Spin information transmission device and method for manufacturing the same

Abstract

It also provides a device that can construct more complex quantum mechanical circuit elements. [Solution] The present invention relates to a spin information transmission device 1 comprising a diamond matrix 3 made of C12 diamond and two vacancy centers 4, particularly NV centers, within the diamond matrix 3, wherein a spin polarization channel 6, particularly made of C13 enriched diamond, extends between the two vacancy centers 4 to enable directional diffusion of spin polarization. The present invention also relates to a method for manufacturing such a spin information transmission device 1.

Description

Technical Field

[0001] The present invention relates to a spin information transmission device including a diamond matrix made of C12 diamond and two vacancy centers, particularly NV centers, within the diamond matrix. The present invention also relates to a method of manufacturing such a spin information transmission device.

Background Art

[0002] The production of synthetic diamond by CVD (chemical vapor deposition) is a common technique in the industry for producing synthetic diamond. In particular, the growth of diamond layers having a thickness of more than 100 nm has been focused on, and the diamond layers are mainly manufactured for use in the gemstone industry and for material processing as cutting tools, for example. In these applications, only the mechanical properties of the produced diamond, such as hardness, are relevant.

[0003] In recent years, synthetic diamond has become increasingly relevant for high-tech applications such as quantum technology or semiconductor technology. In quantum technology, diamond is used as a matrix into which atomic vacancy centers, such as NV (nitrogen vacancy) centers, SiV (silicon vacancy) centers, GeV (germanium vacancy) centers, or SnV (tin vacancy) centers, are introduced.

[0004] In order to make the vacancy centers usable for quantum computing, for example, the vacancy centers are introduced into a matrix enriched with isotope carbon 13 (C13) having a non-zero nuclear spin in contrast to isotope carbon 12 (C12). When the distance between the vacancy center and the C13 atom is sufficiently small, a measurable coupling occurs between the spin of the vacancy center and the spin of the C13 atom, and as a result, these can be used as quantum bits.

[0005] The vacancy centers are located in a layer of diamond enriched with C13. If this layer has a sufficient density of C13 atoms, and therefore C13 nuclear spin, the spin polarization can diffuse in any direction throughout the diamond layer. However, directional diffusion of spin polarization within the diamond material, which is generated as spin information by the quantum manipulation of vacancy centers, is therefore impossible in these diamond structures. However, such directional diffusion is necessary for fabricating more complex quantum mechanical circuit elements. [Overview of the project]

[0006] Therefore, an object of the present invention is to provide a device that can also construct more complex quantum mechanical circuit elements.

[0007] This objective is achieved in the above-described type of device by a spin-polarized channel, in particular made of C13-enriched diamond, to enable directional diffusion of spin polarization, the spin-polarized channel extending between two vacancy centers and, in particular, connecting the two vacancy centers to each other.

[0008] Spin-polarized channels can enable directional diffusion of polarization between atomic vacancy centers. In particular, spin-polarized channels made of C13-enriched synthetic diamond can substantially restrict the possibility of spin-polarized diffusion to one-dimensional diffusion. One-dimensional diffusion of (nuclear) spin polarization can thus occur, directed along the longitudinal axis of the spin-polarized channel.

[0009] A synthetic diamond matrix, particularly one composed of C12 diamond, can provide a nuclear spin-free layer in which the diffusion of spin polarization is impossible, and consequently, the spin polarization channels in the diamond matrix cannot be bypassed.

[0010] Spin-polarized channels allow spin information transfer devices to transmit quantum information from one vacancy center to another. In particular, this opens up the possibility of using multiple spin information transfer devices to construct more complex quantum mechanical circuit elements, such as fabricating quantum transistors and coherently connecting them to form a network, or qubit register.

[0011] Spin-polarized channels can be enriched to a very high degree with C13. In particular, C13 enrichment in the range of 10% to 99.99%, preferably in the range of 50% to 99.99%, is possible. Such high C13 enrichment ensures efficient polarization diffusion, i.e., spin transfer, in the spin-polarized channels.

