WO2005064636A1 - 電子放出材料とこれを用いた電子放出素子 - Google Patents
電子放出材料とこれを用いた電子放出素子 Download PDFInfo
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- WO2005064636A1 WO2005064636A1 PCT/JP2004/018937 JP2004018937W WO2005064636A1 WO 2005064636 A1 WO2005064636 A1 WO 2005064636A1 JP 2004018937 W JP2004018937 W JP 2004018937W WO 2005064636 A1 WO2005064636 A1 WO 2005064636A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/30—Cold cathodes, e.g. field-emissive cathode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/14—Solid thermionic cathodes characterised by the material
Definitions
- the present invention relates to an electron-emitting material containing a semiconductor and an electron-emitting device using the same.
- electron-emitting materials composed of metal oxides have been widely used for electron sources such as cathode ray tubes.
- the above-mentioned electron-emitting material requires a high temperature to emit electrons.
- an electron emitting material composed of a mixture of barium oxide, strontium oxide, and calcium oxide requires a temperature of about 660 ° C to 670 ° C to obtain a current density of 1 A / cm 2 .
- an electron-emitting material containing a semiconductor is known.
- the work function can be reduced by depositing an element different from the element constituting the semiconductor on the surface.
- J. Vac. Sci. Technol. B, vol. 16, 2224 (1998) reports the relationship between the amount of Cs deposited on the (0001) plane of GaN and the work function. According to reports, as the amount of deposited Cs increased, the value of the work function rapidly decreased from the value on a clean GaN surface to a minimum value. Later, it gradually approaches the value of Cs itself. That is, by the deposition of Cs, an electron-emitting material having a work function smaller than the work functions of the substrate (GaN) and the deposited material (Cs) itself can be obtained.
- an alkali metal, an alkaline earth metal, or an alkali metal or an alkaline earth metal is provided on a step site 104 of a metal substrate 101 made of tungsten having periodic atomic steps on its surface.
- a material has been disclosed in which the work function is reduced by adsorbing oxide atoms 103 of FIG.
- Example 1 of H09 (1997) _223455A / JP when the inclination angle of the (110) plane of the tungsten substrate is 6 ° or more (that is, the step period 102 shown in FIG. 16 is 2.5 nm or less), It is shown that the function can be further reduced (Fig. 17).
- the vertical axis represents the amount of change in work function (eV)
- the horizontal axis represents the tilt angle (°) of the substrate.
- the electron emission material of the present invention includes a semiconductor substrate having a plurality of atomic steps on a surface and a flat portion between two adjacent atomic steps, and an adsorption layer disposed on the flat portion.
- the adsorption layer contains at least one element selected from alkali metal elements, alkaline earth metals, and Sc (scandium).
- Such an electron-emitting material is provided on a semiconductor substrate having a plurality of atomic steps on a surface and a flat portion between two adjacent atomic steps, on an alkali metal element or an alkaline earth metal. It can be produced through a vapor deposition step of vapor depositing at least one element selected from Sc and Sc. By such a vapor deposition step, at least one element selected from the group consisting of an alkali metal element, an alkaline earth metal and Sc is disposed as an adsorption layer on a flat portion.
- An electron-emitting device is an electron-emitting device including an electron-emitting layer containing an electron-emitting material, and an accelerating electrode arranged so as to face the electron-emitting layer.
- FIG. 1 is a diagram schematically showing an example of the structure of the electron-emitting material of the present invention.
- FIG. 2 is a diagram schematically showing the vicinity of the surface of a semiconductor substrate in the electron-emitting material shown in FIG. 1.
- FIG. 3 is a view schematically showing another example of the structure of the electron-emitting material of the present invention.
- FIG. 4 is a schematic view for explaining an example of the surface structure of the electron-emitting material of the present invention.
- FIG. 5 is a diagram schematically showing another example of the structure of the electron-emitting material of the present invention.
- FIG. 6 is a diagram schematically showing a part of a semiconductor substrate in the electron-emitting material shown in FIG.
- FIG. 7 is a diagram schematically showing yet another example of the structure of the electron-emitting material of the present invention.
- FIG. 8 is a cross-sectional view schematically showing one example of the electron-emitting device of the present invention.
- FIG. 9 is a diagram showing a state of a surface of an electron-emitting material of the present invention produced in an example.
- FIG. 10 is a view schematically showing a structure of a surface of a semiconductor substrate used in an example.
- FIG. 11 is a diagram schematically showing a structure of a surface of a semiconductor substrate used in an example.
- FIG. 12A and FIG. 12B are process diagrams schematically showing one example of a method for manufacturing an electron-emitting device of the present invention.
- FIG. 13A and FIG. 13B are process diagrams schematically showing another example of the method for manufacturing an electron-emitting device according to the present invention.
- FIG. 14 is a view schematically showing an example of a change in the surface structure of the semiconductor substrate shown in FIG. 13A.
- FIG. 15A to FIG. 15C are process diagrams schematically showing still another example of the method for manufacturing an electron-emitting device according to the present invention.
- FIG. 16 is a schematic diagram showing an example of a surface structure of a conventional electron emission material.
- FIG. 17 is a view showing an example of a measurement result of a work function of a conventional electron emission material.
- FIG. 1 shows an example of the structure of the electron-emitting material of the present invention.
- the electron-emitting material 1 shown in FIG. 1 has a structure in which an adsorption layer 5 is disposed on a flat portion (terrace surface) 4 of a semiconductor substrate 2 (hereinafter, also referred to as “substrate 2”) having a plurality of atomic steps 3 on its surface. have.
