ES2536491B2 - NANOCAPAS TRANSFER PROCEDURE AND EQUIPMENT FOR THE SAME. - Google Patents

Abstract

Procedure for the transfer of nanolayers and apparatus for carrying out the same, which refers to a procedure for the transfer of a nanolayer (9) from an initial support (6) to a final substrate (14), and to an apparatus for carrying out said transfer. The method comprises a) introducing said nanolayer (9) adhered on its lower face to an initial support (6) in a liquid (13), said liquid (13) contained in a first container (8) whose inner face comprises a coating ( 11) hydrophilic and electrically charged; b) separating the nanolayer (9) from the initial support (6); and c) removing the liquid (13) until the nanolayer (9) is deposited on a final substrate (14). In this way, nano-layers of materials such as graphene, boron nitride, molybdenum disulfide or other two-dimensional layers can be transferred without damaging them, as well as allowing transfer to arbitrary, flexible or rigid final substrates.

Description

Field of the Invention The present invention describes a method of transferring graphene nanocaps, boron nitride, molybdenum disulfide, dicalcogens or other material, generally of two-dimensional structure from an initial support to a final substrate by controlling a liquid on the one that floats the nanolayer, as well as the necessary devices for its realization.

State of the art Nano-layers of two-dimensional materials, such as graphene, hexagonal boron nitride (hBN) or molybdenum disulfide (MoS2), due to physical properties intrinsic to their dimensionality, have a promising future in the fields of electronics , optics or energy. One of the main technological problems related to its use is its transfer from the initial growth support to the final substrate, because the procedure can break or damage the nanolayer. It is possible to make a roll-to-roll transfer procedure as described in US20120258311, US20110315657, but it involves the use of flexible final substrates. Other procedures are carried out manually, generating variability in the quality of the final nanolayer. For example, document US201 00143726 describes a procedure in which the nanolayer bonded to a protective material is deposited on a substrate without any mechanism to control the placement of the nanolayer on the final substrate, giving rise to a problem of variability in the position in which the nanolayer is finally deposited on the final substrate. The previous document also does not detail any method of gradual modification of the liquid that prevents possible damage to the nanolayer during the transfer process.

Brief Description of the Invention The inventors have developed a method and apparatus that solve the aforementioned problems by providing means for a better transfer of nanolayers to the final substrates. By means of the method and apparatus of the invention the variability generated by the manual procedure is eliminated and the use of substrates is added

arbitrary, including flexible or rigid substrates, such as silicon oxide on doped silicon or partially processed silicon wafers.

Thus, according to a first aspect, the present invention relates to a process for the transfer of a nanolayer (9) characterized in that it comprises:

8. insert said nanolayer (9) adhered on its lower face to an initial support

(6) in a liquid (13), said liquid (13) contained in a first container (8) whose inner face comprises a hydrophilic and electrically charged coating (11);

b.

separate the nanolayer (9) from the initial support (6);

C.

remove the liquid (13) until the nanolayer (9) is deposited on a final substrate

(14)

A second aspect of the invention relates to an apparatus for transferring a nanolayer (9) from an initial support (6) to a final substrate (14) comprising a first container (8) adapted to accommodate an initial liquid (13 ), the inner face of said first container (8) comprising a hydrophilic and electrically charged coating (11), means for removing said liquid (1 3) and a substrate holder (15) configured to accommodate said final substrate (14).

One of the advantages of the present invention is the transfer of the nanolayer (9) to the final substrate (14) with a higher quality and lower variability in the results. Thus, a third aspect of the invention relates to a final substrate (14) comprising a nanolayer (9), manufactured according to the process of the invention. These final substrates

(14) of the invention are especially advantageous in the case of rigid final substrates (14), for which existing methods of transfer of nanolayers (9) are performed manually and, due to it, with greater variability in the quality of the nanolayer (9) on the final substrate (14).

Brief Description of the Figures FIG.1A shows a diagram of the elements involved in the procedure during stage a. FIG. 1 B shows a diagram once stage b is finished. where the nanolayer (9) is released from the initial support (6), floating in the liquid (13). FIG. 1 shows a diagram in which the level of the liquid is decreased (13).

FIG.1D shows a diagram in which the liquid (13) is completely removed and the

nanolayer (9) is transferred to the final substrate (14).

FIG. 1 E shows a diagram in which the protective layer (7) is removed outside the system

transfer.

S

F1G.2A shows a diagram in which the final substrate (14) embedded in the substrate holder

(15) aligns with the lifting means (12).

