Method and apparatus for transferring one or more layers of material from initial substrate to target substrate

Abstract

The invention relates to a method and an apparatus for transferring a layer of material from an initial substrate to a target substrate. The apparatus includes a container for containing an electrolyte solution, a substrate holding member arranged inside the container, a voltage source connectable to the material layer and / or the initial substrate, an actuator for moving the target substrate away from the initial substrate or moving the initial substrate away from the target substrate, and a controller for controlling the actuator. The method comprises the steps of:-moving an edge of the target substrate / initial substrate away from the initial substrate / target substrate so as to provide a separation space between the initial substrate and the material layer and having a separation front at a location where the initial substrate and the material layer begin to be separated from each other; and-when the initial substrate, the material layer and the target substrate are at least partially immersed in the electrolyte solution and an electrical potential is applied to the material layer and / or a surface of the initial substrate facing the material layer, the separation space is increased and the separation front is moved along the initial substrate wherein the electrolyte diffuses between the initial substrate and the material layer, the actuator is controlled such that the progress of the separation front is equal to or less than the diffusion velocity of the electrolyte.

Description

Background Art

[0001] The present invention relates to a method and apparatus for transferring one or more material layers from an initial substrate to a target substrate, in particular, wherein the one or more material layers comprise one or more monolayers of atoms, such as monolayer graphene or multilayer graphene.

[0002] Such a method and apparatus is described, for example, in EP 2 928 700 B1. This patent publication describes a method for transferring graphene from a metal substrate on which the graphene is formed to a second substrate. First, the second substrate is attached to the graphene. Then, the metal substrate on which the graphene is formed, the stack of graphene and the second substrate, is immersed in a solution. Subsequently, a mechanical pulling action is used to separate the graphene and the second substrate from the original metal substrate, using bubbles formed electrolytically at the interface between the graphene and the metal, thereby pushing the two layers apart. Summary of the Invention

[0003] A disadvantage of the known methods and devices is that the mechanical pulling action and / or the electrolytic formation of gas bubbles may damage one or more graphene layers.

[0004] The present invention aims to provide a modified and / or alternative method and apparatus for transferring one or more material layers (such as graphene) from an initial substrate to a target substrate. In particular, the method at least significantly reduces (and preferably avoids) damage or loss of a portion of the one or more material layers that occurs during the transfer.

[0005] According to a first aspect, the present invention relates to a method for transferring one or more material layers from an initial substrate to a target substrate, wherein the method comprises the following steps:

[0006] - providing an initial substrate and one or more material layers, wherein the initial substrate contacts and supports the one or more material layers, thereby defining a first interface between the initial substrate and the one or more material layers;

[0007] - providing a target substrate and adhering the target substrate to a surface of the one or more material layers opposite to the first interface;

[0008] - at least partially immersing the initial substrate, the one or more material layers and the target substrate in an electrolyte solution;

[0009] - applying an electric potential to the surface of the initial substrate facing the first interface and / or to one or more material layers; and

[0010] - before or during the step of applying the electrical potential, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate so as to provide a separation space between the initial substrate and the one or more material layers, wherein a separation front is provided at a location where the initial substrate and the one or more material layers begin to separate from each other; and

[0011] - increasing the separation space and moving the separation front along the initial substrate by applying a separation force to the target substrate in a direction away from the initial substrate or applying a separation force to the initial substrate in a direction away from the target substrate using an actuator, wherein the electrolyte diffuses between the initial substrate and the one or more material layers at a diffusion speed, wherein the actuator is controlled so that the progress of the separation front is equal to or less than the diffusion speed of the electrolyte.

[0012] The method of the present invention allows for the controlled delamination of one or more material layers from an initial substrate by applying cation / anion-induced delamination and controlling the separation of the target substrate from the initial substrate. On the one hand, the step of controlling the actuator so that the advancement of the separation front is equal to or less than the diffusion rate of the electrolyte ensures that, in the method of the present invention, the diffusion of the electrolyte, or in other words, the diffusion of the cations and / or anions of the electrolyte and the resulting cation / anion-induced delamination, dominates when transferring the one or more material layers from the initial substrate to the target substrate. As a result, the amount of force required to separate the target substrate and the one or more material layers from the initial substrate is very low, which at least greatly reduces (and preferably avoids) damage or loss of a portion of the one or more material layers that occurs during the transfer.

[0013] As mentioned above, the actuator is controlled so that the progress of the separation front is equal to or less than the diffusion rate of the electrolyte. In this article, the diffusion rate can be measured indirectly, such as by observing the degree of separation of the interface between the initial substrate and one or more layers, without applying a pulling force to indirectly measure the diffusion rate. The method involves ensuring that the separation force applied by the actuator is applied in such a way that the separation front does not further extend into the interface between the initial substrate and one or more layers. Therefore, the diffusion rate of the electrolyte can be indirectly measured or determined by observing the degree of separation of the interface. For example, it can be measured / determined optically, such as by measuring / determining a camera positioned above a container containing the electrolyte and the substrate. The degree of separation and thus the indirect diffusion can be observed by the camera and expressed as a line or profile. The force applied to separate the target substrate and one or more layers from the initial substrate can then be controlled so that the separation front does not extend beyond the expected position of the line or profile indicating the degree of diffusion into the interface between the material layer and the initial substrate.

[0014] According to this method, if diffusion is observed to be not proceeding and / or partially slowing down or stopping at a certain point, the application of the separation force can be suspended to allow diffusion to continue. As diffusion and thus interfacial separation resume, the separation force can be reapplied. In some embodiments, this can be achieved through a feedback loop.

[0015] Observations of diffusion velocity (also called diffusion rate) and separation fronts and the relationship between them are described in further detail below in the Overview section and in the Detailed Description.

[0016] It should be noted that the actuator includes a controllable actuator that can be controlled by a controller (such as a computer or PLC) to perform the desired movement relative to the substrate holding member for holding the initial substrate or the target substrate. The actuator may include a mechanical device, such as a robot, which uses an electric motor, a pneumatic cylinder, or a hydraulic cylinder to provide the desired movement. Alternatively, the actuator may include: a float that floats on the surface of the electrolyte and is connectable to the target substrate; and a liquid level control system for controlling the liquid level of the electrolyte in the container. Such a liquid level control system may include: a controllable valve connected to a drain port for draining the container containing the electrolyte solution to at least partially immerse the initial substrate, one or more material layers, and the target substrate and to lower the liquid level in the container; and a pumping unit for pumping the electrolyte from a storage tank into the container to raise the liquid level in the container.

