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    • 专利摘要:
    Procedure for obtaining microcontacts, obtainable microcontact and use thereof. A method of obtaining microelectrode microcontacts is described in this document. The process of the invention is carried out with a microscope, an xy translation table, and an xyz manipulator. In such a way that on a substrate with an element with some of its dimensions in the adsorbed nanoscale is placed aligned with said element a sample holder has fixed on at least one of its ends a viscoelastic polymer material with a sheet, with a layer of a electrical conductor inorganic material, to later transfer the layer of inorganic material to the substrate by pressure. When removing the pressure, the layer of inorganic material remains adhered to the surface of the substrate taking off from the viscoelastic polymer, to later establish a contact between the inorganic material and at least one external circuit. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2557507A1
    申请号:ES201431108
    申请日:2014-07-23
    公开日:2016-01-26
    发明作者:Guillermo LÓPEZ-POLÍN PEÑA；Pablo ARES GARCÍA；Félix ZAMORA ABADANES；Julio GÓMEZ HERRERO
    申请人:Universidad Autonoma de Madrid；
    IPC主号:
    专利说明:

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    Procedure for obtaining microcontacts, obtainable microcontact and use thereof. OBJECT OF THE INVENTION
    The object of the present invention is part of the technical field of nanotechnology as well as that of electronics.
    The present invention relates to a procedure based on the use of viscoelastic seals for obtaining electric microcontacts as well as their subsequent transfer, and controlled positioning on objects with some dimension in the nanoscale.
    BACKGROUND OF THE INVENTION
    Nanoelectronics and molecular electronics are two important sources of inspiration in modern science. The electrodes are a basic component of any electrical circuit. In studies of electronics at the level of the nanoscale, the electrodes usually serve as a bridge between the nanoscopic regime and the macroscale. The contact resistance between the electrodes and the nanometric objects that are intended to be studied is a key element to adequately understand the electrical properties of these nano-objects. The manufacture of electrodes for molecular electronics studies typically requires a number of steps and techniques that in many cases include evaporation of metal in a vacuum, lithograph, sample cleaning through the use of various chemical agents, etc. There are a large number of systems, such as biomolecules (ie, DNA, proteins), metal-organic threads, and organic molecules, where these procedures are unacceptable because molecular structures may be damaged by exposing them to vacuum, or they may not support high temperatures associated with the evaporation of metals or can be attacked by the chemical agents used to clean the samples of the remains of lithograph masks. In addition, classical methods entail considerable efforts in terms of time and resources that in many cases are not even available in most laboratories.
    In view of the above, a manufacturing and positioning procedure of soft microcontacts on objects that have any of their dimensions in the nanoscale is necessary and to be able to contact them with external circuits, it is also of interest that this procedure allows obtaining microelectrodes that allow the repair of microcontacts and manufacture of nano-micro devices.
    DESCRIPTION OF THE INVENTION
    In a main aspect of the invention there is a method that allows to produce electrical microcontacts with objects with one or more dimensions in the nanoscale, that is, with dimensions comprised in the order of nanometers, as well as repair microcontacts, and the realization of doubles. electrical contacts in objects of nanometric dimensions, to obtain electrical devices and circuits and, in a very particular realization, a transistor could be obtained.
    The procedure described here can be defined as a soft lithograph procedure based on the deterministic transfer of soft microcontacts using viscoelastic polymer seals
    The use of this procedure may be very suitable for contacting molecules and, in particular, molecules that have limited stability to conventional lithography processes; for this, a transfer system is used that is composed of a
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    Optical microscope with zoom, an XY linear translation table and an XYZ micro-manipulator.
    The process of the invention begins with obtaining a material such as graphene sheets of a few layers (GPC) by mechanical microexfoliation of a graphite sample. An adhesive tape comprising these sheets is pressed against a thin strip of transparent viscoelastic polymer (Gel-Film® from Gel-Pak®) that has previously been fixed on an optical microscope sample holder (such that the adhesive tape is pressed comprising these Laminate strongly against the polymer and then move quickly backwards reducing the pressure so that the sheets are stuck to the polymer). The glass sample holder is subject to an XYZ manipulator. Using an optical microscope, a GPC sheet with lateral dimensions greater than nl nm x 100 nm and thickness between approximately 3-40 nm is selected. In this situation, the sample is placed with the elements with at least one dimension in the nanoscale that you want to contact at an XY translation table.
