Method for surface micro- or nano-structuring of a material

Abstract

The invention relates to a method for surface micro- or nano-structuring of a material, characterised in that it comprises an irradiation step (a) consisting in irradiating a localised surface zone of the material with a focused ionic gas beam, the beam being defined by: - a kinetic energy of the ions of between 5 and 30 keV for hydrogen ions, between 10 and 60 keV for helium ions or between 20 and 500 keV for ions having an atomic mass unit of greater than or equal to 12; - a flux set to a value of between 1013 and 1018 ions / cm2 / s; and - a fluence having a value which is derived from a database establishing the link between the nature of the material, the type of ions used and the associated kinetic energy, and the value of the flux in order to obtain surface micro- or nano-structuring of the material, consisting of one or more micro- or nano-structures in the form of sealed hollow blisters.

Description

[0001] DESCRIPTION

[0002] PROCESS FOR MICRO- OR NANO-SURFACE STRUCTURING OF A MATERIAL

[0003] Technical field of the invention

[0004] The invention relates to the field of surface micro- or nano-structuring of a material and more particularly to techniques for obtaining hollow micro- or nanostructures on the surface of a material.

[0005] Technical background

[0006] Lasers can be used to create hollow micro or nanostructures on the surface of a material. Thus, document EP1707531 A1 proposes the use of a focused laser beam to manufacture buried micro-channels. In this case, the method uses the laser-induced deterioration of a resin attached to the surface of the material which will release gas locally to deform the structure by swelling. This technique makes it possible to obtain hollow structures obtained at a minimum depth. For a given material, the positioning in depth, but also the lateral dimensions of the hollow structure obtained are notably linked to the wavelength of the laser.

[0007] It has already been noted that ion implantation of light elements such as hydrogen (H+) and / or helium (He+) combined with thermal annealing (e.g. Smartcut™ process) can produce blisters on the surface of a silicon wafer. This technique allows these blisters to coalesce over large areas in order to cut the wafers very finely. This technique therefore does not provide localized blister control.

[0008] Generally speaking, the methods described above for micro and / or nano structuring the surface of matter do not allow for obtaining hollow structures controlled in terms of depth (or even surface protrusion), position and / or lateral dimensions. These methods can be described as "direct" in the sense that the aim is to obtain the structuring from the material itself.

[0009] Improved control can, however, be achieved by "indirect" methods this time, involving successive and / or alternating steps of deposition, growth, lithography, revelation and stabilization. This may involve using hollow micro- or nano-spheres deposited on the surface of the material, then depositing a thin layer on top, using techniques such as chemical vapor deposition (CVD) or atomic layer deposition (ALD). The positioning, particularly on the surface, and the lateral dimensions of the hollow structure are in fact perfectly controlled, but the material forming the hollow sphere serving as a support for the deposition of the thin layer remains trapped in the structure finally obtained.

[0010] One objective of the invention is to propose a method for micro- or nano-surface structuring of a material.

[0011] Another objective of the invention is to propose a method for surface micro- or nanostructuring of a material making it possible to obtain hollow micro- or nano-structures on the surface of a material.

[0012] Another objective of the invention is to further propose control of the positioning of the or each hollow micro- or nano-structure as well as its dimensions.

[0013] At least one of the aforementioned objectives is achieved by a method of surface micro- or nanostructuring of a material, characterized in that it comprises a step (a) of vacuum irradiation consisting of irradiating a localized surface area of ​​said material with a focused gas ion beam, said beam being defined by:

[0014] - a kinetic energy of the ions between 5 and 30 keV for hydrogen ions, between

[0015] 10 and 60 keV for helium ions or between 20 and 500 keV for ions with an atomic mass unit greater than or equal to 12,

[0016] - a flow fixed at a value between 10 13 and 10 18 ions / cm 2 / s, and

[0017] - a fluence whose value comes from a database linking the nature of said material, the type of ions used and the associated kinetic energy, and the value of the flux to obtain a surface micro- or nano-structuring of the material consisting of one or more micro- or nano-structure(s) in the form of closed hollow blister(s).