- a flat portion 4 is located between adjacent atomic steps 3.
- the adsorption layer 5 contains at least one element A selected from an alkali metal element, an alkaline earth metal element, and Sc (scandium). With such a configuration, the electron-emitting material 1 with a reduced work function can be obtained.
- FIG. 2 shows the vicinity of the surface of the base 2 in the electron-emitting material 1 shown in FIG.
- dangling bonds 53 are present between the atoms 51 located in the atomic step 3 and the atoms 52 located in the flat portion 4 due to the difference in the arrangement of adjacent atoms.
- Direction and number are different. Therefore, in the vicinity of the atomic step 3, the distribution of the charge on the surface of the substrate 2 is deviated, and the distribution is in the direction along the atomic step 3 (in FIG. 2, the direction perpendicular to the paper).
- An array of electric dipoles is formed. It is considered that when the electric dipole is formed, the electronic state of the surface of the substrate 2 changes, and the work function can be reduced.
- the work function is reduced by using the substrate 2 having the atomic steps 3 on the surface.
- the magnitude relation of the black circles indicates the relative positional relation of the atoms (the atoms indicated by the large circles are located in the foreground).
- the illustration of the adsorption layer 5 is omitted.
- the adsorption layer 5 containing the element A is disposed on the flat portion 4 of the base 2. Due to the arrangement of the adsorption layer 5, an electric dipole is further formed between the atoms of the substrate located in the flat portion 4 and the (elements of) the element A adjacent to the atoms.
- the effect of the electric field induced by the electric dipole is expected to be typically on the order of a few nanometers, since the electric field shielding effect of the carrier is relatively small. That is, in the electron emission material of the present invention, the dipole moment induced by the atomic step and the dipole moment induced by the adsorption layer arranged on the flat portion act synergistically, and are merely the original.
- the work function can be further reduced as compared with an electron-emitting material including a substrate having child steps.
- Such a structure can be formed when the element A is arranged on the flat portion 4, for example, by controlling the arrangement amount (evaporation amount) and / or temperature.
- an alkali metal element, an alkaline earth metal element, or an oxide of these elements is arranged at an atomic step (at a step site). (Fig. 16), and no elements are arranged on the flat part. Even in such a configuration, the arranged element induces a dipole moment near the atomic step. However, almost no dipole moment is induced in the flat part, and the interaction between the dipole moment of the atomic step and the dipole moment of the flat part cannot be obtained. For this reason, with the electron-emitting material disclosed in H09 (1997) -223455A / JP, it is difficult to reduce the work function like the electron-emitting material of the present invention.
- Element A is composed of Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium), Ca (calcium), Sr (strontium), Ba (barium) and Sc (Scandium) force
- the adsorption layer 5 preferably further contains oxygen that may contain an element other than the element A.
- oxygen may contain an element other than the element A.
- the state of oxygen in the adsorption layer 5 is not particularly limited, but is preferably a state chemically bonded to the element A.
- the material of the base 2 is not particularly limited, and for example, a semiconductor of a single element such as Si or a compound semiconductor may be used.
- a semiconductor of a single element such as Si or a compound semiconductor may be used.
- a crystalline semiconductor of Si is preferable from the viewpoint of the atomic steps and the ease of forming a crystal plane described later.
- the crystalline semiconductor of Si includes a crystalline semiconductor of SiGe including Ge, a crystalline semiconductor of SiC including C, or a crystalline semiconductor of SiGeC including Ge and C. Strictly speaking, a crystalline semiconductor of Si that does not contain Ge or C can be defined as a “crystalline semiconductor of only Si”.
- a compound semiconductor containing an Illb group element and a Vb group element such as GaAs, InGaAs, InP, GaN, and A1N
- a compound semiconductor containing a lib group element and a VIb group element ZnSe, ZnTe , CdTe, ZnO, etc.
- the flat portion 4 is a region between the atomic steps 3 on the surface of the base 2, and is generally also referred to as a terrace surface (or simply, a terrace).
- the flat part 4 is preferably a crystal plane indicated by a plane index (hkl) (the flat part 4 shown in FIG. 1 is a crystal plane indicated by a plane index (111)).
- the surface indices h, k and If satisfy the expressions 0 ⁇ h ⁇ 3, 0 ⁇ k ⁇ 3 and 0 ⁇ 1 ⁇ 3, and at least one selected from h, k and 1 Two values are positive (no more than one value selected from h, k and 1 can be zero at the same time). In this case, the size of the electric dipole formed between the flat portion 4 and the adsorption layer 5 can be increased.
- a larger electric dipole can be formed in the atomic step 3, and the shape of the atomic step can be made substantially linear at the atomic level in the major axis direction. For this reason, it is necessary to use an electron emission material with a further reduced work function. Can do.
- the substrate 2 has a hexagonal form (the material strength of the substrate 2 such as Zn ⁇ , GaN, and AIN), the crystal plane of the flat portion 4 cannot be indicated by the plane index (hkl). Lastly, the conditions are not applicable.
- the shape of the flat portion 4 is not particularly limited, but it is preferable that the major axes of the adjacent atomic steps 3 are substantially parallel to each other.
- the electronic state of the surface of the base 2 can be changed to a state where the work function is further reduced.
- the length of the flat portion 4 in the direction perpendicular to the long axis direction of the atomic step 3 (the width of the flat portion 4) may be almost constant as shown in FIG. As shown in FIG. 3, it may change periodically.
