EP1938335A1

EP1938335A1 - Reading/writing tip, head and device, and use thereof, and method for making same

Info

Publication number: EP1938335A1
Application number: EP06820155A
Authority: EP
Inventors: Jacques Gierak; David Martrou
Original assignee: Centre National de la Recherche Scientifique CNRS
Current assignee: Centre National de la Recherche Scientifique CNRS
Priority date: 2005-10-21
Filing date: 2006-10-05
Publication date: 2008-07-02
Also published as: FR2892560B1; WO2007045739A1; US8040784B2; FR2892560A1; US20080253020A1; JP5139309B2; JP2009512847A

Abstract

The invention concerns a reading/writing tip configured in the shape of a needle consisting of a core (3) of refractory material covered with a coating (9) of electrically conductive material, and having an outer microscope needle geometry by tunnel effect, to obtain an information concerning a surface (17a) through tunnel-effect microscopy. The needle (2) emits a charged particle from the layer (9) of electrically conductive material, to form the surface. The tip comprises a reservoir (11) capable of being liquefied to flow along the tip.

Description

TIP, HEAD, AND DEVICE FOR READING / WRITING, AND ITS USE, AND METHOD FOR MANUFACTURING SUCH A DEVICE

The present invention relates to tips and heads of read / write devices, read / write devices, and methods of making such devices.

The article "An improved gallium liquid metal ion source geometry for nanotechnology", Van Es et al., Microelectronic Engineering 73-74, (2004); 132-138 describes an example of a source of liquid metal ions. Such a source generally comprises a tip configured in the form of a needle formed of a core of a refractory material (in this article, tungsten) partially covered with a layer of electrically conductive material (in this article, gallium ), said needle having a connection portion to an electric generator for applying an electric potential to the needle, said needle being adapted to be placed in an electrostatic optical system itself in vis-à-vis an electrically conductive substrate having a surface, said needle being adapted to emit a charged particle, of a first polarity, from the layer of electrically conductive material, towards the surface of the substrate under the effect of a difference in electric potential applied by the electrical generator between the substrate and the needle, to form said surface of the substrate, said tip compresses further comprising a reservoir comprising a reserve of the electrically conductive material forming said layer, said reservoir being in fluid communication with said layer, and a heat transfer device adapted to be connected to a heat generator (in this article, the electric generator) and to liquefy the electrically conductive material contained in the reservoir to flow along the tip under the action of the heat generator.

The needle used in such processes is generally of coarse geometry (of the order of 0.4 millimeter in diameter). It makes it possible to generate an ion beam and / or to deposit clusters of material of size of the order of ten or one hundred nanometers on the substrate. The departure of material from the tip on the substrate leads to erosion which is compensated by the flow of material from the reservoir, which material is kept fluid by the heat transfer device.

Furthermore, it is known from the article "Atom-probe field-ion microscopy of high intensity gallium ion source" of Culbertson et al. , a tip of the type described above, wherein the ion emission is carried out at a temperature below the melting temperature of the material to be deposited. It is thus possible to implement ion emission from solid-phase metals. For such peaks, near-atomic accuracy of substrate surface formation can be achieved. However, the autonomy of such sources remains relatively limited, because of the solid nature of the material to be evaporated when it is present on the needle. This solid character prevents the flow of material to the active site of the needle. Therefore, a tank is not used for this type of tip.

In addition, Binnig and Rohrer have presented, for example, in Scanning Tunneling Microscopy from Birth to Adolescence, Review of Modem Physics, Vol. 59, No. 3, Part 1, July 1987, tunneling electron microscopes which include a tip connected to a generator adapted to generate a potential difference between the tip and substrate, to snatch an electron at the tip. Such microscopes can determine information on the surface of the substrate from the measured current flowing between the tip and the substrate.

Each of these functions, however, is implemented today by a separate device.

The invention relates mainly to a read / write tip configured in the form of a needle formed of a core of a refractory material at least partially covered by a layer of electrically conductive material, said needle having a portion of connection to an electric generator for applying an electric potential to the needle, said needle being adapted to be placed in an operating position in the vicinity of an electrically conductive substrate having a surface, said needle having an external geometry of a microscope needle by tunnel effect, and being adapted to be connected, in a reading mode, to a detection system for obtaining information relating to said surface by tunneling microscopy under the effect of a first electric potential difference applied by the electric generator between the substrate and the needle, and said needle being adapted to transmit, in a write mode, a charged particle of a first polarity from the layer of electrically conductive material towards the surface of the substrate under the effect of a second applied electrical potential difference by the electrical generator between the substrate and the needle, of opposite sign to the first potential difference, for forming said surface of the substrate, said tip further comprising a reservoir comprising a reserve of the electrically material conductor forming said layer, said reservoir being in fluid communication with said layer, and a heat transfer device adapted to, when activated, liquefying the electrically conductive material contained in the reservoir to flow along the point. The material flows by capillarity along the tip.