[0017] It should be noted that the method is preferably used to transfer one or more material layers from an initial substrate to a target substrate, wherein the initial substrate is more rigid than the target substrate, or vice versa. Therefore, the method preferably includes the step of moving an edge of the less rigid one of the initial substrate and the target substrate away from the less rigid one of the initial substrate and the target substrate.

[0018] In an embodiment, the potential applied to the surface of the initial substrate facing the first interface is set at a voltage such that cations and / or anions of the electrolyte are intercalated between the one or more material layers and the surface of the initial substrate facing the first interface, and such that the one or more material layers are separated from the initial substrate at the location where the cations and anions of the electrolyte are intercalated. An advantage of using only the potential is that all electrochemically driven reactions are blocked, including gas formation at the first interface.

[0019] In an embodiment, the counter electrode is at least partially immersed in the electrolyte, and wherein the step of applying the electric potential comprises the step of establishing an electric potential difference between the counter electrode and the surface of the initial substrate facing the first interface and / or between the counter electrode and the one or more material layers. Preferably, the electric potential difference is set such that there are substantially no bubbles at the first interface and / or at the one or more material layers. The absence of bubbles further reduces (and preferably avoids) damage or loss of a portion of the one or more material layers during transfer.

[0020] In an embodiment, the method further comprises the steps of detecting the diffusion range of the electrolyte between the one or more material layers and the initial substrate, and controlling the actuator to move the separation front so that the separation front does not exceed the detected diffusion range. In an embodiment, the diffusion range is detected by using an optical sensor, preferably a light detector or a camera, and wherein the actuator is controlled so that the progress of the separation front is such that the visible diffusion range is not exceeded by the separation front. For some materials (such as graphene), the diffusion range of the electrolyte between the one or more material layers and the initial substrate is visible by a change in color or contrast, which allows the diffusion range to be detected by using an optical sensor (such as a light detector or a camera) and controlling the actuator so that the progress of the separation front is such that the visible diffusion range is not exceeded by the separation front.

[0021] It should be noted that the optical sensor is particularly suitable for combination with a substantially optically transparent initial substrate and / or a substantially optically transparent target substrate.It should be noted that the optical transparency does not necessarily need to be in the visible wavelength range, but can also be in the near infrared or infrared wavelength range.

[0022] Additionally or alternatively, in embodiments, to establish and / or maintain an electrical potential or potential difference, the measured current flowing toward the initial substrate and / or toward one or more material layers is used as a measure of the diffusion extent of the electrolyte between the one or more material layers and the initial substrate and / or as a measure of the surface area of ​​the one or more material layers that have been separated from the initial substrate. It should be noted that the measured current also depends on the geometry of the initial substrate and must be considered in order to establish a measure of the diffusion extent. For example, in the case where the shape of the first interface is substantially circular, as the separation front moves along the initial substrate, the length of the separation front changes, which can result in a nonlinear relationship between the measured current and the diffusion extent.

[0023] In an embodiment, the actuator is connected to the target substrate and is configured to pull the edge of the target substrate away from the initial substrate, so as to move the edge of the target substrate away from the initial substrate and / or to increase the separation space and move the separation front along the initial substrate. Alternatively, in an embodiment, the actuator is connected to the initial substrate and is configured to pull the edge of the initial substrate away from the target substrate, so as to move the edge of the initial substrate away from the target substrate and / or to increase the separation space and move the separation front along the initial substrate. An advantage of this embodiment is that the actuator can be arranged above the target substrate, and in particular, at least partially above and outside the container for holding the electrolyte solution, and therefore outside the electrolyte solution.

[0024] In an embodiment, a force sensor is disposed between the actuator and the target substrate, wherein the method further comprises the steps of: measuring the separation force using the force sensor when the edge of the target substrate is pulled away from the initial substrate, and controlling the actuator to slow the pulling of the edge of the target substrate when the measured separation force exceeds a threshold value. Alternatively, in an embodiment, a force sensor is disposed between the actuator and the initial substrate, wherein the method further comprises the steps of: measuring the separation force using the force sensor when the edge of the initial substrate is pulled away from the target substrate, and controlling the actuator to slow the pulling of the edge of the initial substrate when the measured separation force exceeds a threshold value. When the separation force exceeds the threshold value, this indicates that the separation front has exceeded the diffusion range of the electrolyte or is approaching the diffusion range of the electrolyte. In an embodiment, the threshold value of the measured separation force (in Newtons (N)) is 0.1 times or less of the maximum length of the separation front (in meters (m)), preferably 0.05 times or less of the maximum length of the separation front, and more preferably 0.01 times or less of the maximum length of the separation front. For example, for a substantially circular initial substrate (such as a wafer) with a diameter of 100 mm, the maximum length of the separation front is 100 mm. Therefore, the threshold value is 0.1 times 100 mm (i.e., 10 millinewtons (mN) or less), preferably 0.05 times 100 mm (i.e., 5 mN or less), and more preferably 0.01 times 100 mm (i.e., 1 mN or less).

[0025] It should be noted that the measured separation force may depend on, among other things, the bending stiffness of the substrate being peeled. If the substrate being peeled has a considerable bending stiffness, an additional bending force is required to bend the peeled substrate away from the other substrate. Therefore, the force sensor will measure at least a combination of the separation force and the bending force, and preferably, the force measured by the force sensor is at least partially deducted from the portion of the force measured that is caused by the bending force to obtain a value for the measured separation force. Alternatively, a maximum bending force for the particular substrate being peeled is added to a threshold value for the measured separation force in order to obtain a threshold value for the combined separation force and bending force. This maximum bending force can be determined experimentally before using this particular substrate in the method and apparatus of the present invention.

[0026] Additionally or alternatively, when the diffusion of the electrolyte between one or more specific material layers and an initial substrate of a specific type is known or has been determined experimentally, an embodiment of the method further comprises the steps of setting and / or timing the control of the actuator based on the known diffusion so that the progression of the separation front is equal to or less than the known diffusion velocity of the electrolyte. For example, an optical sensor (preferably a photodetector or camera) can be used to determine the diffusion velocity of the electrolyte to detect the diffusion range and monitor its changes over time. A force sensor can also be used to establish a measure of the diffusion velocity of the electrolyte. This embodiment provides the possibility of controlling an apparatus or method for transferring one or more material layers from an initial substrate to a target substrate in a simple manner by moving the target substrate at a speed equal to or less than the known diffusion velocity of the electrolyte, without the need for complex detection and feedback procedures.