- the width of the flat portion 4 changes periodically, the shape of the flat portion 4 is not particularly limited.
- the flat portion 4 is formed by zigzag atomic steps 3 as shown in FIG. Is also good.
- the size of the electric dipole formed at the bend of the atomic step 3 (A and ⁇ ′ in FIG. 3) can be increased.
- the width of the flat portion 4 is not particularly limited, and for example, is preferably lOnm or less as long as it is lOOnm or less.
- the lower limit of the width of the flat portion 4 is not particularly limited, and is preferably, for example, not less than lnm and not less than the size of the unit cell formed by the elements contained in the adsorbing layer 5.
- the minimum value may be applied to the above condition.
- the structure of the adsorption layer 5 is not particularly limited as long as it contains the element A, but the element A is arranged at a part of an adsorption site (for example, a dangling bond) existing on the surface of the flat portion 4. Is preferred.
- the state of the electric dipole generated between the adsorption layer 5 and the flat portion 4 can be further optimized as compared with the case where the element A is arranged at all of the adsorption sites.
- such an adsorbing layer 5 can be formed, for example, by controlling the arrangement amount (evaporation amount).
- the adsorption layer 5 has a structure in which the elements A are periodically arranged. As described above, in the electron-emitting material 1 of the present invention, the adsorption layer 5 is disposed on the flat portion 4, and a low work function is obtained by the electric dipole formed between the adsorption layer 5 and the flat portion 4. Has been realized. At this time, by periodically arranging the element A, a periodic arrangement of the dipole moment induced by the electric dipole becomes possible, and a larger dipole moment can be obtained. Wear.
- the arrangement of the element A in the adsorption layer 5 is not particularly limited. However, as shown in Fig. 4, the arrangement interval of the element A is longer than that of the atomic step 3 in the major axis direction (B- ⁇ '). It is preferable that the direction perpendicular to the axial direction is larger in the direction different from the major axis direction (W> W). This
- the fluctuation of the shape in the atomic order (for example, meandering) in the atomic step 3 is suppressed, and the fluctuation of the dipole moment distribution IJ induced along the atomic step 3 is suppressed. It is considered possible. That is, an electron-emitting material having a further reduced work function can be obtained.
- the obtained work function is not stable, and the value shows a large error range. May be part of the cause.
- the electron-emitting material 1 shown in FIG. 4 such a fluctuation in the work function can be reduced, and a stable electron-emitting material can be obtained.
- FIG. 4 such a fluctuation in the work function can be reduced, and a stable electron-emitting material can be obtained.
- the atom step 3 is schematically shown by a straight line, and the atom of the element A is schematically shown by a circle.
- the unit (unit lattice) of the periodic arrangement of the element A is indicated by a dotted line, and the arrangement of the element A in the unit lattice is omitted.
- the MXN structure means that the size of the unit lattice of the element A in the adsorption layer 5 in a plan view when viewed from a direction perpendicular to the flat portion 4 is a basic unit of the base 2 in the flat portion 4.
- a structure that is M times and N times the lattice (1 X 1 structure) is meant. In such a structure, it is possible to further suppress the occurrence of shape fluctuation in the atomic order in the atomic step 3, and to further suppress the fluctuation of the arrangement of dipole moments induced along the atomic step 3. In other words, a stable electron emission material having a lower work function can be obtained.
- the unit lattice of the element A is preferably N times the unit cell of the base 2 in the major axis direction of the atomic step 3. .
- the value corresponding to the arrangement of the atomic step 3 in the long axis direction is N.
- the values of M and N can be controlled by, for example, selecting the type of element and / or element A contained in the base 2, and controlling the amount of deposition (deposition) of the element A on the flat portion 4.
- the shape of the electron-emitting material 1 is not particularly limited, and may be in the form of particles or a substrate (ie, the shape of the base 2 is not particularly limited, and may be in the form of particles. Or a substrate shape).
- the substrate-shaped electron-emitting material 1 can be formed, for example, by using a semiconductor substrate having atomic steps 3 on its surface as a substrate 2 and arranging an adsorption layer 5 on a flat portion 4 thereof.
- the particulate electron-emitting material 1 can be formed, for example, by crushing the substrate-shaped electron-emitting material 1.
- a substrate having a surface exponential force of the flat portion 4 and inclined at a predetermined direction and angle may be used as the semiconductor substrate used for the base 2.
- the direction and / or angle of the inclination By selecting the direction and / or angle of the inclination, the density and / or direction of the atomic steps on the surface of the substrate can be controlled, and the structure of the adsorption layer 5 can be easily controlled.
- a substrate on which the atomic steps 3 are formed by a growth method or an etching method may be used.
- a growth method or an etching method since the density and / or direction of the atomic steps on the surface of the substrate can be controlled, the structure of the adsorption layer 5 can be easily controlled.
- an atomic step can be formed at an arbitrary density at an arbitrary position on a semiconductor substrate.
- the growth or the etching method for example, the growth or the etching may be stopped when the atomic steps reach a predetermined density.
- the base 2 may be a semiconductor crystal selectively grown on the surface of the semiconductor substrate.
- FIG. 5 shows an example of an electron-emitting material using such a substrate 2.
- the insulating film 12 is disposed on the surface of the semiconductor substrate 11 (the surface index of the surface is (111)).
- a semiconductor crystal is growing.
