METHOD OF GENERATING A DETERMINISTIC COLOR CENTER IN A DIAMOND

Abstract

A method generates at least one deterministic F-center in a diamond layer. By implanting a dopant in the diamond layer and incorporating at least one foreign atom in the diamond layer by low-energy bombardment for the formation of the F-center in a second step, conversion rates of greater than 70% can be achieved. This is a significant increase in relation to undoped diamond, in which the conversion rates are only around 6%. Via doping with a donor, such as phosphorous, oxygen or sulphur, a good conversion into negatively charged F-centers can be achieved, which are used for Qubit applications.

Claims

1-11. (canceled)

12. A method for generating at least one deterministic NV center in a diamond layer, comprising: implanting at least one dopant in the diamond layer, wherein the dopant used is one of lithium, oxygen or sulphur; and incorporating at least one nitrogen atom in the diamond layer by ion bombardment with impurity atoms to form the NV center, wherein the ion bombardment with the impurity atoms has an ionic fluence of up to 10.sup.10 cm.sup.−2.

13. The method according to claim 12, wherein: the ion bombardment with the impurity atoms takes place with an ionic fluence in a range from 10.sup.4 cm.sup.−2 to 10.sup.10 cm.sup.−2, and/or the ion bombardment with the impurity atoms is low-energy with an energy of less than or equal to 100 keV.

14. The method according to claim 13, wherein the ion bombardment with the impurity atoms takes place with an ionic fluence in a range from 10.sup.9 cm.sup.−2 to 10.sup.10 cm.sup.−2.

15. The method according to claim 12, wherein a dopant concentration is in a range 10.sup.17 cm.sup.−3 to 10.sup.19 cm.sup.−3.

16. The method according to claim 12, wherein the dopant implantation is carried out by bombarding the dopants with energies of less than or equal to 150 keV.

17. The method according to claim 12, wherein the dopant implantation is carried out by bombarding the dopants with a dopant fluence in a range of 10.sup.9 cm.sup.−2 to 10.sup.13 cm.sup.−2.

18. The method according to claim 12, wherein the dopant implantation is performed in at least two successively different steps, and further wherein the dopant implantation with each of the two successively different steps is performed by dopant bombardment at a different fluence and/or energy other steps of the at least two successively different steps.

19. The method according to claim 12, wherein a depth of the implanted dopants is at least equal to a depth of the incorporated impurity atoms.

20. The method according to claim 12, wherein a depth of the NV centers in the diamond layer is in a range of 5 nm to 100 nm.

21. The method according to claim 12, wherein, after the donor implantation, a first tempering step takes place, wherein: i) a tempering temperature of a first tempering step is preferably in a range 800° C. to 2000° C.; and/or ii) a time for the first tempering step is preferably between 1 h and 24 h.

22. The method according to claim 21, wherein a second tempering step is performed after the impurity incorporation, wherein: iii) a tempering temperature of a second tempering step is preferably lower than that of the first tempering step and/or in the range 600° C. to 1300° C.; and/or iv) wherein the time for the second tempering step is preferably between 1 h and 24 h.

23. The method according to claim 22, wherein a Fermi level is raised, the raising taking place during the impurity implantation, after the impurity implantation and/or during the second tempering step, the raising taking place by LASER irradiation, electron bombardment or voltage application.

24. The method according to claim 12, wherein the diamond layer is present in a diamond material which is at least of pure quality, a hydrogen content in the diamond layer being less than 10.sup.17 cm.sup.−3.

25. The method according to claim 12, wherein the diamond layer is formed as a surface layer, within a diamond material extending over a greater depth.

26. A diamond layer having at least one deterministic NV.sup.− center and dopants, wherein an impurity species used to form the NV.sup.− center is present in an atomic number in the diamond layer which is at most twice a number of the NV.sup.− centers in the diamond layer, and further wherein the impurity species is nitrogen and wherein lithium, oxygen or sulfur are dopants, a dopant concentration being in a range 10.sup.17 cm.sup.−3 to 10.sup.19 cm.sup.−3.

27. Use of a diamond layer comprising at least one deterministic color center according to claim 26 in the context of a sensor and/or in a context of quantum cryptography and/or in the context of a quantum computing application.

