JPH0222641A - Hole burning substance and production of same - Google Patents

Abstract

PURPOSE:To enable repeating writes at any optional position by using the zero phonon line of an N-V center present in diamond and erasing holes located in any position by irradiating them with exciting light containing no zero phonon line and having energy more than the zero phonon line. CONSTITUTION:The holes once produced by using the zero phonon line of the N-V center present in the diamond are retained semipermanently without changing in the temperature range of 2-120 deg.K and any holes located at optional positions can be erased by the irradiation with the exciting light containing no zero phonon line and having energy more than said line, and synthetic Ib type diamond is used in this process, and in this case, they can be erased more easily by irradiation with exciting light having energy of >=1 phonons in a short time. A color center is formed by irradiating with nutron beams in an amount of 1.5X10<16>-1.5X10<19>/cm<2>, thus permitting a memory to be repeatedly written in and erased off at the optional position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a hole burning substance and a method for producing the same.

As a next-generation memory, research is underway on three-dimensional optical memory that utilizes photochromic effects and hole-burning effects. The present invention relates to a memory material and manufacturing method that utilizes the hole burning effect of the color center of diamond.

[Prior Art] Conventionally, as a hole-burning substance, a substance in which an organic dye such as porphyrin or quinizarin is placed in a matrix such as n-beef sun has been used (``Chemistry and Industry'' Vol. 35, Vol. 9). (1982) pp. 633-635).

In this case, it is necessary to use a hole-burning material brought down to the temperature of liquid helium, and many materials also have the disadvantage that the lifetime of the holes once created is short. On the other hand, materials with semi-permanently long hole lifetimes have the disadvantage that they cannot be erased. In this case, in order to erase the holes, it is necessary to first raise the temperature from the liquid helium temperature to around room temperature, but there is a drawback that if the holes are erased by increasing the temperature, all the holes will be erased.

In addition to organic dyes, alkali halide compounds,
Although there are examples of creating color centers by electron beam irradiation and using them as hole-burning materials, they have the same problems as the organic dyes mentioned above.

Furthermore, there are various color centers (GR) in the diamond.
I, N-V, N3, N3) and conducted hole burning experiments on them [Journal of
Physics, C, Solid State Physics (J, Phys, C.

5solid 5tate Physics, ), No. 17
Volume (1984) 233-236゜R.T. Holly (R.

"l", Horley) et al. ]. Even in this case, there were the following problems.

■If the temperature is not below 20, the hole will disappear.

■Most of the holes disappear in about 15 minutes.

■It is not possible to erase just any hole at the temperature where the hole exists.

[Problems to be Solved by the Invention] The present invention solves the above drawbacks (1) to (3) and provides an excellent hole burning material using a diamond color center.

[Means for Solving the Problems] That is, the present invention solves the problem of N-V present in diamond.
Using the center zero phonon line, the hole once created does not change in the temperature range from 2 to 120℃.
and lasts semi-permanently, and furthermore, the hole at any position can be erased by irradiation with excitation light that does not contain the zero phonon line and has energy greater than the zero phonon line, especially excitation light having energy greater than or equal to 17 years old. Hole-burning materials using synthesized Ib type diamond, which can be erased in a short time by irradiation with is polycrystalline, and the nitrogen-containing imitation in the crystal is lXl
0′e~3X1016~1.5×1019 pieces/cy, 3
1.5×1016~1.5×1
After neutron beam irradiation in the range of 019 to 1.5XIO"/cff", under vacuum of 1 torr or less and 600 to 140
Provided is a method for producing the diamond hole-burning material described above, characterized in that annealing is performed at a temperature range of 0° C. for 1 hour or more.

In the present invention, within the color center of the diamond, N-V
Hole burn the center zero phonon line. This is because the zero phonon line is suitable for hole burning. This approach is suggested in the Journal of Physics, C. Solid State Physics, supra.

Hereinafter, first, the characteristics of the method for manufacturing the hole burning element according to the present invention will be described, and then the characteristics of the material will be described.

Characteristics of the manufacturing method> The characteristics of the manufacturing method according to the present invention are shown in (A) to (T) below.

(a) As a matrix to create a color center,
Synthetic type Ib diamond, nitrogen-containing 1 is IX
1018~3X1016~1.5x1019 pieces/cyx
Synthetic diamonds are single crystals or polycrystals produced by ultra-high pressure synthesis, or polycrystals or single crystals produced by vapor phase synthesis.

(b) To create a color center, use a neutron beam, 1.5X 1016~1.5x1019~1.5X
Irradiate in the range of 10 Ie/ax 2. In addition, in the case of electron beam, 2X 1016 ~ 1.5 x 1019 ~
Irradiate in the range of 1.5×10 16 to 1.5×10 19 electrons/ax”.