- the atomic step 3 is formed on the surface of the base 2, and the adsorption layer 5 is disposed on the flat portion 4 between the atomic steps 3. In such a configuration, the size of the formed electric dipole can be increased.
- FIG. 6 is a schematic diagram in which the vicinity of the vertex located on the bottom surface of the base 2 shown in FIG. 5 is cut and enlarged.
- the adsorption layer 5 may further include a metal element X (hereinafter, also referred to as an element X) other than the element and the element A contained in the substrate 2, .
- element X a metal element X
- Element X and element A Since an electric dipole can be further formed between them, an electron-emitting material having a further reduced work function can be obtained.
- the element X is not particularly limited, but is preferably an element having a large difference in electronegativity from the element A.
- the adsorption layer 5 may contain at least one element selected from Au and Ag as the element X. Just include it.
- Au and Ag have a characteristic that they are easily arranged periodically on the surface of the substrate 2 (that is, in the adsorption layer 5), not only in a large difference in electronegativity with the element A.
- the state of the element X in the adsorption layer 5 is not particularly limited.
- the adsorption region 21 of the element X may be formed in the adsorption layer 5.
- the flat portion 4 has 36 adsorption sites, for example, the element X is arranged in 12 of the adsorption sites, and the element A is arranged in 6 of the adsorption sites. What is necessary is just the state which was performed.
- this state is a state in which the element X and the element A are arranged in the flat portion 4 in a 1/3 atomic layer and a 1/6 atomic layer, respectively. Even when two or more types of elements are adsorbed, the denominator of the numerical value indicating the atomic layer is a value reflecting the number of adsorption sites of the flat portion 4.
- the element X in the adsorption layer 5 is periodically arranged in 1J.
- the periodic arrangement of the element X enables the periodic arrangement of the dipole moments induced by the electric dipoles, so that a larger dipole moment can be obtained.
- the arrangement of the element X in the adsorption layer 5 is not particularly limited, but it is preferable that the arrangement of the element X be described by an M'XN 'structure. Is a natural number that satisfies
- the M ′ X N ′ structure means that the size of the unit cell of the element X in the adsorption layer 5 in the planar view when viewed from the direction perpendicular to the flat
- a structure that is M 'times and N' times the basic unit cell (1 X 1 structure) is meant. With such a structure, it is considered that the occurrence of shape fluctuation in the atomic order in the atomic step 3 can be further suppressed, and the fluctuation of the arrangement of dipole moments induced along the atomic step 3 can be further suppressed.
- the element X and the element A may be arranged in order in at least a part of the region of the adsorption layer 5 (in other words, if at least a part of the element X and the element A is in the above-described state, Good).
- the formed electric dipole can be made larger.
- Such an electron-emitting material 1 can be obtained, for example, by arranging the element X on a flat portion of a semiconductor substrate having an atomic step on the surface and then arranging the element A.
- the electron-emitting device of the present invention will be described.
- the electron-emitting device of the present invention includes an electron-emitting layer containing the above-described electron-emitting material of the present invention, and an electrode that is arranged to face the electron-emitting layer and generates a potential difference between the electron-emitting layer and the electron-emitting layer. It has. Since the electron-emitting device of the present invention includes the electron-emitting layer containing the electron-emitting material having a reduced work function, the electron-emitting device can obtain a high current density at a low heating temperature, and can improve the electron-emitting characteristics. An excellent electron-emitting device can be obtained.
- FIG. 8 shows an example of the electron-emitting device of the present invention.
- An electron-emitting device 51 shown in FIG. 8 is a display device.
- An electron-emitting layer 52 containing the electron-emitting material of the present invention is formed on a substrate 53.
- an acceleration electrode 54 and a phosphor layer 55 formed on a glass substrate 56 are arranged so as to face the electron emission layer 52.
- a striped extraction electrode 57 is arranged between the electron emission layer 52 and the acceleration electrode 544 in a direction perpendicular to the plane of the paper, and the electron emission layer 52, the acceleration electrode 54, and the extraction electrode 57 are electrically connected by a circuit 58. Connected.
- the circuit 58 By applying a potential difference between the extraction electrode 57 and the electron emission layer 52 by the circuit 58 so that the extraction electrode 57 side becomes positive, electrons are emitted from the electron emission layer 52. The emitted electrons are accelerated by a voltage applied between the acceleration electrode 54 and the electron emission layer 52, and then collide with the phosphor layer 55. Since the phosphor layer 55 is excited by the collision and emits light, the electron-emitting device 51 functions as a display. At this time, a high current density can be obtained while the temperature of the electron emission layer 52 is low, so that the electron emission element 51 with reduced power consumption can be obtained.
- Example 1 an electron emission material as shown in FIG. 1 was produced. The fabrication method is shown below
- the substrate temperature was set to 540 ° C.
- Cs was vapor-deposited on the surface of the substrate using a Cs vapor deposition source (manufactured by Saes Getters) to form an adsorption structure, and electron emission was performed. Materials were made.
- Cs deposition was carried out at a vacuum degree of 10. 6 X 10- 7 Pa (8 X 10- 1Q Torr) and the chamber in one, the distance between the surface of the substrate deposition source was set to 3 cm.
- the amount of Cs deposited was determined by observing a diffraction pattern reflecting the structure of the substrate surface while performing the deposition using an electron beam diffractometer.
- Cs was adsorbed on a flat portion of the substrate by 2/3 atomic layer.
- the term “adsorb 2/3 atomic layers” means that, when there are 3n adsorption sites on the surface of the substrate in plan view, the atoms are adsorbed on 2n adsorption sites. .
