JPH01320211A - Hole burning substance and production thereof - Google Patents

Abstract

PURPOSE:To semipermanently retain holes by irradiating a single crystal of synthetic Ib type diamond, etc., with neutron beams and annealing the crystal by heating in vacuum. CONSTITUTION:A Ib type single crystal or polycrytal is obtd. by synthesizing diamond in the stable region or a Ib type single crystal or polycrystal is obtd. by vapor phase synthesis. The crystal is irradiated with 1X10<16>-2X10<19> neutrons per 1cm<2> by neutron beams or 1X10<17>-2X10<20> electrons per 1cm<2> by electron beams and annealed by heating at 600-1,400 deg.C for >=1hr in vacuum of <=1Torr to produce a hole burning substance having a zero-phonon line with N-V center. The zero-phonon line of the substance is then subjected to hole burning with laser light, etc., having >=5X10<-5>W/cm<2> energy density to form holes which undergo no change in the temp. range of 2-120K, do not vanish semipermanently and consists of semipermanent components having about 20sec, about 500sec and >=1hr time constants.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (a) Industrial Application Field Research is underway on three-dimensional optical memories that utilize photochromic effects and hole-burning effects as next-generation memories. TECHNICAL FIELD The present invention relates to a memory material and manufacturing method that utilizes the hole burning effect.

(b) Prior art The conventional technology uses a material in which an organic dye such as porphyrin or quinizarin is placed in a matrix such as n-hexane as a hole burning material. (Chemistry and industry
V o L 35. Nn9.1982 P633~6
35). In this case, it was necessary to lower the hole burning material to the temperature of liquid helium before use. Further, there were problems in that it took a long time to create holes for memorization, and the lifespan of the holes that were created was short.

In addition to organic dyes, there are examples in which alkali halide compounds are irradiated with electron beams to create color centers and used as hole-burning materials, but these have the same problems as the organic dyes mentioned above.

Furthermore, there are various color centers (GRI) in the diamond.
, N-v, H, , N, ) and conducted a hole burning experiment on it. In this case as well, there were the following problems.

(J, Phys, C, 5olid 5ta
te Physics, Vol 17 (198
4) P233-236. R, T, l1orl
ey etc) ■If the temperature is not below 20, the holes will disappear.

■Hole life is about 15 minutes.

■It is necessary to detect holes using microwaves.

The present invention solves the above-mentioned drawbacks (1) to (3) and provides an excellent hole burning material using a diamond color center.

Arrangement of the Invention (a) Means for Solving the Problems In the present invention, N-V of the color centers of a diamond
Hole burn the center zero phonon line. This is because the line is suitable for hole burning. This means is described in J. Phys.
C, 5solid 5tate Physics,
Vol 17 (1984) P233-23
6 is suggested.

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

The characteristics of the manufacturing method according to the present invention are shown below.

(a) As a matrix to create a color center,
Synthetic type Ib diamond is used. (Single crystal or polycrystal by ultra-high pressure synthesis or polycrystal or single crystal by vapor phase synthesis) (a) Use a neutron beam to create the color center, lXl x 1017 pieces/cd ~ 2 x 101s pieces/cd irradiate within the range of In addition, in the case of electron beam, lXl017~I
Irradiate in the range of X 1 x 1017 electrons/al.

(1) The temperature range is 600°C to 1400°C, and 1 t
Annealing is performed for at least 1 hour under a vacuum of orr or less.

Of the above, (a) and (v) are just limitations and are not major features of the present invention. A major feature of the present invention is that a large number of defects are created in a relatively large irradiation range using the neutron beam described in (a). An electron beam may be used, but in this case LX 10'? ~lx 1×1017elect, ro
It requires a fairly high dose of ns/crl.

The NV center concentration produced by the above-mentioned manufacturing method is high. In particular, it was found that zero phonons exhibit the following characteristics and can be used as excellent hole-burning materials.