(1) Annealing is performed under a vacuum of 1 torr or less at 60°C.
It is carried out at a temperature range of 0 to 1400°C, preferably 650 to 1200°C, for 1 hour or more.

Among the above, (a) synthetic type Ib diamond is known, but it is not known that excellent results can be obtained when using one with a nitrogen content in the above range for the production of hole burning materials. .

The most notable feature of the present invention lies in (a) neutron beam or electron beam irradiation conditions. As mentioned above, it is necessary to create a color center under relatively high irradiation conditions.

The N-V center zero phonon produced under the above conditions has a wide wavelength range, exhibits the following characteristics, and functions as an excellent hole-burning material.

(A) Even if the temperature ranges from 2 to 120 degrees Celsius, the holes once created do not disappear.

(B) The created hole is semi-permanent, for example, does not disappear for at least one hour.

(C) Holes are extinguished by excitation light that does not contain zero phonons and has energy greater than the zero phonon line.

In particular, it disappears in a short time, for example, 300 seconds or less, by excitation light having an energy of one phonon or more.

[Function] The function of the manufacturing method according to the present invention will be described, and then the characteristics will be described.

Effect of the manufacturing method> Effect of (a) The N-V center is a bond between one nitrogen atom and a vacancy in diamond. For this reason, type Ib diamond consisting of isolated and dispersed nitrogen is most suitable as the matrix. Type Ib diamonds are created by any of the following five methods.

i) Selected from natural diamonds.

i) Single crystal synthesized by temperature difference method under diamond stability region.

1ii) Polycrystal synthesized by sintering method under diamond stability region.

iv) A single crystal for abrasive grains synthesized by a film growth method under the diamond stability region.

V) Single crystal or polycrystal created by vapor phase synthesis method.

Among these, in the present invention, I of ii), iii), and V)
B-type diamonds are preferred in terms of size and quality.

Although type Ib diamonds i) and iv) can also be used, they are less suitable than the former.

In the present invention, the amount of nitrogen contained in the type Ib diamond is 1X10'' to 3X1016 to 1.5×1019 pieces/C.
jI3 is used. Below the above range, erasure of the hole created once does not occur below 120. Further, above the above range, the concentration of the NV center is too high, making writing and erasing difficult.

Vapor phase synthesis methods include microwave CVD method, DC plasma method, laser PVD method, thermal filament method, thermal filament CVD method, ion beam evaporation method, etc., but type Ib diamond produced by any of these methods has the same Get results.

Effect of (a) In order to create an N-V center in diamond, it is necessary to irradiate energy rays to create vacancies in areas other than the matrix of (a). Therefore, this step is very important, and the following conditions are adopted in the present invention.

i) When a neutron beam is used as the energy beam, 1.5
Irradiation is performed in the range of X 1016 to 1.5×1019 to 1.5X to"pieces/CjI".

ii) When an electron beam is used as the energy beam, 2
10”~1.5 X I O”electrons
/ci'' range.

In this case, even if the zero phonon line at the NV center is hole-burned below the lower limits of i) and ii), the created hole will change if it exceeds 20K. Further, the life of the hole is not stable semi-permanently. Furthermore, even if we irradiate excitation light with energy higher than zero phonon, 1
At temperatures below 20°C, the holes created once cannot be erased.

Further, above the upper limits of i) and ii), the diamond lattice is significantly damaged by the energy rays, and strong absorption occurs in a wide wavelength range. Therefore, a new problem arises in that the zero phonon line at the NV center cannot be clearly detected.

The effect of annealing is to combine the nitrogen atoms in the matrix of (a) with the vacancies created by (b), resulting in N-
It is to create a V center. In the present invention, 600 to 1
It is carried out at a temperature range of 400'C for at least 1 hour under a vacuum of less than 1 torr.

At temperatures below 600° C., absorption due to radiation damage (GRI centers) is not removed and NV centers are not formed. 1
At temperatures above 400'C, destruction of the N-V center occurs. Furthermore, annealing for one hour or less causes the problem that absorption due to irradiation damage cannot be removed. Further, at a vacuum level of 1 torr or more, the surface of the diamond becomes graphitized. If the irradiation dose is large, the GRI center may not be completely removed, but it will be removed at 650° C. or higher. Also, N-V
The center temperature starts to decrease little by little from 1200'C.

Therefore, it is preferable to perform annealing at a temperature of 650 to 1200°C.

Next, we will discuss the effects of the characteristics.

Effects of Characteristics> Effects of (Δ) and (B) As shown in FIG. 1, holes once created do not disappear even in the range of liquid helium temperature to 120°C. When the number reaches 120 or more, the holes start to disappear, and at 300, they disappear considerably. Due to this effect, the hole burning effect, which conventionally did not occur unless liquid helium was used, occurs even at liquid nitrogen temperatures.

