JP2005221354A - Cathode luminescence measuring instrument by means of electron beam source using carbon film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize a low-cost cathode luminescence measuring instrument facilitating measurement operation. <P>SOLUTION: An anode 7 and a movable electrode 4 that moves vertically are provided in a bell jar 1. A carbon film cathode 6 for emitting a low-speed homogeneous electron beam is provided on a surface of a removable cathode holder 5. A light emitting body is provided on a surface of the cathode 7. The interior of the bell jar 1 is evacuated. The cathode holder 5 is moved from the outside of the bell jar 1 by means of the movable electrode 4. With a current supplied from a power supply, the emitting body is caused to emit light by thereto applying electrons. Light of the emitting body is guided for measurement to the exterior of the bell jar 1 by optical fiber 12. Luminance, color tone, spectrum, etc. of a light-emitting phosphor specimen are measured at various electrode intervals, interelectrode voltages, grid voltages, and degrees of vacuum, thereby evaluating the light emission characteristics of the phosphor specimen and establishing the optimum conditions on a field emission device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electron beam-excited luminescence measuring device, and in particular, without using an electron microscope or a high-speed electron beam emission device, a low-speed homogeneous electron beam is generated to illuminate a light-emitting body, and its emission spectrum, intensity, etc. The present invention relates to an electron beam excitation luminescence measuring apparatus for measuring characteristics.

  Conventionally, a device that combines a scanning electron microscope with a photodetector and a spectroscope has been used to observe a light emission phenomenon caused by electron beam excitation of a semiconductor or phosphor material, that is, cathodoluminescence. The feature of this device is that it uses a high-speed electron beam because it uses an electron gun of an electron microscope. It is possible to measure the mapping of the emission intensity by continuously changing the place to do. Since the spectrum measured in this way has information in the vicinity of the band edge and defect information, it is used for quality control of semiconductor wafers and devices.

  On the other hand, in searching for a new substance of an electron beam-excited phosphor material, it is first important whether light is emitted by electron beam excitation. High spatial resolution measurement and luminance mapping are not considered necessary and sufficient conditions. However, at present, an apparatus using a scanning electron microscope is used.

The “evaluation apparatus for electron beam excited phosphor” disclosed in Patent Document 1 is an evaluation apparatus for a phosphor that emits light by a low-speed electron beam. A cathode that emits a low-speed electron beam does not deteriorate even when exposed to the atmosphere, and can emit electrons in a planar distribution. As shown in FIG. 3, an electron-emitting device using field emission is miniaturized and integrated on a substrate to form a planar shape. This electron-emitting device is used as a cathode. The phosphor sample is caused to emit light by the low-speed electron beam emitted from the cathode. By measuring the emission state, the emission characteristics of the phosphor sample are evaluated.
JP-A-6-295678

  However, the conventional measuring apparatus has the following problems. Since a scanning electron microscope is used, the cost of the apparatus is very high, 40 million yen to 80 million yen, and it is not possible to use it even if it is used, and an inexpensive apparatus is desired. In most devices currently in use, the sample is placed in a sample chamber of an electron microscope for measurement, and actual light emission cannot be visually observed.

  In general, when a plurality of cathode filaments are used, an electric field generated by each of them causes the electron trajectory to become non-straight and diffuse so as to draw a parabola. Further, the density of the electron beam at the anode varies depending on the location depending on the distance between the filaments. For these reasons, light emission luminance unevenness is likely to occur. In order to solve these problems, a surface emission type cathode is desirable. Further, when creating a light emitting device by field emission, the distance between the cathode and the anode becomes important, but in most devices, this distance cannot be freely changed.

  The object of the present invention is to provide a cathode luminescence measuring apparatus which solves the above-mentioned conventional problems, has a cathode capable of operating at a low voltage, can obtain a uniform electron beam with high electron emission efficiency, and is easy to measure and low in cost. Is to realize.

  In order to solve the above-described problems, in the present invention, a cathode luminescence measuring device includes a bell jar, an anode provided in the bell jar, a vertically movable cathode provided in the bell jar, and a movable cathode disposed outside the bell jar. An airtight sliding bearing through the movable electrode for movement, a carbon film that emits a low-speed homogeneous electron beam provided on the movable cathode at the tip of the movable electrode, a light emitter provided on the surface of the anode, and electrons to the light emitter The power supply for precisely adjusting and supplying the current for making it shine is applied, and an optical fiber for guiding the light of the light emitter to the outside of the bell jar.

  In the present invention, the following effects can be obtained by configuring as described above. Since a scanning electron microscope is not used, the necessary cost is 5 million yen or less. When combined with the luminescence measuring unit, a cathode luminescence measuring device with a total amount of 10 million yen or less can be realized. The low price is expected to spread widely to many material researchers, and as a result of the spread, new field emission materials can be developed.