- the surface of the prepared electron-emitting material was observed and evaluated using STM and X-ray photoelectron spectroscopy.
- the 6X1 structure of Cs along the atomic steps (the shortest length of the Cs (The axial direction coincides with the long axis direction of the atomic step.) It was found that two rows were formed on the force flat part.
- the work function of the electron-emitting material thus manufactured was measured by the Kelvin probe method and found to be about 1. leV. (The work function measurement method is the same in the following examples.) ).
- the work function of the Si substrate before Cs is deposited is about 4.7 eV, and the work function of the Si substrate with almost no atomic steps on the surface is about 1.7 eV. It can be seen that the work function could be reduced by the presence of the step and the Cs adsorption structure. According to Surf. ScL, vol. 99, p .
- the produced electron-emitting material was placed on a conductive heating plate, and a temperature-current characteristic was measured with a spherical gold electrode (150 zm in diameter) facing the electron-emitting material (The method of measuring the temperature-current characteristics is the same in the following examples).
- the distance between the electron-emitting material and the gold electrode was 2 mm.
- the obtained characteristics followed the Richardson-Dashman equation, and the value of the work function determined from the above characteristics was also about 1. leV. Comparing the temperature-current characteristics of a mixture of barium oxide, strontium oxide, and calcium oxide, which are conventional electron-emitting materials, the same current density was obtained at about 230 ° C lower temperature. In addition, almost the same current density could be obtained even after 10,000 hours of force where the temperature was kept at 440 ° C and the measurement was continued.
- the height of the atomic steps is equal to the spacing between the flat surfaces, but the same effect can be obtained even when the height of the atomic steps is different from the spacing between the flat surfaces.
- the height of the atomic steps was an integral multiple of the spacing between flat surfaces, an electron-emitting material with a reduced work function could be obtained.
- Example 2 an electron emission material as shown in FIG. 1 was manufactured using a P-type Si substrate inclined about 1.7 ° in the [1,1, _2] direction from a (111) plane as a base.
- Example 1 the surface of the substrate was kept clean.
- STM surface of the cleaned substrate
- FIG. 10 an area where the atomic steps 3 were dense (step punch 31) was observed.
- the major axis direction of the step punch 31 is almost the direction of [-1, 1, 0], and in each atomic step 3 in the step punch 31, meandering in the atomic order was observed.
- Cs was vapor-deposited on the surface of the substrate in the same manner as in Example 1. As a result of the observation, Cs was selectively adsorbed to the portion of the step punch 31 which was not in the flat portion 4 on the substrate surface, and grew in the [1, 1, -2] direction as the amount of adsorption increased.
- Example 2 As a result, it was found that an electron-emitting material similar to that of FIG. 1 was finally formed. In addition, the fluctuation of atomic step 3 disappeared with the deposition of Cs. In Example 2, as in Example 1, Cs was adsorbed on the 2Z3 atomic layer.
- the work function of the electron-emitting material thus manufactured was measured and found to be about 1. leV. It is considered that the work function was greatly reduced by the synergistic action of the atomic step and the adsorption structure of Cs-O.
- the obtained characteristics were in accordance with the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was also about 1. leV.
- the same current density was obtained at about 230 ° C lower temperature.
- the measurement was continued while the temperature was kept at 440 ° C, it was possible to obtain almost the same current density after 10,000 hours.
- Example 3 an electron-emitting material was produced in the same manner as in Example 1, except that the atoms adsorbed on the flat portion were changed from Cs to K. However, temperature 400 ° C of the substrate during the deposition, the vacuum degree and 12. 0 X 10- 7 Pa (9 X 10- Torr), was used SAES Getters Co. K deposition source for deposition. In addition, K made 1Z3 atomic layer adsorbed on the flat part of the substrate. When the surface of the manufactured electron-emitting material was evaluated using an electron beam diffraction method, it was found that a K 3 XI structure was formed on the flat portion of the substrate. Further, observation of the surface using STM, it step density of 2.3 10 8/111 Deari, is 3 X 1 structure K along the atomic steps are formed four columns on the flat portion I understood.
- the work function of the electron-emitting material manufactured as described above was measured to be about 1.3 eV. It is considered that the work function was greatly reduced by the synergistic effect of the atomic step and the adsorption structure of K.
- the obtained characteristics were according to the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was about 1.3 eV.
- the same current density was obtained at about 120 ° C lower temperature.
- the temperature was kept at 550 ° C and the measurement was continued, it was possible to obtain almost the same current density after 10,000 hours.
- Example 4 an electron-emitting material was produced in the same manner as in Example 2, except that the atoms adsorbed on the flat portion were changed from Cs to K. However, the conditions at the time of vapor deposition were the same as in Example 3, and K was adsorbed on a flat portion of the substrate by 1/3 atomic layer.
- Atomic step 3 consisted of two types of steps proceeding in the direction [0,1 1,1] and in the direction [1,0,1 1].
- the traveling direction (major axis direction) of the entire atomic step 3 was a direction of [-1, -1, 2] perpendicular to the tilt direction ([-1, 1, 1, 0]) of the substrate.
- the surface of the prepared electron-emitting material was observed using STM. As a result, a K-adsorbing structure was formed in the flat portion 4, and the electron-emitting material as shown in FIG. It turned out that it was obtained. Before and after the adsorption of K, the shape and position of atomic step 3 hardly changed. Further, the step density on the surface of the substrate is IX 10 8 cells / m, 3 X 1 structure K along the atomic steps have been formed in plural on the flat portion.