Thanks to these arrangements, the same tip can be used both as the tip of a tunneling microscope, to implement a read operation of characteristics of the surface of the substrate, and as a writing tip, to form the surface of the substrate, as a source of liquid or solid metal ions. Such a tip has the advantage of being able to easily alternate the steps of writing and reading, which is interesting in practice to be able to easily locate the place where the writing is to be done without having to use an external microscopy system .

To switch from a read function to a write function, simply reverse the potential difference applied between the tip and the substrate.

When writing in liquid metal ion emission mode, the fluidity of the metal covering the core makes it possible to maintain a geometry of the tip which will always be suitable for a subsequent reading.

After writing in solid metal ion emission mode (at lower temperature), a local erosion phenomenon can be obtained at the tip. By the heat transfer device, it is possible to implement a regeneration operation of the tip to make it recover its initial geometry, suitable for the reading mode.

Therefore, the invention proposes a tip adapted to implement three functions that were previously implemented each by means independent.

In preferred embodiments of the invention, one or more of the following arrangements may also be used: the needle has a pointed end adapted to be placed facing said surface, said pointed end having a radius of curvature substantially between 0.1 and 2 micrometers (μm); the core has a tapered body of diameter between 0.1 and 0.4 millimeters (mm) extending through a tapered end of decreasing diameter as the distance to the body increases; the core is made of a material having a substantially higher melting temperature than the electrically conductive material of the layer, said heat transfer device being adapted, when activated, to bring the needle and the reservoir to a temperature between the melting temperatures of the electrically conductive material and the core material; the core is made of a columnar material having a longitudinal micro-channel shaped roughness adapted to allow both the flow of liquefied electrically conductive material along the core at said temperature between the melting temperatures of the electrically conductive material and core material, and retention of the electrically conductive material on the core by capillarity; the reservoir comprises a bubble of the electrically conductive material surrounding the needle in fluid communication with the layer, and the heat transfer device comprises a filament comprising: at least one turn surrounding the needle and embedded in the reservoir of electrically conductive material, and a connection portion to a generator electrical connector adapted to circulate in the filament electrical power adapted to liquefy the electrically conductive material of the reservoir by Joule type effect; said charged particle of a first polarity is a cation.

According to another aspect, the invention relates to a read / write device head comprising a support carrying at least one such point, the support comprising a first connection zone electrically connected to said connection portion of the needle, and adapted to be connected to an electric generator for applying an electric potential to the needle.

According to another aspect, the invention relates to a read / write device head comprising a plurality of supports each carrying such a tip, each support comprising a first connection zone electrically connected to the connection portion of the respective needle. , and adapted to be connected to an electric generator for the application of an independent electric potential to each needle.

According to another aspect, the invention relates to a read / write device comprising: such a read / write device head, a sample holder adapted to receive a substrate comprising a surface portion opposite each tip, a displacement system adapted to generate a relative displacement of the surface and points, an electrical generator connected to the connection portion of each tip for applying a first independent electrical potential difference between the point considered and the surface portion opposite, and a second difference of independent electric potential between the considered tip and the facing surface portion, the second electrical potential difference being of opposite sign to the first electrical potential difference for the tip in question, said electric generator being electrically connected to the heat transfer device to activate it. this.

In a preferred embodiment, provision may furthermore be made for such a device to comprise a detection system electrically connected to the needle and adapted to obtain information relating to said surface by tunneling microscopy under the effect of said first electric potential difference.

According to another aspect, the invention relates to a writing method in which

(a) placing in such an operating position in the vicinity of an electrically conductive substrate having a surface such a reading / writing tip,

(b) an electrical generator applies a second electrical potential difference between the substrate and the needle, of opposite sign to the first potential difference, said needle emitting a charged particle of said first polarity from the layer of electrically conductive material, in direction of the surface of the substrate to form said surface of the substrate.