FIG.2B shows a diagram in which the substrate holder (15) is inserted into the recess

between the lifting means (12) and the bottom of the second container (16).

FIG.2C shows a diagram in which the substrate holder (15) aligns with the first

10

container (8) so that the final transfer is made on the substrate (14).

FIG.3A shows a diagram with the elements of the transfer apparatus.

FIG.3B shows a diagram with the arrangement of the elements in the apparatus of

transfer.

FIGAA shows a diagram of the front view of the proximity sensor (21) with respect to the

fifteen

second container (16).

FIGAB shows a diagram of the side view of the proximity sensor (21) with respect to the

second container (16).

FIGAC shows a diagram of the top view of the proximity sensor (21) with respect to the

second container (16).

twenty

Detailed description of the invention

By "nanolayer" in the present invention is meant a layer of material of up to 1 00

nanometers thick of one or several layers of graphene, hexagonal boron nitride,

molybdenum disulfide or other two-dimensional material or composite materials

25

two-dimensional In a particular embodiment the nanolayer has a thickness of between 0.1 and 20

nanometers In another embodiment between 0.2 and 2 nanometers, in another between 0.2 and 1 nanometer.

In another particular embodiment, the nanolayer has between 1 and 10 nanometers, preferably a

thickness less than 10 nanometers. Alternatively, the nanolayer has a smaller thickness

5 nanometers

30

Device for transferring the nanolayer

The means for removing the liquid (13) admit various configurations and materials.

In a preferred embodiment, said means comprise at least one conduit

connected at a first end to the liquid (13) housed in the first container (8) and in a

35

second end to a first pump configured to drive said liquid (13) to a

collection container (32). Therefore, said means do not require any configuration

4

special more than supporting contact with the liquid (13). For example, in the case that the liquid (13) is acidic in nature, preferably the means for removing the liquid

(13)

they comprise hydrochloric resistant silicone tubes in high concentrations, for example at 20% by volume. The means for removing the liquid (13) can also comprise a second pump configured to introduce liquid (13) into said first container (8). Preferably said first and second pumps are peristaltic pumps.

(28)

and (27), but another type of pump of similar characteristics can be used, such as membrane pumps.

In a preferred embodiment, said first container (8) is located within a second container (16) connected so that the liquid (13) occupies both containers and the first end of the means for removing the liquid (13) is connected to said second container (16).

The coupling of the first container (8) to lifting means (12) configured to generate a recess under said first container (8) makes it possible to load a substrate holder (15) with the final substrate (14) with a lower disturbance of the liquid (13) , and therefore provides better results_

The apparatus of the invention may comprise one or more elements selected from the group consisting of:

to.

temperature control means;

b.

a distance sensor system;

C.

flow control means of a liquid; Y

d.

drying media

As shown in Figure 3A, in order to improve control and automate process steps, the apparatus of the invention may comprise control means connected to one or more elements of the apparatus, for example, to one or more elements selected from the group consisting of temperature control means, distance sensing system, flow control means of a liquid or drying means. In a particular embodiment, the control means comprise a microcontroller (35). The Arduino UNO model has been used, but another microcontroller (35) with the same characteristics as the previous one or a computer can be used.

In a particular embodiment, the temperature control means comprise a heating plate (23) (for example, one that operates with 220 V and thermally dissipates 220 W), a temperature sensor (24) (for example, a TMP36), and finally one or more relays (25) that control the electrical connection of the heating plate (23). The relays (25) are connected to a controller circuit to be able to modify their open / closed state with digital signals from the microcontroller (35).

In another particular embodiment the temperature control means comprise a thermostatic bath system in which the second container (16) is immersed.

In a particular embodiment, the distance sensor system comprises a distance sensor (21), which is an ultrasound detection and emission module designed to measure the distance between its position and the liquid (13) of the first container (8) or the liquid from the second container (16), depending on the configuration adopted. According to a preferred embodiment, said distance sensor (21) is placed on the liquid (13) contained in the second container (16), as shown in Figures 4A, 48 and 4C. Communication with the microcontroller (35) can be done through a control circuit. By defining a minimum level of filling (42) and a maximum level of filling (41) in the microcontroller program (35), better control over the procedure is achieved. In addition to ultrasonic-based distance sensors, it is possible to use distance sensors based on infrared light or switches that float on the liquid

(13).

According to a preferred embodiment, the liquid flow control means are composed of a deionized water tank (31), a waste tank (32), a tube

(30) for the evacuation and filling of the first container (8) or the second container (16), a first peristaltic drainage pump (28), a second peristaltic filling pump (27) and two valves that only allow the flow of liquid in one direction (26). The drying system can be a fan (22) positioned perpendicularly on the final substrate (14), and a controller for switching on and off with digital signals

of the microcontroller (35).