28. A quantum computer comprising the diamond layer according to claim 26.

29. A sensor comprising the diamond layer according to claim 26.

30. A device for quantum cryptography, comprising a diamond layer according to claim 26.

31. Use of a diamond layer manufactured according to claim 12 as a qubit container, in the context of a sensor and/or in a context of quantum cryptographs and/or in the context of a quantum computing application.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 block diagram of the process according to the disclosure,

[0055] FIG. 2 illustration of the sample preparation,

[0056] FIG. 3 concentration distribution of the dopants,

[0057] FIG. 4 method for determining the background signal,

[0058] FIG. 5 method for determining the reference signal,

[0059] FIG. 6 obtained conversion rates for nitrogen,

[0060] FIG. 7 change in fluorescence as a function of the second tempering step and

[0061] FIG. 8 overview of the determined coherence times.

DESCRIPTION

[0062] In FIG. 1 illustrates an example method 10 for producing a deterministic color center.

[0063] In a first step 12, a diamond 14 (type IIa, CVD-grown, “electronic grade”, impurities: [N]<5 ppb, [B]<1 ppb, (001)-face polished, lying upwards) dopants are implanted in a diamond layer 15 (corresponding to the depth extent of the doped region of the diamond or the depth extent of the subsequently generated color centers 54) of the diamond 14. This is done with an ion beam source 16, preferably using an aperture 18 to locally define the implantation.

[0064] The ion beam source 16 has a cesium sputter source acting on different cathodes, after which the sputtered ions are accelerated in an electric field.

[0065] This is followed by an initial annealing step 20 to heal any defects that may have occurred during implantation. Furthermore, this causes the dopants to arrange themselves on the substitution sites in the diamond lattice. Additionally, electrical activation of the dopants occurs so that they readily release their charge. For the first annealing step, a specific first annealing regime is used, which may provide for the application of a specific temperature for a specific time, or different subsequent temperatures applied for specific times in each case.

[0066] Preferably, an oxygen plasma may be used after the first annealing step 20 to clean the surface of any graphite that may be present.

[0067] Subsequently, an ion bombardment 22 is carried out, again with the ion beam source 16, e.g. of the Kaufmann type, in order to incorporate the impurity atoms, whereby preferably the additional aperture 18 with an aperture opening of 50 μm is again used (cf. FIG. 2).

[0068] Finally, a second annealing step 24 is carried out to heal defects created during the incorporation of the impurity atoms or to guide the vacancy defects towards the impurity atoms by increasing their mobility in order to form color centers. For the second annealing step, a specific second annealing regime is used, which may also provide for the application of a specific temperature for a specific time, or different temperatures subsequently applied for specific times in each case.

[0069] Tempering 20, 24 may each be performed using a common tempering method, preferably selected from the group consisting of heating, for example using a hot plate, IR radiant heat and/or LASER irradiation, but other methods may also be used.

[0070] During at least one of steps 22, 24, additional increasing of the Fermi level may be performed, which is preferably performed by LASER irradiation, electron bombardment, or voltage application.

[0071] FIG. 2 shows how individual test samples 30 were prepared.

[0072] Spatially separated doping regions 32, 34, 36 are provided in each case, which are formed by different dopings by means of the first step 12. Individual doping regions can also remain undated for comparison purposes.

[0073] In the context of experimental sample 30, doping region 32 is a boron-doped region, doping region 34 is an undated (intrinsic region), and doping region 36 is a phosphorus-doped region. Other doping regions (not shown) were also used in which oxygen and sulfur were used as dopants.

[0074] In order to achieve the most homogeneous doping of 2×10.sup.17 cm.sup.−3 and 2×10.sup.18 cm.sup.−3, respectively, the implantation of boron/phosphorus was carried out in three steps each (three different energies and three different fluxes).

[0075] The concentration distributions of the dopants shown in FIG. 3 show a very constant plateau with the following fluxes over the depth, which lies between approx. 25 nm and approx. 75 nm with a center at around 50 nm (cf. Tables 1 and 2, simulated using SRIM):

TABLE-US-00001 TABLE 1 Boron Fluence (cm.sup.−2) Fluence (cm.sup.−2) Energy (keV) for 2 × 10.sup.17 cm.sup.−3 for 2 × 10.sup.18 cm.sup.−3 12 5.6 × 10.sup.11 5.6 × 10.sup.12 25 6.4 × 10.sup.11 6.4 × 10.sup.12 40 1.1 × 10.sup.12 1.1 × 10.sup.13

TABLE-US-00002 TABLE 2 Phosphorus Fluence (cm.sup.−2) Fluence (cm.sup.−2) Energy (keV) for 2 × 10.sup.17 cm.sup.−3 for 2 × 10.sup.18 cm.sup.−3 30 3.4 × 10.sup.11 3.4 × 10.sup.12 50 5.1 × 10.sup.11 5.1 × 10.sup.12 90 1.3 × 10.sup.12 1.3 × 10.sup.13

[0076] As part of the first tempering step 20, these generated test samples 30 were tempered, namely, for example, at 1200° C. or 1600° C. for 4 h.