[0027] An alternative embodiment for performing the steps of moving an edge of the target substrate away from the initial substrate and / or increasing the separation space and moving the separation front along the initial substrate further comprises the step of inserting a wedge in a direction substantially parallel to the first interface to push the target substrate away from the initial substrate.

[0028] The methods and apparatus of the present invention are particularly suitable for (but not limited to) use of initial substrates comprising a substantially rigid substrate (preferably a flat substantially rigid substrate), and wherein the surface of the initial substrate facing the first interface is provided with a growth catalyst layer. In embodiments, the substantially rigid substrate comprises a silicon wafer or a sapphire plate, and / or wherein the growth catalyst layer comprises a metal layer, preferably wherein the metal layer comprises Cu and / or Ni. For example, the use of a substantially rigid and preferably highly flat rigid substrate is very advantageous for growing high-quality graphene layers or hexagonal boron nitride layers, because the rigid substrate provides a stable support for these very thin material layers (which may even include layers with a thickness of a single atom), at least during their growth.

[0029] In an embodiment, one or more material layers and / or metal layers are connected to a voltage source for applying an electric potential to the one or more material layers and / or metal layers, or for establishing an electric potential difference between a counter electrode and the one or more material layers and / or metal layers. Thus, the one or more material layers and / or metal layers are used to drive or assist cation / anion induced demixing in the electrolyte, and are combined with the movement of the target substrate as described above. In order to provide an electrical connection to the one or more material layers and / or metal layers, in an embodiment, the target substrate is provided with a cutout, or wherein the target substrate is smaller than the initial substrate, to provide an area for electrically connecting the metal layer and / or one or more material layers to the voltage source.

[0030] In an embodiment, the rigidity of the target substrate is less than that of the initial substrate, preferably, wherein the target substrate comprises a thermal release sheet, a thinned silicon wafer, a glass sheet (preferably borosilicate glass) and / or a plastic sheet (preferably a Plexiglas sheet, a polycarbonate sheet, a polyimide sheet) or the like. Preferably, the target substrate is also rigid so as to provide a suitable carrier for, for example, a high-quality graphene layer or hexagonal boron nitride layer, but the rigidity of the target substrate is lower than that of the initial substrate so as to allow the target substrate to bend so that the edge of the target substrate is moved away from the substantially inflexible initial substrate. On the one hand, when a harder target substrate is used, the bending radius of the target substrate is relatively large, thereby reducing the critical strain on one or more material layers. On the other hand, a larger bending radius makes the opening angle of the separation space smaller, which may hinder the diffusion of electrolytes to the separation front. Therefore, a smaller bending radius and a larger opening angle may be advantageous for the diffusion of electrolytes to the separation front.

[0031] In an embodiment, the method further comprises the step of positioning a cylindrical roller on top of the target substrate, wherein the cylindrical roller is disposed substantially above the separation front and / or separation space, and preferably, the cylindrical roller is configured to move with the moving separation front. The cylindrical roller allows for control and regulation of the movement of the target substrate such that the movement has a desired and constant speed, thereby allowing sufficient time for the cation / anion-induced delamination to complete its operation and preventing variations in the movement of the edge of the target substrate. Furthermore, the diameter of the cylindrical roller can also be used to define the bending radius of the target substrate, i.e., the bending radius is equal to or greater than the radius of the cylindrical roller.

[0032] The method and apparatus of the present invention are well suited for transferring one or more material layers from an initial substrate to a target substrate, wherein the one or more material layers preferably comprise atomically thick layers of material, such as graphene or hexagonal boron nitride (h-BN) layers.

[0033] According to a second aspect, the present invention relates to an apparatus for transferring one or more material layers from an initial substrate to a target substrate, wherein the apparatus comprises:

[0034] a container for containing an electrolyte solution and for at least partially immersing the initial substrate, the one or more material layers, and the target substrate in the electrolyte solution,

[0035] a substrate holding member arranged inside the container, wherein the substrate holding member is configured to hold an initial substrate,

[0036] a voltage source, which may be connected to one or more material layers and / or the initial substrate,

[0037] an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate, and

[0038] A controller is configured to control the actuator to:

[0039] - moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate so as to provide a separation space between the initial substrate and the one or more material layers, wherein a separation front is provided at a location where the initial substrate and the one or more material layers begin to separate from each other; and

[0040] - increasing the separation space and moving the separation front along the initial substrate, wherein the initial substrate, the one or more material layers, and the target substrate are at least partially immersed in an electrolyte solution, and an electric potential is applied to a surface of the initial substrate facing the one or more material layers and / or to the one or more material layers, wherein the electrolyte diffuses between the initial substrate and the one or more material layers, wherein the actuator is controlled so that the advancement of the separation front is equal to or less than the diffusion speed of the electrolyte.

[0041] In an embodiment, the actuator is connectable to the target substrate and configured to pull an edge of the target substrate away from the initial substrate, wherein the apparatus preferably comprises a force sensor connected to the actuator and connectable to the target substrate. In an alternative embodiment, the actuator is connectable to the initial substrate and configured to pull an edge of the initial substrate away from the target substrate, wherein the apparatus preferably comprises a force sensor connected to the actuator and connectable to the initial substrate.

[0042] In an embodiment, the container and / or substrate holding member is movable in a direction having a component parallel to a first interface between the initial substrate and the one or more material layers, preferably wherein the actuator is configured to pull the edge of the target substrate or the edge of the initial substrate in a direction having a component perpendicular to the first interface. This embodiment allows the speed of the container and / or substrate holding member in a direction parallel to the first interface to be controlled to be equal to the speed of the edge of the target substrate pulled in a direction perpendicular to the first interface, which allows the relative position of the separation front relative to the position of the actuator to be maintained at substantially the same point.

[0043] In an embodiment, the actuator comprises a wedge configured for insertion between the initial substrate and the target substrate, preferably in a direction substantially parallel to an interface between the initial substrate and the target substrate, for pushing the target substrate and the one or more material layers away from the initial substrate.

[0044] In an embodiment, the apparatus further comprises an optical sensor, preferably a light detector or a camera, configured to detect diffusion of electrolyte between the one or more material layers and the initial substrate, and wherein the optical sensor is connected to the controller for providing a measure of the diffusion of the electrolyte relative to the separation front.

[0045] In an embodiment, the apparatus further comprises a cylindrical roller arranged above the substrate holding member, wherein the cylindrical roller is configured to abut on top of the target substrate and move along a surface of the target substrate opposite to the initial substrate.

