EP2907154B1 - Semi-transparent photocathode with improved absorption rate - Google Patents
Semi-transparent photocathode with improved absorption rate Download PDFInfo
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- EP2907154B1 EP2907154B1 EP12773306.1A EP12773306A EP2907154B1 EP 2907154 B1 EP2907154 B1 EP 2907154B1 EP 12773306 A EP12773306 A EP 12773306A EP 2907154 B1 EP2907154 B1 EP 2907154B1
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- photocathode
- layer
- diffraction grating
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- photons
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Images
Classifications
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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
- H01J1/34—Photo-emissive cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
- H01J40/02—Details
- H01J40/04—Electrodes
- H01J40/06—Photo-emissive cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
- H01J40/16—Photoelectric discharge tubes not involving the ionisation of a gas having photo- emissive cathode, e.g. alkaline photoelectric cell
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/02—Tubes in which one or a few electrodes are secondary-electron emitting electrodes
Definitions
- the present invention relates to the general field of semi-transparent photocathodes, and more specifically, to that of semi-transparent photocathodes of antimony and alkali metal type, or silver oxide (AgOCs), frequently used in radiation detectors.
- electromagnetic such as, for example, image intensifier tubes and photomultiplier tubes.
- Electromagnetic radiation detectors such as, for example, image intensifier tubes and photomultiplier tubes, detect electromagnetic radiation by converting it into a light or electrical output signal.
- They usually comprise a photocathode for receiving the electromagnetic radiation and in response transmitting a photoelectron flux, an electron multiplier device for receiving said photoelectron flux and in response transmitting a flow of so-called secondary electrons, then an output device for receiving said secondary electron flow and in response transmitting the output signal.
- such a photocathode 1 usually comprises a transparent support layer 10 and a layer 20 of a photoemissive material deposited on a face 12 of said support layer.
- the support layer 10 comprises a front face 11, said receiving, intended to receive the incident photons, and an opposite rear face 12.
- the support layer 10 is transparent vis-à-vis the incident photons, and therefore has a transmittance close to the unit.
- the light emitting layer 20 has an upstream face 21 in contact with the rear face 12 of the support layer 10, and an opposite downstream face 22, called the emission face, from which the generated photoelectrons are emitted.
- the photons pass through the support layer 10 from the reception face 11, then penetrate into the light emitting layer 20.
- the electrons generated move to the emission face 22 of the light emitting layer 20 and are emitted in a vacuum.
- the vacuum is indeed realized inside the detector so that the displacement of the electrons is not disturbed by the presence of gas molecules.
- the photoelectrons are then directed and accelerated to an electron multiplier device such as a microchannel slab or a set of dynodes.
- the yield of the photocathode is conventionally defined as the ratio of the number of photoelectrons emitted to the number of incident photons received.
- the quantum yield is of the order of 15% for a wavelength of 500 nm.
- the quantum yield depends more precisely on the three main stages, mentioned above, of the phenomenon of photoemission: the absorption of the incident photon and the formation of an electron-hole pair; transporting the generated electron to the emitting face of the light emitting layer; and the emission of the electron in a vacuum.
- Each of these three steps has a clean performance, the product of the three yields defining the quantum yield of the photocathode.
- the efficiency ⁇ a of the absorption step is an increasing function of the thickness of the light emitting layer.
- the thicker the photoemissive layer the greater the ratio of the number of photons absorbed to the number of incident photons. Photons that have not been absorbed are transmitted through the photoemissive layer.
- the efficiency ⁇ t of the transport phase that is to say the ratio between the electrons reaching the emission face on the electrons generated, is a decreasing function of the thickness of the light emitting layer. The greater the thickness of the layer, the lower the efficiency is. Indeed, the electrons generated will be all the more likely to recombine with holes that the distance to travel is large.
- the optimum thickness of the light emitting layer is usually between 50 and 200 nm.
- the figure 2 illustrates, for such a photoemissive layer, the evolution of the absorption rate ⁇ a as a function of the wavelength of the incident photons, as well as the reflection rates ⁇ "of the incident and transmission photons ⁇ 'thereof through the photoemissive layer.
- one solution may be to increase the thickness of said layer.
- the increase in the thickness of the light emitting layer although improving the absorption rate, does not lead to an increase in quantum efficiency, especially at long wavelengths, since the transport rate is degraded.
- the main purpose of the invention is to present a semi-transparent photocathode photon detector comprising a light emitting layer having a high incident photon absorption rate and a preserved electron transport rate.
- said photocathode comprises a diffraction grating in transmission capable of diffracting said photons, disposed in the support layer and located at said rear face.
- semi-transparent photocathode means a photocathode whose photoelectrons are emitted from an emission face opposite to the incident photon receiving face. It differs from so-called opaque photocathodes for which electrons are emitted from the photon receiving face.
- the support layer is said to be transparent insofar as it allows the transmission of incident photons.
- the transmittance of the support layer, or ratio of the photons transmitted on the received photons, is therefore close to or equal to unity.
- the incident photons penetrate into the support layer through the so-called reception front surface and pass through it to the opposite rear face.
- angles of incidence, diffraction and refraction of photons are measured relative to the normal to the considered face.
- the angles of incidence and diffraction mentioned above are defined with respect to the normal to the rear face of the support layer at which the diffraction grating is arranged.
- the average apparent thickness for the photons is e .
- the absorption rate of the light emitting layer is then higher than that of the photocathode according to the prior art mentioned above, insofar as it is an increasing function of the thickness, here of the apparent thickness, of the layer. emitting.
- the transport rate is then preserved insofar as it does not depend on the apparent thickness of the light emitting layer seen by the photons, but the actual thickness of it. Indeed, when the photons generate electron-hole pairs, the electrons generated move to the emission face regardless of the propagation direction of the photons.
- the photocathode according to the invention has a high rate of photon absorption and a preserved electron transport rate.
- Said diffraction grating is advantageously etched in the rear face of the support layer.
- Said diffraction grating is preferably arranged so as to delimit at least part of the rear face of the support layer.
- Said diffraction grating is preferably formed of a periodic arrangement of patterns filled with a material having an optical index different from the material of the support layer.
- patterns are meant notches, or notches, or recesses or notches, or scratches having a sinusoidal shape, scale, trapezoidal, made in the support layer.
- the difference between the optical indices of the material of the diffraction grating present in said patterns on the one hand and the material of the support layer on the other hand is greater than or equal to 0.2.
- the pitch of the grating and / or the material of the diffraction grating are chosen so that the photons are diffracted in the photoemissive layer with a diffraction angle strictly greater than arcsine (1 / n p ).
- the photocathode comprises at least one additional diffraction grating capable of diffracting said photons, located in the support layer and disposed close to said first diffraction grating, formed of a periodic arrangement of patterns filled with a material having an optical index different from the material of the support layer.