[0018] The method according to the invention may comprise at least one of the following additional steps, taken alone or in combination:

[0019] - a step (b) consisting of supplying heat to said localized surface area, concomitantly or subsequently to step (a);

[0020] - during step (a), the surface of the material is scanned with the focused ion beam; - before implementing step (a), a vacuum pre-implantation step consisting of irradiating said localized surface area of ​​the material with types of ions other than those used to implement step (a);

[0021] - during the pre-implantation step, the surface of the material is scanned with the focused ion beam, the scanning carried out during step (a) then being the same as that carried out during the pre-implantation;

[0022] - the focused gas ion beam used to implement step (a) comprises at least two different types of ions so as to carry out simultaneous implantation;

[0023] - the micro- or nano-structured material is chosen from: a crystalline or amorphous material, a lamellar type material such as highly oriented pyrolytic graphite, a thin-layer material such as zinc oxide on silicon;

[0024] - the focused gas ion beam used to carry out step (a) is generated with rare gases, for example argon or helium, or gases capable of reacting chemically with said material, for example hydrogen, nitrogen or oxygen;

[0025] - the flow is set to a value between 10 13 and 5.10 17 ions / cm 2 / s, advantageously between 10 13 and 10 17 ions / cm 2 / s, advantageously between 10 13 and 5.10 16 ions / cm 2 / s, still advantageously between 10 14 and 5.10 16 ions / cm 2 / s ;

[0026] - the material being highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) being generated with helium, with a flux fixed at a value between 10 14 and 6.10 16 ions / cm 2 / s, the fluence is between 10 16 and 10 20 ions / cm 2 , especially between 2.10 16 and 6.10 19 ions / cm 2 ;

[0027] - the material being highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) being generated with oxygen at a kinetic energy of between 20keV and 40keV, with a flux fixed at a value of between 10 13 and 2.5.10 15 ions / cm 2 / s, the fluence is between 10 15 and 5.10 17 ions / cm 2 , especially between 4.10 15 and 1,5.10 17 ions / cm 2 ;

[0028] - the material being highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) being generated with nitrogen at a kinetic energy of 20keV, with a flux fixed at a value between 9.4.10 14 and 1,6.10 15 ions / cm 2 / s, the fluence is between 6.4.10 16 and 10 17 ions / cm 2 ; - the material being highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) being generated with argon at a kinetic energy of 92keV, with a flux fixed at a value between 5, 1.10 14 and 1,16.10 15 ions / cm 2 / s, the fluence is between 2.10 16 and 5.5.10 16 ions / cm 2 , especially between 2,3.10 16 and 5, 1.10 16 ions / cm 2 .

[0029] Brief description of the figures

[0030] Other objects and characteristics of the invention will appear more clearly in the following description, made with reference to the appended figures, in which:

[0031] [Fig. 1] is a representative diagram of the part of the experimental installation named PELIICAEN allowing the implementation of the method according to the invention;

[0032] [Fig. 2a] shows the result of 20keV helium implantation into crystalline silicon viewed with a scanning electron microscope;

[0033] [Fig. 2b] is an enlarged sectional view of the large blister seen in [Fig. 2a];

[0034] [Fig. 3a] shows the result of 20keV oxygen implantation in high-density pyrolytic graphite, for a given flux, with a first fluence, visualized with a scanning electron microscope;

[0035] [Fig. 3b] shows the result of 20keV oxygen implantation in high-density pyrolytic graphite, for the same flux given for [Fig. 3a], but with a second fluence, visualized with a scanning electron microscope;

[0036] [Fig. 3c] shows the result of 20keV oxygen implantation in high-density pyrolytic graphite, for the same flux given for [Fig. 3a], but with a third fluence, visualized with a scanning electron microscope;

[0037] [Fig. 4] shows the result of implantation of oxygen at 10keV in high-density pyrolytic graphite, for a given flux and for different fluences, visualized with a scanning electron microscope;