[0046] According to a third aspect, the present invention relates to an apparatus for transferring one or more material layers from an initial substrate to a target substrate, wherein the apparatus comprises:

[0047] a container for containing an electrolyte solution and for at least partially immersing the initial substrate, the one or more material layers, and the target substrate in the electrolyte solution,

[0048] a substrate holding member arranged inside the container, wherein the substrate holding member is configured to hold an initial substrate,

[0049] a voltage source, which may be connected to one or more material layers and / or the initial substrate,

[0050] an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate or to apply a separation force to the initial substrate in a direction away from the target substrate,

[0051] wherein the actuator is connectable to the target substrate or the initial substrate and is configured to pull an edge of the target substrate or the initial substrate away from the initial substrate or the target substrate, wherein the apparatus comprises a force sensor connected to the actuator and connectable to the target substrate or the initial substrate, and

[0052] A controller is configured to control the actuator using the signal from the force sensor.

[0053] According to a fourth aspect, the present invention relates to an apparatus for transferring one or more material layers from an initial substrate to a target substrate, wherein the apparatus comprises:

[0054] a container for containing an electrolyte solution and for at least partially immersing the initial substrate, the one or more material layers, and the target substrate in the electrolyte solution,

[0055] a substrate holding member arranged inside the container, wherein the substrate holding member is configured to hold an initial substrate,

[0056] a voltage source, which may be connected to one or more material layers and / or the initial substrate,

[0057] an actuator, wherein the actuator is configured to apply a separation force to the target substrate in a direction away from the initial substrate or to apply a separation force to the initial substrate in a direction away from the target substrate,

[0058] wherein the actuator is connectable to the target substrate or the initial substrate and is configured to pull an edge of the target substrate or the initial substrate away from the initial substrate or the target substrate, wherein the container and / or the substrate holding member is movable in a direction having a component parallel to a first interface between the initial substrate and the one or more material layers, and wherein the actuator is configured to pull the edge of the target substrate or the initial substrate in a direction having a component perpendicular to the first interface, and

[0059] A synchronization device or synchronization member is provided for synchronizing the movement of the container and / or substrate holding member in a direction parallel to the first interface with the movement of the actuator in a direction perpendicular to the first interface.

[0060] According to a fifth aspect, the present invention relates to an apparatus for transferring one or more material layers from an initial substrate to a target substrate, wherein the apparatus comprises:

[0061] a container for containing an electrolyte solution and for at least partially immersing the initial substrate, the one or more material layers, and the target substrate in the electrolyte solution,

[0062] a substrate holding member arranged inside the container, wherein the substrate holding member is configured to hold an initial substrate,

[0063] a voltage source, which may be connected to one or more material layers and / or the initial substrate,

[0064] an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate or to apply a separation force to the initial substrate in a direction away from the target substrate,

[0065] an optical sensor, preferably a light detector or a camera, configured to detect diffusion of electrolyte between the one or more material layers and the initial substrate, wherein the optical sensor is connected to a controller for providing a measure of the diffusion of the electrolyte relative to a separation front at which the initial substrate and the one or more material layers begin to separate from each other, wherein the controller is configured to control the actuator based on the measure of the diffusion of the electrolyte relative to the separation front.

[0066] The various aspects and features described and illustrated in the specification may, where possible, be applied independently. These individual aspects, in particular the aspects and features described in the accompanying dependent claims, may become the subject of divisional patent applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The invention will be explained with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0068] Figure 1 schematically shows a cross-sectional view of a first example of an apparatus according to the invention;

[0069] Figure 2 schematically shows a cross-sectional view of a second example of a portion of an apparatus according to the invention;

[0070] Figure 3 schematically shows a cross-sectional view of a third example of an apparatus according to the invention;

[0071] Figure 4 schematically shows a cross-sectional view of a fourth example of an apparatus according to the invention; and

[0072] Figure 5 The steps in the method according to the invention are schematically shown.

[0073] It should be noted that in the drawings, like features are indicated by like reference numerals. DETAILED DESCRIPTION

[0074] Hereinafter, examples of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same or equivalent elements or elements having the same or equivalent functions may be denoted by the same or equivalent reference numerals.

[0075] Figure 1 A cross-sectional view of a first example of an apparatus 1 according to the present invention is schematically shown. The apparatus 1 is configured for transferring one or more material layers 2 from an initial substrate to a target substrate 4.

[0076] One or more material layers 3, such as graphene or h-BN, are grown on the flat surface of an initial substrate 2. The present invention preferably uses sapphire disks as initial substrates 2 because they can have highly flat surfaces and are easily accessible. The surface of the initial substrate 2 on which the one or more material layers 3 are to be grown is provided with a growth catalyst layer 5, which is preferably a metal layer, more preferably a metal layer comprising copper (Cu) or nickel (Ni), or a combination of copper (Cu) and nickel (Ni). Other metals are also possible.

[0077] After one or more material layers 3 are disposed on top of the growth catalyst layer 5, a thin polymer layer 6 is disposed on top of the one or more material layers 3. The thin polymer layer 6 is preferably a spin-coated layer containing, for example, polymethyl methacrylate (PMMA), polycarbonate (PC), or polystyrene (PS), but many other polymers are possible. Preferably, a PMMA layer is used as the thin polymer layer 6 because it can be removed from the one or more material layers 3 relatively easily.

[0078] Subsequently, a target substrate 4 is placed on top of the thin polymer layer 6. Examples of such a stack include: sapphire / metal (preferably Cu and / or Ni) / one or more material layers (e.g., graphene or h-BN) / PMMA / target substrate. The target substrate 4 may comprise a thermal release tape as is known in the art, but preferably comprises a rigid substrate such as a thin plate of borosilicate glass or a thinned silicon wafer, wherein the target substrate 4 is less rigid than the initial substrate 2. In the apparatus 1 of the present invention, the less rigid target substrate 4 moves away from the more rigid initial substrate 2.

[0079] It should be noted that in some examples, an additional adhesive layer is arranged between the polymer layer 6 and the target substrate 4. Examples of such stacks include: sapphire / metal (preferably Cu and / or Ni) / one or more material layers (e.g. graphene or h-BN) / PMMA / adhesive / target substrate. An example of an additional adhesive can be a sapphire / metal layer from BrewerScience. HT-10.11 or HT-10.12, but other adhesives can also be used.