[0077] In each of the doping region 32, 34, 36, graphite markers 38 were deposited on the samples for orientation. This was done by high dose implantation of carbon, resulting in graphitization of these regions.

[0078] In addition to the graphite markers 38, various impurity atom regions 40, 42, 44, 46 were then generated by ion bombardment 22. For example, the impurity atom regions 40 each involve carbon as an impurity atom, the impurity atom regions 42 each involve nitrogen as an impurity atom, the impurity atom regions 44 each involve tin as an impurity atom, and the impurity atom regions 46 each involve magnesium as an impurity atom, for example.

[0079] In each case, three different fluxes a, b, c were used, namely, for example, on the basis of test sample 30, a fluence of 10.sup.10 cm.sup.−2 for the impurity atom regions 40a, 42a, 44a, 46a, a fluence of 10.sup.11 cm.sup.−2 for the impurity atom regions 40b, 42b, 44b, 46b and a fluence of 10.sup.12 cm.sup.−2 for the impurity atom regions 40c, 42, 44c, 46.

[0080] For carbon, nitrogen and magnesium, bombardment energies of 28 keV, 40 keV and 50 keV were used in order to generate a depth profile (diamond layer 15, average implantation depth 50 nm) that was as homogeneous as possible over the same depth range as the dopants. For tin, this was not possible due to its atomic mass combined with the limitation of the ion beam source to 100 keV, so that only 80 keV was used there (average implantation depth 25 nm). The cathode material used for the respective bombardment 22 was a carbon cathode for carbon impurity atoms, a .sup.12C.sup.14N cathode for nitrogen impurity atoms, a .sup.24Mg.sup.1H cathode for magnesium impurity atoms and a tin cathode for tin impurity atoms.

[0081] The implantation depths thus achieved corresponded to those of the dopant distribution (diamond layer 15). Furthermore, they were small enough to achieve only a low ion scattering of less than 10 nm, but at the same time large enough to exclude or minimize the described negative effects of the diamond surface.

[0082] The second tempering step 24 was then performed in each case, using different temperatures of 600° C., 800° C., 1000° C. and 1200° C. for this purpose.

[0083] Thereafter, the fluorescence intensities for each of the impurity atom regions 40, 42, 44, 46 with respect to all fluxes a, b, c were determined by a confocal fluorescence microscope, using graphite markers 38 for orientation and retrieval.

[0084] For this purpose, either air or oil objectives and two possible LASER excitations of 532 nm and 488 nm were used. LASER reflection was suppressed with a notch filter and different spectral filters were used to select the desired fluorescence bands: neutral vacancy V.sup.0 (GR1 center with ZPL at 741 nm), NV center (ZPL of NV.sup.0 at 575 nm, ZPL of NV.sup.− at 638 nm), SnV center (ZPL at 620 nm) and MgV center (ZPL at 557 nm).

[0085] The background intensity (I.sub.backg) was determined in a certain region 50 (cf FIG. 4) in which no color centers appeared, and the intensity of these color centers 54 (I.sub.ref) was determined in a geometrically identical region 52 (cf. FIG. 5) in which a countable number of color centers 54 are located.

[0086] The sections shown in FIGS. 4 and 5 have edge lengths of about 10×10 μm.sup.2. Color centers 54 usually appear distinguishable, i.e., countable, in such images when their number does not exceed 3 to 4 per μm.sup.2.

[0087] If the color centers 54 were so countable, the conversion rate could be inferred directly by comparison with the ions that had flowed onto that area.

[0088] If this was not possible, the conversion rate was determined via reference values as follows. The reference value (I.sub.single) per color center 54 is determined as follows:

I.sub.single=(I.sub.ref−I.sub.bckg)/(number of color centers 54 in region 52)

[0089] For any given region 56, the density D.sub.FZ of the color centers 54 can now be determined from the total intensity I.sub.ens from the area S of that region 56 using the following relationship:

D.sub.FZ=1/S*(I.sub.ens−I.sub.backg)/I.sub.single

[0090] From this, the conversion rate UR can be determined by:

UR=D.sub.FZ/(ionic fluence during impurity atom incorporation).

[0091] Finally, the spin coherence time T2 and T2* were determined.