The deionized water tank (31) has sufficient capacity for at least one transfer process, as does the waste tank (32). Between the valves (26) there may be a T-shaped connector, from which a silicone tube (30) comes out which is held at the bottom of the second container (16) at all times.

Using the digital input / output connectors, the microcontroller (35) can control the peristaltic pumps (27, 28), the distance sensor (21), a fan (22) and the relays (25) of the heating plate (23). An analog input connector is required for the temperature sensor (24). The microcontroller (35) can be programmed to automate some of the steps detailed in the transfer procedure described in the present invention. The microcontroller (35) allows connection via a serial port to a computer to keep a record of each transfer.

Procedure of transfer of the nanocapas (9) In addition to the stages a. b. and c., the process of the invention admits variations that introduce additional advantages. In a particular embodiment, the process is carried out inside a first container (8), preferably with a tubular shape, which in turn is preferably located inside a second container (16). The various essential and optional steps that support the process of the invention are described in detail below.

Initial preparation (Fig. 1A) For initial preparation, the entire transfer system can be introduced into a second container (16), which holds the liquid (13) and part of the transfer system inside. The initial liquid (13) has the function of releasing the nanolayer (9) from the initial support (6) and acting as an intermediate support during the rest of the transfer. The nanolayer (9) can be protected by a protective layer (7) of polymer or the like to improve the final properties of the nanolayer (9) after the process, as well as to provide it with electrostatic charge. The average expert in the field knows the materials that can serve as protective layers and can choose between them depending on the technical, practical or economic needs. In a particular embodiment, said protective layer (7) is selected from the group consisting of poly (methyl methacrylate), adhesive tape, glue, polycarbonate and photoresist.

The nanolayer (9), adhered to the initial support (6), is preferably positioned within a first container (8) through an upper opening. In a particular embodiment said

First container (8) is a tube and is coupled to lifting means (12) to generate a recess under the tube that allows a substrate holder (15) to be loaded with the final substrate

(14) embedded in it. In a particular embodiment the final substrate (14) can be pretreated with an adhesion enhancer, preferably by immersing it in a solution of 3-aminopropyltriethoxysilane (APTES).

In the present invention, the substrate holder (15) preferably refers to a piece specially designed to firmly fit the final substrate (14) and handle it without damaging it. In addition, it can be adapted in its design to the required final substrate size and to the shape of the lifting part according to the needs of each case.

The liquid (13) preferably never exceeds the upper limit of said first container (8) to keep the nanolayer (9) inside at all times. As mentioned above, said first container (8) is treated with a hydrophilic coating (11) which is also electrically charged. The coating treatment (11) can be done before starting the procedure with various materials available to the person skilled in the art. In a particular embodiment, the first container (8), preferably a tube, is immersed in a 2% mass solution of PODA (polydiallyldimethylammonium chloride) for 30 seconds, rinsing in water, and subsequently immersing the tube (8) in a 2% mass solution of PSS (polystyrene sodium sulphonate) for 30 seconds. Finally it is rinsed again in water. The coating (11) favors the separation between the nanolayer (9) and the wall of the first container (8) by electrostatic forces, keeping the nanolayer (9) centered inside the first container (8) during the process, without contact with the walls of the first container (8). As the coating (11) is hydrophilic, it is also avoided that effects due to the surface tension of the liquid (13) damage the nanolayer (9). The type of electrostatic charge can be positive or negative, having to be of the same type in both the coating (11) and the nanolayer (9) or the protective layer (7). In a particular embodiment, the type of load used is negative.

Release of the nanolayer (Fig. 1 B) Once the initial preparation is done, the nanolayer (9) must be released from the initial support (6). In the case of a nanolayer (9) on a metal initial support (6), for example Cu, Ni, Ru, Pt or Al, a selective chemical attack can be used by appropriately choosing the composition of the initial liquid (13) to eliminate the initial support (6), without damaging the nanolayer (9). In a particular embodiment the liquid (13) is selected from the group consisting of a solution of iron trichloride, a solution of NaOH, a solution of Hel and a solution of Hel with CUS04. For example, for a nanolayer of graphene grown on copper or nickel by chemical vapor deposition (eVO), the Marble reagent (10 9 CUS04: 50 mi Hel: 50 mi H20) can be used at 40 ° C for approximately 20 minutes. Other solutions can also be used, such as a solution between 1 M and 0.5 M iron trichloride (FeCI3). In another particular embodiment, a NaOH solution can be used and current applied between the initial support (6) and a Pt electrode introduced into the solution. In this way, oxygen and hydrogen bubbles are formed by the dissociation of water between the nanolayer (9) and the initial support (6) that facilitate its separation.