- the diffraction gratings are oriented in distinct directions, and spaced from each other by a negligible distance from the average thickness of the support layer. This distance is approximately one tenth to ten times the wavelength considered.
- the periodic arrangement of patterns of said at least one additional diffraction grating may be shifted in a direction orthogonal to the thickness direction of the support layer relative to the arrangement of said first diffraction grating.
- the diffraction grating and the additional diffraction grating are arranged in the same plane.
- the photoemissive layer may comprise antimony and at least one alkali metal.
- Such a light emitting layer may be made of a material selected from SbNaKCs, SbNa 2 KCs, SbNaK, SbKCs, SbRbKCs or SbRbCs.
- the photoemissive layer may be formed of AgOCs.
- the photoemissive layer preferably has a substantially constant thickness.
- the photoemissive layer preferably has a thickness of less than or equal to 300 nm.
- the invention also relates to an optical photon detection system comprising a photocathode according to any one of the preceding features, and an output device for transmitting an output signal in response to the photoelectrons emitted by said photocathode.
- Such an optical system may be an image intensifier tube or a photomultiplier tube.
- the figures 3 and 4 illustrate a semi-transparent photocathode 1 according to a first preferred embodiment of the invention.
- the photocathode 1 according to the invention can equip any type of photon detector, such as, for example, an image intensifier tube or an electron multiplier tube.
- the function of the photocathode is to receive a stream of incident photons and to emit electrons, called photoelectrons, in response.
- It comprises a transparent support layer 10, a layer 20 of a light-emitting material and, according to the invention, at least one diffraction grating 30 capable of diffracting the incident photons.
- the support layer 10 is a layer of a transparent material on which the photoemissive layer 20 is deposited.
- the transmittance of the support layer 10 is therefore substantially equal to unity.
- At least one transmission diffraction grating 30 is disposed in the support layer 10 at said rear face 12.
- the diffraction grating 30 is formed of a periodic arrangement of patterns 31 filled with a material having an optical index different from the material of the support layer 10.
- patterns are meant indentations, notches, recesses, notches or scratches, having a sinusoidal, scale, trapezoidal or other shape, practiced in the support layer.
- the difference between the optical indices of the material of the diffraction grating 30 present in said patterns 31 on the one hand and the material of the support layer 10 on the other hand is greater than or equal to 0.2.
- the diffraction grating 30 is notably characterized by the distance, called grating pitch, between two neighboring patterns 31.
- the pitch of the network is defined according to the wavelength of the incident photons, so as to be able to diffract them.
- the diffraction grating 30 may be arranged in the support layer 10 at the rear face 12, thus delimiting at least part of the rear face 12.
- the diffraction grating may be disposed inside the support layer and located in the immediate vicinity of the rear face, at a negligible distance from it with respect to the thickness of the support layer.
- the rear face 12 of the support layer 10 is substantially flat. However, it may be curved in the case of a photocathode itself having a defined curvature.
- the diffraction grating 30 is located in the support layer 10, so that the material filling the patterns 31 of the network does not protrude from said patterns.
- the material filling the patterns 31 may, in a variant, form a layer between the rear face 12 of the support layer and the light emitting layer 20.
- the light emitting layer 20 is disposed against the rear face 12 of the support layer 10.
- the light emitting layer 20 has a substantially constant average thickness, denoted e.
- the thickness is preferably less than or equal to 300 nm.
- the light emitting layer 20 is made of a suitable semiconductor material, preferably an alkaline antimony compound.
- a suitable semiconductor material preferably an alkaline antimony compound.
- Such an alkaline material may be selected from SbNaKCs, SbNa 2 KCs, SbNaK, SbKCs, SbRbKCs or SbRbCs.
- the light emitting layer 20 may also be formed of AgOCs silver oxide.
- the emission face 22 can be treated with hydrogen, cesium or cesium oxide to reduce its electronic affinity.
- the photoelectrons which reach the downstream face 22 of emission of the photoemissive layer 20 can be extracted naturally and thus be emitted in a vacuum.
- An electrode (not shown) forming an electron reservoir is in contact with the light emitting layer 20 and is brought to an electric potential.
- It can be arranged against a lateral face of the light emitting layer 20, so as not to diminish or disrupt the emission of electrons from the downstream face 22 of emission.
- the electron reservoir allows the recombination of the holes generated by the incident photons.
- the overall electrical charge of the light emitting layer 20 remains substantially constant.
- the photoemissive layer 20 is sufficiently thin so that the electrons generated move naturally to the emission face 22.
- Photons enter the photocathode 1 through the front face 11 of receiving the support layer 10.
- diffraction grating 30 They are then diffracted by the diffraction grating 30 and transmitted in the light emitting layer 20. They have statistically a diffraction angle substantially greater, in absolute value, at the angle of incidence, the angles of incidence and diffraction are defined. compared to normal at the back 12.
- e d e ⁇ - ⁇ max + ⁇ ⁇ max + ⁇ F ⁇ d cos d d ⁇ d
- e is the actual thickness of the layer
- ⁇ max is the maximum angle of incidence on the network.
- the apparent average thickness e d of the light emitting layer is substantially greater than its real thickness e, ie the average distance traveled by the photons in the layer is substantially greater than in the interior art. As a result, a higher percentage of the diffracted photons is absorbed.
- Electrons generated propagate in the photoemissive layer 20 to the downstream face 22 of emission where they are emitted in vacuum.
- the transport rate of the light emitting layer 20 is substantially equal to that of a photocathode according to the prior art. that is, without a diffraction grating. The transport rate is thus preserved.
- the photocathode 1 according to the invention thus has a high absorption rate and a transport rate preserved, which leads to optimized quantum efficiency, especially for energies close to the threshold of photoemission.
- the photocathode 1 according to the invention can be performed as follows.
- the support layer 10 is made of a suitable transparent material, for example quartz or borosilicate glass.
- the patterns 31 of the diffraction grating 30 are etched in the support layer 10 at the rear face 12 by known etching techniques, such as, for example, holography and / or ion etching and even etching techniques. by diamond.
- the patterns 31 are then filled with a diffraction material whose optical index is different from that of the support layer, such as, for example, Al 2 O 3 (n ⁇ 1, 7), TiO 2 (n ⁇ 2, 3-2, 6) or Ta 2 O 5 (n ⁇ 2.2), or even HfO 2 .
- a diffraction material whose optical index is different from that of the support layer, such as, for example, Al 2 O 3 (n ⁇ 1, 7), TiO 2 (n ⁇ 2, 3-2, 6) or Ta 2 O 5 (n ⁇ 2.2), or even HfO 2 .
- This material can be deposited by known techniques of physical vapor deposition, such as, for example, sputtering ( sputtering ), evaporation, or EBPVD electron beam vapor deposition ( electron beam physical vapor deposition, in English).
