• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    System for a microscope of atomic forces. The present invention relates to a system comprising a lever-tip assembly and a magnetic nanopillar located on the tip end of the lever-tip assembly that has been deposited using the focused electron beam-induced deposition technique. Furthermore, the present invention relates to a magnetic force microscope comprising said system and to the use of said system or microscope for carrying out simultaneous topographic and magnetic studies and/or manipulation of samples of micro and nanometric size in liquid medium, preferably from biological samples. Therefore, the present invention is encompassed in the area of nanotechnology, specifically in the area of the manufacture of devices for the characterization of samples of micro and nanometric size. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2711860A1
    申请号:ES201731292
    申请日:2017-11-03
    公开日:2019-05-07
    发明作者:Ruíz-Castellanos Miriam Jaafar；Teresa Nogueras Jose María De；Barahona Agustina Asenjo；Navarro Javier Pablo；García Pablo Ares；Dominguez Cesar Magen；Herrero Julio Gomez
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；Universidad Autonoma de Madrid；Universidad de Zaragoza；Fundacion Agencia Aragonesa para la Investigacion y el Desarrollo ARAID；
    IPC主号:
    专利说明:

    [0001]
    [0002]
    [0003]
    [0004] The present invention relates to a system comprising a set lever tip and a magnetic nanopilar located on the tip end of the lever-tip assembly that has been deposited by the technique of deposition induced by focused electron beam. Furthermore, the present invention relates to a microscope of magnetic forces comprising said system and to the use of said system or microscope for the realization of simultaneous topographic and magnetic studies and / or manipulation of samples of micro and nanometer size in liquid medium, preferably of biological samples.
    [0005]
    [0006] Therefore, the present invention is encompassed in the area of nanotechnology, specifically in the area of the manufacture of devices for the characterization of samples of micro and nanometer size.
    [0007]
    [0008] BACKGROUND OF THE INVENTION
    [0009]
    [0010] The atomic force microscope (atomic force microscope AFM) is one of the most versatile tools for the topographical study and manipulation of samples of micro and nanometer size. One of the great advantages of this technique is its ability to study different properties simultaneously, so! as the fact of working in different work environments: from ultra high vacuum conditions (in English ultra high vacuum UHV), to studying systems that are immersed in liquid medium and usual atmospheric conditions.
    [0011]
    [0012] The operation of the AFM is based on the interaction of a sharp point with the surface of the sample or system to be studied. Said tip comprises a base joined to the lever by one of its faces whose end, which is the element of the tip farthest from the base, acts as a probe of the microscope. The tip may have different geometries (pyramidal, conical, etc.), it being necessary that, to ensure a good spatial resolution, its end is very sharp, that is, it has a small radius of curvature. The tip is located on a microlever that has a fixed and a free end, specifically the tip is located on the free end of the microlever
    [0013]
    [0014] Apart from the control electronics, the essential element that limits the resolution and sensitivity of the system is the tip-lever assembly: on the one hand the size of the apex of the tip that makes the functions of the microscope probe and on the other the mechanical properties of the lever. Different research groups and commercial companies have offered different solutions to improve the resolution and sensitivity.
    [0015]
    [0016] The Magnetic Forces Microscope (MFM) is a variant of the AFM in which both the topography and the magnetic interaction between a tip and a sample are measured. It is necessary to have specific tips for this microscope variant. In the market these tips are similar to those used in AFM but it includes a magnetic coating, typically Co. This means that, in general, the lateral resolution of the MFM is worse than that of the AFM since it is highly conditioned by the geometry of said tips. , in particular, by the radius of curvature of the end, which increases with the coatings. In addition, the sensitivity is determined by the parameters of the lever on which the tip is located. In the specific case of the MFM there is also another important parameter, the magnetic leakage field created by the MFM tips. (See Figure 1)
    [0017]
    [0018] The MFM operates in dynamic modes, in which the sensitivity is proportional to the value of the quality factor Q of the lever resonance. With respect to the use of said microscope in liquid medium, there is an additional associated disadvantage: the decrease of said quality factor Q of the resonance of the lever due to the higher density of the medium. This makes the signal / noise ratio much worse than in the air measurements for the same lever.
    [0019]
    [0020] In the literature we can find several works where the MFM tips are modified to, for example, decrease the magnetic material of the probe; we can find the use of nanoelements located at the end of a commercial tip such as carbon nanotubes coated with magnetic material, magnetic nanowires or magnets of nanometer size. It is also common to find works aimed at the use of different coating mechanisms to optimize the MFM response or the manipulation of the final domain at the tip. These modifications have not resulted in an improvement for the use of the MFM technique in liquid medium.
    [0021]
    [0022] Therefore, it is necessary to develop new tip-lever systems to be used in MFM that serve to carry out measurements of micro and nanometer sized samples in liquid medium, including measurements of biological samples.
    [0023]
    [0024] DESCRIPTION OF THE INVENTION
    [0025]
    [0026] The present invention relates to a system comprising a set lever tip (or cantilever-tip) and a magnetic nanopilar located on the end of the tip of the lever-tip assembly that has been deposited by the technique of deposition induced by electron beam focused
    [0027]
    [0028] Said system is suitable to carry out simultaneous topographic, magnetic and / or manipulation studies of samples of micro and nanometric size by microscopy of magnetic forces in liquid medium; since stable signals are obtained with little noise.