[0080] It should be further noted that, in an alternative method, a target substrate that is more rigid than the initial substrate can also be used. In this case, in the apparatus 1 of the present invention, the less rigid initial substrate 2 is moved away from the more rigid target substrate 4. The following examples involve a combination of a more rigid initial substrate and a less rigid target substrate. However, the apparatus and method can also be applied to transfer one or more material layers from a less rigid initial substrate to a more rigid target substrate.

[0081] like Figure 1 As further schematically shown in FIG. , the device according to this first example comprises:

[0082] a container 7 for containing an electrolyte solution 8 and for at least partially immersing the initial substrate 2, the one or more material layers 3, and the target substrate 4 in the electrolyte solution 8;

[0083] a substrate holding member 9 arranged inside the container 7 , wherein the substrate holding member 9 is configured to hold the more rigid one of the initial substrate 2 and the target substrate 4 , in this example, the initial substrate 2 ;

[0084] a voltage source 10 connected to a counter electrode 11 arranged inside the container 7;

[0085] an actuator 12 configured to apply a separation force toward the less rigid one of the initial substrate 2 and the target substrate 4 in a direction away from the more rigid one of the initial substrate 2 and the target substrate 4, in this example, applying a separation force toward the target substrate 4 in a direction away from the initial substrate 2; and

[0086] The controller 13 is used to control the device 1 , in particular the actuator 12 .

[0087] The actuator 12 is mounted on a frame 19 which is connected to the container 7 .

[0088] In use, the initial substrate 2, the one or more material layers 3, and the target substrate 4 are immersed in an electrolyte solution 8. The electrolyte solution 8 diffuses at least between the initial substrate 2 and the one or more material layers 3. A potential difference is established between the counter electrode 11 and the surface of the initial substrate 2 facing the one or more material layers 3, in particular between the counter electrode 11 and the growth catalyst layer 5, so as to provide electrochemical delamination of the one or more material layers 3 from the growth catalyst layer 5 of the initial substrate 2. The one or more material layers 3, in particular graphene, are delaminated using the electrolyte solution 8 in which cations and anions can be intercalated between the one or more material layers 3 and the growth catalyst layer 5.

[0089] In addition, the actuator 12 is connected to the target substrate 4 via a connecting member 16 and is controlled by the controller 13 to lift the edge of the target substrate 4 away from the initial substrate 2, thereby providing a separation space 17 between the initial substrate 2 and the one or more material layers 3. A separation front 18 is provided at the position where the initial substrate 2 and the one or more material layers 3 begin to move and separate. In particular, when the target substrate 4 includes a semi-rigid substrate (such as a borosilicate glass sheet or a thinned silicon wafer), the actuator 12 pulls the target substrate 4, causing it to bend slightly away from the initial substrate 2, thereby providing a larger diffusion path for the electrolyte solution 8 to diffuse into the separation space 17.

[0090] Thus, the present invention utilizes a combination of moving the edge of the target substrate 4 by means of an actuator and using electrochemical delamination in such a way that the electrochemical delamination is dominant and the movement of the target substrate 4 exerts less mechanical stress and / or force on the one or more material layers 3. In other words, the actuator 12 is controlled to increase the separation space 17 and move the separation front 18 along the initial substrate 2 such that the advancement of the separation front 18 is equal to or less than the diffusion rate of the electrolyte solution 8 between the initial substrate 2 and the one or more material layers 3.

[0091] There are several ways to ensure that diffusion and thus electrochemical stratification dominates:

[0092] The first option is to detect the diffusion range of the electrolyte solution 8 and / or the intercalation range of the cations and anions of the electrolyte solution 8 between the one or more material layers 3 and the initial substrate 2 by using an optical sensor 15, preferably a light detector or camera. For some materials (e.g., graphene), when using a transparent polymer layer 6 and a target substrate 4, the diffusion range of the electrolyte solution 8 and / or the intercalation range of the cations and anions of the electrolyte solution between the one or more material layers 3 and the initial substrate 2 is visible through a change in color or contrast. The optical sensor 15 is connected to a controller 13 for transmitting data collected by the optical sensor 15 to the controller 13. The controller 13 is connected to an actuator 12 for controlling the actuator 12 based on the data from the optical sensor 15 in a manner such that the advancement of the separation front 18 does not approach or exceed the visible detected diffusion range of the electrolyte solution 8 and / or the intercalation of the cations and anions of the electrolyte solution 8, which can ensure that when the one or more material layers 3 are transferred from the initial substrate 2 to the target substrate 4, diffusion and thus electrochemical delamination dominate.

[0093] It should be noted that the separation front 18 located at the position where the initial substrate 2 and one or more material layers 3 begin to separate from each other can also be detected by the optical sensor 15, which allows the use of the optical sensor 15 to detect the separation front 18 on the one hand and the diffusion range of the electrolyte solution 8 and / or the intercalation range of the cations and anions of the electrolyte solution 8 on the other hand.

[0094] A second option is to arrange a force sensor 14 between the actuator 12 and the target substrate 4. When diffusion and, thus, electrochemical delamination, dominate when transferring one or more material layers 3 from the initial substrate 2 to the target substrate 4, the force F required to move the target substrate 4 away from the initial substrate 2 is small. Therefore, the force sensor 14 can be used to measure the separation force F when pulling the edge of the target substrate 4 away from the initial substrate 2. The force sensor 14 is connected to the controller 13 for sending data collected by the force sensor 14 to the controller 13. The controller 13 is connected to the actuator 12 for controlling the actuator 12 based on the data from the force sensor 14 in such a way that when the measured separation force F exceeds a threshold value, the pulling of the edge of the target substrate 4 by the actuator 12 is slowed down. When the separation force F exceeds the threshold value, this indicates that the separation front 18 is approaching or has exceeded the diffusion range of the electrolyte solution 8 and / or the intercalation range of the cations and anions of the electrolyte solution 8. Experiments have shown that when transferring a graphene layer from a silicon wafer (initial substrate 2) and a copper layer (growth catalyst layer 5) to a thermal release tape (target substrate 4) using a thin PMMA polymer layer 6, the separation force F is below 10 mN when diffusion and, therefore, electrochemical delamination dominates. Therefore, a separation force F value of 10 millinewtons (mN) or less can be used as a threshold value.