[0038] [Fig. 5a] shows the result of 40keV oxygen implantation in high-density pyrolytic graphite, for a given first flux and for different fluences, visualized with a scanning electron microscope; [Fig. 5b] shows the result of 40keV oxygen implantation in high-density pyrolytic graphite, for a given flux lower than the flux given for [Fig. 5a] and for different fluences all higher than the fluences of [Fig. 5a], visualized with a scanning electron microscope;

[0039] [Fig. 6a] shows the result of helium implantation at 10keV into crystalline silicon and under flux and fluence conditions adapted to structure the surface of the material, visualized with a scanning electron microscope;

[0040] [Fig. 6b] shows the result of hydrogen implantation at 10keV in crystalline silicon and under flux and fluence conditions adapted to structure the surface of the material, visualized with a scanning electron microscope;

[0041] [Fig. 7a] shows the result of helium implantation at 10keV in crystalline silicon and under suitable flux and fluence conditions to structure the surface of the material, by performing different linear scans, visualized with a scanning electron microscope;

[0042] [Fig. 7b] shows the result of helium implantation at 10keV in crystalline silicon and under suitable flux and fluence conditions to structure the surface of the material, by performing a circular scan, visualized with a scanning electron microscope

[0043] [Fig. 8a] shows the result of implantation of helium at 10keV into high-density pyrolytic graphite with simultaneous implantation of oxygen at 40keV and under flux and fluence conditions adapted to structure the surface of the material, visualized by scanning electron microscope;

[0044] [Fig. 8b] shows the result of implantation of helium at 10 keV into high-density pyrolytic graphite with pre-implantation of oxygen at 40 keV and under flow and fluence conditions adapted to structure the surface of the material, visualized by scanning electron microscope.

[0045] Detailed description of the invention

[0046] The invention relates to a method for surface micro- or nano-structuring of a material. In the context of the invention, a nano-structure is a structure in which at least two dimensions are less than a micron. Similarly, in the context of the invention, a micro-structure is a structure in which at least two dimensions are less than a millimeter. Still in the context of the invention, the concept of "surface" or "surface" designates a structure located at most 1 micron deep.

[0047] The method according to the invention mainly consists in implementing a (a) vacuum irradiation step consisting of irradiating a localized surface area of ​​said material with a focused gas ion beam characterized, for a given type of ions, by a kinetic energy of these ions in a given range, characterized by a fixed flux in a given range (number of ions per unit of surface and unit of time) and characterized by a fluence (number of ions per unit of surface) judiciously chosen as a function of the other parameters previously cited including the nature of the implanted material.

[0048] By "vacuum" we mean a pressure less than or equal to 10' 6 mbar (also called secondary vacuum). Typically, one can operate at around 10' 8 mbar.

[0049] First of all, the beam ions should have a kinetic energy of between 5 and 30 keV for hydrogen (H), between 10 and 60 keV for helium (He) and between 20 and 500 keV for ions with an atomic mass unit greater than or equal to 12. This range of kinetic energy values ​​makes it possible to manage, depending on the type of ions considered (H, He or other) and as a first approximation, a depth of implantation of the ions in the irradiated material, therefore the positioning in depth of said localized zone. If the kinetic energy is too low, the ions diffuse towards the surface and do not contribute to a localized accumulation of the gas likely to lead to a structuring of the surface of the material, and in particular to a hollow structure. On the contrary, if the kinetic energy is too high, the gas is accumulated too deep to allow a deformation on the surface of the material.The level of kinetic energy also influences the temperature level reached in the localized area, and therefore also possibly the pressure in this localized area.

[0050] Then, it should be noted that the beam is characterized by a flux fixed at a value between 10 13 and 10 18 ions / cm 2 / s. Fixing the flux in this range allows to manage as a first approximation the temperature level reached at the localized zone of irradiation by the ions. For flux values ​​lower than 10 13 ions / cm 2 / s, swelling of the material can be observed without obtaining a surface structure, in particular a hollow structure. On the contrary, for flux values ​​greater than 10 18 ions / cm 2 / s, we can observe pulverization effects of the hollow structure mainly due to excessively high temperatures reached locally. It should also be noted that the temperature level will possibly have an effect on the pressure.