Modification of the liquid composition In a particular embodiment, once the nanolayer (9) is released, the liquid (13) is modified. With the released nanolayer floating in the liquid (13) inside the first container (8), the composition of the liquid can be changed by partially withdrawing the initial liquid and replacing it with a final liquid, usually water that has been removed the ions (deionized). This process of dilution of the initial liquid is preferably carried out very gradually in the first container (8), preferably a tube, so that the nanolayer (9) keeps floating stable in the center of the tube at all times. According to this particular embodiment, deionized water is added until the content of the initial liquid is less than 50% by volume, preferably between 1 and 40% by volume, more preferably between 1 and 10% by volume, more preferably until the initial liquid content is less than 10% by volume. In a particular embodiment, deionized water is added until the initial liquid content is less than 8% by volume. For example, the content of the initial liquid, once diluted in deionized water, is 10% by volume. In a particular embodiment, means for pH measurement are used to choose the number of dilution steps of the initial liquid (13) in which the initial liquid dilution process is stopped. This dilution process can be repeated one or more times.

The liquid exchange (13) is carried out by means of a tube (30), for example of silicone, which reaches the bottom of the second container (16). The tube (30) can be connected to two tanks, a tank (31) containing the liquid (13) that will be used to modify the composition in the first container (8), for example, with deionized water, and another tank

(32) initially empty, which serves to receive the liquid (13) from the total or partial emptying of the first container (8), the second container (16) or both. Peristaltic pumps are preferable for controlling the filling / emptying flow, since they allow low enough flows not to affect the nanolayer (9) floating in the liquid (13).

Transfer to the final substrate (Figs. 1 and 10) According to a particular embodiment, in case the substrate holder (15) with the final substrate (14) was not yet in position, it is introduced into the bottom of the second container (16 ). In accordance with this embodiment, it slides under the lifting means

(12) until the final substrate (14) is aligned with the first container (8), as shown in Figures 2A, 28 and 2C. The process can be monitored from the top opening of the first container (8).

Once the final substrate (14) is at the bottom of the container aligned with the first container (8), the liquid is gradually withdrawn. When removing all the liquid (13), the nanolayer (9) is deposited in the final substrate (14), in a centered position. During emptying, the nanolayer (9) remains centered inside the first container (8).

Depending on the characteristics of the final substrate (14), a liquid layer may remain between the final substrate (14) and the nanolayer (9). To remove this layer of liquid, means can be used for the generation of gas stream or for the generation of heat,

or a combination of both. For example, by applying a flow of air generated by a fan (22) in combination with the evaporation by temperature from a heating plate (23) that is close to the final substrate, under the second container

(16)

Removal of the protective layer (Fig. 1E) Once the nanolayer adheres to the final substrate, the substrate holder (15) and the final substrate (14) can be removed from the lifting means (12) and the first container (8) , keeping the protective layer (7) adhered to the nanolayer. The protective layer (7) can be removed without affecting the nanolayer (9) in a later step. The method of removing the protective layer (7) will depend in each case on the nature thereof and the person skilled in the art can choose from several known in the state of the art. For example, in the case of a protective layer (7) based on poly (methyl methacrylate) (PMMA) it can be removed using acetone at a temperature between 40 ° C and 56 ° C.

Description of a preferred embodiment of the invention

A description of a particular configuration of the apparatus of the invention and its operation is given below.

In a microcontroller (35) three possible states are configured:

one.

"Stop" status: no flow.

2.

"Filling" status: Filling from the deionized water tank (31) to the second container (16).

3.

"Emptying" status: Emptying from the second container (16) to the waste tank (32).

Following the scheme shown in Figure 38, in the initial preparation phase, a silicone tube (30), a fan (22) and a distance sensor (21) must be placed in the correct position.

During the release phase of the nanolayer (9), the microcontroller (35) maintains a constant temperature by actuating a relay (25) that connects and disconnects a heating plate (23) from the electric current. The temperature is measured through a temperature sensor (24). A predefined time interval of 20 minutes is maintained at that temperature. This time may vary depending on the nature of the initial support (6) and the liquid (13).