[0095] A third solution is to set and / or time the control of the actuator 12 based on a known diffusion rate so that the progress of the separation front 18 is equal to or less than the known diffusion rate of the electrolyte solution 8 and / or the intercalation rate of the cations and anions of the electrolyte solution 8 between the one or more material layers 3 and the initial substrate 2. This solution is convenient when the diffusion rate of the electrolyte solution 8 and / or the intercalation rate of the cations and anions of the electrolyte solution 8 between the one or more material layers 3 and the initial substrate 2 is known or has been determined experimentally. For example, an optical sensor 15 (preferably a light detector or camera) can be used to determine the diffusion rate of the electrolyte to detect the diffusion range and monitor its changes over time. A force sensor 14 can also be used to establish a measure of the diffusion rate of the electrolyte.

[0096] It should be noted that when the apparatus and method are used to transfer one or more material layers from a less rigid initial substrate to a more rigid target substrate, the layered structure of the initial substrate 2 and the one or more material layers 3 and the target substrate 4 are then arranged in an inverted position on the substrate holding member 9. That is, the more rigid target substrate is attached to and held by the substrate holding member 9, and the connecting member 16 of the actuator 12 is connected to the edge of the initial substrate.

[0097] It should be further noted that the actuator 12 comprises a controllable actuator that can be controlled by a controller 13 (such as a computer or PLC) for performing the desired movement of the connecting member 16 relative to the substrate holding member 9. The actuator 12 can include a mechanical device, such as a robot, that uses an electric motor, a pneumatic cylinder, or a hydraulic cylinder to provide the desired movement.

[0098] As an alternative to using a connecting member 16 to connect the actuator 12 to the edge of the less rigid of the initial substrate 2 and the target substrate 4, a wedge 20 can be used to move the edge and / or increase the separation space between the initial substrate 1 and the target substrate 3 by inserting the wedge 20 in a direction substantially parallel to the surface of the growing catalyst layer 5 to push the target substrate 3 and the one or more material layers 2 away from the initial substrate 2, as shown in FIG. Figure 2 Schematically shown. The device comprising the wedge 20 may be provided with an actuator connected to the wedge 20, and the actuator is configured to push the wedge 20 with a force F' in a direction substantially parallel to the surface of the growth catalyst layer 5. Additionally or alternatively, the device comprising the wedge 20 may be provided with an actuator connected to the substrate holding member 9, and the device is configured to move the substrate holding member 9 back and forth in a direction V' substantially parallel to the surface of the growth catalyst layer 5, wherein the wedge 20 may at least be maintained in a fixed position in a direction parallel to the surface of the growth catalyst layer 5 during the lifting of the edge and / or the increase of the separation space.

[0099] It should be noted that Figure 2 The size of the wedge 20 in FIG is highly exaggerated to more clearly illustrate the effect of the wedge 20 inserted between the growth catalyst layer 5 and the one or more material layers 3. In practice, the angle of the wedge is preferably less than 45 degrees. Preferably, the wedge includes an end 21 having a radius of curvature, wherein the radius of curvature at the end of the wedge is preferably less than 0.5 times the thickness of the polymer layer and the adhesive layer (if present).

[0100] Figure 3 A cross-sectional view of a third example of an apparatus according to the invention is schematically shown. In this example, the actuator or actuator assembly comprises:

[0101] a float 30 that floats at the surface of the electrolyte solution 8 and is connectable to the target substrate 6; and

[0102] A liquid level control system is used to control the liquid level of the electrolyte solution 8 in the container 7, wherein the liquid level control system includes: a controllable valve 33, which is connected to the output port or discharge port of the container 7, for removing the electrolyte solution 8 from the container 7 and lowering the liquid level in the container 7; and a pumping unit 36, which is used to pump the electrolyte solution 8' from the storage tank 34 into the container 7 to raise the liquid level in the container 7.

[0103] In this example, a controllable valve 33 is arranged in an output pipe 32, which connects the output port or drain of the container 7 with a storage tank 34. The electrolyte solution 8' from the storage tank 34 can be pumped into the container 7 by means of a pumping unit 36 ​​arranged in input pipes 35, 37, which connect the input port of the container 7 with the storage tank 34. Both the controllable valve 33 and the pumping unit 36 ​​are connected to the controller 13 and can be controlled by the controller.

[0104] In addition, the float 30 may be provided with a force sensor 31, which is arranged between the float 30 and the target substrate 4. The force sensor 31 is connected to the controller 13 for transmitting data collected by the force sensor 31 to the controller 13. The controller 13 is connected to a controllable valve 33 and a pumping unit 36 ​​for controlling the liquid level of the electrolyte solution 8 in the container 7 based on the data from the force sensor 31, in such a way that when the measured separation force F exceeds a threshold value, the pull of the float 31 on the edge of the target substrate 4 is slowed down by reducing the increase in the electrolyte liquid level.

[0105] It should be noted that the device in the third example does not include a counter electrode. A voltage source 10 is connected to ground potential on one hand and to the growth catalyst layer 5 on the other hand, so as to apply a potential to the growth catalyst layer 5, thereby enabling cations / anions of the electrolyte to intercalate between the one or more material layers 3 and the growth catalyst layer 5, thereby causing cation / anion-induced delamination of the one or more material layers 3 and the growth catalyst layer 5.

[0106] It should be noted that Figure 3 The example of the device 1 of the present invention shown can also be compared with the above reference Figure 1 The counter electrodes discussed work together. It should be further noted that, as Figure 1 The examples of the apparatus of the present invention shown may also be found in the examples above with reference to Figure 3 The discussed case operates without the counter electrode 11 .

[0107] Furthermore, the apparatus may comprise a cylindrical roller 40 arranged above the substrate holding member 9 such that, in use, the cylindrical roller 40 is configured to abut against a side of the target substrate 4 opposite to the initial substrate 2. Figure 3 As schematically shown, the cylindrical roller 40 is arranged substantially above the separation front 18 and / or the wedge-shaped separation space 17. Preferably, the cylindrical roller 40 is configured to move together with the moving separation front 18. The cylindrical roller 40 allows the movement of the target substrate 4 away from the initial substrate 2 to be controlled and regulated so that the movement has a desired and constant speed, thereby allowing the electrochemical reaction sufficient time to complete its work and prevent the separation of the target substrate 4 from the initial substrate 2 from being altered, or vice versa. Additionally or alternatively, the cylindrical roller 40 is configured to control and regulate the curvature of the semi-rigid target substrate 4 when it is bent upward. For a flexible target substrate 4, the diameter of the cylindrical roller 40 can be used to define the bending radius of the target substrate 4, i.e., the bending radius is equal to or greater than the radius of the cylindrical roller 40.