[0012] The atomic vacancy centers may be NV centers (nitrogen vacancy centers), SiV centers (silicon vacancy centers), GeV centers (germanium vacancy centers), and / or SnV centers (tin vacancy centers).

[0013] Preferably, the spin polarization channel is located above the vacancy center. By locating the spin polarization channel above the vacancy center, directional diffusion of spin polarization can occur in a plane different from the plane in which spin polarization is generated by quantum manipulation of the vacancy center. In particular, directional diffusion of spin polarization can occur in layers having a different chemical composition from the layer in which the vacancy center is located.

[0014] "Upward" refers to the orientation of void centers that face away from the interior of the diamond matrix, particularly away from the substrate. In particular, "upward" can generally refer to the orientation aligned with the direction of growth.

[0015] The spin-polarized channel may be positioned above the hole center such that one hole center is located below each of the opposing ends in the diametrical direction of the spin-polarized channel.

[0016] It is also advantageous when the spin-polarized channels are covered with a C12 diamond protective layer. In particular, a pure C12 diamond protective layer can protect the spin-polarized channels on the side facing away from the diamond matrix. By using nuclear spin-free C12 in the diamond protective layer, spin shielding of the spin-polarized channels facing outward from the device can be achieved to protect against spin noise. The C12 diamond protective layer may have a thickness of at least 50 nm, preferably at least 100 nm.

[0017] In one embodiment, the diamond matrix is ​​placed on a diamond substrate. The diamond substrate can form a mechanically and chemically stable substrate for the diamond matrix. The diamond matrix can be chemically bonded to the diamond substrate and, in particular, grown on it.

[0018] The two vacancy centers can be located at distances of 5 nm to 100 μm, and especially 500 nm to 1 μm. In this way, spin polarization can be moved between two distant points for quantum mechanical applications.

[0019] Furthermore, the spin-polarized channels can have a width in the range of 1 nm to 10 μm, preferably 5 nm to 100 nm, and / or a length in the range of at least 5 nm, preferably at least 500 nm, particularly preferably 500 nm to 1 μm, more preferably 1 μm to 5 μm, and / or a thickness in the range of 0.5 nm to 100 nm, preferably 1 nm to 10 nm. Using spin-polarized channels of this length, spin polarization can be directionally moved over long distances for quantum mechanical applications. When using spin-polarized channels of this width and / or thickness measured perpendicular to the plane of the diamond matrix, the possibility of spin-polarized diffusion in the spin-polarized channel can easily be limited to one-dimensional diffusion along the length of the spin-polarized channel.

[0020] Furthermore, it may be advantageous if the diamond matrix has a thickness of at least 50 nm, and especially at least 100 nm. In this way, the diamond matrix can provide a mechanically stable layer for accommodating vacancy centers.

[0021] In the above-described type of method, in order to achieve the above-described objective, it is proposed that the method includes the steps of growing a diamond matrix consisting of C12-enriched diamond on a diamond substrate, particularly an ultra-high-purity diamond substrate, by CVD; introducing vacancy centers into the diamond matrix; growing a C13-enriched diamond layer thereon; and partially removing the C13-enriched diamond layer, particularly by etching, in order to form spin-polarized channels.

[0022] This method makes it possible to manufacture a spin information transfer device according to the present invention, which includes a spin polarization channel that can enable directional diffusion of polarization between hole centers. The features described in relation to the spin information transfer device according to the present invention can be used individually or in combination in this method as well. This provides the same advantages as already described.

[0023] In particular, by growing a diamond matrix made of C12-enriched diamond on an ultra-high purity diamond substrate by CVD, it is possible to prevent the undesirable intrusion of foreign atoms, i.e., non-carbon atoms, from the diamond substrate into the diamond matrix during further processing steps. The ultra-high purity diamond substrate may have a residual nitrogen concentration of less than 5 ppb (parts per billion) remaining within it as a result of the manufacturing of the diamond substrate.

[0024] The diamond matrix may have a thickness of at least 50 μm, and in particular at least 100 μm, measured along its growth direction on the diamond substrate.