[0051] It should be noted that the flux can be more precisely set to a value between 10 13 and 5.10 17 ions / cm 2 / s, advantageously between 10 13 and 10 17 ions / cm 2 / s, more advantageously between 10 13 and 5.10 16 ions / cm 2 / s, or even more advantageously between 10 14 and 5.10 16 ions / cm 2 / s.

[0052] Finally, it should also be noted that irradiation is characterized by a fluence (ions / cm 2). The fluence allows to manage as a first approximation the quantity of gas injected into the irradiated zone and therefore, if necessary, the pressure within the hollow micro- or nano-structure likely to be generated by the process. For a fluence that is too low, we do not observe the appearance of any surface structuring, in particular a hollow structure. On the contrary, for a fluence that is too high, the hollow structure is then of uncontrolled shape or is purely damaged.

[0053] As mentioned, since temperature and pressure are linked, the various parameters mentioned above all contribute, in combination, to defining the geometry of the hollow micro- or nano-structure thus obtained on the surface of the material. By geometry, we mean the shape and dimensions of the hollow micro- or nano-structure. Indeed, the geometry of the micro- or nano-structure depends on the quantity of ions (and therefore gas) implanted at a given energy and the local rise in temperature so that the material can deform under the effect of the increase in pressure.

[0054] More specifically, it should be noted that the surface micro- or nano-structuring of the material obtained at the end of the process ultimately consists of one or more micro- or nanostructures^) in the form of closed hollow blister(s). This is what is meant by hollow micro- or nano-structure. This can be seen with the examples provided later.

[0055] From a practical point of view, once the type of ions carried by the focused gas ion beam has been chosen (H, He or other), we then know in which range the kinetic energy must be located. We also know in which flux range we must operate. On the other hand, the fluence remains to be adapted to obtain a surface micro- or nano-structuring of the material. However, the range of adequate values ​​for the fluence to obtain such a structuring of the surface of the material then depends on the type of ions used (H, He or other) and the associated kinetic energy, and the nature of the said material (HOPG for "Highly Oriented Pyrolytic Graphite" according to the Anglo-Saxon terminology which translates as highly oriented pyrolytic graphite, silicon or other).

[0056] During step (a), in order to obtain a surface micro- or nano-structuring of the material, the beam therefore has a fluence whose value comes from a database linking the nature of said material, the type of ions used and the associated kinetic energy, and the value of the flux.

[0057] Below we present several examples to give an overview of such a database, in this case for HOPG as the material to be implanted, with four types of ions (He, N, O and Ar) and the respective associated kinetic energies.

[0058] So for example, if the material is highly oriented pyrolytic graphite (HOPG) and the focused gas ion beam used to implement step (a) is generated with helium (ion type = helium in this case) at a kinetic energy of 10keV (implantation depth = 82nm), and the flux set to a value between 10 14 and 6.10 16 ions / cm2 / s, then the adequate fluence to obtain a surface micro- or nano-structuring of the material is actually between 10 16 and 10 20 ions / cm 2 , especially between 2.10 16 and 6.10 19 ions / cm 2 .

[0059] As another example, if the material is highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) is generated with oxygen (ion type = oxygen in this case) at a kinetic energy between 20 and 40keV (implantation depth of 40nm for 20keV and 75nm for 40keV), and the flux set at a value between 10 13 and 2.5.10 15 ions / cm 2 / s, then the adequate fluence to obtain a micro- or nano-surface structuring of the material is between 10 15 and 5.10 17 ions / cm 2 , especially between 4.10 15 and 1,5.10 17 ions / cm2 In this case, we see that the adequate range of fluence is more restricted than that mentioned for the previous example with helium.

[0060] In yet another example, if the material is highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) is generated with nitrogen (ion type = nitrogen in this case) at a kinetic energy of 20keV (implantation depth of 43nm), and the flux set to a value between 9.4.10 14 and 1.6.10 15 ions / cm 2 / s, then the adequate fluence to obtain a surface micro- or nano-structuring of the material is between 6.4.10 16 and 10 17 ions / cm 2 .