- physical vapor deposition such as, for example, sputtering ( sputtering ), evaporation, or EBPVD electron beam vapor deposition ( electron beam physical vapor deposition, in English).
- the known techniques of chemical vapor deposition such as, for example, the atomic layer deposition (ALD) may also be used, as well as the so-called hybrid techniques, such as, for example, the reactive sputtering and ion beam assisted deposition (IBAD).
- IBAD reactive sputtering and ion beam assisted deposition
- the rear face 12 is polished so as to remove any surplus of diffraction material projecting from the patterns 31 of the diffraction grating 30.
- the rear face is polished without being flush with the rear face.
- a uniform layer of diffraction material remains present on the rear face 22, in continuity with the patterns.
- a thin diffusion barrier may then be deposited to prevent any migration / chemical interaction between the material of the light emitting layer and the material of the diffraction grating.
- the thickness of the diffusion barrier is chosen sufficiently thin (less than ⁇ / 4 and preferably of the order of ⁇ / 10).
- the photoemissive layer 20 is then deposited by one of the deposition techniques mentioned above.
- a type S25 photocathode 1 may be implemented in the following manner.
- the support layer 10 is made of quartz.
- the diffraction grating 30 is etched in the support layer 10 at the rear face 12 in the form of a periodic arrangement of grooves 31 parallel to each other.
- the grooves 31 have a width of 341 nm and a depth of 362 nm.
- the pitch of the grating that is to say the distance separating two adjacent and parallel grooves 31, is 795 nm.
- the grooves 31 are filled for example with TiO 2 , whose optical index is between 2.3 and 2.6.
- TiO 2 can be deposited by the known Atomic Layer Deposition (ALD) technique.
- ALD Atomic Layer Deposition
- a step of polishing the rear face 12 is performed to remove any surplus of diffraction material projecting from the grooves 31.
- the rear face 12 is substantially flat, and delimited in part by the material (quartz) of the support layer 10 and partly by the material (TiO 2 ) for diffraction of the grooves 31 of the diffraction grating 30.
- the photoemissive layer 20 is finally made of SbNaK or SbNa 2 KCs and is deposited on the rear face 12 of the support layer 10 so as to have a thickness of 50 to 240 nm substantially constant.
- the figure 5 illustrates the evolution of the quantum efficiency as a function of the wavelength of the incident photons, for such a photocathode on the one hand and for a photocathode according to the example of the prior art previously described on the other hand.
- the quantum yield of the photocathode according to the invention is of the order of 18% whereas it is of the order of 10% in the case of a photocathode without a diffraction grating, which gives an improvement of nearly 80% in quantum efficiency.
- the figure 6 illustrates a photocathode according to a second embodiment of the invention.
- the diffraction grating 30 is advantageously sized so that the average diffraction angle ⁇ d (taking into account the angular distribution F ( ⁇ d )) is strictly greater than arcsin (1 / n p ) where n p is the optical index of the light emitting layer. More specifically, the pitch p of the grating and / or the optical index of the diffraction material filling the patterns 31 are chosen so that the average diffraction angle ⁇ d is strictly greater than arcsin (1 / n p ).
- the quantum yield of the photocathode is therefore further improved, in particular for photons of energy close to the photoemission threshold.
- the figure 7 illustrates a photocathode, seen from above, according to a third embodiment of the invention, in which two diffraction gratings 30, 40 are present in the support layer 10 at the rear face 12.
- the photocathode differs from the first preferred embodiment only in the presence of an additional diffraction grating 40 in the support layer 10.
- This additional network 40 is disposed near the first diffraction grating 30, upstream thereof according to the direction of propagation of the photons.
- These two networks 30, 40 are oriented in distinct directions, preferably orthogonal, and are spaced from each other by a negligible distance from the thickness of the support layer, for example from a distance of the order of ⁇ / 10 to 10 ⁇ .
- the additional network 40 is not the same as the first diffraction grating 30 previously described.
- the first diffraction grating and the additional grating are made in the same plane in a two-dimensional pattern whose transmission function is the product of the respective transmission functions of the first network and the additional network.
- the two-dimensional pattern can be obtained by holographic techniques.
- the angular distribution is more spread out than in the first embodiment and the apparent thickness of the light emitting layer 20 for photons is more important, which improves the absorption rate.
- this embodiment is not limited to two diffraction gratings. A greater number of diffraction gratings of different directions may be present in the backing layer at the back.
- the photocathode described above can be integrated into an optical photon detection system.
- an optical system comprises an output device adapted to convert the photoelectrons into an electrical signal.
- This output device may comprise a CCD matrix, the optical system being known by the acronym EB-CCD (Electron Bombarded CCD).
- the output device may comprise a CMOS matrix on thinned and passivated substrate, the optical system then being known by the acronym EBCMOS (Electron Bombarded CMOS).
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Description
La présente invention se rapporte au domaine général des photocathodes semi-transparentes, et plus précisément, à celui des photocathodes semi-transparentes de type à antimoine et métal alcalin, ou à oxyde d'argent (AgOCs), fréquemment utilisées dans les détecteurs de rayonnement électromagnétique, tels que, par exemple, les tubes intensificateurs d'image et les tubes photomultiplicateurs.The present invention relates to the general field of semi-transparent photocathodes, and more specifically, to that of semi-transparent photocathodes of antimony and alkali metal type, or silver oxide (AgOCs), frequently used in radiation detectors. electromagnetic, such as, for example, image intensifier tubes and photomultiplier tubes.
Les détecteurs de rayonnement électromagnétique, tels que, par exemple, les tubes intensificateurs d'image et les tubes photomultiplicateurs, permettent de détecter un rayonnement électromagnétique en le convertissant en un signal de sortie lumineux ou électrique.Electromagnetic radiation detectors, such as, for example, image intensifier tubes and photomultiplier tubes, detect electromagnetic radiation by converting it into a light or electrical output signal.
Ils comportent habituellement une photocathode pour recevoir le rayonnement électromagnétique et émettre en réponse un flux de photoélectrons, un dispositif multiplicateur d'électrons pour recevoir ledit flux de photoélectrons et émettre en réponse un flux d'électrons dits secondaires, puis un dispositif de sortie pour recevoir ledit flux d'électrons secondaires et émettre en réponse le signal de sortie.They usually comprise a photocathode for receiving the electromagnetic radiation and in response transmitting a photoelectron flux, an electron multiplier device for receiving said photoelectron flux and in response transmitting a flow of so-called secondary electrons, then an output device for receiving said secondary electron flow and in response transmitting the output signal.