[0025] A diamond matrix enriched with 12C, especially consisting of C12, can be easily manufactured on a diamond substrate by growing it on the diamond substrate by CVD. A diamond matrix made of C12-enriched diamond can provide a nuclear spin-free layer, and vacancy centers can be introduced into this layer. In this way, it is possible to prevent the diffusion of spin polarization into the diamond matrix, and thus prevent the bypass of the spin polarization channel.

[0026] For the growth of the diamond matrix by CVD, C12-enriched methane gas can be used.

[0027] To introduce vacancy centers, ions can be implanted into the diamond matrix. For ion implantation, ions, for example nitrogen ions in the case of NV centers, can be accelerated onto the diamond matrix. The ions can come to rest within the diamond matrix at a depth corresponding to the acceleration energy, and thus create vacancies along their paths. By a subsequent annealing process, the ions and vacancies can combine to form vacancy centers, for example NV centers in the case of ion-introduced nitrogen. Ion implantation can be carried out, in particular, using nitrogen-15 ions (15N+) at an energy of 0.1 keV to 5 keV, preferably 1 keV, and / or at a dose of at least 10 11 15N+ / cm.

[0028] Ion implantation can be carried out in a controlled manner, in particular by using a mask that covers the diamond matrix and allows ion implantation only into some predetermined regions of the diamond matrix.

[0029] Ion implantation can be carried out such that vacancy centers are created under a specific end of the spin polarization channel.

[0030] By growing a C13-enriched diamond layer, a diamond layer containing C13 nuclear spins can be created, particularly on a diamond matrix that does not contain C13 nuclear spins. The C13-enriched diamond layer may also contain C12 in addition to C13, and may particularly contain mainly C12. The C13-enriched diamond layer can be grown directly on the diamond matrix. The C13-enriched diamond layer may have a thickness in the range of 0.5 nm to 100 nm, preferably 1 nm to 10 nm. When growing the diamond layer, it may be possible to set the layer thickness with nm accuracy by using a very low growth rate, which is lower than the growth rate that is normally used.

[0031] By partially removing the C13-enriched diamond layer, spin-polarized channels can be easily formed without modifying the diamond matrix. Partial removal of the C13-enriched diamond layer can be carried out so that it is completely removed in some areas, particularly in areas where spin-polarized channels are not to be formed. In particular, the C13-enriched diamond layer can be easily partially removed by etching. For this purpose, a lithographic etching process can be used. In this process, the areas of the diamond layer intended to form spin-polarized channels can be covered with a mask, and as a result, only the areas of the C13-enriched diamond layer not covered by the mask are etched away. The mask can be applied to the C13-enriched diamond layer as a photoresist. The C13-enriched diamond layer partially covered with the photoresist can then be exposed, thus enabling selective etching.

[0032] To increase the coherence time of vacancy centers, it may be provided to grow a C12 diamond protective layer on the spin-polarized channel. The C12 diamond protective layer can protect the spin-polarized channel from adverse influences from the surface of the spin information transfer device. The C12 diamond protective layer may be ultra-high purity, i.e., substantially 99.9% enriched with C12, and may not contain C13 in particular. By using nuclear spin-free C12 in the diamond protective layer, spin shielding of the spin-polarized channel toward the outside of the device can be achieved to protect against spin noise.

[0033] The C12 diamond protective layer can be grown to a thickness of at least 50 nm, preferably at least 100 nm.

[0034] Advantageously, C13-enriched diamond layers can be grown by CVD using C13-enriched methane gas. By growing diamond using a C13-enriched growth gas, particularly methane gas, the diamond layer can be easily enriched with C13. The density of C13 nuclear spins within the grown synthetic diamond layer can be adjusted based on the degree to which the growth gas is enriched with C13.