[0061] As a final example, if the material is highly oriented pyrolytic graphite and the focused gas ion beam used to implement step (a) is generated with argon (ion type = argon in this case) at a kinetic energy of 92keV (implantation depth of 77nm), and the flux set to a value between 5, 1.10 14 and 1, 16.10 15 ions / cm 2 / s, then the adequate fluence to obtain a surface micro- or nano-structuring of the material is between 2.10 16 and 5.5.10 16 ions / cm 2 , especially between 2,3.10 16 and 5, 1.10 16 ions / cm 2 .

[0062] Taking into account all the examples provided above, without consideration of the type of ions envisaged, taking into account the range of fluxes envisaged for the implementation of step (a), namely between 10 13 and 10 17 ions / cm 2 / s, we note that the fluence will in all cases be between 10 15 and 10 2 ° ions / cm 2 when the material is HOPG.

[0063] Furthermore, for all the examples provided above, it was observed that the lower the fixed flux, the more the range of adequate values ​​for the fluence shifts towards high values, whether for the lower bound or for the upper bound. On the contrary, the higher the fixed flux, the more the range of adequate values ​​for the fluence will shift towards low values, whether for the lower bound or for the upper bound.

[0064] This can be generalized to all types of implanted materials.

[0065] The material to be micro- or nano-structured can be chosen from: a crystalline or amorphous material (e.g. silicon), a lamellar type material such as highly oriented pyrolytic graphite (HOPG) which is made up of a stack of graphene planes, or a thin-film material such as zinc oxide (ZnO) on silicon.

[0066] The focused gas ion beam used to perform step (a) is generated with noble gases such as argon or helium or gases capable of chemically reacting with the implanted material such as hydrogen, nitrogen or oxygen.

[0067] Specific examples of tests performed are provided later.

[0068] It is possible to envisage a step (b) consisting of supplying heat to the level of said localized surface area, concomitantly or subsequently to the localized irradiation step. This supply of heat then aims to enable the material to deform (malleability) under the increase in the local pressure of the implanted gas. This additional energy can be supplied simultaneously or alternately with the ion implantation, it can be of a radiative nature by additional continuous or pulsed beams (ions, photons, electrons) or by localized or non-localized ohmic heating of the sample.

[0069] Furthermore, before implementing step (a), a vacuum pre-implantation step can be provided consisting of irradiating said localized surface area of ​​the material with types of ions other than those used to implement (a). For example, when the material is silicon, the pre-implantation can be carried out with oxygen. Such pre-implantation can in particular make it easier to manage the geometry of the hollow micro- or nano-structure, because this will make it possible to limit the diffusion of the ions subsequently implanted during step (a). Furthermore, this can make it possible to change the properties of the material and therefore its response to implantation during step (a). This can therefore be of interest for managing the geometry of the hollow micro- or nano-structure.

[0070] Alternatively, it may be envisaged that the focused gas ion beam used to implement step (a) comprises at least two different types of ions so as to carry out simultaneous implantation. It is thus possible, for example, to implant oxygen and helium simultaneously.

[0071] In the case of lamellar materials (such as HOPG), the method according to the invention makes it possible to control the exfoliation of the surface by the implantation of ions from the focused gas ion beam. This is also the case by ion pre-implantation combined with the implantation itself (step (a)).

[0072] Furthermore, during step (a), it is possible to scan the surface of the material with the focused gas ion beam. Indeed, as the ions are implanted in the material, a blister forms locally and initially, this blister swells to become the micro- or nano-structure of the desired geometry. By moving the beam relative to the sample or vice versa, it is possible to create micro- or nano-structures with much more varied geometries. Thus, localized implantation without scanning typically makes it possible to create a hollow micro- or nano-structure of spheroidal or hemispherical shape on the surface of the material, with diffusion occurring in the same way in all directions. Implementing scanning will make it possible to generate other shapes, for example lines or others. Such scanning can also take place during the pre-implantation step.In this case, the scan performed during step (a) is the same as that performed during the pre-implantation step.

[0073] Figure 1 is a representative diagram of a device D, used to implement the method according to the invention.