In addition, the created holes do not disappear semi-permanently, making it possible to put them into practical use.

Effect of (C) This effect is the greatest feature of the present invention.

Once formed, conventional holes could only be erased by raising the temperature to near room temperature. However, when this process is performed, holes in the entire area are erased, and it is not possible to erase only holes at arbitrary positions.

Hole burning using a zero phonon line according to the present invention makes it possible to eliminate holes at any position by applying excitation light that does not contain zero phonons and has energy greater than zero phonons. In particular, 171
By applying excitation light with an energy of 77 or more, holes can be eliminated in a short time. This effect makes it possible to repeatedly write and erase holes at arbitrary positions using hole burning.

[Example] Example 1 Using the temperature difference method, 5.50 Pa and 1350 to 142
Under pressure and temperature conditions of 0'C, the size is 3 to 3.2 karat, and the nitrogen content is 5 x 1017 to 5 x 1020 pieces/cj
Five type Ib diamonds in the I3 range were created.

Furthermore, the diamond sample is 7III (width) x 6i
Each was processed to a size of x (length) x (0, 2 to 3) Rx (thickness).

After irradiating the sample with a neutron beam at a dose of 1.2 x 10'7 particles/cm'', the sample was heated at 800°C under a vacuum of 10-1 torr.
Annealing treatment was performed for 10 hours. The nitrogen content in the sample was calculated from the absorption coefficient at 1130 cm-' in infrared spectroscopy. In addition, the color center created in the sample was measured using an ultraviolet-visible spectrometer.

Hole burning measurements were performed as follows.

As shown in FIG. 2, a hole was first formed by irradiating a sample 16 with a laser beam 17 oscillated by a laser 11. Sample 16 was set in a cryostat indicated by a dotted line. The laser beam 17 was turned off by the shutter 12.

The holes were observed by passing the laser beam 18 oscillated by the laser 13 through the attenuation filter 14 and then measuring the intensity of the transmitted light 19 with the detector 15.

Moreover, typical observation results are shown in FIG. A curve 21 shows the transmitted light intensity observed by the detector 15.

The horizontal axis represents time, and the vertical axis represents intensity.

Let Ip be the intensity of transmitted light in the detector 15 before hole burning. When the laser beam 17 is applied to the sample from the shutter 12 at time 22 in FIG. 3, a hole is formed and the transmitted intensity increases by ΔIH. At time point 23, when the shutter is closed, the short-time component is relaxed and the semi-permanent component Δlp remains. The presence of holes is investigated by the intensity ratio of ΔI p/I p.

In this example, a wavelength tunable laser that is a combination of an Ar'' laser and a Gy laser was used.The oscillation wavelength was 638 nm.
It was m. The results are shown in Table 1.

In addition, the presence or absence of hole erasure was determined by adjusting the output wavelength of the laser u to the first phonon wavelength of the N-V center in Fig. 2, opening the shutter 12, and checking the intensity of the transmitted light 19. .

Example 2 Using plasma CVD method, under a pressure of 25 torr, 2
, 200 μm of diamond was grown on the Si substrate at a growth rate of 7 μth order/hour while plasma was generated at a high frequency of 4 Hz and nitrogen element was doped.

Thereafter, a diamond thin film obtained by treating and dissolving the Si substrate with acid was used as a sample. The obtained thin film was polycrystalline. The thin film was cut into 6 pieces, and 5 of them were cut into 8×10 pieces.
16~1.5x1019~3X1016~1.5x10
Neutron beam irradiation was performed in the range of 19 atoms/Cx''.The remaining sample was chemically analyzed and the nitrogen content was measured, which was 4X1019 atoms/ax3.The sample was Q, 1to
Annealing was performed at 650° C. for 1 hour under a vacuum of RR, and hole burning and erasing experiments were performed in the same manner as in Example 1. The results are shown in Table 2.

In addition to the above-mentioned vapor phase synthesis method, the same results as in this example were obtained by using a DC plasma method, a thermal filament method, a thermal filament CVD method, an ion beam evaporation method, a microwave plasma method, and a laser PVD method. It was done. In addition to Si substrates, M□ and WSTi.

Zr, Hf and their alloys or carbides, SiO,
, Al1,03, SiC, and diamond single crystal were used as substrates, similar results were obtained.

When a diamond single crystal was used as a substrate, a single crystal thin film was obtained.

Example 3 Five RB-type synthetic diamonds (2, 8 to 3.2 carats) and 6 M
It was processed into a size of IX 6 mm x 1 mm.