[0092] It was found that the conversion rate for NV-centers 54 for intrinsic diamond is about 6%-8%.

[0093] Doping with sulfur, oxygen, phosphorus or boron can significantly increase the conversion rate (sulfur: 75%, oxygen: 7%, phosphorus: 50% and boron:40%—see FIG. 6). However, only sulfur, oxygen and phosphorus can generate NV.sup.−-centers that enable qubits. These values were obtained with the following parameters: For doping, fluences and energies of phosphorus: 40 keV at 4.1×10.sup.12 cm.sup.−2 and 80 keV at 4.1×10.sup.12 cm.sup.−2, oxygen: 25 keV at 2.1×10.sup.12 cm.sup.−2 and 50 keV at 4.2×10.sup.12 cm.sup.−2, sulfur: 40 keV at 1.6×10.sup.12 cm.sup.−2 and 80 keV at 3.7×10.sup.12 cm.sup.−2 and boron: 25 keV at 2.1×10.sup.12 cm.sup.−2 and 50 keV at 4.2×10.sup.12 cm.sup.−2 were used, while impurity implantation with nitrogen was done at a maximum fluence of 10.sup.10 cm.sup.−2 and an energy of 40 keV.

[0094] Although this was not to be expected, very high conversion rates can therefore be achieved, especially with sulphur.

[0095] A higher temperature in the second annealing step 24 may result in a higher conversion rate to NV.sup.− centers (cf. FIG. 7, where this is shown by the difference in normalized fluorescence spectra for phosphorus as a dopant and an annealing change from 600° C. to 800° C. for different samples), which can be explained by the fact that the higher temperature cures vacancies acting as acceptors and also causes a higher mobility of vacancies from the nitrogen.

[0096] FIG. 8 shows that the coherence times for sulfur doping are excellent, i.e., as high as if there were no doping at all but an intrinsic diamond. For oxygen the coherence times are still very good, while for phosphorus doping not so good coherence times can be achieved.

[0097] Similar results were obtained for magnesium and tin, so that overall, it can be stated that doping can significantly increase the conversion rates. In this context, doping with a donor, such as phosphorus, oxygen or sulfur, can achieve a very good conversion rate into negatively charged color centers, which can be used for qubit applications.

[0098] Due to the high conversion rates, this gives a possibility to generate color centers deterministically in diamond.

[0099] A Feature 1 of the disclosure is a method (10) for generating at least one deterministic color center (54) in a diamond layer (15), characterized in that: [0100] in a first step (12), at least one dopant is implanted in the diamond layer (15), and [0101] in a second step (22), at least one impurity is incorporated in the diamond layer (15) by means of low-energy ion bombardment to form the color center (54), the ion bombardment (22) with impurities having an ionic fluence of up to 10.sup.10 cm.sup.−2.

[0102] A feature 2 of the disclosure is a method (10) according to feature 1, characterized, [0103] in that a donor, preferably phosphorus, oxygen, sulphur or lithium, or an acceptor, preferably boron, is used as the dopant and/or [0104] in that the impurity atom is selected from the group consisting of nitrogen, magnesium, carbon, lead, boron, noble gases, silicon, transition metals and tin.

[0105] A feature 3 of the disclosure is a method (10) according to any one of features 1 or 2, characterized, [0106] in that the color center is a NV.sup.−-center (54) and/or [0107] in that the ion bombardment (22) with impurity atoms having an ionic fluence in the range 10.sup.4 cm.sup.−2 to 10.sup.10 cm.sup.−2, preferably in the range 10.sup.7 cm.sup.−2 to 10.sup.10 cm.sup.−2, most preferably in the range 10.sup.8 cm.sup.−2 to 10.sup.10 cm.sup.−2, in particular in the range 10.sup.9 cm.sup.−2 to 10.sup.10 cm.sup.−2.

[0108] A feature 4 of the disclosure is a method (10) according to any one of the features 1 through 3, characterized, [0109] in that the dopant concentration is in the range 10.sup.17 cm.sup.−3 to 10.sup.19 cm.sup.−3, preferably between 1×10.sup.18 cm.sup.−3 and 9×10.sup.18 cm.sup.−3, and/or [0110] in that the dopant implantation (12) is carried out by bombardment with the dopants, in particular with energies of less than or equal to 150 keV and/or a dopant fluence in the range from 10.sup.9 cm.sup.−2 to 10.sup.13 cm.sup.−2, preferably in the range from 10.sup.10 cm.sup.−2 to 10.sup.12 cm.sup.−2, in particular in the range from 10.sup.11 cm.sup.−2 to 10.sup.12 cm.sup.−2, and/or [0111] in that the dopant implantation (12) takes place in at least two successively different steps, the dopant implantation (12) preferably taking place by dopant bombardment at different fluences and/or energies.