In some embodiments, one and / or the other of the following provisions may also be provided: during step (b) the surface is formed by depositing on the surface a particle of electrically conductive metal wrenched from the layer of the tip under the effect of said second potential difference; during step (b), the heat transfer device maintains the solid state of the electrically conductive material contained in the reservoir and the along the tip; during step (b) the surface is formed by etching the surface by impact of an electrically conductive metal particle torn off from the tip layer, under the effect of said second potential difference; during step (b), the heat transfer device maintains in the liquid state the electrically conductive material contained in the reservoir and along the tip; the electric generator applies to the heat transfer device sufficient electrical power to maintain in the liquid state the electrically conductive material of the reservoir and the layer; during step (a), a plurality of such read / write tips are placed in the operating position in the vicinity of an electrically conductive substrate having a surface, each being connected to an electrical generator for application an independent electric potential for each needle, and the step (b) is implemented independently for each needle; between two successive steps (b), a relative movement is applied to the substrate and to at least one point.

According to another aspect, the invention relates to a method of regenerating such a read / write tip, in which a step (c) is implemented in which the heat transfer device liquefies the material electrically. conduct contained in the tank, and flows it along the tip.

According to another aspect, the invention relates to a reading method in which

(d) place in an operating position at adjacent an electrically conductive substrate having a surface such a tip,

(e) an electric generator applies between the substrate and the needle a first electrical potential difference,

(f) a detection system connected to said needle obtains information relating to said surface by tunneling microscopy under the effect of said first electric potential difference.

In one embodiment, provision can further be made for applying a movement relative to the tip and the substrate, and steps (d), (e), and (f) are repeated.

According to another aspect, the invention relates to a surface treatment method in which at least one such reading method is implemented successively with the same point and a method chosen from among such a writing method and such a method. regeneration.

According to another aspect, the invention relates to a computer program comprising portions of program code for executing the steps of such a method when said program is executed on a computer.

According to another aspect, the invention relates to a method of manufacturing a read / write tip in which:

(z) forming a core of a refractory material,

(y) the core is at least partially covered with a layer of electrically conductive material, to form a needle a connection portion to an electric generator for applying an electric potential to the needle, being defined in said needle said needle being adapted to be placed in an operating position in the vicinity of an electrically conductive substrate having a surface,

(x) the needle is given the external geometry of a tunneling microscope needle, said needle being adapted to be connected in a read mode to a detection system for obtaining a surface-related information by tunneling microscopy under the effect of a first electric potential difference applied by the electric generator between the substrate and the needle, and said needle being adapted to emit, in a writing mode, a particle charged with a first polarity from the layer of electrically conductive material, in direction of the surface of the substrate under the effect of a second electric potential difference applied by the electric generator between the substrate and the needle, of sign opposite to the first potential difference, for forming said surface of the substrate,

(w) placing in a fluid communication with said layer a reservoir comprising a reserve of the electrically conductive material forming said layer, and (v) binding to said needle a heat transfer device adapted to, when activated, liquefying the electrically conductive material contained in the reservoir and for flowing along the tip.

In certain embodiments, it is furthermore possible to implement one and / or the other of the following provisions: during step (z):

(zl) the core is etched by chemical etching, to increase the capillarity of the core to the electrically conductive material by forming longitudinal micro-channels therein, steps (w) and (y) are simultaneously performed by immersing in a bath of electrically conductive material melted the core having a filament having: a connection portion to a generator electrical connector adapted to circulate in the filament electrical power adapted to liquefy the electrically conductive material of the reservoir, and

at least one turn surrounding the needle and embedded in the reservoir of electrically conductive material.

Other features and advantages of the invention will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings.

On the drawings:

FIG. 1 is a partial schematic view of a read / write tip,

FIG. 2 is a schematic perspective view of a read / write head incorporating the tip of FIG. 1;

FIG. 3 is a schematic view of a read / write device incorporating the head of FIG. 2;

FIG. 4 is a block diagram of the read / write device of FIG. 3,

FIGS. 5a, 5b, 5c and 5d are diagrams corresponding to FIG. 4 of the reading / writing device, respectively in liquid metal ion source writing modes, ion source mode writing modes; of solid metal, in read mode, and in regeneration mode,

FIG. 6 is a diagram corresponding to FIG. 3 of a read / write device according to a second embodiment,

FIGS. 7a and 7b are diagrams each representative of a step of manufacturing a read / write tip, and

FIG. 8a represents an example of peak geometry according to two embodiments, taken by scanning electron microscopy, and - Figure 8b shows an enlargement of the end of the first embodiment of Figure 8a.

