and the low success rate.

[0004] Therefore, it is necessary to take measures to overcome the drawbacks of existing technologies, including compatibility with sample conditions, degree of mechanical damage and low transfer success rate.

[0005] The present invention combines the application of focused ion beam in sample preparation at the mesoscopic scale and the low-dimensional material transfer method to propose a method suitable for transferring such mesoscopic samples to a target substrate. Compared with traditional manipulator sample transfer, it has greater sample compatibility and preparation success rate. Summary of the invention

[0006] The purpose of the present invention is to provide a method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic scale, so as to solve the problem of sample preparation and transport measurement of a single crystal at a mesoscopic scale.

[0007] To this end, the present invention provides a method for transferring FIB samples to substrates for transport measurement at a mesoscopic size, which is characterized in that it includes the following steps: an etching step: polishing the single crystal sample to be etched to a smooth and flat surface, adhering the polished single crystal sample to the stage of the FIB double-beam system through carbon glue, and obtaining the target sample slice S in the order of depositing a protective layer, digging grooves up and down, rough cutting, cutting U-shaped grooves, fine trimming, and cutting amorphous particles; a sampling step: removing the single crystal sample on the stage of the FIB double-beam system, adhering the sample to a three-axis sampling stage through carbon glue, and covering the surface of the single crystal sample with a layer of PDMS gel, and then probing downward. The needle squeezes the thin-sheet sample S so that the connection on its side breaks naturally and it is naturally adsorbed on the PDMS gel; transfer step: when the surface of the single crystal sample is captured by the sample thin sheet, peel off the PDMS gel, stick it to the glass slide, and fix the glass slide together with the metal clip to the clip placement position above the transfer table, transfer the thin-sheet sample S to the electrode substrate on the thin-sheet transfer device, and remove the metal clip after standing; deposition step: put the prepared electrode substrate into the FIB vacuum chamber, use a focused ion beam to deposit the set metal at the place where the thin-sheet sample contacts the electrode, and then use the FIB to etch the thin-sheet sample into the required pattern for testing.

[0008] This method has strong compatibility with geometric factors such as size and thickness of the target sample and substrate, and can minimize mechanical damage during sample transfer and preparation.

[0009] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0011] Figure 1 The target thin slice sample obtained by focused ion beam (FIB) etching refinement is shown;

[0012] Figure 2 A schematic diagram showing the upper and lower probe sampling on stage B is shown;

[0013] Figure 3 A schematic diagram showing the preliminary acquisition of a target sample S from a single crystal sample is shown;

[0014] Figure 4 A schematic diagram showing the adhesion of PDMS gel to a glass slide;

[0015] Figure 5A schematic diagram showing the three-dimensional structure of PDMS gel adhered to a glass slide;

[0016] Figure 6 A schematic structural diagram of a sample transfer device is shown;

[0017] Figure 7 A schematic diagram showing the peeling of the thin sheet sample S onto the electrode substrate;

[0018] Figure 8 A schematic diagram showing the electrode substrate being placed in a FIB vacuum chamber to deposit metal Pt;

[0019] Fig. 9 A schematic diagram showing the use of FIB to etch a thin-film sample into a standard Hall shape;

[0020] Fig.10 A picture of the final sample is shown. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0022] Combined with reference Figures 1 to 10 An embodiment of the present invention provides a method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic size. The method flow can be divided into the following steps: an etching step, a sampling step, a transfer step, and a deposition step.

[0023] Etching steps: The single crystal sample 1 to be etched is slightly polished to a smooth and flat surface without any special protrusions on the surface. The polished single crystal sample is adhered to the stage of the FIB dual-beam system through conductive carbon glue. The target sample slice 2 is obtained in the order of depositing a protective layer, digging grooves up and down, rough cutting, cutting U-shaped grooves, fine trimming, and cutting amorphous. The sample slice is recorded as S, as shown in Figure 1 The thin slice in the groove 4 shown is the target sample 2.

[0024] Preferably, the sample slice S is located in the groove of the single crystal sample in an upright posture, and the sample slice S is connected to the single crystal sample 1 only through the side connection 3 and is disconnected at other positions.

[0025] Sampling steps: remove the single crystal sample 1 on the stage of the FIB dual-beam system, adhere the sample to the three-axis sampling stage 5 with carbon glue, cover the surface of the single crystal sample with a layer of PDMS gel 6, and then adjust the direction of the three-axis sampling stage to focus the microscope 7 on the surface of the thin slice sample.

[0026] At this time, the lower probe 8, with a tip diameter of 1-2 microns, is adjusted through the three axes of the probe stage 9 to align the tip with the center of any groove above or below the thin sample S. By adjusting the height of the probe, the probe is pressed down to achieve the effect of PDMS squeezing the thin sample S. After lightly pressing to a certain extent, the connection next to the thin sample S will naturally break, such as Figure 2 shown.