[0035] Furthermore, it may be advantageous to perform ion implantation to introduce vacancy centers into the diamond matrix, followed by high-temperature annealing, particularly in a vacuum. By implanting ions and then annealing at a high temperature, ions can be introduced into the diamond matrix and then combined with vacancies during the high-temperature annealing to form vacancy centers. High-temperature annealing is preferably performed in a vacuum, and more preferably at 10°C. -7 This can be carried out at a temperature of 1000°C for 3 hours under a pressure of less than mbar.

[0036] Preferably, partial removal of the C13-enriched diamond layer is performed by controlled plasma etching, particularly ICP, of the surface of the C13-enriched diamond layer. Controlled plasma etching allows for the controlled removal of diamond material from the surface of the C13-enriched diamond layer with nanometer precision. Controlled plasma etching can be achieved by inductive plasma etching (ICP) or reactive ion etching (RIE). Inductive plasma etching can be achieved by igniting an inductively coupled plasma, particularly an oxygen plasma or an Ar / SF6 plasma (SF6: sulfur hexafluoride), and applying an accelerating voltage to the diamond layer to accelerate reactive ions. [Brief explanation of the drawing]

[0037] Further details and advantages of the spin information transmission device and method according to the present invention will be described below, by example, based on exemplary embodiments of the present invention schematically shown in the drawings. The drawings are as follows. [Figure 1] Figures 1a to 1f show the individual steps of the manufacturing method according to the present invention, and the spin information transmission device according to the present invention. [Modes for carrying out the invention]

[0038] To better distinguish the individual layers, they are shown spaced apart in the subfigures (Figures 1a to 1f). However, in the spin information transfer device 1 and during its fabrication, these layers are in close proximity to each other in the growth direction W.

[0039] Figure 1a shows the first step in manufacturing the spin information transmission device 1. A diamond matrix 3 is grown on a pure diamond substrate 2 by CVD. A C12-containing growth gas 8 is used during CVD growth. For the growth of the diamond matrix 3, this growth gas 8 does not contain C13, and as a result, the diamond matrix 3 does not contain nuclear spin when growth is complete. Methane gas can be used as the growth gas 8.

[0040] In this way, a diamond matrix 3 is formed on the diamond substrate 2 along the growth direction W. This diamond matrix 3 has a thickness M of at least 50 nm to 100 nm. Therefore, this layer is thick enough to accommodate the void centers 4 introduced in the next step, so that they do not penetrate the diamond substrate 2.

[0041] As the diamond matrix 3 grows, void centers 4 are introduced into the diamond matrix 3, as shown in Figure 1b.

[0042] To introduce vacancy centers 4 into the diamond matrix 3, ion implantation is performed first. In this process, for example, nitrogen-15 ions (15N+) are implanted with an energy of 1 keV and 10 11 Ions are accelerated onto the diamond matrix 3 at a dose of 15 N+ / cm. The ions then come to rest within the diamond matrix 3 at a depth corresponding to the acceleration energy. On their way to this resting position, the ions create vacancies within the diamond matrix 3 as they pass through the material.

[0043] To introduce ions into the diamond matrix 3 as intended, the diamond matrix 3 is pre-masked. During this masking, only the areas on the surface of the diamond matrix 3 where the vacancy centers 4 are intended to be located are left uncovered. The unmasked areas during ion implantation may be spaced, for example, about 5 nm to 100 μm apart from each other, and as a result, the two vacancy centers 4 in the subsequent spin information transfer device 1 are positioned at a distance of about 5 nm to 100 μm from each other.

[0044] Following ion implantation, the system consisting of the diamond substrate 2 and the diamond matrix 3 undergoes high-temperature annealing. This high-temperature annealing is performed in a vacuum at 10°C to eliminate undesirable chemical reactions. -7 This is carried out at a pressure of less than mbar. The system is heated to a temperature of over 1000°C for 3 hours. At these temperatures, ions and vacancies introduced into the diamond matrix 3 can combine to form vacancy centers 4. For example, by implanting nitrogen-15 ions and then annealing at a high temperature, NV centers are introduced into the diamond matrix 3 as vacancy centers 4.