In the different figures, the same references designate identical or similar elements.

Figure 1 (not to scale for ease of understanding) partially represents a reading / writing tip. This tip 1 is generally in the form of a needle 2 having a substantially cylindrical body 3 extending both in a proximal portion 4 and a medial portion 5 of the tip, and a pointed end 6 extending into a distal portion 7 of the tip in extension of the body 3. The external geometry of the pointed end 6, which extends over a few tenths of a millimeter is that of a tunneling microscope tip. The end radius of curvature of the tip is substantially between 0.1 and 2 micrometers, preferably between 0.3 and 1 micrometer, as measured by scanning microscopy. As such, the outer surface 6a of the pointed end 6 will be given any suitable geometry for the use of the read / write head as a tunneling microscope needle.

The needle 2 comprises a long tapered core 8 of a refractory material, such as for example tungsten and covered with a thin layer 9 of an electrically conductive material, such as for example gold. By way of example, in the embodiment shown, the core 8 is formed of a 0.25 mm diameter tungsten wire covered at least partially, and at least in the distal portion 7, with a film of gold a few microns thick.

In the middle portion 5 of the tip 1 are a few turns 10a, 10b, 10c of an electric filament 10. These turns, three in number in Figure 1, for example, are wound around the axis longitudinal of the needle 2 in the middle portion and are for example made of a tungsten wire of about 0.1 mm in diameter. In the example shown, the turns form a circle with a diameter of about 0.5 mm surrounding a reservoir 11 of the electrically conductive material.

As shown in FIG. 2, the tip 1 which has just been described is mounted on a read / write device head 12 such as, for example, a tunneling microscopy head with an outside diameter of a few millimeters. Such a head 12 comprises for example a central capillary 13 adapted to be connected to an electric generator (not shown in Figure 2) and a plurality of cross members 14a, 14c electrically isolated from each other.

The tip 1, shown in Figure 1, comprising the needle 2 and the filament 10 having a first end 10d and a second end 10e between which the turns 10a, 10b, 10c extend is electrically connected to the head 12, D firstly, the proximal portion 4 of the tip is electrically connected to the central capillary 13 fed from the first cross member 14a. At this point, the first end 10d of the filament 10 is electrically connected to the needle 2 to form a single point of electrical contact. To close the electric heating circuit, the second end 10e of the filament 10 is electrically connected to one of the insulated crosspieces, for example the cross member 14b, for example by crimping, or by spot welding.

As shown in Figure 3, the first and second cross 14a, 14c are connected to an electric generator 15 which will be described in more detail later in relation to Figures 4 and 5a to 5d. The cross member 14c is electrically connected to the capillary 13. The read / write head 12 is placed near a sample holder 16 which carries a substrate 17 having a surface 17a oriented towards the tip 1 and intended to be read or formed by the tip 1. The distance between the tip 1 and the surface 17a is for example of the order of one hundred microns. The electric generator 15 is also electrically connected to the sample holder 16 for the application of a potential difference between the substrate 17 and the tip 1.

A displacement device 18 is adapted to apply a relative movement of the surface 17a and the tip 1 in one, two or three dimensions. Such a displacement device may conventionally be a displacement device of the type used in tunneling microscopy, such as, for example, a device based on piezoelectric elements capable of elongating under the effect of the passage of a current. electric in the material. In the example shown, as represented by the three arrows, X, Y, Z, the sample holder can be moved along the three directions relative to the read / write head which remains fixed. Other alternative embodiments are possible. In particular, the adjustment of the height of the tip 1 relative to the surface 17a of the substrate can be carried out by moving in the Z direction the head 12 relative to the sample holder remaining fixed in this direction, while the "horizontal" movement Along the X or Y directions is carried out at the level of the sample holder 16.

In the example presented, the electric generator 15 comprises firstly a current generator 19 connected to the two crosspieces 14a and 14c for circulating a heating current in the filament 10. The electric generator 15 also comprises a voltage generator 20 adapted to apply a potential difference of a first sign between the tip and the substrate 17, or a potential difference of a second sign opposite the first sign between these two elements.

As such, one could simply provide to reverse the polarization of a single voltage generator. According to a variant, as shown in FIG. 4, it is possible to use two voltage generators 20a, 20b, independent of reversed polarity. A switch 21 makes it possible to control the choice of the generator 20a or the generator 20b, depending on whether it is positioned on the terminals a or b of the switch.