[0027] Since PDMS is a viscous gel, it naturally adsorbs the thin slice sample during the pressing process, and finally the thin slice will naturally fall on the PDMS gel. Figure 3 As shown, the initial acquisition of the target sample S is completed and removed for use.

[0028] Transfer steps: After the single crystal sample surface is captured by the sample slice, peel off the PDMS gel, stick it to the glass slide Z, and fix the glass slide together with the metal clip to the clip placement position above the transfer table, such as Figure 4 and Figure 5 As shown, the PDMS gel 6 is adhered to a glass slide 11 , and a metal clip 12 is placed above the glass slide.

[0029] The sample transfer work is carried out on the transfer platform 13, such as Figure 6 As shown, the purpose is to transfer the thin-sheet sample to the substrate of the standard six electrodes. First, find the thin-sheet sample S on the PDMS gel through the microscope objective 14, calibrate the long-axis direction of the sample on the gel, and then focus the microscope on the substrate on the stage below to find the position of the standard six electrodes. Adjust the direction of the substrate electrode according to the long-axis direction of the sample calibrated before, keep the current direction of the substrate electrode consistent with the current direction of the sample to be tested, and then slowly drop the metal clamp 12 to make the thin-sheet sample S contact the electrode substrate. After standing for three minutes, lift the metal clamp, and the thin-sheet sample S will fall off on the electrode substrate. Its plane pattern is as shown in FIG. Figure 7 As shown, the transfer of the thin slice sample is completed.

[0030] Deposition step: Place the prepared electrode substrate into the FIB vacuum chamber and use a focused ion beam to deposit metal Pt at the contact point between the thin film sample and the electrode, such as Figure 8 Finally, the thin film sample is etched into a standard Hall shape by FIB for testing, such as Fig. 9 . Record the length, width and thickness of the sample at this time for subsequent data processing. The final sample is shown in the figure below. Fig.10 shown.

[0031] The purpose of the present invention is to propose a method for sample preparation and transport measurement of single crystals at the mesoscopic scale, that is, a new mesoscopic sample preparation method based on the application of focused ion beam sample preparation at the mesoscopic scale and the low-dimensional material transfer method. The present invention overcomes the unnecessary cost waste and time loss caused by sample preparation in the prior art in this research field, and greatly improves the efficiency of sample preparation in this research direction. To a large extent, excellent target samples can be prepared quickly and accurately for subsequent research.

[0032] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for transferring FIB samples to substrates for transport measurements at mesoscopic scale, It is characterized in that The following steps are involved: Etching step: polish the single crystal sample to be etched to a smooth and flat surface, adhere the polished single crystal sample to the stage of the FIB dual-beam system through carbon glue, and obtain the target sample slice S in the order of depositing a protective layer, digging grooves up and down, rough cutting, cutting U-shaped grooves, fine trimming, and cutting amorphous. Sampling steps: remove the single crystal sample on the stage of the FIB dual-beam system, adhere the sample to the three-axis sampling stage through carbon glue, and cover the surface of the single crystal sample with a layer of PDMS gel. Then, lower the probe and squeeze the thin slice sample S to naturally break the connection on its side and naturally adsorb it on the PDMS gel. Transfer step: After the single crystal sample surface is captured by the sample slice, the PDMS gel is peeled off and pasted onto a glass slide, and the glass slide together with the metal clip is fixed to the clip placement position above the transfer table, and the slice sample S is transferred to the electrode substrate on the slice transfer device, and the metal clip is removed after standing still; Deposition step: Place the prepared electrode substrate into the FIB vacuum chamber, use a focused ion beam to deposit the set metal where the thin film sample contacts the electrode, and then use the FIB to etch the thin film sample into the required pattern for testing. In the etching step, the sample slice S is located in the trench of the single crystal sample in an upright position, and the sample slice S is connected to the single crystal sample only through the connection at the side and is disconnected at other positions.

2. The method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic size according to claim 1, It is characterized in that In the sampling step, the direction of the three-axis stage is adjusted to focus the microscope on the surface of the thin sample. The diameter of the probe tip is selected to be on the scale of 1-2 microns. The position of the probe tip is adjusted by the three axes of the probe stage to align the tip with the center of any groove above or below the thin sample S. The height of the probe is adjusted to press down the thin sample S to naturally break the connection on its side, and the thin sample S is naturally adsorbed on the PDMS gel.

3. The method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic size according to claim 1, It is characterized in that In the transfer step, first find the thin film sample S on the PDMS gel through the microscope objective, calibrate the long axis direction of the sample on the gel, and then focus the microscope on the substrate on the stage below. According to the previously calibrated long axis direction of the sample, find the electrode position in the electrode substrate, then drop the metal clip to make the thin film sample S contact with the electrode substrate. After standing for a predetermined time, lift the metal clip.

4. The method for transferring a FIB sample to a substrate for transport measurement at a mesoscopic size according to claim 1, It is characterized in that During the deposition step, the parameters of the length, width, and thickness of the final sample are recorded for subsequent data processing.

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