Comme le montre la
La couche support 10 comporte une face avant 11, dite de réception, destinée à recevoir les photons incidents, et une face arrière 12 opposée. La couche support 10 est transparente vis-à-vis des photons incidents, et présente donc une transmittance proche de l'unité.The
La couche photoémissive 20 présente une face amont 21 en contact avec la face arrière 12 de la couche support 10, et une face aval 22 opposée, dite face d'émission, de laquelle sont émis les photoélectrons générés.The
Ainsi, les photons traversent la couche support 10 à partir de la face de réception 11, puis pénètrent dans la couche photoémissive 20.Thus, the photons pass through the
Ils sont ensuite absorbés dans la couche photoémissive 20 et y génèrent des paires électrons-trous. Les électrons générés se déplacent jusqu'à la face d'émission 22 de la couche photoémissive 20 et sont émis dans le vide. Le vide est en effet réalisé à l'intérieur du détecteur pour que le déplacement des électrons ne soit pas perturbé par la présence de molécules de gaz.They are then absorbed into the
Les photoélectrons sont ensuite dirigés et accélérés vers un dispositif multiplicateur d'électrons tel qu'une galette de microcanaux ou un ensemble de dynodes.The photoelectrons are then directed and accelerated to an electron multiplier device such as a microchannel slab or a set of dynodes.
- une couche support transparente présentant une face avant pour recevoir lesdits photons et une face arrière opposée, et
- une couche photoémissive disposée sur ladite face arrière et présentant une face d'émission opposée, destinée à recevoir lesdits photons à partir de ladite couche support et à émettre en réponse des photoélectrons à partir de ladite face d'émission.
- a transparent support layer having a front face for receiving said photons and an opposite rear face, and
- a light emitting layer disposed on said rear face and having an opposite emitting face, intended to receive said photons from said support layer and to emit photoelectrons from said emission face.
Le rendement de la photocathode, dit rendement quantique, est classiquement défini comme le rapport du nombre de photoélectrons émis sur le nombre de photons incidents reçus.The yield of the photocathode, called quantum efficiency, is conventionally defined as the ratio of the number of photoelectrons emitted to the number of incident photons received.
Il dépend notamment de la longueur d'onde des photons incidents et de l'épaisseur de la couche photoémissive.It depends in particular on the wavelength of the incident photons and the thickness of the photoemissive layer.
A titre illustratif, pour une photocathode de type S25, le rendement quantique est de l'ordre de 15% pour une longueur d'onde de 500nm.As an illustration, for a S25 type photocathode, the quantum yield is of the order of 15% for a wavelength of 500 nm.
Le rendement quantique dépend plus précisément des trois étapes principales, mentionnées précédemment, du phénomène de photoémission : l'absorption du photon incident et la formation d'une paire électron-trou ; le transport de l'électron généré jusqu'à la face d'émission de la couche photoémissive ; et l'émission de l'électron dans le vide.The quantum yield depends more precisely on the three main stages, mentioned above, of the phenomenon of photoemission: the absorption of the incident photon and the formation of an electron-hole pair; transporting the generated electron to the emitting face of the light emitting layer; and the emission of the electron in a vacuum.
Chacune de ces trois étapes présente un rendement propre, le produit des trois rendements définissant le rendement quantique de la photocathode.Each of these three steps has a clean performance, the product of the three yields defining the quantum yield of the photocathode.
Cependant, les rendements des étapes d'absorption et de transport sont directement dépendants de l'épaisseur de la couche photoémissive.However, the yields of the absorption and transport steps are directly dependent on the thickness of the photoemissive layer.
Ainsi, le rendement εa de l'étape d'absorption est une fonction croissante de l'épaisseur de la couche photoémissive. Plus la couche photoémissive est épaisse, plus le rapport du nombre de photons absorbés sur le nombre de photons incidents est important. Les photons qui n'auront pas été absorbés sont transmis au travers de la couche photoémissive.Thus, the efficiency ε a of the absorption step is an increasing function of the thickness of the light emitting layer. The thicker the photoemissive layer, the greater the ratio of the number of photons absorbed to the number of incident photons. Photons that have not been absorbed are transmitted through the photoemissive layer.
Par contre, le rendement εt de la phase de transport, c'est-à-dire le rapport entre les électrons atteignant la face d'émission sur les électrons générés, est une fonction décroissante de l'épaisseur de la couche photoémissive. Plus l'épaisseur de la couche est importante, plus le rendement Et est faible. En effet, les électrons générés auront d'autant plus de chance de se recombiner avec des trous que la distance à parcourir est grande.On the other hand, the efficiency ε t of the transport phase, that is to say the ratio between the electrons reaching the emission face on the electrons generated, is a decreasing function of the thickness of the light emitting layer. The greater the thickness of the layer, the lower the efficiency is. Indeed, the electrons generated will be all the more likely to recombine with holes that the distance to travel is large.
Aussi, il existe une épaisseur optimale qui maximise le produit du taux d'absorption εa avec le taux de transport εt, et donc le rendement quantique.Also, there is an optimal thickness which maximizes the product of the absorption rate ε a with the transport rate ε t , and thus the quantum yield.
A titre illustratif, pour la photocathode de type S25 fréquemment utilisée dans les tubes intensificateurs d'image, l'épaisseur optimale de la couche photoémissive, réalisée en SbNaK ou SbNa2KCs, est habituellement entre 50 et 200 nm.As an illustration, for the type S25 photocathode frequently used in image intensifier tubes, the optimum thickness of the light emitting layer, made of SbNaK or SbNa 2 KCs, is usually between 50 and 200 nm.
La
Il apparaît que, pour les grandes longueurs d'onde, notamment les longueurs d'onde proches du seuil de photoémission, le taux d'absorption εa diminue fortement alors que le taux de transmission ε' augmente.It appears that, for the long wavelengths, in particular the wavelengths close to the photoemission threshold, the absorption rate ε a decreases sharply while the transmission rate ε 'increases.
Ainsi, pour les photons incidents de 800µm de longueur d'onde, seuls 40% d'entre eux sont absorbés alors que 60% sont transmis au travers de la couche photoémissive.Thus, for incident photons of 800μm wavelength, only 40% of them are absorbed while 60% are transmitted through the light emitting layer.
Pour diminuer le taux de transmission de la couche photoémissive au profit du taux d'absorption dans le but d'augmenter le rendement quantique, notamment aux grandes longueurs d'onde, une solution peut consister à augmenter l'épaisseur de ladite couche.To reduce the transmission rate of the light-emitting layer in favor of the absorption rate in order to increase the quantum yield, especially at long wavelengths, one solution may be to increase the thickness of said layer.
Ainsi, augmenter l'épaisseur à 280nm de la couche photoémissive mentionnée précédemment conduit, pour la longueur d'onde de 800µm, à un taux d'absorption de 64%, au lieu de 40%, et à un taux de transmission diminué à 36%.Thus, increasing the thickness at 280 nm of the photoemissive layer mentioned above leads, for the wavelength of 800 .mu.m, to an absorption rate of 64%, instead of 40%, and to a transmission rate decreased to 36%. %.