The first voltage generator 20a is adapted to use the write mode read / write device (liquid or solid metal ion source). As such, one can for example use a generator of the type applying to the tip 1 a positive voltage of the order of 0 to 5 kilovolts, the sample holder 16 being connected to ground. The current delivered by the first generator 20a is of the order of 1 to 10 microamps for example.

As a second voltage generator 20b, it can apply a negative voltage of the order of a few volts to the tip 1 while the sample holder 16 is connected to the substrate. A current that can be less than 1 pico ampere, up to about 300 nanoamperes can then flow between the tip and the substrate.

The read / write device just described can be used in write mode as a source of liquid metal ion, as shown in Fig. 5a. By placing the switch 21 on the position a, the first generator 20a applies a positive potential difference of the order of a few kilovolts between the tip 1 and the substrate 17. Simultaneously, the current generator 19 activates the transfer device. heat by circulating in the filament 10 a sufficient current (for example of the order of a few amperes for the geometry presented) to heat, at level of turns, the electrically conductive material at a temperature at least equal to its melting temperature. With the geometry shown, a power of 1.5 W is sufficient to reach a temperature of 1000 ⁰ C at the reservoir. In this mode of operation, in liquid ion emission writing mode, a Taylor cone is formed at the end of the tip, due to the opposite actions of the applied electric field, which tends to pull ions from the tip, and the surface tension of the liquid metal film covering the needle. The potential difference applied between the tip 1 and the substrate 17 forms an ion beam of the electrically conductive metal of the layer 9 by field evaporation. These will form the portion facing the substrate 17. This is for example etched under the impact of the ions in question. Resolution patterns of the order of one hundred nanometers can be formed as well. The erosion due to the extraction of material from the tip 1 is compensated by the flow along the needle of the electrically conductive material of the liquefied tank 11 by the turns of the filament which transfer energy from the current generator 19. The material located at the end of the needle is thus renewed continuously, which makes it possible to have a write mode having a long life. As shown in FIG. 5b, the read / write device can be used in write mode, by emitting a solid metal ion beam 23 by placing switch 21 in position a. In this position, the first voltage generator 20a applies a positive potential difference of a few kilovolts between the tip

I and the substrate 17. In this mode, the current generator emits a current in the filament adapted to heat the electrically conductive material of the reservoir.

II at a temperature below the melting temperature of this material, and typically about melting temperature to activate the surface diffusion phenomenon. In this mode, an ion beam 23 is torn off from an atomically sized site located at the end of the tip 1 towards the substrate 17, to form the surface 17a thereof, to deposit ions of the material therein. in question. The resolution of the patterns thus formed can reach a few nanometers. Such a mode does not have a very long life, because of the solid nature of the layer in this mode, which prevents the flow of material along the needle.

As shown in FIG. 5c, by placing the switch 21 in the position b, the second voltage generator 20b applies a negative potential difference of a few volts between the tip 1 and the substrate 17 for a reading mode operation by microscopy. tunnel effect. Under the effect of this potential difference, a current of the order of the nanoampère for example flows between the tip 1 and the substrate 17, and the tip 1 then operates as a tunneling microscopy tip. A suitable detection device 24 of the type used in tunneling microscopy to derive information relating to the surface 17a of the substrate 17 from the measured current is used to detect this information. Such a detection device being conventional in the field of tunnel microscopy, it will not be described in more detail here. Atomic resolution can be obtained on a Gallium Arsenide substrate, with the system described here.

As shown in Figure 5d, in a regeneration mode, the outer geometry of the end of the needle 2 can be renewed. Indeed, for example following the writing in solid metal ion emission mode, the end of the tip 1 may have been subjected to strong erosion, and it is appropriate to renew the geometry of this end for the subsequent uses of the tip 1. In this mode, without applying a potential difference between the tip 1 and the substrate 17, the electrically conductive material contained in the tank is liquefied by heating applied by the current generator 19, to flow this material along the tip until it returns to its original geometry.