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

(B) The created hole will not disappear semi-permanently.

(C) The created hole has a time constant of about 20 seconds and a time constant of about 50 seconds.
It consists of a semi-permanent component that lasts about 0 seconds to more than an hour.

(D) A hole can be created if the laser beam has an energy density of 5 XIQ-'w /cr1 or more.

E.) Effects The effects of the manufacturing method according to the present invention will be described, and then the effects of the characteristics will be described. The characteristics of the manufacturing method according to the present invention are (
a) As mentioned in the section on means to solve the problem, (7)
) There are three terms: (a) and (t). The following will be explained in order.

[Effect of (a)]

The N-V center consists of one nitrogen atom in the diamond,
It is a combination of vacancies. For this reason, type Ib diamond consisting of isolated and dispersed nitrogen is most suitable as the matrix. RB type diamonds are produced by the following five methods.

i) Selected natural diamonds 11) Single crystal synthesized by temperature difference method under diamond stability region.

iii) 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.

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

Among these, the present invention found that ii), 1ii), and v) are preferable in terms of high quality. Also, methods i) and iv) are not very suitable. Further, 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., and similar results were obtained in all cases.

[Effect of (a)]

To create an N-V center in a diamond, (
A) It is necessary to irradiate energy rays to create vacancies in areas other than the matrix. This step is very important, and the present invention has found that the following method is suitable.

l) When a neutron beam is used as the energy beam lX1
Irradiation is performed in the range of 0.016 to 2×10'' pieces/cm2.

Ii) When an electron beam is used as the energy beam I
1017~I X 1020electrons/
Irradiate within the ai 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 was not stable semi-permanently.

Moreover, 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. For this reason, a new problem arises in that the zero phonon line at the NV center cannot be clearly detected.

[Effect of (tsu)]

The action of annealing combines the nitrogen atoms in the matrix in (a) with the vacancies created in (b), resulting in N
-Create a V center. In the present invention, the temperature is 600°C to 1400°C.
It has been found that it is effective to carry out the test under a vacuum of 1 torr or less at a temperature range of 1 hour or more.

At temperatures below 600° C., absorption due to radiation damage (GRI centers) is not removed and NV centers are not formed. 14
At temperatures above 00°C, destruction of the NV center occurred. Furthermore, annealing for less than one hour caused a problem in that absorption due to irradiation damage could not be removed. Furthermore, at a vacuum level of 1 torr or more, the surface of the diamond became graphitized.

Next, we will discuss the effects of the characteristics.

The characteristics according to the present invention range from (Δ) to (D) as described in the section (a) Means for Solving the Problem. The winter effect will be explained below.

[Action of (Δ)(B))] As shown in Fig. 3, holes once created do not disappear even when the temperature of the liquid f(e is in the range from 120°C to 120°C. When the temperature exceeds 120°C, the holes begin to disappear, and Due to this effect, the hole burning effect, which conventionally did not occur unless liquid He was used, can now occur even at liquid nitrogen temperatures.

Also, since the created hole does not disappear semi-permanently,
Great progress has been made towards practical application.

[Effect of (C)] The created hole consists of three segments with different time constants. Of these, semi-permanent components lasting longer than a few hours could be detected with laser light.

Conventionally, detection was only possible using microwaves, but the effects of the present invention have made it possible to fabricate an optical memory with high two-dimensional integration density and fast response. Furthermore, it has been found that the hole according to the present invention, unlike conventional holes, does not respond to microwaves and can withstand electromagnetic disturbance.

[Effect of (D)] This effect makes it possible to create holes using weak laser light. In addition, the time required to create holes is short, making it possible to create a small and inexpensive optical memory using a semiconductor laser or the like as the excitation light.

Example-1 Synthesis was performed using a temperature difference method at a pressure of 5.4 GPa and a temperature of 1400°C. 2ct nitrogen containing ffi 90ppm ib
A molded diamond was machined to a size of 6x 6X l mm.