    [0029]
    [0030] The term "samples of micro and nanometric size" encompasses both isolated biological samples and nanomaterials such as nanoparticles or nanowires that can be used in applications such as contrast enhancement in nuclear magnetic resonance, hyperthermia in cancer treatments and administration. of drugs.
    [0031]
    [0032] The term "biological sample" includes, but is not limited to, cells, tissues and / or biological fluids of an organism, obtained by any method known to one skilled in the art and comprising proteins, viruses, bacteria, cells, nucleic acids or capsids. vincas that comprise magnetic material inside. The biological sample can be a tissue, for example, a biopsy or a fine needle aspiration, or it can be a sample of fluid, such as blood, plasma, serum, urine, tears, sweat, cerebrospinal fluid, aqueous humor, vitreous humor, etc.
    [0033]
    [0034] The term "isolated biological sample" refers in the present invention to those proteins, viruses, bacteria, cells, nucleic acids or vinyl capsids that They comprise magnetic material inside.
    [0035]
    [0036] In the present invention, "liquid medium" is understood as that medium whose state of aggregation is liquid.The definition encompasses fluids such as buffer solutions, culture media and isolated biological samples and organic-inorganic hybrid solutions that help to stabilize the sample and make it viable for its study by force microscopy techniques in liquid medium.
    [0037]
    [0038] "Culture medium" means any solution comprising nutrients necessary for division and / or differentiation, or for the recovery or isolation of cells in culture. Said cultivation is carried out under favorable conditions of temperature and pH. The culture medium is selected, but not limited, from the list comprising DMEM (Dulbecco's Modified Eagle's Medium), RPMI 1640, F12, F10, MCDB 131, MEM (Minimum Essential Media) or DMEM / F12. In addition, the culture medium can be supplemented with other components, such as, but not limited to, CO2, O2, serum or serum substitute, amino acids, antibiotics, etc. However, any culture medium known in the state of the art for cell culture can be used. For growth, division and / or differentiation, etc. of the cells in culture may be necessary periodic renewal of said medium, or the addition of new culture medium, or the recovery of part of the medium in which the cells are located.
    [0039]
    [0040] The lever-tip assembly of the present invention has essential characteristics such as a stiffness determined by the force constant and the resonance frequency, and a geometry for the well defined assembly, so that, together with the magnetic nanopilar, they allow the obtaining of high resolution images of micro and nanometer sized samples in liquid medium, particularly of biological samples.
    [0041]
    [0042] Furthermore, the present invention relates to a microscope of magnetic forces comprising the system described above and to the use of the system or microscope for the realization of simultaneous topographic and magnetic studies or manipulation of micro and nanometer sized samples in liquid medium, preferably of biological samples.
    [0043] In a first aspect, the present invention refers to a system for simultaneous topographic, magnetic and / or manipulation studies of samples of micro and nanometric size by force microscopy in liquid medium, characterized in that it comprises:
    [0044] - a lever-tip assembly comprising
    [0045] - a lever or cantilever with a first face and a second face, where at least the second face reflects the laser wavelength of the magnetic forces microscope and where said lever has a resonance frequency in air of between 75 kHz and 145 kHz , a force constant with a value between 0.02 Nm-1 and 0.14 Nm-1, a thickness less than 0.3 pm, a length between 30 pm and 40 pm and a width between 10 pm and 20 pm; Y
    [0046] - a tip comprising a base attached to the lever by a first face and an end which is the tip element farthest from the base with a radius of curvature of less than 25 nm, preferably between 6 nm and 10 nm, and a distance between the base of the tip and the free end of the lever between 6 pm and 8 pm;
    [0047] where the minimum distance from the free end of the lever to the base of the tip is between 1 pm and 2 pm;
    [0048] - and a magnetic nanopilar with a diameter between 40 nm and 90 nm and a length between 0.3 pm and 1.7 pm;
    [0049] where the nano-pillar is placed on the tip end of the lever-tip assembly.
    [0050]
    [0051] The lever-tip or cantilever-tip assembly comprises a lever or soft cantilever, characterized by having a resonance frequency in air between 75 kHz and 145 kHz, a force constant with a value between 0.02 Nm-1 and 0, 14 Nm-1, and a geometry defined by a thickness less than 0.3 pm, a length between 30 pm and 40 pm and a width between 10 pm and 20 pm.
    [0052]
    [0053] As mentioned in the state of the art, the geometry of the lever or cantilever is not limiting, although it is preferably rectangular or triangular.
    [0054]
    [0055] In a preferred embodiment of the system of the present invention, the lever of the lever-tip assembly has a thickness of less than 0.3 μm.
    [0056]
    [0057] The lever should reflect the laser wavelength of the force microscope magnetic particles on at least one of their faces, specifically on the face opposite the tip, that is, the second face. Therefore, said second face is typically covered by a metal such as Au, Pt, Cr or Al. In the present invention said face is called the first face. In a preferred embodiment of the system of the present invention, the lever is covered by a conductive coating on both sides, by the first and the second face, which allows to avoid the problems of load when manufacturing the pillars.
    [0058]
    [0059] The end of the tip must have a suitable radius of curvature in order to be able to support the nanopillars on the tip without losing stability and being completely adhered to the end of the tip.
    [0060]
    [0061] The tip of the lever-tip or cantilever-tip assembly of the present invention comprises a base attached to the lever by the first face and an end which is the tip element furthest from the base. The base of the tip can have different geometries, it can be a circle, a triangle, a square, etc.
