NANOFILED STRUCTURE AND METHOD FOR CREATING SUCH A STRUCTURE
Patent Information
- Application Number
- FR2017052286
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2017-03-20
- Publication Date
- 2025-03-14
- Estimated Expiration
- 2037-03-20
Smart Images
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Abstract
Description
If the material density at the receiving ends is too low, the membrane can be punctured, particularly at the structure's edge, due to the fineness of the nanowires and / or the large distance between them. Such damage is obviously undesirable. To prevent this, the material density (expressed as a percentage above) must be sufficiently high. To achieve a high material density at the receiving ends, a nanowire device as described previously is used. Alternatively, or in addition, a device with a high surface density of nanowires can be used, for example, on the order of 10¹⁰ nanowires per cm² on the surface. The combination of a high nanowire density and a nanowire device with a specific geometry, such as the one described previously, is favorable for transferring a membrane without damage or tearing. In another embodiment, the nanowire heads may not be frustoconical with a polygonal cross-section, but may have any other shape. In particular, the heads may be prismatic as shown in Figure 3. In this case, the diameter of the head 12' is greater than the diameter of the body 11'. Assuming the nanowires are grown by molecular beam epitaxy, a judicious choice of nanowire growth conditions makes it possible to obtain an enlarged head, notably with a "nail head" geometry. In another embodiment, the nanowires may not have a light-emitting diode (LED) structure. Indeed, a nanowire structure as described above may not be used to emit light. In other applications, nanowires may be made of silicon-based materials or other semiconductor materials, such as those belonging to the family arsenides or based on any other material (metal, polymer, ceramic) on which there is an interest in depositing a membrane to ensure the continuity of an electrical injection and / or the application of a potential. An embodiment of a process for making a structure 100 comprising a membrane 3 forming an electrode and a plurality of nanowires 1 is described below with reference to figures 4 to 9. In a first phase, a membrane device 3, 34 is made, comprising the membrane 3 covered with a layer 34. In a second phase, a nanowire device 10 is made or shaped as described above, or a nanowire device which differs from what has been described above in that the nanowires have a structure in which a head cannot be distinguished from a body, i.e. for example a structure with constant or substantially constant dimensions or cross-section over the entire length of the nanowires. In a third phase, the membrane device 3, 34 is placed on the nanowire device 10, notably by transfer. The membrane device is placed directly onto the nanowires at the receiving end surfaces of the membrane. The membrane device adheres to the receiving end surfaces through Van der Waals forces. Thus, according to this method, the membrane device is positioned directly on the receiving ends. The membrane device is positioned so that the electrically conductive and / or transparent layer of the membrane device comes into direct contact with the nanowires, notably directly at the contact of the receiving ends of the nanowires. Thus, the membrane device is placed on the nanowires without having been previously positioned: - a filler material between the different nanowires, or - a barrier layer on the nanowires, in particular a barrier layer resting on the free ends of the nanowires. In a fourth phase, the structure is rinsed with a solvent, for example acetone, specifically to dissolve a layer 34 of the membrane device, or more precisely, to dissolve a resin layer of the membrane device. In this fourth phase, a layer 4 of a second electrically conductive material can then be optionally deposited onto the membrane 3, as shown in Figure 9. The second material can be identical to the first material. This optional deposition step allows, for example, the membrane to be mechanically reinforced by thickening it. The first and second phases can be executed in any order. They can also be executed in parallel or simultaneously. In the first phase, the following steps can be implemented. In a first step, a second substrate 31 is provided, for example a silicon wafer. In a second step, as shown in Figure 4, a sacrificial layer 32 is deposited on the second substrate, for example a layer of metal, in particular a layer of nickel or copper. In a third step, as shown in Figure 5, a layer 3 of the first material is deposited onto the sacrificial layer, for example, a layer approximately 30 nm thick or a layer approximately 20 nm thick. This layer constitutes membrane 3. In a fourth step, as shown in Figure 6, a layer 34 of resin is deposited on the first material layer. In a fifth step, as shown in Figure 7, the sacrificial layer 32 is chemically attacked, for example with a FeCl3 solution. This yields a membrane (formed of layers 3 and 34) as shown in Figure 7. Preferably in the second phase, the device 10 is shaped or fabricated, for example by molecular beam epitaxy, metal-organic vapor deposition, or etching. A judicious choice of process parameters allows for the production of an enlarged head. In particular, a judicious choice of growth conditions for nanowires by molecular beam epitaxy allows for the production of an enlarged head. Thanks to the device and process described above, it is possible to fabricate a transparent and conductive electrode on micro- or nano-pillars, each of which has a flat surface at its apex larger than the diameter of the pillar. This is achieved by applying or transferring a transparent and conductive membrane onto these apex surfaces. The geometry and density of the apex surfaces ensure optimized electrical contact while preventing the membrane from being punctured by the pillars. As previously mentioned, an interesting application of the invention concerns the fabrication of LED structures. It should be noted that in the case of organic LEDs, which can be damaged by conventional metal coating techniques, the transfer solution is a gentle technique that preserves the integrity of the membrane during its placement. It should also be noted that any structure with wire elements can be used for the device and process described in this document, regardless of the density or size of the wire elements. Contact can therefore be established, in particular, on single photon emitters or on various photonic objects (microdisks). The use of depositional conductive membranes is not limited to LEDs. This type of membrane can also be depositionalized onto any type of nanowire or nanopillar produced using bottom-up or top-down technology. The transfer of an indium tin oxide (ITO) membrane has been described previously. However, in addition to ITO, any membrane made of another material can theoretically be transferred, provided that it can be easily detached from the original substrate, for example via chemical etching of a sacrificial layer.