5×1016 to 1.5×1019 to 5×10 to the sample
Electron beam irradiation was performed at a dose of 16 to 1.5 x 1019 electrons/cm". Thereafter, under a vacuum of 1 torr,
Annealing was performed at 00'C for 5 hours. The nitrogen content was determined in the same manner as in Example 1.

The presence of color centers and the elimination of hole burning holes were measured. The results are shown in Table 3. Example 4 The sample used in Experiment No. 24 in Example 3 was prepared as follows.
The formation of holes was investigated by varying the temperature between 5 and 300 degrees Celsius. The results are shown in FIG. 1 and Table 4.

As shown in FIG. 1, it can be seen that even after about 10 hours, the increase in the transmitted light due to the holes does not change below 120 and continues semi-permanently.

Note that 1 to 3 in FIG. 1 indicate temporal changes in transmitted light intensity.

Example 5 Using the samples used in Experiment Nos. and 3 in Example 1, hole writing and erasing experiments were conducted as described below.

The details of the experiment are shown below. All experiments were conducted at a sample temperature of 120K.

■ Examine whether holes are formed even if the wavelength is changed.

(2) Examine whether it is erased by excitation light of 630 nm (irradiation with excitation light of zero phonon or higher, not including the zero phonon line).

(2) Examine whether it is erased by excitation light of 580 nm and 550 nm (irradiation with excitation light for children aged 17 years or older).

■ Repeat steps ■ and ■ to determine whether writing and erasing is possible.

In order to change the wavelength of (2), an etalon was incorporated into the gray laser shown at 11.13 in FIG. 2 to enable minute wavelength changes. The wavelength of the excitation light (for writing) 17 for hole burning is changed, and the shutter 1
2 was opened and sample 16 was irradiated. The transmitted light wavelength 18 was also varied in the vicinity of wavelength 17 using an etalon, and the presence or absence of holes was investigated by measuring the hole profile.

To erase the holes ① and ②, change the wavelengths 17 and 18 to the same value in advance, open the shutter 12, and
After creating a hole on 6, Sha.

635.585.550 and only 17 wavelengths
The holes were irradiated at different wavelengths, and the hole erasure was determined from the change in the intensity of the transmitted light 19.

The results are shown in Table 5.

As can be seen from Table 5, in the range of the zero phonon line,
It can be seen that it is an excellent memory that can be written at any wavelength, erased in a short time by irradiating it with excitation light having an energy greater than (1) phonon, and can be repeatedly written and erased.

[Effects of the Invention] As explained above, it has become possible to provide a memory using hole burning that allows repeated writing and erasing at any position.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the temporal change in the intensity of light transmitted through the hole when the temperature is changed. 1 and 2.3 represent the transmitted light intensity at each temperature, Ib represents the transmitted light intensity before the hole is created, and ΔIp represents the increase in the transmitted light due to the hole. FIG. 2 is a schematic diagram of an apparatus for measuring hole creation and deletion. 11 is a laser for creating and erasing holes;
12 is a Nyanotar, 13 is a hole measurement laser, 14
is an attenuation filter, 15 is a detector for measuring transmitted light,
Reference numeral 16 indicates a sample, 17 indicates a laser beam for hole creation or erasure, 18 indicates a laser beam for hole measurement, and 19 indicates transmitted light. Moreover, the dotted line around the sample 16 indicates a cooling taliostat. FIG. 3 shows an example of hole measurement. Ip represents the transmitted light intensity of the sample before hole formation, and ΔIH1Δlp represents the increase in transmitted light caused by hole formation. 21 is the intensity of transmitted light, 22 is the time when the shutter is opened,
23 indicates the closing point. Patent applicant Sumitomo Electric Industries, Ltd. Representative Patent attorney Haka Aoyama Figure 1 Time (soup)

Claims (1)

[Claims] 1. Using the N-V center zero phonon line existing in diamond, the number of holes once created is 2 to 12.
It is characterized in that it persists semi-permanently without changing in the temperature range of 0K, and that the hole at any position can be erased by irradiation with excitation light that does not contain the zero phonon line and has energy greater than the zero phonon line. Hole-burning material using synthesized type Ib diamond. 2. The diamond hole burning material according to claim 1, wherein the holes can be erased in a short time by irradiation with excitation light having an energy of one phonon or more. 3. Ib type single crystal or polycrystal synthesized in the diamond stability region or Ib type single crystal or polycrystal synthesized in the gas phase, and the nitrogen content in the crystal is 1×
10^1^■ ~ 3 x 10^2^0 diamonds/cm^3, 1.5 x 10^1^6 - 1.5 x 10^
After neutron beam irradiation in the range of 1^9 pieces/cm^2, 1to
3. The method for producing a diamond hole-burning material according to claim 1 or 2, characterized in that annealing is carried out under a vacuum of RR or lower and at a temperature range of 600 to 1400° C. for 1 hour or more.