    [0062]
    [0063] The magnetic nanopilar is located on the tip end of the tip or cantilever-tip assembly and has a diameter between 40 nm and 90 nm and a length between 0.3 pm and 1.7 pm. That is, the optimal aspect ratio (length / diameter) varies between 7 and 28.
    [0064]
    [0065] A common material used in the manufacture of levers or projections and tips for AFM and MFM is a silicon monocrystal or a highly doped silicon monocrystal. Silicon nitride is also commonly used to manufacture levers or cantilevers.
    [0066]
    [0067] It is a magnetic nanopilar since it acts as a probe in a microscope of magnetic forces. In a preferred embodiment of the system of the present invention, the magnetic nanopilar contains cobalt (Co) or iron (Fe); the Fe has a magnetic moment greater than the Co so that the nanopillars of Fe have a higher magnetization value than those of the Co. In addition, preferably the system of the present invention has a content of Co or Fe in the nanopilar greater than 80. % in atomic percentage which guarantees an adequate magnetic signal. The metal part of the deposit is what gives the nanopilar its magnetic properties, so a high percentage of Co or Fe ensures a good functioning of the system.
    [0068] In another preferred embodiment of the present invention and in order to avoid possible oxidations of the nanopilares, said nanopilares are preferably coated with Pt-C because their growth rate by means of the technique of deposition induced by focused electron beam is very high, which makes it suitable for this coating process.
    [0069]
    [0070] A second aspect of the present invention relates to the manufacturing process of the system described above, characterized in that it comprises a step (a) of depositing the nanopilar on the end of the tip of the lever assembly by means of the technique of deposition induced by electron beam Focused (from the English Focused Electron Beam Induced Deposition, FEBID).
    [0071]
    [0072] By means of a gas injector (GIS), a precursor gas is introduced around the end of the tip, such as Co2 (CO) 8 or Fe2 (CO) 9 for the Co or Fe nanopilies, respectively. decomposes to form a nanopile when it interacts with an electron beam. The use of the precursor gas Co2 (CO) 8 allows the fabrication of Co nanopillars, while the use of the Fe2 (CO) 9 precursor gas allows the fabrication of Fe nanopiles. In both cases, when the electron beam interacts with the precursor gas, this decomposes producing a deposit that forms the nanopilar.
    [0073]
    [0074] The advantage of FEBID is the ability to select the position on the substrate, the length and diameter of the deposit / nanopilar and its composition.
    [0075]
    [0076] Said procedure is a fast, reproducible and reliable alternative for the fabrication of systems suitable for microscopy of magnetic forces that involves the growth of a well-defined geometry in the form of nanometric-sized (diameter and height) pillars manufactured by FEBID.
    [0077]
    [0078] To obtain good quality cobalt nanopillars (nominal external diameter between 60 and 90 nm) it is recommended to use the following conditions:
    [0079] • an interaction volume generated for an acceleration voltage between 3 kV and 5 kV,
    [0080] • a gas dissociation capacity for a current between 50 pA and 100 pA Y
    [0081] • a gas flow supplied with a working pressure 9x10-6 mbar with an error of 10%, the base pressure being 1.4 x 10 "6 mbar.
    [0082]
    [0083] In the case of iron nanopiles (nominal external diameter between 40 nm and 60 nm), the appropriate values are:
    [0084] • an interaction volume generated for an acceleration voltage between 3 kV and 5 kV,
    [0085] • a gas dissociation capacity for a current between 43 pA and 86 pA and • a gas flow supplied with a working pressure of 6 x 10 "6 mbar with an error of 10%, with a base pressure of 1.4 x 10 "6 mbar.
    [0086]
    [0087] On the other hand, the adjustment of the deposition time allows to modulate the length of the nanopillars. Likewise, the importance of an optimal adjustment of the astigmatism and the focus of the electron microscope where nanopiles are grown, key aspects to generate nanowires of precise and convenient dimensions, should be highlighted.
    [0088]
    [0089] Another aspect of the invention relates to a magnetic force microscope characterized in that it comprises the system described above suitable for the realization of simultaneous topographic, magnetic and / or manipulation studies, of micro and nanometer size samples, by microscopy of forces in half liquid.
    [0090]
    [0091] The last aspect of the present invention relates to the use of the system or of the microscope described above for carrying out simultaneous topographic, magnetic and / or manipulation studies of micro and nanometer sized samples in liquid medium; particularly for biological samples. More particularly, where the biological samples are proteins, viruses, bacteria, cells, nucleic acids or viral capsids comprising magnetic material inside them.
    [0092]
    [0093] Another preferred embodiment of the present invention relates to the use of the system or of the microscope described above for carrying out simultaneous topographic, magnetic and / or manipulation studies of nanomaterials such as nanoparticles or nanowires that can be used in applications such as improvement of contrast in nuclear magnetic resonance, hyperthermia in treatments of cancer and drug administration. Specifically for obtaining the magnetic properties of nanomaterials (such as nanoparticles or nanowires) that determine the effectiveness of their application in biomedicine. The properties of the nanomaterials that can be obtained with this system are: the determination of the configuration of domains in different states of remanence, information on the investment process of the magnetization, information on the field of leakage created by the nanostructures and state of aggregation of the nanostructures according to their size, conditions of substrate preparation, functionalization of the material, liquid medium or magnetic field. These properties serve to determine their viability as elements for nuclear magnetic resonance, for hyperthermia combined with mechanical damage in cancer treatments and administration of drugs.