[0108] It should be noted that if Figure 3 The example of the device 1 of the invention shown can also work without the cylindrical roller 40, and such a cylindrical roller 40 can also be used in applications such as Figure 1 In the example shown of the device 1 of the invention.

[0109] Figure 4 A cross-sectional view of a fourth example of an apparatus 1 according to the present invention is schematically shown. The apparatus 1 of this fourth example is substantially identical to the apparatus of the first example, except that the container 7 and substrate holding member 9 are movable in a direction V substantially parallel to the first interface between the initial substrate 2 and the one or more material layers 3. In this example, movement of the container 7 and substrate holding member 9 is provided by a conveyor having rollers 51, 52 rotatably connected to a conveyor frame 53. Furthermore, the actuator 12 and optical sensor 15 are not directly connected to the container 7, but rather to the conveyor frame 53, and are preferably arranged to be stationary relative to the conveyor frame 53 and not to move with the container 7. Thus, the apparatus 1 of this fourth example allows for compensation for horizontal deviations in the position where the connecting member 16 connects to the target substrate 4 due to upward bending of the target substrate 4. Any horizontal deviations can be compensated by moving the container 7 and substrate holding member 9 using the conveyors 51, 52.

[0110] Preferably, the apparatus 1 includes a synchronization device or synchronization member for synchronizing the movement of the container 7 and substrate holding member 9 in a direction parallel to the first interface with the movement of the actuator 12 in a direction perpendicular to the first interface. The synchronization device can be provided by a controller 13, which is then configured to control the speed of the container 7 and substrate holding member 9 in a direction parallel to the first interface V to be equal to the speed at which the edge of the target substrate 4 is pulled in a direction perpendicular to the first interface. Alternatively, the synchronization member can include a mechanical coupling located between the actuator 12 and the conveyors 51, 52 so that they move synchronously; when the actuator 12 moves the connecting member 16 upward, the same actuator 12 moves the conveyor to the right via the mechanical coupling (not shown). Preferably, the synchronization device is configured so that the relative position of the separation front 18 relative to the position of the actuator 12 remains substantially at the same point.

[0111] It should be noted that Figure 4 The examples of the apparatus of the present invention shown may also be found in the examples above with reference to Figure 3 The discussed case operates without the counter electrode 11 .

[0112] Figure 5 The steps in the method according to the present invention are schematically shown. In particular, when the method starts at 51, the method comprises the following steps:

[0113] 52: Providing an initial substrate and one or more material layers, wherein the initial substrate contacts and supports the one or more material layers, thereby defining a first interface between the initial substrate and the one or more material layers;

[0114] 53: Providing a target substrate, and adhering the target substrate to a surface of the one or more material layers opposite to the first interface;

[0115] 54: at least partially immersing the initial substrate, the one or more material layers, and the target substrate in an electrolyte solution provided with a counter electrode;

[0116] 55: establishing a potential difference between the counter electrode and the surface of the initial substrate facing the first interface; and

[0117] 56: before or during the step of establishing the potential difference, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate so as to provide a wedge-shaped separation space between the initial substrate and the one or more material layers, wherein a separation front is provided at a position where the initial substrate and the one or more material layers begin to move and separate;

[0118] 57: Enlarging the separation space and moving the separation front along the initial substrate by applying a separation force to the target substrate in a direction away from the initial substrate or applying a separation force to the initial substrate in a direction away from the target substrate using an actuator, wherein an electrolyte diffuses between the initial substrate and the one or more material layers, and

[0119] 58 : Controlling the actuator so that the advancement of the separation front is equal to or less than the diffusion rate of the electrolyte until the complete target substrate and one or more material layers are separated from the initial substrate, and the method ends at 59 .

[0120] It should be understood that the above description is included to illustrate the operation of the preferred embodiment and is not intended to limit the scope of the invention. From the above discussion, various variations that will be obvious to those skilled in the art are also included within the scope of the invention.

[0121] In summary, the present invention relates to a method and apparatus for transferring a material layer from an initial substrate to a target substrate. The apparatus comprises a container for containing an electrolyte solution, a substrate holding member disposed within the container, a voltage source connectable to the material layer and / or the initial substrate, an actuator for moving the target substrate away from the initial substrate or the initial substrate away from the target substrate, and a controller for controlling the actuator. The method comprises the following steps:

[0122] - moving an edge of the target / initial substrate away from the initial / target substrate so as to provide a separation space between the initial substrate and the material layer and to have a separation front where the initial substrate and the material layer begin to separate from each other; and

[0123] -When the initial substrate, the material layer and the target substrate are at least partially immersed in an electrolyte solution and an electric potential is applied to the material layer and / or the surface of the initial substrate facing the material layer, the separation space increases and the separation front moves along the initial substrate, wherein the electrolyte diffuses between the initial substrate and the material layer, wherein the actuator is controlled so that the progress of the separation front is equal to or less than the diffusion speed of the electrolyte.

Claims

1. A method for transferring one or more material layers from an initial substrate to a target substrate, wherein: The method comprises the following steps: - providing the initial substrate and the one or more material layers, wherein the initial substrate contacts and supports the one or more material layers, thereby defining a first interface between the initial substrate and the one or more material layers; - providing a target substrate and adhering the target substrate to a surface of the one or more material layers opposite to the first interface; - at least partially immersing the initial substrate, the one or more material layers and the target substrate in an electrolyte solution; - applying an electric potential to the surface of the initial substrate facing the first interface and / or to the one or more material layers; and - before or during the step of applying the electrical potential, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate so as to provide a separation space between the initial substrate and the one or more material layers, wherein a separation front is provided at a location where the initial substrate and the one or more material layers begin to separate from each other; as well as - increasing the separation space and moving the separation front along the initial substrate by applying a separation force to the target substrate in a direction away from the initial substrate or applying a separation force to the initial substrate in a direction away from the target substrate using an actuator, wherein the electrolyte diffuses between the initial substrate and the one or more material layers, wherein the actuator is controlled so that the progress of the separation front is equal to or less than the diffusion rate of the electrolyte.

2. The method according to claim 1, wherein The method further comprises the steps of detecting a diffusion range of the electrolyte between the one or more material layers and the initial substrate, and controlling the actuator to move the separation front such that the separation front does not exceed the detected diffusion range.

3. The method according to claim 2, wherein: The diffusion range is detected by using an optical sensor, preferably by using a light detector or a camera, and wherein the actuator is controlled such that the detachment front progresses such that the visible diffusion range is not exceeded by the detachment front.