After irradiating the sample with a neutron beam at a dose of 5 x 101 S to 5 x 10'' particles/cat, annealing treatment was performed at 900°C for 20 hours under a vacuum of 10-''torr. Using a visible spectrometer. The existence of an N-V center was confirmed.The nitrogen content in the RB diamond was determined from the absorption coefficient at 1130 am-' in infrared spectroscopy.Figure 1
A hole was opened in the zero phonon line of the N-V center using the method shown in Figure 2. In the figure, sample 6 is exposed to laser 1.
A hole was formed by applying a laser beam 7 to the hole. Further, the shutter 2 was used to turn off the irradiation of the laser beam 7. To observe the hole, laser beam 8 is oscillated by laser 3.
After passing through an attenuation filter 4, the sample was passed through, and the transmitted light intensity was measured with a detector 5.

Figure 2 shows typical observation results. 11 in Figure 2
The 0 curve shows the value measured by the detector shown in 5 in Figure 1. The horizontal axis shows time, and the vertical axis shows transmitted light intensity. The strength before hole burning is shown in p in Figure 2.

When the sample is irradiated with the laser beam 7 oscillated by the laser 1 by the shutter 2, a hole is generated at time 12, and the transmitted light intensity increases. When the irradiation light 7 is cut off by the shutter 2 at time 13, the negative hole is recovered, but
There is an intensity ΔIp that does not return semi-permanently. This Δr
Use p as memory.

In this example, 0.5 mW of He is used as laser 1 or 3.
-Ne laser was used. Further, a filter 4 having an attenuation rate of 1/10.0 was used. The measurement results are shown in Table-1. The sample was cooled by a taliostat.

Table 1 * Ip and Δrp indicate the transmitted light intensity and increase in FIG. 2, respectively.

Example 2 Diamond synthesized in a vapor phase was irradiated with an electron beam of 5 MeV with an energy in the range of 101' to 1021 electrons/CIl+. Diamond synthesized in a vapor phase is produced by plasma CVD.
By the method, under a pressure of -30 torr, plasma is generated with a high frequency of 2.4 GHz, and 5μ is doped while doping with nitrogen element.
The substrate was grown to a thickness of 100 μm on a Si substrate at a growth rate of m/Hr, and then the Si substrate was treated with an acid to dissolve it.

The obtained thin film was polycrystalline. Also, DC plasma method,
Diamond thin films synthesized by microwave plasma method, laser PVD method, hot filament method, hot filament CVD method, and ion beam evaporation method were used, but results similar to those of this example were obtained. In addition to Si substrates, Mo,
W, Ti, Zr.

Hf, WC, 5iOz, SiC, MoC, TiC
, ZrC, IIfC.

Similar results were obtained using U, O, diamond single crystals, and the like. When a diamond single crystal was used as the substrate, a single crystal was obtained.

The synthetic diamond irradiated with the electron beam was annealed under a pressure of 1 torr for 5 hours at 600"c, and then hole-burned and measured using the same method as in Example 1. The results are shown in Table 2.

The lasers 1 and 3 required for the measurement were wavelength tunable by combining A'- and Dye lasers. The output was 5 mW, and the filter 4 was 1/1.
One with an attenuation factor of 000 was used.

Example-3 Three samples prepared under the same conditions as in Experiment Nα3 in Example 1 were prepared, and the intensity and temperature dependence of transmitted light were examined in the same manner as in Example-1. The temperature is 7.5K.

120 and 300K were selected and measured. The results are shown in Figure 3.

Each dotted line 2], 22 and 23 in Figure-3 are experiment Nn2
1 (measured at 7,5), Nα22 (120K),
The transmitted light intensity curve is shown as a function of the time after closing the shutter 2 at Nα23 (300K>. The vertical axis represents the transmitted light intensity;
Time is shown on the horizontal axis. rp in Figure-3 is 7 in Figure-1
Indicates the transmitted light intensity before a hole is formed by the laser beam shown in , and 8hp indicates the increase in transmitted light caused by the formed hole.