[0045] These vacancy centers 4 are shown in the diagram as pairs of spots symbolizing the coupling between introduced ions and vacancies. The arrows in these pairs symbolize the non-zero spin of the vacancy centers 4, and together with these non-zero spins, these pairs can couple to the spin-polarized channels 6 that are later formed.

[0046] Figures 1c and 1d show the growth of the C13-enriched diamond layer 5 that occurs after the introduction of the vacancy center 4. The diamond layer 5 is also grown by CVD and has a thickness D of approximately 1 nm after growth.

[0047] Similar to the growth on the diamond matrix 3, a C12-containing gas, particularly methane, is used as the growth gas. However, this growth gas is enriched with C13. Therefore, the diamond layer 5 grown on the diamond matrix 3 is also enriched with C13. This makes it possible to later generate spin-polarized channels 6 located above the vacancy centers 4.

[0048] By enriching diamond layer 5 with C13, this layer contains C13 atoms with non-zero nuclear spin. Thus, the C13 atoms are in contrast to the other C12 atoms in diamond layer 5, which have no nuclear spin, i.e., zero nuclear spin. This nuclear spin allows the C13 atoms to couple with the spin of the vacancy centers 4, enabling them to transmit spin polarization. C13 atoms with nuclear spin are shown in Figure 1d as spots with arrows symbolizing the nuclear spin.

[0049] Furthermore, it can be seen that the diamond matrix 3, located beneath the diamond layer 5, contains nuclear spin-free C12 atoms and therefore contains very few diamond atoms with nuclear spin. In the diamond layer 5, only the vacancy centers 4 possess nuclear spin. Therefore, diffusion of spin polarization from the vacancy centers 4 to the diamond matrix 3 is impossible.

[0050] However, in the C13-enriched diamond layer 5, spin polarization can diffuse in any direction. Therefore, directional diffusion of spin polarization cannot be achieved in the diamond layer 5 shown in Figures 1c and 1d.

[0051] To enable directional diffusion of spin polarization, spin polarization channels 6 must be formed from the diamond layer 5, as shown in Figure 1e. For this purpose, the C13-enriched diamond layer 5 is partially removed, leaving only the spin polarization channels 6.

[0052] For this purpose, a lithographic ICP etching process is used. Regions of the diamond layer 5 intended to form spin-polarized channels 6 are coated with photoresist. The thus masked diamond layer 5 can be exposed to plasma 9. In the unmasked regions, the C13-enriched diamond layer 5 is thus removed in a controlled manner.

[0053] After removal, the remaining C13-enriched diamond layer 5 is entirely composed of long, thin spin-polarized channels 6 made of C13-enriched diamond. In the illustrated exemplary embodiment, these spin-polarized channels 6, after formation, have a width B in the range of 5 nm to 100 nm, a length L in the range of approximately 5 nm to 100 μm, and a thickness D in the range of 0.5 nm to 100 nm.

[0054] The spin-polarized channel 6 still contains C13 atoms with nuclear spin. The spin-polarized channel 6 is located above the vacancy centers 4 and extends between them, thus allowing for directional diffusion of spin polarization between the two vacancy centers 4.

[0055] Although the fabrication of a single spin-polarized channel 6 has been described above, multiple spin-polarized channels 6 between different vacancy centers 4 in the diamond matrix 3 can also be fabricated in parallel using the same method. For example, the spin information transmission device 1 can be fabricated to have multiple spin-polarized channels 6 on the same diamond matrix 3 in order to obtain, for example, a quantum transistor or a qubit register.

[0056] Figure 1f shows how a C12 diamond protective layer 7 is additionally provided to the spin information transmission device 1 after the spin-polarized channel 6 has been formed. For this purpose, the spin-polarized channel 6 is covered with the C12 diamond protective layer 7.

[0057] The C12 diamond protective layer 7 is grown by the CVD process, similar to the diamond matrix 3. The spin-polarized channels 6 and the areas of the diamond matrix 3 from which the diamond layer 5 has been completely removed serve as a base for the growth of the C12 diamond protective layer 7.