    The sample is observed through the glass sample holder with the viscoelastic polymer with the GPC sheet attached to it. By inspection with the optical microscope a suitable region is located in the sample, previously determined and known to comprise elements with at least one dimension in the nanoscale, and then the XYZ manipulator is moved to align the GPC sheet with this region. At this time, using the XYZ manipulator, the polymer is pressed strongly against the surface of the sample and then slowly moved backwards decreasing the pressure. This is the critical point of the procedure: as the viscoelastic shows moderate adhesion at low speeds, the GPC sheet adheres to the surface of the sample detached from that of the polymer; This process is carried out manually, and through monitoring through the microscope, the contact, the adhesion of the material (graphene for example) and the removal of the thin strip of viscoelastic polymer are appreciated.
    Finally, with the help of the optical microscope, the GPC sheet is contacted with an external circuit, for example, or another desired element, contact which is preferably made with silver paint. A similar procedure can be performed with a thin sheet (tens of nanometers) of metal, such as gold, obtaining equivalent results.
    DESCRIPTION OF THE DRAWINGS
    To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical realization of the same, a set of drawings is attached as an integral part of said description. where with illustrative and non-limiting character, the following has been represented:
    Figures 1a-1c. They show some illustrations of the transfer system and its utilization. Figure 1a shows an illustration of the system where the substrate (1) can be seen with elements (11) with at least one of its dimensions in the nanoscale located on its surface, and as it is located in the transfer system consisting of a microscope (2) optical zoom, an XY translation table (6) and an XYZ manipulator (4). Figure 1b shows an illustration of the macroscopic contact process carried out by silver paint. Figure 1c shows an optical microscope image showing the GPC laminate (in white tone) and the silver paint (in dark gray texture, to the right of the image).
    Figures 2a-2d. They show a series of illustrations of the implementation of the invention by contacting carbon nanotubes. Figure 2a shows a topography of AFM showing the edge of the GPC sheet microelectrode comprised in the calculation of figure 1c (right area of figure 2a, lighter and more uniform area delimited by a diagonal line which is the
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    edge of the GPC sheet). In the upper corner there is a profile taken along the gray line that shows the height of the sheet. An arrow marks the position of the nanotube. Figure 2b shows a topography of AFM showing the edge of the GPC sheet microelectrode applying 4V between the tip and the sample to increase the contrast of the nanotube. Figure 2c shows a detail of Figure 2a, where the region in which the electrical characterization has been carried out is appreciated; Likewise, diagrams of the electrical circuits corresponding to the nanotube and microelectrode are shown in the left part of Figure 2c. Figure 2d shows a graph representing characteristics of current versus voltage in the nanotube (dashed line) and in the microelectrode (continuous line).
    Figure 3a-3d. They show a series of illustrations of the implementation of the invention by contacting nanocintas MMX. Figure 3a shows an optical microscope image showing a GPC sheet on a silicon oxide substrate with MMX nanocins adsorbed thereon. The fine lines that are observed in the microelectrode reflect nanocintas adsorbed under it. The image in the upper corner shows the geometry and composition of an MMX polymer chain. Each nanocint is composed of thousands of these chains. Figure 3b shows an AFM topography of the region within the calculation in Figure 3a where a nanocint is visible protruding from the GPC sheet. Figure 3c shows a topography image of AFM showing a nanocint contacted with a gold microelectrode. The sheet was obtained from a piece of gold film previously evaporated on a glass substrate in a manner similar to how GPC sheets are obtained. Figure 3d shows a graph showing characteristics of current versus voltage taken with the GPC sheet (dashed line) and with gold (continuous black line).
    Figures 4a-4h. They show a series of illustrations of the implementation of the invention for microcircuit repair. Figure 4a shows an electric circuit made using an evaporation mask to evaporate Au / Cr with the shape of the circuit to be used. The tracks of the Au / Cr circuit (in the form of an inverted T and T) contact the graphene - GPC sheet. Figure 4b shows a circuit after being scratched with a tungsten carbide tip. Figure 4c shows a circuit repaired with the GPC sheet. Figure 4d shows a graph of electrical characteristics of the intact circuit (broken line) and repaired (continuous line) referred to in Figures 4a-4c. Figures 4f-4g show a series of microcircuit repair illustrations that were shortened by an infrared laser and the repair was carried out using a gold foil. Figure 4h shows a graph of electrical characteristics of the intact circuit (broken line) and repaired (continuous line) referred to in Figures 4e-4g.
    Figures 5a and 5b. They show a series of photographs where double contact can be seen in a cobalt-iron nanowire. Figure 5a shows two sheets of GPC contacting a nanowire. To the left and right you can see the macroscopic contacts of silver paint. Figure 5b shows a magnification of the area enclosed by the calculation in Figure 5a, where the nanowire and the two microcontacts are clearly seen.