As can be seen from the results of experiments Nα21, 22, and 23 in Figure 3, the time change of transmitted light is the same between 7.5 and 120;
The formation of the holes is the same. However, at 300K, Δ
T p /T p '-0.05 or so, indicating that the hole component is significantly lost.

Example 4 One sample prepared under the same conditions as in Experiment Nα3 in Example 1 was prepared, and the intensity and time change of transmitted light were examined in the same manner as in Example 1. The experiment was carried out at a temperature of 80°C.

Note that the measurement start time was defined as the time when the shutter indicated by 2 in Figure 1 was closed (the end of hole burning). The results are shown in Table-3. It can be seen that even after 10 hours, the increase due to the hole is preserved semi-permanently.

Example-5 Under the same conditions as those produced in Experiment Nα4 in Example 1,
Four samples were prepared. Example using the device shown in Figure 1-
The same measurements as in 1 were performed. In this example, the shutter was opened at the time 12 shown in Figure 2, and we investigated how the intensity of the transmitted light 11 changes depending on the intensity of the hole forming laser beam 7 shown in Figure 1. Ta. Table 4 shows the results.
Shown below.

Note that the hole formation time refers to the time required for the transmitted light intensity to increase by 10% due to hole burning. (
(Time for ΔIH/Ip to reach 0.10 in Figure 2) It was found that the energy intensity of the laser beam required to form holes in this way should be 5 x 1O-5W/cut or more.

C. Effects of the invention As mentioned above, hole burning is now possible at an unprecedentedly high temperature range (2 to 120K), holes are formed in a short time, and the holes once formed can last semi-permanently. .

The present invention has facilitated the practical application of three-dimensional memory using hole burning.

[Brief explanation of the drawing]

FIG. 1 shows a method for measuring hole burning. 1.7 is a hole forming laser and laser light, 3.8
indicates observation laser and laser light. Further, 2 is a shutter, 4 is an attenuation filter, 5 is a measurement detector, and 6 is a sample. Figure 2 shows typical measurement results. 11 indicates the transmitted intensity curve. FIG. 3 shows the relationship between transmitted light intensity and time when the experimental temperature was varied from 7.5 to 300 K. Dotted lines 21.22°23 indicate the measurement results at 7.5K, 120K, and 300K, respectively. 20th year of construction

Claims (5)

[Claims] (1) Using the zero phonon line of the N-V center that exists in diamond, the number of holes created once is 2 to 1.
A hole-burning material using synthetic type Ib diamond that does not change in the temperature range of 20K and lasts semi-permanently. (2) The hole burning material according to claim 1, wherein the holes are formed by a laser beam of 5×10^-^5 W/cm^2 or more. (3) The hole burning material according to claim 1, wherein the holes are made of a semi-permanent component with time constants of approximately 20 seconds, 500 seconds, and 1 hour or more. (4) To create a hole-burning material, use Ib type single crystal or polycrystal synthesized under the diamond stability region or Ib type single crystal or polycrystal synthesized in vapor phase,
After irradiating with neutron beam in the range of ^1^5 to 2 x 10^1^9 pieces/cm^2, under vacuum of 1 torr or less and at 600℃
4. The method for producing a hole burning material according to claim 1, 2 or 3, wherein the annealing is performed at a temperature range of 1400 DEG C. for 1 hour or more. (5) To create a hole-burning material, use Ib type single crystal or polycrystal synthesized under the diamond stability region or Ib type single crystal or polycrystal synthesized in vapor phase,
After electron beam irradiation in the range of ^1^7 to 2 x 10^2^0 pieces/cm^2, under vacuum of 1 torr or less and at 600 °C ~
4. The method for producing a hole burning material according to claim 1, 2 or 3, wherein the annealing is performed at a temperature range of 1400° C. for 1 hour or more.