With the aid of the device which has just been described, it is possible, for example, to perform the following surface treatment:

the head 12 is placed opposite the sample holder 16,

in the liquid metal ion-emission writing mode, alignment marks are formed by ion etching, while possibly making a relative horizontal displacement (perpendicular to the direction of the ion emissions) of the tip by relation to the substrate,

when used later, in read mode, the marks previously formed are detected, then the tip is moved relative to the sample 16, to the point where a structure is to be formed in the substrate 16,

in write mode by emission of a solid metal ion beam, the surface of the substrate 17 is formed in the desired manner, then

in regeneration mode, the external geometry of the needle 2 is regenerated for a subsequent reading or writing.

As shown in FIG. 6, many read / write heads 12 (2 shown in FIG. 6) can work in parallel with respect to a single substrate 17 to form the surface of this substrate. The needles of these heads may all have the same electrically conductive material, or drop different. The operating mode of each head 12, as well as its position in the transmission direction Z can be set independently by a central unit 25 according to a pre-established method. The central unit 25 can also control the movement in the two other directions X and Y of the substrate 17. It will be noted that the automation and the systematization of the operations which have just been described can be predefined and controlled by a computer program loaded with memory of the central unit 25. In the device of FIG. 6, as in the device presented above, it is also possible to provide an acceleration device 26 comprising a mask 27 pierced with openings 28, for example a few nanometers in diameter. 2. This acceleration device may also comprise electrodes 29a, 29b on the upper faces (facing the needle 2) and lower faces (facing the substrate 17) brought to polarities adapted to accelerate the beam of light. ions emitted from the needle 2.

As regards the possible applications of the device which has just been described, it is possible, for example, to provide, in biology, for the substrate 17 to be a biological molecule or a cell into which one or several atoms, whose influence on the studied structure is to be evaluated, and that a change in the properties of the studied cell is detected in reading mode following the deposit previously made. With the aid of the device of FIG. 6, it is thus possible to carry out a battery of tests in parallel using very small quantities of reagents.

As an application, nanoscale data storage is provided by storing information on the surface in write mode and accessing them in read mode.

By way of application, provision is also made read mode, to locate the location of a nano electronic component on a substrate, then, in writing mode, to form an electrical structure such as a wire connecting this nano electronic component to an external electronic component, or other, for the power supply of the nano component.

Note that the heating regeneration function can be implemented before each read or write operation to regenerate the external geometry of the tip, if necessary, or to rid the tip, by thermal evaporation, of impurities (by example oxides) that have been deposited on them since its last use.

For the manufacture of such a tip, one can begin by making a wire in a refractory material for forming the core of the needle. For example, a tungsten wire is produced by hot pressing of tungsten powder in an extruder. The outer surface of the wire thus formed is roughened to increase the capillarity of this surface. This roughening may for example be carried out by electrolytic etching of the wire in a soda bath for a few minutes in alternating current. This step makes it possible to form a nano-colon structure in the surface of the core which allows the flow of the molten metal along the surface, and its retention.

The filament is for example made as a tungsten wire having the previously described geometry and is wound around the core, and the assembly can be fixed on the head of the device 12 as shown in Figure 7a. The elongated form of the distal end of the core is obtained by a suitable method, for example by electrochemistry. Then, after having connected the head 12 to the current generator, a heating current is circulated in the filament, in order to purify the core in particular oxides present on the surface of the nucleus. Then, as shown in Figure 7b, there is a crucible 30 containing electrically conductive material which is to be coated core. The material in question, which will be the material deposited in the writing mode, preferably has a melting temperature which is substantially lower than the melting temperature of the refractory material forming the core, so that it is possible to melt only this material while bearing this at a suitable temperature lower than the melting temperature of the core material. Also, for the electrically conductive material in question, it will be possible to choose a material that does not form an alloy with the refractory material of the core. In the example presented, the crucible 30 contains molten gold by circulating a high current, for example of the order of one hundred amperes, in a filament 31 surrounding the crucible 30. By soaking the tip 1 in the molten gold crucible, the gold is deposited by capillarity on the core, to form the layer 9 of electrically conductive material. In addition, the reservoir 11 is formed by capillary action of the gold on the one hand on the core 8 in the median portion and on the other hand on the turns 10a, 10b and 10c of the filament 10.

FIG. 8a represents, on the left, the end of a tungsten core, taken by scanning electron microscopy, at a magnification 44, the scale representing 500 microns, before immersion in a bath of molten gold, for a first embodiment of concave core. On the right, a convex variant.

Figure 8b shows a magnification of the first embodiment at 2774 magnification, the scale being 10 microns. The columnar structures formed in the core in the form of longitudinal micro-channels are distinguishable on this scale, as shown schematically by broken lines on Figure 8b. The liquefied electrically conductive material flows in these channels, which protects it from external contaminations.