    [0094]
    [0095] Throughout the description and the claims the word "comprises" and its variants do not intend to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will emerge partly from the description and partly from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.
    [0096]
    [0097] BRIEF DESCRIPTION OF THE FIGURES
    [0098]
    [0099] Figure 1. Schematic of the system of a magnetic force microscope.
    [0100]
    [0101] Figure 2. Technical features of Nanoworld Arrow lever-point systems (source: http: //www.nanoworld.com/electrostatic-force-microscopy-afm-tip-arrow-efm). (a) Side View (b) Rear view (c) Front view
    [0102]
    [0103] Figure 3. Technical characteristics of the lever-tip systems Budget Sensors (Data taken from the source: https://www.budgetsensors.com/force_modulation_afm_probes_electri_alignment_groo ves.html).
    [0104] Figure 4. Technical characteristics of Olympus biolever mini lever-tip systems (source: http://probe.olympus-global.com/en/product/bl_ac40ts_c2).
    [0105]
    [0106] Figure 5. Resonance curves of two levers type Biolever mini without pillar (a) and with pillar (b).
    [0107]
    [0108] Figure 6. (a) Image of the lever obtained by SEM (b) Cut made with the ion beam prior to the deposit of the nanopilar.
    [0109]
    [0110] Figure 7. Comparison of topography (d), (e) (f) and magnetic signal (g), (h), (i) obtained in a high density hard disk with different points: (a) (d) and (g) commercial tip of Budget sensors, (b), (e) and (h) punta-nanopilar of Co and (c), (f), (i) puntananopilar de Fe.
    [0111]
    [0112] Figure 8. MFM images of a multilayer CoPt sample grown by sputtering that presents an anisotropic perpendicular. The images have been obtained with commercial tip Budget Sensors (a) and tip with nanopilar of Co (b).
    [0113]
    [0114] Figure 9. Graph of sensitivity to the OOP component (out of plane, of the English outof-plane) and IP (in the plane, of the English in-plane) as a function of the nanopilar section. We call sensitivity to the magnetic contrast measured with the MFM in the different samples under the same conditions. The data correspond to the lever-tip assemblies named from 1 to 7 in table 5. The section of the nanopiles has been evaluated according to their diameter and is represented divided by 1000.
    [0115]
    [0116] Figure 10. Resonance curves of the same lever of Nanosensors PPP-MFMR in three different environments: water, air and high vacuum. Adapted from, P. Ares, M. Jaafar, A. Gil, J. Gomez-Herrero and A. Asenjo, Small 11 (36) 4731-6 (2015)
    [0117]
    [0118] Figure 11. Comparison of the topographic (a), (d) and magnetic (b), (e) images of a standard sample (high density hard disk) acquired with the same tip of the Nanosensors type PPP-MFMR under ambient conditions (upper panel) and in water (lower panel).
    [0119]
    [0120] Figure 12. Comparison of the topographic (a), (d) and magnetic (b), (e) images of a standard sample (high density hard disk) acquired with the same point of the Team Nanotec type of force constant 0 , 7 Nm-1 under ambient conditions (upper panel) and in water (lower panel).
    [0121] Figure 13. Comparison of the topographic images (a), (c), (e) and magnetic (b), (d), (f) of a standard sample (high density hard disk) acquired with the same point of the type Mikro-masch HQ: NSC36 / Co-Cr / Al BS with constant forces around 0.6 Nm-1 under ambient and water conditions.
    [0122]
    [0123] Figure 14. Comparison of the topographic (a), (d) and magnetic (b), (e) images of a standard sample (high density hard disk) acquired with the same tip of the Olympus biolever mini type (force constant) 0.01 Nm-1) with a Fe nanopilar grown at its end under ambient conditions (upper panel) and in water (lower panel). It is observed that the images in both media are of comparable quality having very little noise the MFM signal in liquid.
    [0124]
    [0125] Figure 15. Comparison of the topographic (a) and magnetic (b) images of a standard sample (high density hard disk) acquired with the same tip of the Olympus biolever mini type (force constant of 0.01 Nm-1 ) with a Fe nanopilar grown at its end under ambient conditions after having measured in water and after one year of its manufacture. It is observed that the images are of comparable quality to the original ones, having not lost the magnetic signal in any case.
    [0126]
    [0127] EXAMPLES
    [0128]
    [0129] In the following, the invention will be illustrated by means of tests carried out by the inventors, which highlights the effectiveness of the product of the invention.
    [0130]
    [0131] Figure 1 refers to a system scheme of a magnetic force microscope.
    [0132]
    [0133] Figure 1 (a) comprising a photodiode (1), a laser (2), a lever assembly (3), a piezoelectric (4) shows a topographic non-contact image (5) and a non-contact image of MFM (6).
    [0134]
    [0135] Figure 1 (b) refers to the lever-tip assembly (3) and the nanopilar (14). In said figure 1 (b) the thickness (7), the width (8) and the length (9) of the lever can be seen, thus! as the length of the base of the tip (11), the base-end distance of the tip (12) and the radius of curvature of the tip end (13). In this same figure 1 (b) you can estimate the free end distance of the lever to the base of the tip (10) of the lever-tip assembly (3) of the magnetic force microscope.