Cependant, cela entraîne une forte diminution du taux de transport dans la mesure où les électrons générés ont davantage de distance à parcourir jusqu'à la face d'émission de la couche photoémissive, et donc davantage de chances de se recombiner.However, this results in a large decrease in the transport rate since the electrons generated have more distance to travel to the emitting face of the light emitting layer, and therefore more chances to recombine.
Aussi, l'augmentation de l'épaisseur de la couche photoémissive, bien qu'améliorant le taux d'absorption, ne conduit pas à une augmentation du rendement quantique, notamment aux grandes longueurs d'onde, puisque le taux de transport est dégradé.Also, the increase in the thickness of the light emitting layer, although improving the absorption rate, does not lead to an increase in quantum efficiency, especially at long wavelengths, since the transport rate is degraded.
L'invention a principalement pour but de présenter une photocathode semi-transparente pour détecteur de photons, comportant une couche photoémissive présentant un taux d'absorption des photons incidents élevé et un taux de transport des électrons préservé.The main purpose of the invention is to present a semi-transparent photocathode photon detector comprising a light emitting layer having a high incident photon absorption rate and a preserved electron transport rate.
Pour ce faire, l'invention a pour objet une photocathode semi-transparente pour détecteur de photons, comportant :
- une couche support transparente présentant une face avant pour recevoir lesdits photons et une face arrière opposée, et
- une couche photoémissive disposée contre ladite face arrière et présentant une face d'émission opposée, destinée à recevoir lesdits photons à partir de ladite couche support et à émettre en réponse des photoélectrons à partir de ladite face d'émission.
- a transparent support layer having a front face for receiving said photons and an opposite rear face, and
- a light emitting layer disposed against said rear face and having an opposite emitting face, intended to receive said photons from said support layer and to emit in response photoelectrons from said emission face.
Selon l'invention, ladite photocathode comporte un réseau de diffraction en transmission apte à diffracter lesdits photons, disposé dans la couche support et situé au niveau de ladite face arrière.According to the invention, said photocathode comprises a diffraction grating in transmission capable of diffracting said photons, disposed in the support layer and located at said rear face.
Par photocathode dite semi-transparente, on entend une photocathode dont les photoélectrons sont émis à partir d'une face d'émission opposée à la face de réception des photons incidents. Elle se distingue des photocathodes dites opaques pour lesquelles les électrons sont émis à partir de la face de réception des photons.By so-called semi-transparent photocathode means a photocathode whose photoelectrons are emitted from an emission face opposite to the incident photon receiving face. It differs from so-called opaque photocathodes for which electrons are emitted from the photon receiving face.
La couche support est dite transparente dans la mesure où elle permet la transmission des photons incidents. La transmittance de la couche support, ou rapport des photons transmis sur les photons reçus, est donc proche ou égale à l'unité.The support layer is said to be transparent insofar as it allows the transmission of incident photons. The transmittance of the support layer, or ratio of the photons transmitted on the received photons, is therefore close to or equal to unity.
Ainsi, les photons incidents pénètrent dans la couche support par la face avant dite de réception et la traversent jusqu'à la face arrière opposée.Thus, the incident photons penetrate into the support layer through the so-called reception front surface and pass through it to the opposite rear face.
Ils sont alors diffractés par le réseau de diffraction en direction de la couche photoémissive.They are then diffracted by the diffraction grating towards the photoemissive layer.
Ils pénètrent dans la couche photoémissive avec un angle de diffraction sensiblement différent de l'angle d'incidence.They penetrate into the photoemissive layer with a diffraction angle substantially different from the angle of incidence.
Par définition, les angles d'incidence, de diffraction et de réfraction des photons sont mesurés par rapport à la normale à la face considérée. Ainsi, les angles d'incidence et de diffraction mentionnés précédemment sont définis par rapport à la normale à la face arrière de la couche support au niveau de laquelle est disposé le réseau de diffraction.By definition, the angles of incidence, diffraction and refraction of photons are measured relative to the normal to the considered face. Thus, the angles of incidence and diffraction mentioned above are defined with respect to the normal to the rear face of the support layer at which the diffraction grating is arranged.
Lorsqu'un photon arrive sur le réseau de diffraction avec un angle d'incidence sensiblement nul, il pénètre dans la couche photoémissive avec un angle de diffraction non nul. De manière générale, pour une distribution donnée de l'angle d'incidence, on observe une distribution sensiblement plus étalée de l'angle de diffraction.When a photon arrives on the diffraction grating with a substantially zero angle of incidence, it enters the light emitting layer with a non-zero diffraction angle. In general, for a given distribution of the angle of incidence, a substantially more spreading distribution of the diffraction angle is observed.
Ainsi, pour une épaisseur de la couche photoémissive, notée e et mesurée suivant la direction d'épaisseur de celle-ci, l'épaisseur apparente moyenne pour les photons est e.E(1/|cosα d |) où αd est l'angle de diffraction des photons et E(.) désigne la moyenne prise sur la distribution angulaire de l'angle de diffraction des photons.Thus, for a thickness of the light emitting layer, noted e and measured in the thickness direction thereof, the average apparent thickness for the photons is e . E (1 / | cosα d |) where α d is the diffraction angle of the photons and E (.) Is the mean taken from the angular distribution of the diffraction angle of the photons.
Le taux d'absorption de la couche photoémissive est alors plus élevé que celui de la photocathode selon l'art antérieur mentionnée précédemment, dans la mesure où il est une fonction croissante de l'épaisseur, ici de l'épaisseur apparente, de la couche photoémissive.The absorption rate of the light emitting layer is then higher than that of the photocathode according to the prior art mentioned above, insofar as it is an increasing function of the thickness, here of the apparent thickness, of the layer. emitting.
De plus, le taux de transport est alors préservé dans la mesure où il ne dépend pas de l'épaisseur apparente de la couche photoémissive vue par les photons, mais de l'épaisseur réelle de celle-ci. En effet, lorsque les photons génèrent des paires électrons-trous, les électrons générés se déplacent jusqu'à la face d'émission indépendamment du sens de propagation préalable des photons.In addition, the transport rate is then preserved insofar as it does not depend on the apparent thickness of the light emitting layer seen by the photons, but the actual thickness of it. Indeed, when the photons generate electron-hole pairs, the electrons generated move to the emission face regardless of the propagation direction of the photons.
Ainsi, la photocathode selon l'invention présente un taux élevé d'absorption des photons et un taux de transport des électrons préservé.Thus, the photocathode according to the invention has a high rate of photon absorption and a preserved electron transport rate.
Cela permet d'améliorer le rendement quantique de la photocathode.This improves the quantum yield of the photocathode.