[0074] This device D comprises a source of gaseous element ions 10 connected to a focused ion beam column 20 allowing the positioning and shaping of the focused gas ion beam. It is therefore the components 10, 20 which make it possible to obtain the ion beam.

[0075] The device D also comprises a positioning table 30, advantageously multi-axis. This makes it possible to position an ECH sample of the material that one seeks to structure on the surface. This positioning can be both in location according to the different directions X, YZ of the space of an orthogonal reference but also at an angle relative to the direction of propagation of the focused ion beam.

[0076] The device D may optionally provide a localized heating means 40 which may come from ions, electrons or photons (e.g. laser), supplied continuously or pulsed.

[0077] Finally, the device D may include visualization means. Thus, a scanning electron microscope SEM may be considered allowing the observation of the structures obtained on the surface of the material (sample). The device D may also include a secondary electron detector 50 in order to carry out ion and electron imaging if necessary.

[0078] All of the above means open into or are located in a vacuum chamber designated by the dotted lines.

[0079] Examples

[0080] All the following examples were carried out "under vacuum" and more precisely around 10' 8 mbar. A first test was carried out with device D (experimental setup) described previously in crystalline silicon with localized implantation of helium at 20 keV.

[0081] Figure 2a shows the implantation results visualized with a scanning electron microscope (SEM). In this figure 2a, we note the presence of a small blister and a larger blister, in turn obtained from a small blister and a disk-shaped scan to enlarge the diameter of the small blister.

[0082] Figure 2b is an enlarged sectional view of the large blister of Figure 2a. Note in Figure 2b that the blister has a hollow structure.

[0083] As can be seen in Figure 2(b), the resulting structure is a closed hollow blister (a section was made to see its internal structure).

[0084] From there, the conditions under which such a hollow structure can be obtained on the surface of a material have been specified.

[0085] The method according to the invention was implemented on HOPG under the following conditions: implantation of oxygen with a kinetic energy of 20keV, constant flux of 9.10 14 ions / cm 2 / s, for different values ​​of the fluence.

[0086] Figures 3a, 3b and 3c show images obtained using a scanning electron microscope (SEM) for respective fluences of 2.6.10 16 ions / cm 2 (figure 3a) where no surface structuring is observed (no blister), 3.3.10 16 ions / cm 2 (figure 3b) where we see the presence of a blister (hollow structure in this case, namely a closed hollow blister) and 10 17 ions / cm 2 (figure 3c) where we see that the blister has disappeared, the surface, degraded, no longer being structured.

[0087] Here, we therefore illustrate a value of the adequate fluence (figure 3b) once the other parameters are given (type of ions and kinetic energy given, fixed flux, material = HOPG).

[0088] The method according to the invention was then implemented still in HOPG under the following conditions: implantation of oxygen at 10keV, constant flux of 2.19.10 14 ions / cm 2 / s, and variable fluence. Figure 4 shows an image taken with a scanning electron microscope (SEM) for the following fluences (from left to right): 2.19.10 14 , 2.19.10 15 , 4,38.10 15 , 1.09.10 16 , 1.75.10 16 , 2,39.10 16 , 4.38.10 16 , 6.57.10 16 and 1.09.10 17 ions / cm 2 .

[0089] In all cases, we see in Figure 4 that there is no appearance of blisters (in this case hollow structures, namely closed hollow blisters). Each time, a surface defect is obtained which cannot be described as surface structuring (uncontrolled). Increasing the fluence beyond the highest fluence value tested would not allow a controlled structuring of the surface of the material to be obtained (in particular a hollow structure, namely a closed hollow blister). This is to be compared with the results shown in support of Figure 3b where the kinetic energy, fixed at 20keV, is sufficient to generate said blisters for certain flux and fluence conditions.

[0090] The method according to the invention was then implemented still in HOPG under the following conditions: implantation of oxygen at 40keV,

[0091] - constant flow fixed at 7.8.10 14 ions / cm 2 / s (figure 5a), or at 3.07.1014 ions / cm 2 / s (figure 5b), and

[0092] - variable fluence for a given flow: from 4.68.10 16 at 6.63.10 16 ions / cm 2 in steps of 0.325.10 16 ions / cm 2 in Figure 5a and 1.04.10 17 and 1,23.10 17 ions / cm 2 in Figure 5b.