    [0136]
    [0137] 1. Growth of nanopillars on commercial tips
    [0138]
    [0139] Growths of cobalt and iron deposits were made in the form of magnetic nanopillars (14) in three dimensions (3D) through FEBID. To carry out this manufacturing process, by means of a gas injector (Gas Injection System, GIS) a precursor gas is introduced in the area of interest that is decomposed by its interaction with an electron beam, thus producing a nanodeposito. In this example, Co2 (CO) 8 is used as the precursor gas for cobalt deposits and Fe2 (CO) 9 for iron deposits.
    [0140]
    [0141] The content of Co or Fe is around 80% in atomic percentage with respect to the total composition of the nanopile. This compositional characterization is carried out by X-ray spectroscopy by dispersive energy (from the English Energydispersive X-ray spectroscopy, EDS). The best signal-to-noise ratios can be achieved with Fe pillars, since diameters of up to 40 nm can be achieved while retaining a high iron content as shown below. Iron also has a greater magnetic moment than cobalt, thus giving rise to deposits with a high magnetization value. These pillars can be easily coated with a Pt-C tank thus preventing oxidation processes.
    [0142]
    [0143] • The growth process has been carried out in three different types of lever-tip systems.
    [0144]
    [0145] to. Lever-Tip System type Nanoworld Arrow EFM
    [0146]
    [0147] The technical data of this type of levers are shown in table 1.
    [0148]
    [0149]
    [0150]
    [0151]
    [0152] Table 1- Data supplied by the manufacturer
    [0153]
    [0154] The material of the lever (and the original tip) is a highly doped Si crystal with a resistivity around 0.01-0.025 Ohmcm to avoid static charges. Said material is chemically inert and perfectly valid for its use in measurements in liquid medium or electrochemical cells; It also offers a high value of the quality factor Q which results in a high sensitivity in the measurements.
    [0155]
    [0156] Figure 2 shows the Nanoworld Arrow lever-tip system.
    [0157]
    [0158] The shape of the lever is rectangular with a triangular termination. In this preferred embodiment of the lever-tip assembly (3) of the magnetic force microscope, the width (8) and the length (9) of the lever can be seen. It is a lever without intrinsic mechanical tension. The position of the tip on the lever at the end of said lever is chosen in such a way as to facilitate positioning in the area of interest; that is, it facilitates the deposition procedure of nanopillars (14).
    [0159]
    [0160] The geometry of the original tip is a tetrahedron with a typical height of 10 - 15 pm. The radius of curvature is less than 25 nm.
    [0161]
    [0162] Both the lever on both sides and the tip have a coating of PtIr 23 nm thick. This coating allows good electrical contact and increases the reflectance of the laser by a factor of 2.
    [0163]
    [0164] b. Lever-Tip System type Budget Sensors ElectriMulti75-G
    [0165]
    [0166] The geometrics of this type of levers are the most common and used in the different modes of the AFM. The technical data of these levers are shown in Table 2 and Figure 3. In this preferred embodiment of the lever-tip assembly (3) of the magnetic force microscope, Figure 3 (a) shows the base-end distance of the tip ( 12), the free end distance of the lever to the base of the tip (10) and the radius of the tip: angle of the half-cone (15). In addition, the width (8) and the length (9) of the lever are shown in FIG. 3 (b).
    [0167]
    [0168]
    [0169]
    [0170]
    [0171] Table 2- Data supplied by the manufacturer
    [0172]
    [0173] The material of the lever (and the original tip) is a Si monocrystal. The entire lever-tip assembly has an electrical conductor coating of a layer composed of 5 nm Cr and 25 nm Pt. This coating improves the reflectivity of the laser.
    [0174]
    [0175] c. Lever-Tip System type Olympus biolever mini
    [0176]
    [0177] The technical data of these non-magnetic levers are shown in Table 3 and Figure 4. In the side view of this preferred embodiment of the lever-tip assembly of the magnetic force microscope, the effective length of the tip (16), the distance base-end of the tip (12), the length of the lever (9), the end of the lever (17) and the free end distance of the lever to the base of the tip (10).
    [0178]
    [0179]
    [0180]
    [0181] Table 3- Data supplied by the manufacturer
    [0182] The lever material is silicon nitride while the original tip is silicon. On the side of the tip there is no coating while on the opposite side is coated by an Au layer to improve the reflectivity of the laser. To avoid loading problems during the fabrication of the nanopillars the lever is covered with carbon tapes (on both sides).
    [0183]
    [0184] The characteristics of this lever-tip system that make them optimal for working in liquid medium are their high values of resonance frequency in both air and water together with the low value of the force constant (around 0.1 Nm-1). ). For this reason, the sensitivity / noise ratio in these levers (as already mentioned in previous documents) is the one necessary to obtain images with similar qualities in air and water. As we already highlighted, there is no magnetic commercial probe that meets these conditions.
    [0185]
    [0186] Another additional advantage is that said lever-tip system allows us to work with high scanning speeds (ie, short data acquisition times). Likewise, the material from which the levers are made (silicon nitride) makes it compatible with simultaneous fluorescence measurements. As can be seen in Figure 5, the fact of growing the magnetic pillar in this type of levers does not affect in any way its mechanical properties as shown in the two resonance curves presented (a) and (b) ). With the rest of the levers presented the same thing happens.