- the work function of the electron-emitting material manufactured as described above was measured to be about 1.2 eV. It is considered that the work function was greatly reduced by the synergistic effect of the atomic step and the adsorption structure of K. Although the step density of the obtained electron-emitting material is smaller than that of the electron-emitting material prepared in Example 3, the step density was reduced due to the presence of bent portions (A and A 'shown in Fig. 3) in atomic step 3. It is considered that the work function could be reduced as compared with Example 3.
- the obtained characteristics were according to the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was also about 1.2 eV.
- the same current density was obtained at about 120 ° C lower temperature.
- the temperature was kept at 550 ° C and the measurement was continued, it was possible to obtain almost the same current density after 10,000 hours.
- Example 5 an electron emission material was manufactured using a semiconductor crystal selectively grown on the surface of a semiconductor substrate as a base. The manufacturing method will be described with reference to FIGS. 12A and 12B.
- the surface of the Si substrate 11 was cleaned in the same manner the surface as in Example 1 (crystal face (111)), board temperature 630 ° C, the oxygen partial pressure 2. 66 X 10- 4 Pa (2 X 10- 6 Torr) and at oxidation conditions the retention time of 10 minutes to form an oxide film 12 (film thickness 0.3 nm).
- the temperature of the substrate 11 was gradually raised to around 720 ° C., and the oxide film 12 was partially thermally desorbed to form a window 13 (FIG. 12A).
- the temperature was raised while observing the surface of the substrate 11 (the oxide film 12) using STM, and when the window 13 reached a predetermined size, the temperature of the substrate 11 was lowered. And the progress of thermal desorption was stopped. Normally, in this method, the thermal desorption of the oxide film 12 starts at random, so that the size of the window 13 does not become uniform.However, a plurality of windows 13 of the order of nm are formed on the surface of the substrate 11. it can.
- the substrate 2 made of a Si crystal was selectively grown on the window 13. Since disilane decomposition and Si growth hardly occur on the surface of the oxide film 12 with few dangling bonds, the Si crystal grew selectively only on the window 13. Observation by STM while growing the Si crystal confirmed that two-dimensional growth occurred for each layer.
- the shape of the Si crystal was substantially triangular pyramid or truncated triangular pyramid, reflecting the symmetry of the substrate 11, and as the growth progressed, the slope of the side surface became larger. When the slope reached about 8 °, the introduction of disilane was stopped, and the growth of the Si crystal was stopped.
- Example 2 Cs was vapor-deposited on the surface of the Si crystal as the base 2 to prepare an electron-emitting material. Observation of the surface of the prepared electron-emitting material using STM confirmed the structures shown in FIGS. 5 and 6, and the shape of the Si crystal was almost maintained before and after the deposition of Cs. Further, the step density of the Si crystal surface is 4.5 10 8/111 Deari, Cs is the surface of the oxide film 12, Les almost adsorption was not.
- the work function of the electron-emitting material thus manufactured was measured and found to be about 1. leV. It is considered that the work function was greatly reduced by the synergistic effect of the atomic step and the adsorption structure of K.
- the obtained characteristics were in accordance with the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was also about 1. leV.
- the same current density was obtained at about 230 ° C lower temperature.
- the measurement was continued while the temperature was kept at 440 ° C, it was possible to obtain almost the same current density after 10,000 hours.
- Example 6 an electron emission material as shown in FIG. 7 was produced.
- the fabrication method is shown below [0079] First, in a the chamber within a vacuum degree 1 ⁇ 33 X 10- 8 Pa ( 1 X 10- 1Q Torr), [ one 1, - 1, 2] from (111) plane direction about 9 . Five. The surface of the sloping Si substrate (resistivity of less than lk Q cm due to boron doping) was heated to 1200 ° C several times by energizing heating to make it clean.
- the substrate temperature was set to 600 ° C.
- Au was vapor-deposited on the surface of the substrate using an Au vapor deposition source in which gold was adhered to a tungsten filament.
- Au deposition, the distance between the row-,, surface and the evaporation source of the substrate at a vacuum degree of 4 X 10- 7 P a (3 X 10- 1Q Torr) and the chamber in one was 15c m.
- the substrate temperature was set to 300 ° C., and using a Cs vapor deposition source (manufactured by Saes Getters), Cs was vapor-deposited on the surface of the substrate to form an adsorption structure, and electron emission was performed. Materials were made. Cs deposition was carried out at a vacuum degree of 10. 6 X 10- 7 Pa (8 X 10- 1Q Torr) and the chamber in one, the distance between the surface of the substrate deposition source was set to 3 cm. The deposition amount of Au and Cs was determined by observing the diffraction pattern reflecting the structure of the substrate surface while performing evaporation using an electron beam diffractometer. In Example 6, 1/3 atomic layer of Au and 1/6 atomic layer of Cs were adsorbed on the flat portion of the substrate.
- a Cs vapor deposition source manufactured by Saes Getters
- the surface of the fabricated electron-emitting material was observed and evaluated using STM and X-ray photoelectron spectroscopy.
- the 5X1 structure of Au along the atomic steps (the minor axis (The direction coincides with the long axis direction of the atomic steps.)
- the flat part was formed, and the width of the flat part was almost the same as the size of the unit cell of the 5X1 structure of Au.