Il est à noter que le rendement quantique pour les grandes longueurs d'onde, donc proche du seuil de photoémission, est significativement augmenté, dans la mesure où les photons avec de telles longueurs d'onde avaient tendance, selon l'exemple de l'art antérieur cité précédemment, à être davantage transmis qu'absorbés.It should be noted that the quantum yield for the long wavelengths, thus close to the threshold of photoemission, is significantly increased, insofar as the photons with such wavelengths tended, according to the example of the prior art cited above, to be more transmitted than absorbed.
Ledit réseau de diffraction est avantageusement gravé dans la face arrière de la couche support.Said diffraction grating is advantageously etched in the rear face of the support layer.
Ledit réseau de diffraction est, de préférence, disposé de manière à délimiter au moins en partie la face arrière de la couche support.Said diffraction grating is preferably arranged so as to delimit at least part of the rear face of the support layer.
Ledit réseau de diffraction est, de préférence, formé d' un arrangement périodique de motifs remplis d'un matériau présentant un indice optique différent du matériau de la couche support.Said diffraction grating is preferably formed of a periodic arrangement of patterns filled with a material having an optical index different from the material of the support layer.
Par motifs, on entend des échancrures, ou entailles, ou évidements ou encoches, ou rayures présentant une forme sinusoïdale, à échelle, trapézoïdale, pratiqués dans la couche support.By patterns are meant notches, or notches, or recesses or notches, or scratches having a sinusoidal shape, scale, trapezoidal, made in the support layer.
De préférence, la différence entre les indices optiques du matériau du réseau de diffraction présent dans lesdits motifs d'une part et du matériau de la couche support d'autre part est supérieure ou égale à 0,2.Preferably, the difference between the optical indices of the material of the diffraction grating present in said patterns on the one hand and the material of the support layer on the other hand is greater than or equal to 0.2.
Avantageusement, le pas du réseau et/ou le matériau du réseau de diffraction sont choisis de sorte que les photons sont diffractés dans la couche photoémissive avec un angle de diffraction strictement supérieur à arcsin(1/np ).Advantageously, the pitch of the grating and / or the material of the diffraction grating are chosen so that the photons are diffracted in the photoemissive layer with a diffraction angle strictly greater than arcsine (1 / n p ).
Selon un autre mode de réalisation, la photocathode comprend au moins un réseau de diffraction supplémentaire apte à diffracter lesdits photons, situé dans la couche support et disposé à proximité dudit premier réseau de diffraction, formé d'un arrangement périodique de motifs remplis d'un matériau présentant un indice optique différent du matériau de la couche support.According to another embodiment, the photocathode comprises at least one additional diffraction grating capable of diffracting said photons, located in the support layer and disposed close to said first diffraction grating, formed of a periodic arrangement of patterns filled with a material having an optical index different from the material of the support layer.
Les réseaux de diffraction sont orientés selon des directions distinctes, et distants les uns des autres d'une distance négligeable par rapport à l'épaisseur moyenne de la couche support. Cette distance est environ d'un dixième à dix fois la longueur d'onde considérée.The diffraction gratings are oriented in distinct directions, and spaced from each other by a negligible distance from the average thickness of the support layer. This distance is approximately one tenth to ten times the wavelength considered.
L'arrangement périodique de motifs dudit au moins un réseau de diffraction supplémentaire peut être décalé suivant une direction orthogonale à la direction d'épaisseur de la couche support par rapport à l'arrangement dudit premier réseau de diffraction.The periodic arrangement of patterns of said at least one additional diffraction grating may be shifted in a direction orthogonal to the thickness direction of the support layer relative to the arrangement of said first diffraction grating.
Alternativement, le réseau de diffraction et le réseau de diffraction supplémentaire sont disposés dans le même plan.Alternatively, the diffraction grating and the additional diffraction grating are arranged in the same plane.
La couche photoémissive peut comprendre de l'antimoine et au moins un métal alcalin.The photoemissive layer may comprise antimony and at least one alkali metal.
Une telle couche photoémissive peut être réalisée en un matériau choisi parmi SbNaKCs, SbNa2KCs, SbNaK, SbKCs, SbRbKCs ou SbRbCs.Such a light emitting layer may be made of a material selected from SbNaKCs, SbNa 2 KCs, SbNaK, SbKCs, SbRbKCs or SbRbCs.
Alternativement, la couche photoémissive peut être formée d'AgOCs.Alternatively, the photoemissive layer may be formed of AgOCs.
La couche photoémissive présente, de préférence, une épaisseur sensiblement constante.The photoemissive layer preferably has a substantially constant thickness.
La couche photoémissive présente, de préférence, une épaisseur inférieure ou égale à 300nm.The photoemissive layer preferably has a thickness of less than or equal to 300 nm.
L'invention porte également sur un système optique de détection de photons comportant une photocathode selon l'une quelconque des caractéristiques précédentes, et un dispositif de sortie pour émettre un signal de sortie en réponse aux photoélectrons émis par ladite photocathode.The invention also relates to an optical photon detection system comprising a photocathode according to any one of the preceding features, and an output device for transmitting an output signal in response to the photoelectrons emitted by said photocathode.
Un tel système optique peut être un tube intensificateur d'image ou un tube photomultiplicateur.Such an optical system may be an image intensifier tube or a photomultiplier tube.
D'autres avantages et caractéristiques de l'invention apparaîtront dans la description détaillée non limitative ci-dessous.Other advantages and features of the invention will become apparent in the detailed non-limiting description below.
On décrira à présent, à titre d'exemples non limitatifs, des modes de réalisation de l'invention, en se référant aux dessins annexés, dans lesquels :
- La
figure 1 , déjà décrite, est une vue schématique en coupe transversale d'une photocathode selon un exemple de l'art antérieur ; - La
figure 2 , déjà décrite, illustre un exemple d'évolution des taux d'absorption, de transmission et de réflexion en fonction de la longueur d'onde d'une couche photoémissive de 140nm d'épaisseur d'une photocathode du type S25 selon un exemple de l'art antérieur ; - La
figure 3 est une vue schématique en coupe transversale de la photocathode selon un premier mode de réalisation préféré de l'invention ; - La
figure 4 est une vue schématique en coupe transversale agrandie d'une partie de la photocathode illustrée sur lafigure 3 ; - La
figure 5 illustre un exemple d'évolution du rendement quantique en fonction de la longueur d'onde pour une photocathode selon l'art antérieur et pour une photocathode selon le premier mode de réalisation préféré de l'invention ; - La
figure 6 est une vue schématique en coupe transversale de la photocathode selon un autre mode de réalisation préféré de l'invention, dans lequel les photons diffractés sont réfléchis totalement au niveau de la couche d'émission de la photocathode ; et - La
figure 7 est une vue schématique en coupe transversale de la photocathode selon un autre mode de réalisation préféré de l'invention, dans lequel la photocathode comprend deux réseaux de diffraction.