    [0187]
    [0188] Optimum parameters for the deposition process of the nanopillars
    [0189]
    [0190] In order to guarantee the success in the form and composition of the nanopillars, numerous tests were carried out in function of the various existing growth parameters. Thus, for example, the appropriate value of the acceleration voltage, of the electron current or of the gas flow was determined to obtain nanopillars of an adequate diameter and purity.
    [0191]
    [0192] For cobalt deposits, it was estimated that the volume of interaction generated by a voltage of 5 kV, the dissociation capacity of the gas for a current of 86 pA and the flow of gas supplied with a working pressure of around 10 "5 mbar (base pressure of 1.4 x 10" 6 mbar) produces good quality nanopillars.
    [0193]
    [0194] In the case of iron deposits, the ideal values were 3 kV for the acceleration voltage, 43 pA for the electron current and 6 x 10 "6 mbar for the working pressure (base pressure of 1.4 x 10 "6 mbar).
    [0195]
    [0196] On the other hand, the adjustment of the deposition time allows to modulate the length of the nanopillars. Likewise, the importance of an optimal fit of the astigmatism and the focus of the electron microscope where the nanopillars are grown, key aspects to generate nanopillars of precise and convenient dimensions, should be highlighted.
    [0197]
    [0198] In general, FEBID deposits are commonly made on flat substrates where the diffusion of the precursor gas molecules is optimal. However, the tips lack said flat surface, so depending on the material a cut at the tip end is necessary by means of an ion beam (Focused Ion Beam, FIB). This process can be carried out quickly in the interior of the Dual Beam using a focused ion beam that eliminates the material it affects by means of a roughing process (in English milling).
    [0199]
    [0200] Figure 6 shows (a) an image of the lever-tip system obtained by scanning electron microscopy (SEM) and (b) Cutting done with the ion beam prior to the deposit of the nanopilar.
    [0201]
    [0202] Next, table 4 details the optimal parameters that have been found for cobalt and iron deposits.
    [0203]
    [0204]
    [0205]
    [0206] Table 4. Parameters associated with cobalt and iron deposits.
    [0207] Next, table 5 shows the dimensions of several nanopiles grown on the different types of tips used.
    [0208]
    [0209]
    [0210]
    [0211]
    [0212] Table 5. Dimensions of the resulting nanopiles.
    [0213]
    [0214] Characterization of a high density hard disk and multi-layer sample of CoPt by MFM on air
    [0215]
    [0216] The tips functionalized with nanopillars 1 to 11 have been used to characterize standard samples such as high density hard disks. Figure 7 shows the comparison of magnetic signal between the contrast obtained in a high density hard disk with a commercial tip (BUDGET SENSORS MULTI-M CoCr coating ~ 50 nm), a tip-nanopilar Co and a nanopilar tip of Faith.
    [0217]
    [0218] According to these images the contrast and therefore the sensitivity is comparable. In addition, the nanopilar tips present the possibility of modeling the magnetic configuration of them to carry out a quantitative study.
    [0219] From the MFM measurements, qualitative data can be extracted from which tip creates more or less magnetic field vector (in English stray field) evaluating the modifications that the tip creates in a pattern sample consisting of multilayers of CoPt with perpendicular anisotrope. Figure 8 compares two magnetic images obtained with commercial Multi-M Budget Sensors (Figure 8a) and with a tip nanopilar of Co similar to tip n ° 8 of Table 5 (Figure 8b). The structure of domains obtained with the tip-nanopilar of Co allows to see the starting configuration of the sample while the image obtained with the commercial tip is influenced by the high vector of the magnetic field (stray field) of the tip. The image obtained with nanopilar tip has a similar distribution of domains with upward magnetization and downward magnetization as would be expected from a demagnetized state. In the image obtained with a commercial tip, it does not correspond to a demagnetized state because dominions with magnetization parallel to the field of the tip predominate. The distribution of these two types of domains is decompensated as a consequence of the inversion of magnetization in the sample due to the field of escape of the tip.
    [0220]
    [0221] Another advantage of these nano-tip tips is their greater magnetic hardness, which allows working under higher magnetic fields and also prevents the modification of the magnetic properties of the tip due to the field created by the sample. In the case of the commercial tip, on average the coercive field is 35 mT while, in the case of nanopiles, the coercive field varies between 50 mT and 60 mT.
    [0222]
    [0223] From the MFM results shown in Figures 7 and 8 the contrast of the MFM signal can be evaluated. Figure 9 shows a comparative table with the signals of MFM obtained in the two mentioned samples: multilayers of CoPt (with an out-of-plane anisotropy out of plane OOP) and hard disks of high density with anisotropla in the plane ( of English in plane IP). The section of the nanopillars at the end has also been calculated. As we can see in the case of Fe there is a correlation between the IP signal (in the plane) and the section, the greater the section, the greater the sensitivity to the magnetization in the plane. On the contrary, we observed that the sensitivity of the nanopillary of Fe to the magnetization OOP (out of plane) decreases with the section of the same. The behavior of the Co nanopillars is not so easily correlated with the section of them due to the appearance of transverse domains or vortices at the ends of these structures. However, if the coherence is maintained in that the IP and OOP sensitivity of the Co nanopiles is opposite. This allows us to select for each sample to be studied, the composition and geometry of the nanopiles depending on which component of the magnetization we want to measure.
    [0224]
    [0225] Characterization of a high density hard disk by MFM in water
    [0226]
    [0227] to. Use of lever-tip systems without nanopiles in water
    [0228]
    [0229] Commercial magnetic tips have been used from different companies and with different coatings and force constants.