    PREFERRED EMBODIMENT OF THE INVENTION
    In a first preferred embodiment of the invention, the process of the invention can be implemented to contact carbon nanotubes (CNTs).
    To carry out the procedure described herein, there is a substrate (1) comprising at least one element (11) adsorbed with any of its dimensions in the nanoscale and use is made of a transfer system as shown in Figures 1a and 1b where a glass sample holder for optical microscopes is placed in a manipulator (4). The sample holder has a viscoelastic polymer material (3) attached to one of its ends, comprising at least one sheet which in turn comprises at least one
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    layer of an inorganic material (5) electrically conductive, preferably graphene layers, to be transferred to the surface of a substrate (1) pressing it against said substrate (1), subsequently making a deposit of a material between the microelectrode and a circuit external to generate contact (7).
    As can be seen in Figure 2, there is a sample with carbon nanotubes adsorbed on a surface of the substrate (1), said nanotubes as elements (11) with some of their dimensions in the nanoscale that were deposited from a suspension by drip deposit (called "drop casting") on the substrate which, in this case, is mica functionalized with aminopropyltriethoxysilane (APTS). The concentration of nanotubes was adjusted to be 1-2 nanotubes for every 25 pm2 , as seen in Figure 2a, which shows an topography of AFM taken inside the green box of Figure 1c, where the nanotube is identified by labeling with an arrow.The edge of the sheet is extremely well defined and no trace of contamination or degradation is observed throughout the microcontacts manufactured by thermal evaporation usually have much wider and less defined edges. to the same region as in figure 2a but now a potential of 4 V has been applied between the tip and the sample with which the nanotube is highlighted. Figure 2c is a magnification of the area enclosed in the green square of Figure 2a. Figure 2c also shows the associated electrical circuit diagrams. Figure 2d shows the dependencies of the current versus the voltage corresponding to a contact (7) between the nanotube and the microelectrode (light gray and black curves, respectively).
    The calculation of the slope of these electrical characteristics gives 25 kQ and 55 kQ in the microelectrode and in the nanotube, respectively. We can estimate that the microelectrode / nanotube contact resistance is about 30 kQ, which can be considered quite low even when conventional microelectrodes are used. The images of microscopla of atomic forces (AFM) were acquired with a system of Nanotec Electronica SL. Two different types of AFM probes were used in the experiments. The results of Figure 2 were obtained with probes made entirely of RMN-25PT300 metal from Rocky Mountain Nanotechnology. For the results in Figure 3, Cr / Pt ElectriMulti75-G coated probes from the BudgetSensors firm were used.
    For the results obtained by AFM in conductance mode (which can be seen in Figures 2 and 3) at least a certain region of the sample that at least partially comprises an element (11) with any of its dimensions in the nanoscale is located, such as a CNT, images were taken in the amplitude modulation mode. Once the element (11) with any of its dimensions in the nanoscale is located, a force curve versus distance is made on it and at the point of maximum indentation of the AFM tip a current curve is made in front of at voltage
    In a possible example of microcontact application and its method of obtaining the invention, there is the application of soft microelectrode transfer to electrically contact nanocintas of MMX platinum-based polymers. MMX platinum-based polymers are chains of dimethyl subunits with two platinum centers connected by four dithioacetate ligand bridges and an iodine atom connecting the metal subunits (top in figure 1a). By sublimation of monocrystals of [Pt2 (dta) 4i] n (dta = dithioacetate) in a SiO2 / Si substrate, nanocintas are formed with a high degree of structural perfection. Each nanocint is composed of thousands of MMX chains of about 0.8 nm in diameter parallel to each other interacting with van der Waals forces. MMX polymers are a perfect example of an element (11) with some of its dimensions in the nanoscale, based on molecules that are very difficult to contact electrically when adsorbed by drip deposit (drop casting in English); since the chains deposited in this way are co-absorbed with a certain amount of molecules of
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    solvent that evaporates when exposed to the vacuum necessary to evaporate microelectrodes, creating defects along the chain and converting them into insulators.
    Figure 3a shows an optical microscope image in which a layer of graphene of few layers (GPC) transferred to a surface of silicon oxide can be seen (the substrate (1) is a monocrystalline silicon with 300 nm of grown oxide thermally) with MMX nanocintas adsorbed by sublimation. The image also allows to see the shadows of several nanocints completely covered by the sheet. Figure 3c is a topography of AFM showing a nanocint partially covered by the GPC sheet having a very well defined edge. According to the profile, inserted in the upper corner of the figure, the edge of the microelectrode has a height of about 5 nm.