4. The method according to claim 1, 2 or 3, wherein: The actuator is connected to the target substrate and is configured to pull the edge of the target substrate away from the initial substrate, so as to move the edge of the target substrate away from the initial substrate and / or to increase the separation space and move the separation front along the initial substrate, or The actuator is connected to the initial substrate and is configured to pull the edge of the initial substrate away from the target substrate, so as to move the edge of the initial substrate away from the target substrate and / or increase the separation space and move the separation front along the initial substrate.

5. The method according to claim 4, wherein A force sensor is arranged between the actuator and the target substrate, wherein the method further comprises the steps of: using the force sensor to measure the separation force when the edge of the target substrate is pulled away from the initial substrate, and controlling the actuator to slow down the pulling of the edge of the target substrate when the measured separation force exceeds a threshold value, or A force sensor is arranged between the actuator and the initial substrate, and the method further includes the following steps: when the edge of the initial substrate is pulled away from the target substrate, using the force sensor to measure the separation force, and when the measured separation force exceeds a threshold, controlling the actuator to slow down the pulling of the edge of the initial substrate.

6. The method according to claim 5, wherein: The threshold value of the measured separation force (in Newtons) is 0.10 times or less of the maximum length of the separation front (in meters), preferably 0.05 times or less of the maximum length of the separation front, and more preferably 0.01 times or less of the maximum length of the separation front.

7. The method according to claim 1, wherein The diffusion of the electrolyte between one or more layers of specific material and an initial substrate of a specific type is known or has been determined experimentally or using the steps of a method according to any one of claims 2 to 6, and wherein the method further comprises the step of setting and / or timing the control of the actuator in accordance with the known diffusion so that the progression of the separation front is equal to or less than the known diffusion rate of the electrolyte.

8. The method according to any one of claims 1 to 7, wherein The step of moving the edge and / or the step of increasing the separation space and moving the separation front along the initial substrate further comprises the step of inserting a wedge in a direction substantially parallel to the first interface to push the target substrate away from the initial substrate.

9. The method according to any one of claims 1 to 8, wherein The initial substrate comprises a substantially rigid substrate, preferably a flat substantially rigid substrate, and wherein a surface of the initial substrate facing the first interface is provided with a growth catalyst layer.

10. The method according to claim 9, wherein: The substantially rigid substrate comprises a silicon wafer or a sapphire plate, and / or wherein the growth catalyst layer comprises a metal layer, preferably wherein the metal layer comprises Cu and / or Ni.

11. The method according to claim 10, wherein: The metal layer is connected to a voltage source for applying an electric potential to the metal layer, preferably, wherein the target substrate is provided with a cutout, or wherein the target substrate is smaller than the initial substrate, to provide an area for electrically connecting the metal layer to the voltage source.

12. The method according to any one of claims 1 to 11, wherein The method further comprises the step of positioning a cylindrical roller on top of the target substrate, wherein the cylindrical roller is arranged substantially above the separation front and / or the separation space, and the cylindrical roller is configured to move with the moving separation front.

13. The method according to any one of claims 1 to 12, wherein The rigidity of the target substrate is less than that of the initial substrate. Preferably, the target substrate includes a heat release sheet, a thinned silicon wafer, a glass sheet and / or a plastic sheet, etc. The glass sheet is preferably borosilicate glass, and the plastic sheet is preferably a resin glass sheet, a polycarbonate sheet, or a polyimide sheet.

14. The method according to any one of claims 1 to 13, wherein The one or more material layers include a graphene layer or a hexagonal boron nitride (h-BN) layer.

15. An apparatus for transferring one or more material layers from an initial substrate to a target substrate, wherein: The device includes: a container for containing an electrolyte solution and for at least partially immersing the initial substrate, the one or more material layers, and the target substrate in the electrolyte solution, a substrate holding member disposed inside the container, wherein the substrate holding member is configured to hold the initial substrate or the target substrate, a voltage source connectable to the one or more material layers and / or the initial substrate, an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate or to apply a separation force to the initial substrate in a direction away from the target substrate, and A controller is configured to control the actuator to: - moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate so as to provide a separation space between the initial substrate and the one or more material layers, wherein a separation front is provided at a location where the initial substrate and the one or more material layers begin to separate from each other; and - increasing the separation space and moving the separation front along the initial substrate, wherein the initial substrate, the one or more material layers and the target substrate are at least partially immersed in the electrolyte solution, and an electric potential is applied to the surface of the initial substrate facing the one or more material layers and / or to the one or more material layers, wherein the electrolyte diffuses between the initial substrate and the one or more material layers, and wherein the actuator is controlled so that the progress of the separation front is equal to or less than the diffusion rate of the electrolyte.

16. The apparatus according to claim 15, wherein The actuator is connectable to the target substrate and is configured to pull an edge of the target substrate away from the initial substrate, wherein the apparatus preferably comprises a force sensor connected to the actuator and connectable to the target substrate, or The actuator is connectable to the initial substrate and is configured to pull an edge of the initial substrate away from the target substrate, wherein the apparatus preferably comprises a force sensor connected to the actuator and connectable to the initial substrate.

17. The apparatus according to claim 16, wherein The container and / or the substrate holding member is movable in a direction having a component parallel to the first interface between the initial substrate and the one or more material layers, preferably wherein the actuator is configured to pull the edge of the target substrate in a direction having a component perpendicular to the first interface, or The actuator is configured to pull the edge of the initial substrate in a direction having a component perpendicular to the first interface.

18. Apparatus according to claim 15, 16 or 17, wherein The actuator includes a wedge configured to be inserted between the initial substrate and the target substrate, preferably in a direction substantially parallel to an interface between the initial substrate and the target substrate, for pushing the target substrate and the one or more material layers away from the initial substrate.

19. The apparatus according to any one of claims 15 to 18, wherein The apparatus further comprises an optical sensor, preferably a light detector or a camera, configured to detect diffusion of the electrolyte between the one or more material layers and the initial substrate, and wherein the optical sensor is connected to the controller for providing a measure of diffusion of the electrolyte relative to the separation front.

20. The apparatus according to any one of claims 15 to 19, wherein The apparatus further comprises a cylindrical roller disposed above the substrate holding member, wherein the cylindrical roller is configured to abut on top of the target substrate and move along a surface of the target substrate opposite to the initial substrate, or Wherein, the cylindrical roller is configured to abut on top of the initial substrate and move along a surface of the initial substrate opposite to the target substrate.

Images