    [0230]
    [0231] - Lever-Tip System type Nanosensors PPP-MFMR
    [0232]
    [0233] These commercial levers have a force constant around 2 Nm-1 and a resonance frequency around 75 kHz (values in air). With this probe model, the magnetic signal detection of a reference sample, as well as magnetic nanoparticles in a liquid medium, is achieved for the first time. Its magnetic coating is an alloy of Co-Cr.
    [0234]
    [0235] -System Lever-Tip type Team Nanotec HR-MFM
    [0236]
    [0237] It is a commercial magnetic probe with a nominal force constant of around 0.7 Nm-1 and resonance frequency of 45 kHz. The magnetic coating is an alloy of Co.
    [0238]
    [0239] - Lever-Tip System Mikro-masch HQ: NSC36 / Co-Cr / Al BS.
    [0240]
    [0241] It is a commercial chip with three rectangular levers with nominal force constants of 0.6 Nm-1, 1 Nm-1 and 2 Nm-1 whose resonance frequencies are: 65 kHz, 60 kHz and 130 kHz respectively. They have a magnetic coating of Co with a small layer of Cr.
    [0242]
    [0243] The most standard commercial probe model was used, from the company Nanosensors . The problem of the resulting images is the low signal-noise ratio. In the middle In the case of the liquid, the quality factor of the leverage oscillation decreases drastically. In Figure 10 we show the resonance curves of the Nanosensors levers mentioned above in three different environments: air, liquid and high vacuum. As we can see, the quality factor goes from a value close to 200 in air to be around 5 in liquid medium.
    [0244]
    [0245] The sensitivity of the MFM signal (change in frequency or phase of the oscillation) depends on the resonance frequency and the quality factor as
    [0246]
    [0247]
    [0248]
    [0249]
    [0250] Where Af is the smallest change in frequency detectable by thermal noise, f0 is the resonance frequency, kBT the thermal energy at a given temperature, B is the bandwidth, k the force constant, Q the quality factor and < z2osc> the mean quadratic value of the oscillation amplitude of the lever. For the type of tips shown in Figure 10 (resonance frequency 75 kHz, force constant 3 Nm-1), considering the same force constant and amplitude, the sensitivity of the lever worsens as it passes from air to water in a factor ~ 4.5.
    [0251]
    [0252]
    [0253]
    [0254] According to the following equation, to improve the sensitivity of the measurement we need a resonance frequency, w0, high and a force constant, k, as low as possible.
    [0255]
    [0256]
    [0257]
    [0258] However, when the force constant decreases, an increase in noise is expected, following the relationship
    [0259]
    [0260]
    [0261]
    [0262]
    [0263] In Figure 11 we show the result of measuring in ambient conditions (air) and medio ilquido (water) with the commercial standard probe where the increase in signal noise is clearly observed when changing media. It is observed that in liquid medium (water) the signals are stable, with similar intensity but more noisy than in air.
    [0264]
    [0265] When the commercial probe for MFM Team Nanotec of constant 0.7 Nm-1 is used, we managed to have stable signal in liquid medium without problems. But as shown in Figure 12 we do not significantly improve the results obtained with the commercial levers of MFM of 3 Nm "1 shown in Figure 12. This is due to the fact that, although we have an improvement in terms of sensitivity (in around a factor of 2) we also worsen the images by noise (approximately the same factor, given the value of their resonance frequency in water) .Therefore, our signal-noise ratio stays approximately the same as in the results already published by The manufacturers of these magnetic probes, it is observed that in medium liquid (water) the signals are stable, with similar intensity but more noisy than in air.
    [0266]
    [0267] When the Mikro-masch probe is used, the manufacturers comment that it is likely that a strong oxidation of the coating will occur and that the probes are not valid for measurements in liquid medium (water) as experimentally shown below. In Figure 13 it can be seen that it is not possible to stabilize the topographic signal in water. After drying and re-measuring in the air, a clear decrease in the magnetic signal and an increase in the radius of the tip can be seen as seen in the topographic signal. These results are compatible with the prediction made by the manufacturers themselves in relation to a coating oxidation. When drying and re-measuring in air, the topographic point worsens its lateral resolution while the magnetic part remains similar in this parameter, but its intensity has drastically reduced.
    [0268]
    [0269] b. Use of lever-tip systems with Co or Fe nanopillars in liquid medium
    [0270]
    [0271] In the present invention, the controlled growth of magnetic nanopillars at the end of the AFM tip / probe (non-magnetic) is chosen using FEBID. A specific probe is chosen to operate in liquid medium such as Olympus biolever mini (whose silicon nitride lever has a resonance frequency in 110 kHz air; force constant 0.09 Nm-1, length 38 μm, width 16 μm and thickness 0.2 μm). On the tetragonal silicon tip, 7 pm high and the final radius of 8 nm, a magnetic nanopilar is grown. These probes ensure a high resonance frequency in liquid (25 kHz), so! as a value in the very low force constant (between 0.02 - 0.14 Nm-1).
    [0272]
    [0273] An important advantage of the deposit of nanopillars will be that we can control the field of leakage of the tip (in English stray field) changing the size of the pillar (length and / or diameter). In particular, high-torque tips can be grown even on the optimal levers for liquid measurements such as the Olympus Lever-Tip Biolever mini system. This fact will not be possible by making complete deposits (sputtering, evaporation, etc.) due to the curvature of these soft levers, confirmed in internal communication by some of the commercial companies.