Claims

1. A read / write tip configured as a needle (2) formed of a core (3) of a refractory material at least partially covered by a layer (9) of electrically conductive material, said needle having a connection portion (4) to an electric generator (15) for applying an electric potential to the needle, said needle being adapted to be placed in an operating position in the vicinity of an electrically conductive substrate having a surface (17a), said needle having an external tunnel needle microscope needle geometry, and being adapted to be connected, in a reading mode, to a detection system (24) for obtaining information relative to said surface by tunneling microscopy under the effect of a first electric potential difference applied by the electric generator (15) between the substrate and the needle, and said needle being nt adapted to emit, in a writing mode, a charged particle, of a first polarity, from the layer (9) of electrically conductive material, towards the surface (17a) of the substrate under the effect of a second electric potential difference applied by the electrical generator between the substrate and the needle, of opposite sign to the first potential difference, for forming said surface of the substrate, said tip further comprising a reservoir (11) comprising a reserve of the material electrically conductive medium forming said layer, said reservoir being in fluid communication with said layer, and a heat transfer device (10) adapted, when activated, for liquefying the electrically conductive material contained in the tank to flow along the tip.

2. The read / write tip of claim 1 wherein the needle has a pointed end adapted to be placed opposite said surface, said pointed end having a radius of curvature substantially between 0.1 and 2 micrometers (microns). .

A read / write tip according to claim 1 or claim 2, wherein the core (3) comprises a tapered body having a diameter of between 0.1 and 0.4 millimeters (mm) extending at one end (6). tapered in diameter decreasing as the distance to the body increases.

4. Read / write tip according to one of the preceding claims wherein the core (3) is made of a material having a substantially higher melting temperature than the electrically conductive material of the layer, said heat transfer device ( 10) being adapted, when activated, to carry the needle and the reservoir at a temperature between the melting temperatures of the electrically conductive material and the core material.

A read / write tip according to claim 4 wherein the core (3) is made of a columnar material having a longitudinal micro-channel shaped roughness adapted to allow both the flow of liquefied electrically conductive material along the core at said temperature between the melting temperatures of the electrically conductive material and the core material, and the retention of the electrically conductive material on the core by capillarity.

6. Read / write tip according to one of preceding claim wherein the reservoir (11) comprises a bubble of the electrically conductive material surrounding the needle in fluid communication with the layer (9), and wherein the heat transfer device comprises a filament (10) comprising: at least one turn (10a, 10b, 10c) surrounding the needle and embedded in the reservoir of electrically conductive material, and a connecting portion to an electric generator (19) adapted to circulate in the filament electrical power adapted to liquefy the material electrically tank conductor by Joule type effect.

The read / write tip of any one of the preceding claims, wherein said charged particle of a first polarity is a cation.

8. Read / write device head comprising a support (12) carrying at least one tip (1) according to one of the preceding claims, the support comprising a first connection zone (13) electrically connected to said connection portion of the needle (2), and adapted to be connected to an electric generator (15) for applying an electrical potential to the needle.

9. Read / write device head comprising a plurality of supports (12) each carrying a tip (1) according to one of claims 1 to 7, each support comprising a first connection zone electrically connected to the connection portion ( 13) of the respective needle, and adapted to be connected to an electric generator (15) for the application of an independent electric potential to each needle.

10. A read / write device comprising: a read / write device head according to claim 8 or claim 9, a sample holder (16) adapted to receive a substrate having a surface portion (17a) facing each tip, a displacement system (18) adapted to generate a relative displacement of the surface and spikes, an electrical generator (15) connected to the connection portion of each tip for applying a first independent electric potential difference between the considered tip and the facing surface portion, and a second independent electrical potential difference between the considered tip and the facing surface portion, the second electrical potential difference being opposite sign to the first electrical potential difference for the tip considered, said electrical generator being electrically connected to the heat transfer device (10) of the tip considered to activate this one.

11. A read / write device according to claim 10 comprising a detection system (24) electrically connected to the needle and adapted to obtain information relating to said surface by tunneling microscopy under the effect of said first potential difference electric.

12. Writing method in which

(a) placing in a working position in the vicinity of an electrically conductive substrate (17) having a surface a read / write tip (1) according to one of claims 1 to 7,

(b) an electric generator (15) applies a second electrical potential difference between the substrate and the needle, of opposite sign to the first potential difference, said needle emitting a charged particle of said first polarity from the layer of electrically conductive material, towards the surface of the substrate to form said surface of the substrate.