  In addition, it can be made much easier than the Spindt-type field emission cathode used in the “electron beam-excited phosphor evaluation apparatus” disclosed in Patent Document 1, which requires many manufacturing processes, and the electron The emission efficiency is also high, and operation at a lower voltage is possible. Enables surface-emitting electron beam emission. Further, a more uniform electron beam can be obtained than the cathode which is a point irradiation type assembly disclosed in Patent Document 1, and the cathode can be easily replaced and detached.

  Furthermore, the measurer can visually confirm the state of light emission, and the distance between the electrodes can be freely adjusted from outside the vacuum vessel. Thereby, it is possible to easily optimize the interelectrode distance and the applied voltage, which are important parameters in the field emission light emitting device.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

  In the embodiment of the present invention, a light emitter is provided on the surface of the anode in the bell jar, and a carbon film cathode for emitting a low-speed homogeneous electron beam is provided on the surface of the removable cathode holder at the tip of the movable electrode. After evacuating the tube, move the removable cathode holder from the outside of the bell jar, supply current from the power source to illuminate the illuminator with light, and then measure the luminescence by guiding the light of the illuminator out of the bell jar using an optical fiber. It is a measuring device.

The structure of the cathode luminescence measuring apparatus in the Example of this invention is demonstrated. FIG. 1 is a conceptual diagram of a cathodoluminescence measuring apparatus according to an embodiment of the present invention. FIG. 2 is a partial conceptual diagram of a modified example of the cathodoluminescence measurement apparatus. In FIG. 1, a bell jar 1 is a transparent bell jar made of quartz or the like. A quartz bell jar is used as the lid of the vacuum vessel for emission spectrum measurement. The flange 2 is a member for vacuum-sealing the bell jar 1. Since the O-ring is used to maintain the airtightness between the bell jar 1 and the flange 2, it is less expensive than an apparatus using a gasket. The ultimate vacuum can be as high as 10 ^-6 torr. The current introduction terminal 3 is a current introduction terminal that can move the movable cathode through the bearing. The movable electrode 4 is an electrode for moving the removable cathode holder. The range of the vertical movement distance can be selected according to the application, and the vertical movement accuracy is about 0.1 mm. Well-known precision driving means (not shown) is provided. The movable distance and movable accuracy are appropriately set according to the purpose.

  The detachable cathode holder 5 is a holder for attaching a cathode. The carbon film cathode 6 is a carbon film cathode having a high electron emission efficiency, produced by vaporizing carbon graphite (nanocarbon) on a Ni or silicon wafer by CVD or the like. It is a cold cathode that utilizes electrons extracted by the field emission effect. Compared with cathode materials such as carbon nanotubes in the research stage, an electron beam with uniform intensity can be obtained.

  The anode 7 is an anode made of a transparent electrode and quartz glass. The anode fixing leaf spring 8 is a leaf spring for fixing the anode. The anode holder 9 is a member for holding an anode made of a transparent electrode and quartz glass. A transparent electrode is used for the anode electrode, and quartz glass is used for the substrate for supporting the electrode. This anode is attached to a donut-shaped metal plate having an insulating support rod as a leg. This metal holder is connected to an anode current introduction terminal (not shown) by an appropriate metal wire.

  The optical filter 10 is a filter that transmits or blocks light of a specific wavelength, or an ND filter that attenuates light of all wavelengths. The insulating support bar 11 is a member that supports the anode. The optical fiber 12 is a member for guiding the light of the light emitter to the outside of the bell jar. The optical fiber fixing jig 13 is a member for fixing the optical fiber. The optical fiber feedthrough 14 is an airtight member for passing the optical fiber outside the bell jar.

  The anode support rod has grooves, and various optical filters and lenses can be inserted into the grooves. Thereby, when the emission intensity is high, the intensity can be reduced by the filter, and when the emission intensity is low, the amount of light can be obtained by the condenser lens. By these measures, the emission spectrum can be appropriately measured within the sensitivity range of the photodetector. By measuring the absorption spectra of the transparent electrode and the quartz substrate in advance, an accurate spectrum of the phosphor can be obtained.

  An optical fiber that transmits light emitted from the phosphor is placed in a vacuum apparatus. When the light emission is weak, a light collecting device is introduced into the vacuum vessel. The optical fiber is attached directly under the anode, and the light emitted from the phosphor is observed through the transparent electrode and the quartz substrate. The position of the optical fiber can be adjusted freely. By arranging the optical fiber directly under the anode, the solid angle can be increased, and the light from the phosphor can be efficiently taken into the optical fiber. An optical fiber feedthrough is used to introduce the optical fiber into the vacuum apparatus. If the optical fiber is introduced into the vacuum apparatus, the bell jar need not be made of quartz.