    [0274]
    [0275] Another advantage of this type of lever-tip systems type Olympus biolever mini is that these systems can be protected from oxidation by growing a small layer of protective material.
    [0276]
    [0277] Finally, when measuring in MFM the fact that the probe is a pillar instead of a pyramid, allows a closer approach to the surface of the samples under study by minimizing the interaction van der Waals. This fact also contributes significantly to the substantial improvement in the MFM signal. Figure 14 shows the calibration measured with this type of probes, showing a clear improvement compared to commercial probes (see previous figures). In fact, it is possible to equalize the quality of the image (the signal / noise ratio) with the measurements in the air.
    [0278]
    [0279] In order to evaluate the stability of the systems of the present invention, it has also been found that the signal does not decrease when drying and re-measuring. It also does not worsen with respect to the typical storage of the probes. Figure 15 shows the measurements of MFM in air after one year of storage and after being used in water.
    权利要求:
    Claims (11)
    [1]
    1. System for simultaneous topographic studies (5), magnetic (6) and / or manipulation of samples of micro and nanometric size by force microscopy in liquid medium, characterized in that it comprises:
    - a lever-tip assembly (3) comprising
    - a lever with a first face and a second face, where at least the second face reflects the wavelength of the laser (2) of the magnetic force microscope and where said lever has a resonance frequency in air of between 75 kHz and 145 kHz, a force constant with a value of between 0.02 Nm-1 and 0.14 Nm-1, a thickness (7) of less than 0.3 μm, a length (9) of between 30 μm and 40 μm and a width (8) of between 10 pm and 20 pm; Y
    - a tip comprising a base joined to the lever by a first face and an end which is the tip element farthest from the base with a radius of curvature (13) of less than 25 nm and a distance between the base of the tip and free end of the lever (10) between 6 pm and 8 pm;
    where the minimum distance from the free end of the lever to the base of the tip (10) is between 1 pm and 2 pm;
    - and a magnetic nanopilar (14) with a diameter between 40 nm and 90 nm and a length between 0.3 pm and 1.7 pm;
    where the nanopilar (14) is located on the tip end of the lever assembly.
    [2]
    The system according to claim 1, characterized in that the first and second face of the lever of the lever-tip assembly (3) reflect the wavelength of the laser (2) of the microscope of magnetic forces.
    [3]
    The system according to claim 1 or 2, characterized in that the magnetic nanopilar (14) contains cobalt or iron.
    [4]
    4. The system according to any of claims 1 to 3, characterized in that the content of cobalt or iron in the nanopilar is greater than 80% in atomic percentage.
    [5]
    The system according to any of claims 1 to 4, characterized in that the radius of curvature of the tip (13) is between 6 nm and 10 nm.
    [6]
    Method of obtaining the system according to any of claims 1 to 5, characterized in that it comprises a step (a) of depositing the nanopilar (14) on the tip end of the lever-tip assembly (3) by the technique of Induced deposition by focused electron beam.
    [7]
    7. Microscope of magnetic forces characterized by comprising a photodiode (1), a laser (2), a piezoelectric (4) shows a topographic non-contact image (5), a non-contact image of MFM (6) , and the system according to any of claims 1 to 5.
    [8]
    8. Use of the system according to any of claims 1 to 5 or of the microscope according to claim 7 for the realization of topographic (5) and magnetic (6) and / or manipulation studies of samples of micro and nanometer size in liquid medium.
    [9]
    9. Use of the system according to claim 8, wherein the samples are biological samples.
    [10]
    10. Use according to any of claims 8 or 9, wherein the biological samples are proteins, viruses, bacteria, cells, nucleic acids or viral capsids comprising magnetic material therein.
    [11]
    11. Use according to claim 8, wherein the samples are nanomaterials such as nanoparticles, nanowires that can be used in applications such as contrast enhancement in nuclear magnetic resonance, hyperthermia in cancer treatments or drug administration.
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    同族专利:
    公开号 | 公开日
    WO2019086745A3|2019-06-20|
    ES2711860B2|2020-06-15|
    WO2019086745A2|2019-05-09|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP0759537A2|1995-08-18|1997-02-26|Ronald C. Gamble|A scanning force microscope with optical device|
    US5874669A|1997-10-16|1999-02-23|Raymax Technology, Inc.|Scanning force microscope with removable probe illuminator assembly|
    US20070114400A1|2003-04-25|2007-05-24|National Institute Of Information And Communications Technology, Incorporated|Probe|
    JP2006292739A|2005-03-18|2006-10-26|Univ Of North Carolina At Chapel Hill|Method and system for sticking magnetic nano wire to object, and device formed therefrom|
    WO2007077842A1|2005-12-28|2007-07-12|Japan Science And Technology Agency|Nano probe and fabrication method thereof|
    US20070014148A1|2004-05-10|2007-01-18|The University Of North Carolina At Chapel Hill|Methods and systems for attaching a magnetic nanowire to an object and apparatuses formed therefrom|CN112960644A|2021-02-03|2021-06-15|中国科学院长春光学精密机械与物理研究所|Controllable growth method of electron beam induced carbon-based nano structure based on needle point enhancement|
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    PCT/ES2018/070709| WO2019086745A2|2017-11-03|2018-11-05|System for an atomic force microscope|
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