[0093] In all the test conditions mentioned above, blisters (in this case hollow structures, i.e. closed hollow blisters) are visualized. However, it can be seen in Figure 5a that the blisters begin to deteriorate from a fluence of approximately 6.10 16 ions / cm 2 . We note in Figure 5b that the blisters have larger dimensions than those in Figure 5a (the scale is the same in both figures), which shows that it is possible with a lower flux to have higher fluences to make the blisters grow without them degrading.

[0094] Then, the method according to the invention was implemented on crystalline silicon under the following conditions: implantation of helium with a kinetic energy of 10 keV (figure 6a), implantation of hydrogen with a kinetic energy of 10 keV (figure 6b), under flux and fluence conditions capable of allowing the creation of blisters (in this case hollow structures, namely closed hollow blisters).

[0095] Figure 6a shows the blisters obtained by implanting helium and Figure 6b shows the blisters obtained by implanting hydrogen. It is noted that the structures are reproducible in both cases and that the height of the outgrowth is greater in the case of helium compared to the case of hydrogen. This is mainly due to the fact that hydrogen is implanted more deeply than helium.

[0096] Further tests were then carried out to demonstrate the possibility of achieving different geometric shapes by scanning the surface of the implanted material.

[0097] Thus, in Figures 7a and 7b, an implantation made in crystalline silicon with helium at 10 keV can be visualized using a scanning electron microscope, of course with the flow and fluence conditions adapted to define blisters (in this case hollow structures, namely closed hollow blisters), by carrying out different types of scanning. In Figure 7a, parallel lines are defined (by means of linear scans) whose width does not exceed one micron and about 40 microns in length. In Figure 7b, a toroidal shape is defined (by means of a circular scan) with an internal "diameter" of approximately between 2.6 and 3 microns and an external diameter of the order of 5 microns.

[0098] Similarly, in Figures 8a and 8b, we can visualize under a scanning electron microscope (SEM) an implantation made with helium at 10 keV in HOPG with a simultaneous implantation (Figure 8a) and a pre-implantation (Figure 8b) of oxygen at 40 keV, of course with the flow and fluence conditions adapted to define blisters (in this case hollow structures, namely closed hollow blisters). In Figure 8a, we observe spheroid shapes of different diameters, some forming hollow nanostructures and others hollow microstructures (the largest spheroid shown has a diameter exceeding one micron). In Figure 8b, we have a particular spheroid, forming a nanostructure with a diameter of approximately 600nm.It is therefore noted that carrying out a simultaneous implantation of two different types of ions (in this case oxygen and helium) or a pre-implantation of one type of ion (in this case oxygen) followed by an implantation of another type of ion (in this case helium) all other things being equal results in a different structuring of the surface of the implanted material. It should be noted that the structures obtained with the different tests carried out are stable to consider an effective application.

[0099] The invention can find various applications.

[0100] Thus, with HOPG (as a reminder, made up of stacking graphene planes) as implanted material, we can envisage thanks to the process according to the invention: an increase in the specific surface area: controlling localized exfoliation would allow, in the case of lamellar type samples like HOPG, to increase the specific surface area of ​​the material considered compared to carbon nanospheres while keeping the advantages of a massive sample (no possible dispersion); sensors and energy conversion: the hollow cells formed by the process according to the invention contain inside a gas which can act on the wall during energy absorption (photons or phonons for example). Graphene being recognized as a material having piezoelectric properties, the forces induced by the gas on the walls could be measured by this effect.

[0101] Thus, we can also foresee more general applications for defining metamaterials, for example to improve the stealth of an aircraft whose external surface would be structured in this way.