The writing method according to claim 12, wherein during step (b) the surface is formed.

(17a) by depositing on the surface a particle of electrically conductive metal torn from the layer of the tip under the effect of said second potential difference.

A method of writing according to claim 13, wherein in step (b) the heat transfer device (10) maintains the electrically conductive material contained in the reservoir in the solid state and along the from the tip.

15. Writing method according to claim 12 wherein, during step (b) the surface is formed by etching the surface by impact of a particle of electrically conductive metal torn from the layer (9) of the tip under the effect of said second potential difference.

The writing method according to claim 15, wherein during step (b), the heat transfer device (10) maintains in the liquid state the electrically conductive material contained in the reservoir and along from the tip.

The writing method as claimed in claim 16, wherein the electric generator (15) applies to the heat transfer device (10) sufficient electric power to maintain in the liquid state the electrically conductive material of the reservoir and the layer .

18. Writing method according to one of claims 15 to 17, wherein, during step (a), is placed in the operating position in the vicinity of a substrate (17) electrically conductive having a surface a plurality of spikes (1) read / write according to any one of claims 1 to I ₁ each being connected to an electric generator (15) for applying an independent electric potential to each needle, and wherein the step (b) ) is implemented independently for each needle.

19. Writing method according to one of claims 12 to 18, wherein between two steps (b) successive, applies a movement relative to the substrate (17) and has at least one tip (1).

20. A method of regenerating a read / write tip according to one of claims 1 to 7, wherein it implements a step (c) during which the heat transfer device (10) liquefies the material electrically conductive contained in the reservoir, and flows it along the tip.

21. Reading method in which

(d) placing in a position of operation in the vicinity of an electrically conductive substrate having a surface a read / write tip according to one of claims 1 to I ₁

(e) an electric generator applies between the substrate and the needle (2) a first electric potential difference,

(f) a detection system (24) connected to said needle obtains information relating to said surface by tunneling microscopy under the effect of said first electric potential difference.

22. A read method according to claim 21, wherein a relative motion is applied to the tip and the substrate, and steps (d), (e), and (f) are repeated.

23. A surface treatment method in which is carried out successively with the same tip at least one reading method according to one of claims 21 to 22 and a method selected from a write method according to one of claims 12 to 19, and a regeneration method according to claim 20.

A computer program comprising portions of program code for performing the steps of a method according to any of claims 12 to 23 when said program is executed on a computer (25).

25. A method of manufacturing a read / write tip in which:

(z) forming a core (3) of a refractory material,

(y) the core is at least partially covered with a layer (9) of electrically conductive material, to form a needle (2) a connection portion to an electric generator for the application of an electric potential to the needle , being defined in said needle, said needle being adapted to be placed in an operating position in the vicinity of an electrically conductive substrate having a surface,

(x) the needle is given the external geometry of a tunneling microscope needle, said needle (2) being adapted to be connected in a read mode to a detection system (24) for obtaining an information relating to the surface by tunneling microscopy under the effect of a first electric potential difference applied by the electrical generator between the substrate and the needle, and said needle being adapted to emit, in a mode of writing a charged particle of a first polarity from the layer (9) of electrically conductive material, towards the surface of the substrate under the effect of a second difference of electric potential applied by the electric generator between the substrate and the needle, of opposite sign to the first potential difference, for forming said substrate surface,

(w) placing in fluid communication with said a reservoir (11) comprising a reserve of the electrically conductive material forming said layer, and (v) a suitable heat transfer device (10) is connected to said needle, when activated, to liquefy the electrically conductive material contained therein in the tank and to make it flow along the tip.

A method of manufacturing a read / write tip according to claim 25, wherein in step (z):

(zl) the core (3) is roughened by etching to increase the capillarity of the core to the electrically conductive material by forming longitudinal microchannels therein.

27. A method of manufacturing a read / write tip according to one of claims 25 to 26 wherein it implements the steps (w) and (y) simultaneously immersing in a bath of molten electrically conductive material the core (2) having a filament (10) having: a connection portion (10d) to an electric generator adapted to circulate in the filament electrical power adapted to liquefy the electrically conductive material of the reservoir, and at least one turn ( 10a) surrounding the needle and embedded in the reservoir of electrically conductive material.