- the 5x1 structural force of Cs is formed on a flat part, and a part of Cs atoms is placed on Au atoms (that is, a state where Au atoms and Cs atoms are arranged in order from the flat part side). )Met .
- Cs atoms not on Au atoms were adsorbed on the surface of the substrate.
- the work function of the electron-emitting material manufactured as described above was measured and found to be about 1. leV.
- the Cs adsorption structure and the Au adsorption structure It is considered that the work function was significantly reduced.
- the obtained characteristics were according to the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was also about 1. leV. Comparing the temperature-current characteristics of a mixture of barium oxide, strontium oxide and calcium oxide, the same current density was obtained at about 220 ° C lower temperature. When the measurement was continued while the temperature was kept at 430 ° C, it was possible to obtain almost the same current density after 10,000 hours.
- Example 7 an electron emission material as shown in FIG. 7 was manufactured using a P-type Si substrate inclined at about 8.5 ° in the [1,1, ⁇ 2] direction from the (111) plane as a base.
- Example 6 the surface of the substrate was cleaned.
- STM surface of the cleaned substrate
- FIG. 13A a region where the atomic steps 3 were dense (step punch 31) was observed.
- the major axis direction of the step punch 31 is almost the direction of [ ⁇ 1, 1, 0], and in each of the atomic steps 3 in the step punch 31, meandering in the atomic order was observed.
- Example 6 Cs was adsorbed to the flat portion by 1/6 atomic layer. Observation of the surface of the fabricated electron emission material using STM revealed that a 5 X 1 structure of Au and a 5 X 1 structure of Cs were formed along the atomic steps.
- the work function of the electron-emitting material thus manufactured was measured and found to be about 1. leV. It is considered that the work function was greatly reduced by the synergistic action of the atomic step, the Cs adsorption structure and the Au adsorption structure.
- the obtained characteristics were according to the Richardson-Dashman equation, and the value of the work function obtained from the above characteristics was also about 1. leV. Comparing the temperature-current characteristics of a mixture of barium oxide, strontium oxide and calcium oxide, the same current density was obtained at about 220 ° C lower temperature. When the measurement was continued while the temperature was kept at 430 ° C, it was possible to obtain almost the same current density after 10,000 hours.
- Example 8 similarly to Example 7, after forming the adsorption structure of Au and Cs, using the same method as in Example 2, the produced electron-emitting material was exposed to an oxidizing atmosphere, and Cs and O was chemically coupled. The chemical bond between Cs and O was confirmed in the same manner as in Example 2.
- the work function of the thus-produced electron-emitting material was measured to be about 1.05 eV. It is considered that the work function was greatly reduced by the synergistic effect of the atomic step, the Cs- ⁇ adsorption structure and the Au adsorption structure.
- Example 9 an electron-emitting material was produced in the same manner as in Example 6, except that the atom adsorbed on the flat portion after the formation of the Au adsorption structure was changed from Cs to K. However, 300 ° the temperature of the substrate when you deposited K C, the degree of vacuum and 12. 0 X 10- 7 Pa (9 X 10- 1Q Torr), the deposition Used a K evaporation source manufactured by SAES Getters. ⁇ was adsorbed by 1/6 atomic layer.
- the work function of the electron-emitting material thus manufactured was measured to be about 1.3 eV.
- Example 10 as in Example 5, a semiconductor crystal was selectively grown on the surface of a semiconductor substrate, and an electron emission material was produced using the formed semiconductor crystal as a base.
- the surface of the Si substrate 11 was cleaned in the same manner the surface as in Example 6 (the crystal plane (111)), board temperature 620 ° C, the oxygen partial pressure 2. 66 X 10- 4 Pa (2 X 10- 6 Torr) and at oxidation conditions the retention time of 10 minutes to form an oxide film 12 (film thickness 0.3 nm).
- the temperature of the substrate 11 was gradually raised to around 720 ° C., and the oxide film 12 was partially thermally desorbed to form a window 13.
- a disilane (Si H), 4 X 10- 2 Pa (3 X 10- 4 Torr) partial pressure introduced city chamber one, on the window 13, made of Si crystal substrate 2 was selectively grown.
- the force to grow the Si crystal was observed by STM using STM, and it was confirmed that two-dimensional growth occurred for each layer.
- the shape of the Si crystal was substantially a triangular pyramid or a truncated triangular pyramid, reflecting the symmetry of the substrate 11.
- the slope of the side surface increased. When the slope became about 15 °, the introduction of disilane was stopped, and the growth of the Si crystal was stopped.
- step punch 31 a region where the atomic steps 3 were dense (step punch 31) was observed.
- the major axis direction of the step punch 3 1 is almost the direction of [1, ⁇ 1, 0].
- the substrate temperature was set to 600 ° C, and a 1/3 atomic layer of Ag was deposited on the surface of the Si crystal using an Ag deposition source in which silver was attached to a tungsten filament. Ag deposition was performed by vacuum degree 4 X 10- 7 Pa (3 X 10- 1Q Torr) and the chamber in one, the distance between the surface and the vapor Chakugen of Si crystals was 15cm.
- Ba was adsorbed by 1Z6 atomic layer in the same manner as in Example 6 to produce an electron emission material.
- STM surface of the prepared electron emission material
- the adsorption layer 5 containing the adsorption structure 21 of Ba was formed on the flat part, and the Ag along the atomic step 3 was observed. It was found that the 3X1 structure of and the 3X1 structure of Ba were formed.