- The
figure 1 , already described, is a schematic cross-sectional view of a photocathode according to an example of the prior art; - The
figure 2 , already described, illustrates an example of changes in absorption, transmission and reflection as a function of the wavelength of a light emitting layer 140nm thick of a S25 type photocathode according to an example of the prior art; - The
figure 3 is a schematic cross-sectional view of the photocathode according to a first preferred embodiment of the invention; - The
figure 4 is an enlarged cross-sectional schematic view of a portion of the photocathode illustrated in FIG.figure 3 ; - The
figure 5 illustrates an example of evolution of the quantum yield as a function of the wavelength for a photocathode according to the prior art and for a photocathode according to the first preferred embodiment of the invention; - The
figure 6 is a schematic cross-sectional view of the photocathode according to another preferred embodiment of the invention, wherein the diffracted photons are totally reflected at the emission layer of the photocathode; and - The
figure 7 is a schematic cross-sectional view of the photocathode according to another preferred embodiment of the invention, wherein the photocathode comprises two diffraction gratings.
Les
Il est à noter que les échelles ne sont pas respectées, pour privilégier la clarté du dessin.It should be noted that the scales are not respected, to favor the clarity of the drawing.
La photocathode 1 selon l'invention peut équiper tout type de détecteur de photons, tel que, par exemple, un tube intensificateur d'image ou un tube multiplicateur d'électrons.The
La photocathode a pour fonction de recevoir un flux de photons incidents et d'émettre en réponse des électrons, dits photoélectrons.The function of the photocathode is to receive a stream of incident photons and to emit electrons, called photoelectrons, in response.
Elle comprend une couche support 10 transparente, une couche 20 d'un matériau photoémissif et, selon l'invention, au moins un réseau de diffraction 30 apte à diffracter les photons incidents.It comprises a
La couche support 10 est une couche d'un matériau transparent sur laquelle est déposée la couche photoémissive 20.The
Elle est dite transparente dans la mesure où les photons incidents la traversent sans être absorbés. La transmittance de la couche support 10 est donc sensiblement égale à l'unité.It is said to be transparent insofar as the incident photons pass through it without being absorbed. The transmittance of the
Elle comporte une face avant 11, dite face de réception des photons, et une face arrière 12 opposée.It comprises a
Au moins un réseau de diffraction 30 en transmission est disposé dans la couche support 10 au niveau de ladite face arrière 12.At least one
Dans le mode de réalisation préféré de l'invention illustré sur les
Le réseau de diffraction 30 est formé d'un arrangement périodique de motifs 31 remplis d'un matériau présentant un indice optique différent du matériau de la couche support 10.The
Par motifs, on entend des échancrures, entailles, évidements, encoches ou rayures, présentant une forme sinusoïdale, à échelle, trapézoïdale ou autre, pratiqués dans la couche support.By patterns are meant indentations, notches, recesses, notches or scratches, having a sinusoidal, scale, trapezoidal or other shape, practiced in the support layer.
La différence entre les indices optiques du matériau du réseau de diffraction 30 présent dans lesdits motifs 31 d'une part et du matériau de la couche support 10 d'autre part est supérieure ou égale à 0,2.The difference between the optical indices of the material of the
Le réseau de diffraction 30 est notamment caractérisé par la distance, appelée pas du réseau, entre deux motifs 31 voisins. Le pas du réseau est défini en fonction de la longueur d'onde des photons incidents, de manière à pouvoir les diffracter.The
Comme le montre en détail la
Alternativement, le réseau de diffraction peut être disposé à l'intérieur la couche support et situé à proximité immédiate de la face arrière, à une distance de celle-ci négligeable par rapport à l'épaisseur de la couche support.Alternatively, the diffraction grating may be disposed inside the support layer and located in the immediate vicinity of the rear face, at a negligible distance from it with respect to the thickness of the support layer.
Il est à noter que la face arrière 12 de la couche support 10 est sensiblement plane. Elle peut cependant être courbe dans le cas d'une photocathode présentant elle-même une courbure définie.It should be noted that the
Sur la
La couche photoémissive 20 est disposée contre la face arrière 12 de la couche support 10.The
Elle présente une face amont 21, en contact avec la face arrière 12 de la couche support 10, et une face aval 22 opposée, dite face d'émission des photoélectrons.It has an
La couche photoémissive 20 présente une épaisseur moyenne sensiblement constante, notée e. L'épaisseur est de préférence inférieure ou égale à 300nm.The
La couche photoémissive 20 est réalisée en un matériau semi-conducteur adapté, de préférence un composé alcalin à base d'antimoine. Un tel matériau alcalin peut être choisi parmi SbNaKCs, SbNa2KCs, SbNaK, SbKCs, SbRbKCs ou SbRbCs. La couche photoémissive 20 peut également être formée en oxyde d'argent AgOCs.The
La face d'émission 22 peut être traitée à l'hydrogène, au césium ou à l'oxyde de césium pour diminuer son affinité électronique. Ainsi, les photoélectrons qui atteignent la face aval 22 d'émission de la couche photoémissive 20 peuvent s'en extraire naturellement et être ainsi émis dans le vide.The emission face 22 can be treated with hydrogen, cesium or cesium oxide to reduce its electronic affinity. Thus, the photoelectrons which reach the
Une électrode (non représentée), formant réservoir d'électrons, est au contact de la couche photoémissive 20 et est portée à un potentiel électrique.An electrode (not shown) forming an electron reservoir is in contact with the
Elle peut être disposée contre une face latérale de la couche photoémissive 20, pour ne pas diminuer ou perturber l'émission des électrons à partir de la face aval 22 d'émission.It can be arranged against a lateral face of the
Le réservoir d'électrons permet la recombinaison des trous générés par les photons incidents. Ainsi, la charge électrique globale de la couche photoémissive 20 reste sensiblement constante.The electron reservoir allows the recombination of the holes generated by the incident photons. Thus, the overall electrical charge of the
Il est à noter que la couche photoémissive 20 est suffisamment mince pour que les électrons générés se déplacent naturellement jusqu'à la face d'émission 22.It should be noted that the
Il n'est donc pas nécessaire de générer un champ électrique dans la couche photoémissive 20 pour assurer le transport des électrons jusqu'à la face d'émission. La génération d'un tel champ électrique nécessiterait en effet de déposer deux électrodes de polarisation, l'une contre la face amont 21 de la couche photoémissive 20 et l'autre contre la face aval 22 d'émission.It is therefore not necessary to generate an electric field in the
Le fonctionnement de la photocathode selon l'invention est décrit ci-après.The operation of the photocathode according to the invention is described below.