During the phase of modifying the composition of the liquid (13), partial emptying and filling of liquid from the second container (16) are performed. In this phase the liquid flow control system and the liquid level sensor are used. The emptying state of the initial liquid (13) is started until the minimum filling level (42) is reached. Immediately afterwards, the state of filling with distilled water begins until the maximum level of filling (41) is reached. At this point, you can wait 5 minutes for the system to stabilize.

This successive emptying and filling process can be repeated until the necessary dilution state is reached. A repetition of six times has given good results. The liquid flow control system, the temperature control system, the central control system and the drying system are used in the transfer phase to the final substrate (14).

The flow control system is placed in an emptying state for the time necessary to empty the second container (16) completely. After that time, the fan (22) is activated and the temperature control system is turned on at 30 ° C. Finally, after about 20 minutes, all systems are turned off and the substrate holder (15) is removed next to the final substrate (14) with the nanolayer (9) already transferred.

Claims (21)

1. Procedure for the transfer of a nanolayer (9) characterized in that it comprises: a. introducing said nanolayer (9) adhered on its lower face to an initial support (6) in a liquid (13), said liquid (13) contained in a first container (8) whose inner face comprises a hydrophilic and electrically charged coating (11); b.separate the nanolayer (9) from the initial support (6); e.remove the liquid (13) until the nanolayer (9) is deposited on a final substrate (14).

2.

The method according to claim 1, wherein the nanolayer (9) comprises on its upper face a protective layer (7) provided with electrostatic charge.

3.

The method according to claim 2, wherein said protective layer (7) is selected from the group consisting of poly (methyl methacrylate), adhesive tape, glue, polycarbonate and photoresist.

Four.

The method according to any of the previous steps in which the separation of the nanolayer (9) from the initial support (6) in step b. It is produced by chemical attack on the initial support (6).

5.

The method according to claim 4, wherein the initial support (6) is a metal and is separated from the nanolayer (9) by choosing as liquid (13) one selected from the group consisting of a solution of FeCI3, a solution of NaOH , a solution of HCI and a solution of Hel with CUS04.

6.

The method according to claim 5, wherein the initial support (6) is selected from the group consisting of Cu, Ni, Ru, Pt and Al.

7.

The method according to any of the preceding claims, wherein before the step c., The composition of the liquid (13) is modified.

8.

The process according to claim 7, wherein the composition of the liquid (13) is modified by diluting with deionized water.

9.

The method according to any of the preceding claims, wherein the nanolayer (9) is one or more layers of a material that is selected from the group consisting of graphene, boron nitride and molybdenum disulfide.

10.

The process according to any of the preceding claims, wherein the final substrate (14) is immersed at the beginning of the process.

eleven.

The method according to any of the preceding claims, wherein the surface of the final substrate (14) is treated with an adhesion enhancer.

12.

The process according to claim 11, wherein said adhesion enhancer is 3-aminopropyltriethoxysilane.

13.

Apparatus for transferring a nanolayer (9) from an initial support (6) to a final substrate (14) comprising a first container (8) adapted to accommodate an initial liquid (13), the inner face of said first container comprising (8) a hydrophilic and electrically charged coating (11), means for removal of said liquid (13) and a substrate holder (15) configured to accommodate said final substrate (14).

14.

An apparatus according to claim 13, wherein said means for removing the liquid (13), comprise at least one conduit connected at a first end to the liquid (13) housed in the first container (8) and at a second end to a first pump configured to drive said liquid (13) to a collection container (32).

fifteen.

An apparatus according to claim 14, wherein said conduit is also connected to a second pump configured to introduce a liquid (13) into said first container (8)

16.

An apparatus according to any one of claims 13 to 15, wherein said first container (8) is located within a second container (16) connected so that the liquid (13) occupies both containers and the first end of the means for removal of the liquid (13) it is connected to said second container (16).

17.

An apparatus according to any one of claims 13 to 16, comprising one or more elements selected from the group consisting of:

to.

temperature control means;

b.

a distance sensor system;

C.

flow control means of a liquid; Y

d.

drying media

18.

An apparatus according to claim 17, comprising control means connected to one or more of said elements selected from the group consisting of temperature control means, distance sensing system, flow control means of a liquid or means of dried

19.

An apparatus according to any of claims 13 to 18, wherein said first container (8) is coupled to lifting means (12) configured to generate a recess under said first container (8) that allows loading a substrate holder

(15) with the final substrate (14). 14

twenty.

A final substrate (14) comprising a nanolayer (9) manufactured according to the method defined in any one of claims 1 to 12.

twenty-one.

A final substrate (14) according to claim 20, comprising two or more nano-layers (9) manufactured sequentially according to the method defined in any one of claims 1 to 12.