  The operation of the cathode luminescence measuring apparatus in the embodiment of the present invention configured as described above will be described. First, an outline of the operation will be described. As shown in FIG. 1, a carbon film cathode 6 that emits a low-speed homogeneous electron beam is provided on the surface of the removable cathode holder 5, and a light emitter is provided on the surface of the anode 7. The inside of the bell jar 1 is evacuated, and the removable cathode holder 5 is moved from the outside of the bell jar 1 by the movable electrode 4. A current is supplied from a power source, and light is emitted from the light emitter by hitting electrons. The light from the illuminant is guided out of the bell jar 1 by the optical fiber 12 and measured. The light emission characteristics of the phosphor sample are evaluated by measuring the luminance, color tone, spectrum, and the like of the phosphor sample that has emitted light.

The measurement method will be described in detail. A light emitter is set on the surface of the anode 7 and the inside of the bell jar 1 is evacuated. Data of quantum conversion rates (external quantum efficiency = internal quantum efficiency / extraction efficiency) of various light emitters can be measured, and characteristics of light emitters such as a single crystal can be easily examined. Since the device structure is simple, sample setup and the like are easy. The degree of vacuum in the container can be adjusted from atmospheric pressure to about 10 ^-6 torr. The atmosphere of the vacuum vessel can be changed to various gases as required. By arranging a thermocouple in the immediate vicinity of the sample, the change in the sample temperature due to electron irradiation can be measured. Since a transparent bell jar made of quartz or the like is used, the state of light emission can be visually observed.

  The movable cathode is moved from outside the bell jar 1. The distance between the electrode plates can be adjusted from outside the vacuum. The distance (d) between the anode and the cathode can be freely controlled, and the electric field strength (E = V / d) can be changed to a desired value and measured. The electron beam density can be adjusted by changing the electric field strength according to the distance between the electrode plates and the applied voltage. The electron beam density can also be adjusted by changing the area of the cathode. The electron dose can also be adjusted by adding a net-like extraction (grid) electrode shown in FIG. 2 between the anode and the cathode. Since the input power can be obtained by measuring the current flowing between the electrodes, the relationship between the input power and the light emission intensity, that is, the optimum light emission efficiency can be investigated.

  A current is supplied from a power source, electrons are applied to the light emitter, and the light emitter is illuminated. The applied voltage (V) is about 50 V to 10 kV, the emission current is about 0.1 to 1 mA, and the pulse width can be adjusted and controlled in the range of 2 to 8 μsec. The light from the light emitter is measured from outside the bell jar 1. By measuring the luminance, color tone, spectrum, and the like of the emitted light emitter (phosphor sample), the light emission characteristics of the light emitter (phosphor sample) are evaluated. The sample temperature can also be measured from room temperature to 700 ° C. with a radiation thermometer (not shown). As described above, measurement under various conditions is possible by adjusting the distance between electrodes, the voltage between electrodes, and the grid voltage. This makes it possible to investigate the characteristics of the phosphor in detail and to emit light by field emission. The optimum conditions of the device can be investigated.

  As described above, in the embodiment of the present invention, the cathode luminescence measuring apparatus is provided with a light emitter on the surface of the anode in the bell jar, and a low-speed homogeneous electron beam on the surface of the removable cathode holder of the movable electrode. A carbon film cathode that emits light is evacuated, the inside of the bell jar is evacuated, the removable cathode holder is moved from outside the bell jar, current is supplied from the power source to irradiate the light emitter with electrons, and the optical fiber exits the bell jar Since the measurement is performed by guiding the light of the luminescent material, the luminescent property can be evaluated by measuring the luminance, color tone, spectrum, and the like of the emitted phosphor sample.

  The cathodoluminescence measuring apparatus of the present invention is most suitable as an apparatus for investigating the characteristics of light emitters such as single crystal phosphors and establishing the optimum conditions for field emission devices.

The conceptual diagram of the cathode luminescence measuring apparatus in the Example of this invention, The partial conceptual diagram of the modification of the cathode luminescence measuring device in the Example of the present invention, It is a conceptual diagram of the conventional light-emitting body measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bell jar 2 Flange 3 Current introduction terminal 4 Movable electrode 5 Removable cathode holder 6 Carbon film cathode 7 Anode 8 Anode fixing leaf spring 9 Anode holder
10 Optical filter
11 Insulating support rod
12 optical fiber
13 Optical fiber fixing jig
14 Optical fiber feedthrough

Claims (1)

A bell jar, an anode provided in the bell jar, a vertically movable cathode provided in the bell jar, an airtight sliding bearing through which a movable electrode for moving the movable cathode from outside the bell jar, and the movable A carbon film that emits a low-speed homogeneous electron beam provided on the movable cathode at the tip of the electrode, a light emitter that is provided on the surface of the anode, and a current that is applied to the light emitter to cause the light to shine is precisely adjusted. A cathode luminescence measuring apparatus comprising: a power supply to be supplied; and an optical fiber for guiding light from a light emitter to the outside of the bell jar.

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