[0112] A feature 5 of the disclosure is a method (10) according to any one of the features 1 through 4, characterized, [0113] in that the depth of the implanted dopants is at least equal to the depth of the incorporated impurity atoms and/or [0114] in that the depth of the color centers (54) in the diamond layer (15) is in the range from 5 nm to 100 nm, preferably in the range from 10 rim to 50 nm, particularly preferably in the range from 10 nm to 30 nm, and in particular is between 20 nm and 30 nm.

[0115] A feature 6 of the disclosure is a method (10) according to any one of the features 1 through 5, characterized, in that after donor implantation (12) a first tempering step (20) is performed, wherein: [0116] i) the tempering temperature of the first tempering step (20) is preferably in the range 800° C. to 2000° C., in particular in the range 800° C. to 1400° C. and preferably in the range 1000° C. to 1200° C. and/or [0117] ii) the time for the first tempering step (20) is preferably between 1 h and 24 h, in particular between 2 h and 10 h, preferably between 3 h and 6 h.

[0118] A feature 7 of the disclosure is a method (10) according to any one of the features 1 through 6, characterized in that a second tempering step (24) is performed after the impurity incorporation (22), wherein: [0119] iii) the tempering temperature of the second tempering step (24) is preferably lower than that of the first tempering step (20) and/or preferably in the range 600° C. to 1300° C., in particular in the range 800° C. to 1000° C. and/or [0120] iv) wherein the time for the second tempering step (24) is preferably between 1 h and 24 h, in particular between 2 h and 10 h, preferably between 3 h and 6 h.

[0121] A feature 8 of the disclosure is a method (10) according to any one of the features 1 through 7, characterized in that an increase of the Fermi level is performed, the increase preferably being performed during the impurity implantation (22), after the impurity implantation (22) and/or during the second annealing step (24), the increase being performed in particular by LASER irradiation, electron bombardment or voltage application.

[0122] A feature 9 of the disclosure is a method (10) according to any one of the features 1 through 8, characterized [0123] in that the diamond layer (15) is present in a diamond material (14) having at least pure quality, the hydrogen content in the diamond layer (15) preferably being less than 10.sup.17 cm.sup.−3, and/or [0124] in that the diamond layer (15) is formed as a layer, preferably as a surface layer, within a diamond material (14) extending over a greater depth.

[0125] A feature 10 of the disclosure is a diamond layer (15) having at least one deterministic color center (54), characterized in that the impurity species used to form the color center (54) is present in an atomic number in the diamond layer (15) which is at most twice the number of the color center (54) in the diamond layer (15).

[0126] A feature 11 of the disclosure is a use of a diamond layer (15) having at least one deterministic color center (54) according to claim 10 or fabricated according to any one of the features 1 through 9 as a qubit container, preferably in the context of a sensor and/or in the context of quantum cryptography and/or in the context of a quantum computing application.

[0127] Unless otherwise indicated, all features of the present disclosure may be freely combined with each other. Also, unless otherwise indicated, the features described in the figure description may be freely combined with the other features as features of the disclosure. In this regard, a restriction of individual features of the examples to combination with other features of the examples is expressly not envisaged. In addition, representational features of the diamond coating can also be used as process features in a reformulated form, and process features can be used as representational features of the diamond coating in a reformulated form. Such a reformulation is thus automatically disclosed.

LIST OF REFERENCE SYMBOLS

[0128] 10 example process for the production of a deterministic color center
12 first step, implantation of dopants
14 diamond
15 diamond layer
16 ion beam source
18 aperture
20 first tempering step
22 second step, ion bombardment
24 second tempering step
30 trial sample
32, 34, 36 doping regions
38 graphite marker
40, 42, 44, 46 impurity atom regions
50 certain region of the diamond layer without color centers
52 geometrically identically sized region as the certain region 50
54 color centers, NV centers
56 arbitrary region
a, b, c impurity atom regions 40, 42, 44, 46 with different ion fluxes
D.sub.FZ density of color centers 54 using the following relationship from the
I.sub.backg background intensity
I.sub.ens total intensity
I.sub.ref intensity of color centers 54
I.sub.single reference value
S area of the region 56
T2, T2* spin coherence times
UR conversion rate