[0058] Since C13-free growth gas 8 is used for the growth of the C12 diamond protective layer 7, the C12 diamond protective layer 7 becomes nuclear spin-free once growth is complete.

[0059] This C12 diamond protective layer 7 can protect the spin-polarized channels 6 from external adverse influences and can help increase the coherence time of the vacancy centers 4. This is achieved by the fact that the C12 diamond protective layer 7 is C13-free. Therefore, there are no diamond atoms with nuclear spins that could be coupled to the spin of the vacancy centers 4 or spin-polarized channels 6 and thus adversely affect the coherence time.

[0060] Furthermore, the C12 diamond protective layer 7 can function as a protective layer to protect the spin-polarized channel 6 from mechanical damage.

[0061] By using the C12 diamond protective layer 7, it is possible to provide a spin information transmission device 1 that is even more stable and reliable than the spin information transmission device 1 without a diamond protective layer, as shown in Figure 1e.

[0062] The C12 diamond protective layer 7 has a thickness S in the range of 50 nm to 100 nm. The C12 diamond protective layer may have the same thickness as the diamond matrix 3. In this way, the spin-polarized channel 6 is symmetrically encapsulated and protected in the center of the layer system consisting of the C12 diamond protective layer 7 and the diamond matrix 3.

[0063] According to the spin information transmission device 1 and its manufacturing method described above, it becomes possible to provide a device that can transmit spin information in a directional manner. [Explanation of Symbols]

[0064] 1. Spin Information Transfer Device 2 Diamond substrate 3 Diamond Matrix 4 Hole center 5 Diamond Layer 6. Spin-polarized channels 7 C12 Diamond Protective Layer 8 Growth gases 9 Plasma B Width D Thickness L Length M thickness S thickness W growth direction

Claims

1. A spin information transmission device (1) comprising a diamond matrix (3) made of C12 diamond and two vacancy centers (4), particularly NV centers, within the diamond matrix (3), characterized by a spin polarization channel (6) made of C13 enriched diamond, particularly for enabling directional diffusion of spin polarization, wherein the spin polarization channel extends between the two vacancy centers (4).

2. The spin information transmission device (1) according to claim 1, characterized in that the spin polarization channel (6) is positioned above the void center (4).

3. The spin information transmission device (1) according to claim 1 or 2, characterized in that the spin polarization channel (6) is covered with a C12 diamond protective layer (7).

4. The spin information transmission device (1) according to any one of claims 1 to 3, characterized in that the diamond matrix (3) is arranged on a diamond substrate (2).

5. The spin information transmission device (1) according to any one of claims 1 to 4, characterized in that the spin polarization channel (6) has a width (B) of 1 nm to 10 μm, a length (L) of at least 5 nm, preferably at least 500 nm, particularly preferably in the range of 500 nm to 1 μm, and / or a thickness (D) in the range of 0.5 nm to 100 nm.

6. The spin information transmission device (1) according to any one of claims 1 to 5, characterized in that the diamond matrix (3) has a thickness (M) of at least 50 nm, and more particularly at least 100 nm.

7. A method for manufacturing a spin information transmission device (1), - A process of growing a diamond matrix (3) made of C12-enriched diamond on a diamond substrate (2), particularly an ultra-high-purity diamond substrate, using CVD, - A step of introducing the void center (4) into the diamond matrix (3), - A step of growing a C13-enriched diamond layer (5) on the diamond matrix (3), A method comprising the step of partially removing the C13-enriched diamond layer (5) in particular by etching to form a spin-polarized channel (6).

8. The method according to claim 7, characterized in that a C12 diamond protective layer (7) is grown on the spin-polarized channel (6) in order to increase the coherence time of the vacancy center (4).

9. The method according to any one of claims 7 or 8, characterized in that the C13-enriched diamond layer (5) is grown by CVD using C13-enriched methane gas.

10. The method according to any one of claims 7 to 9, characterized in that the partial removal of the C13-enriched diamond layer (5) is performed by controlled plasma etching of the surface of the C13-enriched diamond layer (5), particularly by ICP.

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