    The nanocints were also contacted using gold sheets transferred from a glass substrate coated with a 30 nm thick gold film. To prepare a suitable surface for soft microelectrode transfer, the evaporation of the gold film was performed using a transmission electron microscope sample holder which is a grid composed of 60 pm square holes separated by 25 pm Ni bars. The surface with the resulting evaporation was pressed against the viscoelastic polymer thus obtaining a good number of gold pieces of micrometric size that were subsequently transferred to the sample with MMX nanocints. The topography of AFM shown in Figure 3c shows an irregular but well defined edge. The electrical characterization by AFM using a gold microelectrode (figure 3d, light curve) shows a contact resistance similar to that obtained with the GPC microelectrode (dark curve of figure 3d). These characteristics are similar to those obtained with thermally evaporated gold microelectrodes using a suitable mask.
    In another possible application of the microcontact and its method of obtaining the invention there is its application to repair two simple microcircuits such as those shown in Figure 4. Figure 4a shows a GPC sheet (region enclosed in the circle) contacted by two Au / Cr microelectrodes manufactured using an evaporation mask. The corresponding electrical characterization is shown in Figure 4d (dashed dashed line). To demonstrate the capabilities of the procedure, the microcircuit's upper microelectrode has been scratched using a tungsten carbide tip removing part of the metal (Figure 4b). The microcircuit was repaired by a GPC sheet that covers the damaged part. The electrical resistance of the repaired circuit is 410 Q, less than twice the initial circuit (dashed dashed line in Figure 4d). Figure 4e shows a second circuit in which a nanocint of GPC (region marked by the calculation) has been contacted. In this case, the upper part of the microcircuit was cut using an infrared laser and repaired in a similar way to the previous case (see figures 4f and 4g); The electrical resistance of the repaired circuit is 423 Q. As can be seen in Figure 4h, the repair carried out produced a change in the resistance of the circuit; similar to what happened in the previous case of repair.
    权利要求:
    Claims (9)
    [1]
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    1. Procedure for obtaining microcontacts by means of a transfer system comprising:
    • an optical microscope (2) with zoom,
    • an XY translation table (6), and
    • a manipulator (4) XYZ,
    the method of obtaining microcontacts being characterized in that it comprises:
    • placing in the transfer system a sample comprising a substrate (1) which in turn comprises adsorbed at least one element (11) with any of its dimensions in the nanoscale,
    • place a glass sample holder for optical microscopy under the optical microscope (2) where said sample holder has a viscoelastic polymer material (3) at least one of its ends, comprising at least one sheet of an inorganic conductor material (5) electric,
    • align a sheet with a specific region of the sample, a region that comprises at least partially the element (11) with any of its dimensions in the nanoscale,
    • transfer the sheet of inorganic material (5) to the surface of the substrate (1) by applying pressure,
    • remove the pressure so that the sheet of inorganic material (5) is adhered to the surface of the substrate (1) peeling off the surface of the viscoelastic polymer (3), and
    • establish a contact (7) between the sheet of inorganic material (5) and at least one external circuit.
    [2]
    2. Procedure according to revindication 1 characterized in that the inorganic material sheet material (5) is selected from: graphene and gold.
    [3]
    3. Method according to claim 2 characterized in that the sheet of inorganic material (5) is a graphene sheet of a few layers (GPC) and has lateral dimensions greater than 10 pm x 100 pm and a thickness between 3 nm and 40 nm.
    [4]
    4. Method according to claim 1 characterized in that it comprises initially performing a characterization of the sample to determine the region comprising at least one element (11) with some of its dimensions in the nanoscale.
    [5]
    5. Procedure according to claim 5 characterized in that the characterization is performed by atomic force microscopy (AFM) techniques.
    [6]
    6. Procedure according to claim 1 characterized in that the contact (7) is carried out by means of silver paint.
    [7]
    7. Microcontact obtainable by the method described in any one of claims 1 to 6.
    [8]
    8. Use of the microcontact according to claim 7 to contact a characterization system to electrically characterize an element (11) with any of its dimensions in the nanoscale.
    [9]
    9. Use of the microcontact according to claim 7 to perform repairs in microcircuits by reestablishing contact therein.
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    同族专利:
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    ES2557507B1|2016-11-08|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN106430084B|2016-11-18|2017-12-01|北京大学|A kind of single micro nano structure transfer device and its transfer method|
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