Claims
Claims 1. Method for producing a structure (100) comprising a membrane (3) of a first material, in particular indium-tin oxide, in contact with receiving ends (13) of a plurality of nanowires (1), the method comprising the following steps: - Conformation of a nanowire device (10) comprising the receiving ends (13), the receiving ends being shaped so as to form flat surfaces, - Placement, by transfer, of a membrane device (3; 34) directly on the nanowires at the level of the flat surfaces of the receiving ends of the membrane.
2. Method according to claim 1, characterized in that it comprises a step of depositing a layer (4) of a second electrically conductive material on the membrane (3), in particular a step of depositing a layer of a second material identical to the first material.
3. Method according to one of the preceding claims, characterized in that the membrane is transparent and electrically conductive and / or in that the membrane is intended to form an electrode and / or in that the nanowires are light-emitting diode structures.
4. Method according to one of the preceding claims, characterized in that it comprises a step of producing the membrane device (3, 34), comprising the following steps: - Provide a second substrate (31), in particular a silicon wafer; - Deposit, on the second substrate, a sacrificial layer (32), in particular of metal, in particular nickel or copper, - Deposit, on the sacrificial layer, a layer (3) of first material, in particular a layer approximately 30 nm thick, - Deposit, on the layer of first material, a layer (34) of resin, - Chemically attack the sacrificial layer, for example with a FeCh solution.
5. Method according to one of the preceding claims, characterized in that, following the step of placing the membrane device on the nanowires at the receiving ends, the structure is rinsed with a solvent, in particular so as to dissolve a layer (34) of the membrane device, in particular so as to dissolve a layer of resin of the membrane device.
6. Method according to one of the preceding claims, characterized in that the step of shaping the nanowire device is carried out by molecular beam epitaxy or by organometallic vapor phase epitaxy or by etching.
7. Method according to one of the preceding claims, characterized in that the shaping step comprises shaping the device so that it comprises a first substrate (2), the nanowires being arranged on the first substrate, in particular the nanowires being arranged perpendicularly or substantially perpendicularly on a surface (21) of the first substrate, and / or such that the nanowires are prismatic or substantially prismatic and / or such that the nanowires have light-emitting diode structures.
8. Method according to one of the preceding claims, characterized in that the shaping step comprises shaping the receiving ends so that they form a flat or substantially flat discontinuous surface.
9. Method according to the preceding claim, characterized in that the shaping step comprises shaping the device so that the ratio of the sum of the areas of the surfaces of the receiving ends to the continuous area of the surface of a membrane intended to come into contact with the receiving ends is greater than 80% or greater than 90% or greater than 95%.
10. Method according to one of the preceding claims, characterized in that the shaping step comprises the shaping of nanowires so that the nanowires have a geometry that expands or widens towards the receiving ends and / or in that the shaping step comprises the shaping of nanowires so that the nanowires constitute micro-pillars or nanopillars including the receiving ends whose surfaces have dimensions greater than those of the diameters of the nanowires at a distance from the receiving end.
11. Method according to one of the preceding claims, characterized in that the shaping step comprises the shaping of nanowires so that they each comprise a body (11; 11') and a head. (12; 12'), the head having a receiving end (13), the surface of the receiving end having an area 20% greater, or even 50% greater, than the area of a section(s) of the body of a nanowire, in particular than the area of a section(s) of the nanowire measured parallel to the receiving end at least 2 pm away from the receiving end or than the area of a section(s) of the nanowire measured parallel to the receiving end in the middle of the nanowire.
12. Method according to the preceding claim, characterized in that the shaping step comprises the shaping of the bodies of the nanowires into stacks of a layer (111) of n-type GaN, a layer (112) of InGa and a blocking layer (113).
13. Method according to one of claims 11 and 12, characterized in that the shaping step comprises the shaping of the heads of the nanowires into stacks of a layer (121) of p-type GaN and a layer (122) of p++-type GaN.
14. Method according to one of claims 1 to 11, characterized in that the shaping step comprises the shaping of the nanowires made of silicon-based material.
15. Structure (100), in particular light-emitting diode (100) with nanowires, obtained by implementing the production method according to one of claims 1 to 14.