- the work function of the electron-emitting material thus manufactured was measured and found to be about 1. leV. It is considered that the work function was greatly reduced by the synergistic action of the atomic step, the adsorption structure of Ba—O, and the adsorption structure of Ag.
- Example 10 the window was formed using the thermal desorption phenomenon of the oxide film.
- the electron beam was emitted by electric field electron emission.
- a window may be formed by irradiating the oxide film with an incident energy of 20 eV or more for a predetermined time. In this method, for example, a window having a uniform size with a diameter of about 20 nm can be formed.
- the method using thermal desorption and the method using electron emission can be performed without limiting the surface index and the inclination angle of the substrate surface.
- the method of forming a substrate having atomic steps on the surface did not affect the obtained work function value.
- the same effect can be obtained by using any method, such as an etching method, a growth method, a deposition method, or a combination of these methods by a physical or chemical method. did it.
- P (phosphorus) and B (boron) which are the trace elements constituting the semiconductor, are segregated near the surface of the substrate, a comb-shaped atomic step can be formed to form a substrate having atomic steps. Even so, the same effect was obtained.
- the force using the (111) plane of Si as the flat portion is the surface index (hkl) force of the flat portion.
- the formula 0 ⁇ h, k, 1 ⁇ 3 (where h, k and 1 The same effect could be obtained even when at least two values selected from satisfies (). At this time, the value of the work function obtained was smaller as the atomic steps were steeper and the height of the atomic steps was larger.
- the conductivity type of Si did not affect the obtained work function value. Similar effects can be obtained even when a substrate made of a semiconductor of a single element such as Ge or C, or a substrate made of a compound semiconductor such as SiGe, GaAs, InGaAs, InP, GaN, or A1N is used. Was completed.
- Example 11 the electron-emitting device shown in FIG. 8 was manufactured using the electron-emitting material manufactured in Examples 1-2, and its characteristics were evaluated.
- the electron-emitting material 1 prepared in Examples 1-2 was used as it was as the substrate 53 and the electron-emitting layer 52.
- the substrate 2 in the electron-emitting material 1 was the substrate 53, and the adsorbing layer 5 was the electron-emitting layer.
- An extraction electrode 57 of a mesh shape (100 mesh) made of stainless steel was disposed at a distance of 2 mm from the electron emission layer 52, and both were electrically connected by a circuit 58.
- an acceleration electrode 54 made of ITO and a phosphor layer 55 containing a ZnS-based phosphor formed on a glass substrate 56 are arranged so as to face the electron emission layer 52. And the electron emission layer 52 were electrically connected by a circuit 58.
- the electron-emitting device 51 thus manufactured is housed in a vacuum chamber, and a voltage of 100 V is applied between the extraction electrode 57 and the electron-emitting layer 52, and a voltage of 3 kV is accelerated between the accelerating electrode 54 and the electron-emitting layer 52. Upon application of a voltage, light emission from the phosphor layer 55 was confirmed.
- the emission luminance varies the amount of current applied to the phosphor layer 55, the voltage applied between the extraction electrode 57 and the electron emission layer 52, and the energy of the electrons applied to the phosphor layer 55 to the acceleration electrode. It could be controlled by changing it by the voltage applied between 54 and the electron emission layer 52.
- the powdered electron-emitting material (prepared in Examples 12 and 13) was ground and mixed with an organic and / or organic binder, and applied to a substrate. Similar results were obtained when the layer 52 was formed.
- Example 12 In Example 12, an electron-emitting device was manufactured in the same manner as in Example 11, and its characteristics were evaluated. However, the electron-emitting material produced in Example 7 was used.
- the temperature of the electron-emitting layer 52 was set to 440 ° C, and a voltage of 100 V was applied between the extraction electrode 57 and the electron-emitting layer 52. A current density of / cm 2 was obtained.
- the present invention it is possible to provide an electron-emitting device having lower power consumption and higher Z or higher current density than the conventional one and having excellent electron-emitting characteristics.
- the electron-emitting device of the present invention is not particularly limited, and can be applied to various electronic devices such as a display, a cathode ray tube, an emitter, a light source, and an electron gun.
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JPH0817332A (ja) * | 1993-07-05 | 1996-01-19 | Matsushita Electric Ind Co Ltd | 電界放射型電子素子およびその製造方法 |
JPH09223455A (ja) * | 1996-02-16 | 1997-08-26 | Hitachi Ltd | 表面構造制御法およびこれを利用した電子源および平面ディスプレィ |
JP2000508110A (ja) * | 1996-04-01 | 2000-06-27 | ザ リージェンツ オブ ザ ユニヴァーシティー オブ カリフォルニア | イオン注入を用いた仕事関数の変更方法 |
JP2004319203A (ja) * | 2003-04-15 | 2004-11-11 | Matsushita Electric Ind Co Ltd | 電子放出材料 |
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JPH0817332A (ja) * | 1993-07-05 | 1996-01-19 | Matsushita Electric Ind Co Ltd | 電界放射型電子素子およびその製造方法 |
JPH09223455A (ja) * | 1996-02-16 | 1997-08-26 | Hitachi Ltd | 表面構造制御法およびこれを利用した電子源および平面ディスプレィ |
JP2000508110A (ja) * | 1996-04-01 | 2000-06-27 | ザ リージェンツ オブ ザ ユニヴァーシティー オブ カリフォルニア | イオン注入を用いた仕事関数の変更方法 |
JP2004319203A (ja) * | 2003-04-15 | 2004-11-11 | Matsushita Electric Ind Co Ltd | 電子放出材料 |
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