Claims

CLAIMS 1. Method for surface micro- or nano-structuring of a material, characterized in that it comprises a step (a) of vacuum irradiation consisting of irradiating a localized surface area of ​​said material with a focused gas ion beam, said beam being defined by: - an ion kinetic energy of between 5 and 30 keV for hydrogen ions, between 10 and 60 keV for helium ions or between 20 and 500 keV for ions with an atomic mass unit greater than or equal to 12, - a flow fixed at a value between 10 13 and 10 18 ions / cm 2 / s, and - a fluence whose value comes from a database linking the nature of said material, the type of ions used and the associated kinetic energy, and the value of the flux to obtain a surface micro- or nano-structuring of the material consisting of one or more micro- or nano-structure(s) in the form of closed hollow blister(s).

2. Method for surface micro- or nano-structuring of a material according to claim 1, characterized in that it comprises a step (b) consisting of supplying heat to the level of said localized surface zone, concomitantly or subsequently to step (a).

3. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that during step (a), the surface of the material is scanned with the focused ion beam.

4. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that it comprises, before implementing step (a), a vacuum pre-implantation step consisting of irradiating said localized surface area of ​​the material with types of ions other than those used to implement step (a).

5. Method for surface micro- or nano-structuring of a material according to the preceding claim, characterized in that during the pre-implantation step, the surface of the material is scanned with the focused ion beam, the scanning carried out during step (a) then being the same as that carried out during the pre-implantation.

6. Method for surface micro- or nano-structuring of a material according to one of claims 1 to 3, characterized in that the focused gas ion beam used for implementing step (a) comprises at least two different types of ions so as to carry out simultaneous implantation.

7. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that the micro- or nano-structured material is chosen from: a crystalline or amorphous material, a lamellar type material such as highly oriented pyrolytic graphite (HOPG), a thin-layer material such as zinc oxide (ZnO) on silicon.

8. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that the focused gas ion beam used to implement step (a) is generated with rare gases, for example argon or helium, or gases capable of reacting chemically with said material, for example hydrogen, nitrogen or oxygen.

9. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that the flux is fixed at a value between 10 13 and 5.10 17 ions / cm 2 / s, advantageously between 10 13 and 10 17 ions / cm 2 / s, advantageously between 10 13 and 5.10 16 ions / cm 2 / s, advantageously between 10 14 and 5.10 16 ions / cm 2 / s.

10. Method for surface micro- or nano-structuring of a material according to one of the preceding claims, characterized in that the material is highly oriented pyrolytic graphite (HOPG) and the focused gas ion beam used to implement step (a) is generated with helium, with a flux fixed at a value between 10 14 and 6.10 16 ions / cm 2 / s, the fluence is between 10 16 and 10 20ions / cm 2 , especially between 2.10 16 and 6.10 19 ions / cm 2 .

11. Method for surface micro- or nano-structuring of a material according to one of claims 1 to 9, characterized in that the material is highly oriented pyrolytic graphite (HOPG) and the focused gas ion beam used to implement step (a) is generated with oxygen at a kinetic energy of between 20keV and 40keV, with a flux fixed at a value of between 10 13 and 2.5.10 15 ions / cm 2 / s, the fluence is between 10 15 and 5.10 17 ions / cm 2 , especially between 4.10 15 and 1,5.10 17 ions / cm 2 .

12. Method for surface micro- or nano-structuring of a material according to one of claims 1 to 9, characterized in that the material is highly oriented pyrolytic graphite (HOPG) and the focused gas ion beam used to implement step (a) is generated with nitrogen at a kinetic energy of 20keV, with a flux fixed at a value between 9.4.10 14 and 1.6.10 15 ions / cm 2 / s, the fluence is between 6.4.10 16 and 10 17 ions / cm 2 .

13. Method for surface micro- or nano-structuring of a material according to one of claims 1 to 9, characterized in that the material is highly oriented pyrolytic graphite (HOPG) and the focused gas ion beam used to implement the step (a) being generated with argon at a kinetic energy of 92keV, with a flux fixed at a value between 5, 1.10 14 and 1, 16.1015 ions / cm 2 / s, the fluence is between 2.10 16 and 5.5.10 16 ions / cm 2 , especially between 2,3.10 16 and 5, 1 .10 16 ions / cm 2 .

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