Des photons pénètrent dans la photocathode 1 par la face avant 11 de réception de la couche support 10.Photons enter the
Ils traversent la couche support 10 jusqu'à la face arrière 12 de celle-ci.They pass through the
Ils sont ensuite diffractés par le réseau de diffraction 30 et transmis dans la couche photoémissive 20. Ils présentent statistiquement un angle de diffraction sensiblement supérieur, en valeur absolue, à l'angle d' incidence, les angles d'incidence et de diffraction sont définis par rapport à la normale à la face arrière 12.They are then diffracted by the
Plus précisément, si l'on note α=α i l'angle d'incidence sur le réseau, f(α) la distribution angulaire du faisceau incident, αd l'angle de diffraction, la distribution angulaire du faisceau diffracté peut s'écrire :
La distribution angulaire du faisceau diffracté est par conséquent plus étalée que celle du faisceau incident. Les électrons voient une couche photoémissive 20 d'épaisseur moyenne apparente :
L'épaisseur moyenne apparente ed de la couche photoémissive est sensiblement supérieure à son épaisseur réelle e, autrement dit la distance moyenne parcourue par les photons dans la couche est sensiblement plus importante que dans l'art intérieur. Il en résulte qu' un pourcentage plus élevé des photons diffractés est absorbé.The apparent average thickness e d of the light emitting layer is substantially greater than its real thickness e, ie the average distance traveled by the photons in the layer is substantially greater than in the interior art. As a result, a higher percentage of the diffracted photons is absorbed.
L'absorption des photons diffractés entraîne la génération de paires électrons-trous. Les électrons générés se propagent dans la couche photoémissive 20 jusqu'à la face aval 22 d'émission où ils sont émis dans le vide.The absorption of diffracted photons leads to the generation of electron-hole pairs. Electrons generated propagate in the
Dans la mesure où le transport des électrons dans la couche photoémissive 20 est indépendant de la direction de propagation préalable des photons, le taux de transport de la couche photoémissive 20 est sensiblement égal à celui d'une photocathode selon l'art antérieur, c'est-à-dire sans réseau de diffraction. Le taux de transport est ainsi préservé.Insofar as the transport of the electrons in the
La photocathode 1 selon l'invention présente ainsi un taux d'absorption élevé et un taux de transport préservé, ce qui conduit à un rendement quantique optimisé, notamment pour les énergies proches du seuil de photoémission.The
La photocathode 1 selon l'invention peut être réalisée comme suit.The
La couche support 10 est réalisée en un matériau transparent adapté, par exemple en quartz ou en verre borosilicate.The
Les motifs 31 du réseau de diffraction 30 sont gravés dans la couche support 10 au niveau de la face arrière 12 par des techniques connues de gravure, telles que, par exemple, les techniques d'holographie et/ou de décapage ionique, voire de gravure par diamant.The
Les motifs 31 sont ensuite remplis par un matériau de diffraction dont l'indice optique est différent de celui de la couche support, comme, par exemple, de l'Al2O3 (n~1, 7), du TiO2 (n~2, 3-2, 6) ou du Ta2O5 (n~2,2), voire du HfO2.The
Ce matériau peut être déposé par des techniques connues de dépôt physique en phase vapeur, telles que, par exemple, la pulvérisation cathodique (sputtering, en anglais), l'évaporation, ou le dépôt physique en phase vapeur à faisceau d'électrons EBPVD (electron beam physical vapeur déposition, en anglais). Les techniques connues de dépôt chimique en phase vapeur, telles que, par exemple, le dépôt en couche atomique ALD (atomic layer deposition, en anglais) peuvent également être utilisées, ainsi que les techniques connues dites hybrides, telles que, par exemple, la pulvérisation réactive et le dépôt assisté par faisceau d'ions (IBAD pour ion beam assisted deposition, en anglais).This material can be deposited by known techniques of physical vapor deposition, such as, for example, sputtering ( sputtering ), evaporation, or EBPVD electron beam vapor deposition ( electron beam physical vapor deposition, in English). The known techniques of chemical vapor deposition, such as, for example, the atomic layer deposition (ALD) may also be used, as well as the so-called hybrid techniques, such as, for example, the reactive sputtering and ion beam assisted deposition (IBAD).
Selon une première variante avantageuse, illustrée en
Selon une seconde variante, non représentée, la face arrière est polie sans pour autant affleurer au niveau de la face arrière. Il en résulte qu'une couche uniforme de matériau de diffraction reste présente sur la face arrière 22, en continuité avec les motifs.According to a second variant, not shown, the rear face is polished without being flush with the rear face. As a result, a uniform layer of diffraction material remains present on the
Quelle que soit la variante, une fine barrière de diffusion peut être ensuite déposée pour prévenir toute migration/interaction chimique entre le matériau de la couche photoémissive et le matériau du réseau de diffraction. L'épaisseur de la barrière de diffusion est choisie suffisamment mince (moins de λ/4 et de préférence de l'ordre de λ/10).Whatever the variant, a thin diffusion barrier may then be deposited to prevent any migration / chemical interaction between the material of the light emitting layer and the material of the diffraction grating. The thickness of the diffusion barrier is chosen sufficiently thin (less than λ / 4 and preferably of the order of λ / 10).
Dans tous les cas, la couche photoémissive 20 est ensuite déposée par l'une des techniques de dépôt précédemment mentionnées.In all cases, the
A titre illustratif, une photocathode 1 de type S25 selon le premier mode de réalisation préféré de l'invention peut être réalisée de la manière suivante.By way of illustration, a
La couche support 10 est réalisée en quartz.The
Le réseau de diffraction 30 est gravé dans la couche support 10 au niveau de la face arrière 12, sous forme d'un arrangement périodique de rainures 31 parallèles les unes aux autres.The
Les rainures 31 présentent une largeur de 341nm et une profondeur de 362nm. Le pas du réseau, c'est-à-dire la distance séparant deux rainures 31 voisines et parallèles, est de 795nm.The
Les rainures 31 sont remplies par exemple de TiO2, dont l'indice optique est compris entre 2,3 et 2,6.The
Le TiO2 peut être déposé par la technique connue de dépôt de couche atomique (ALD, pour Atomic Layer Deposition, en anglais).TiO 2 can be deposited by the known Atomic Layer Deposition (ALD) technique.
Une étape de polissage de la face arrière 12 est effectuée pour enlever tout surplus de matériau de diffraction en saillie hors des rainures 31.A step of polishing the
Ainsi, la face arrière 12 est sensiblement plane, et délimitée en partie par le matériau (quartz) de la couche support 10 et en partie par le matériau (TiO2) de diffraction des rainures 31 du réseau de diffraction 30.Thus, the
La couche photoémissive 20 est enfin réalisée en SbNaK ou SbNa2KCs et est déposée sur la face arrière 12 de la couche support 10 de manière à présenter une épaisseur de 50 à 240 nm sensiblement constante.The
La
On remarque que le rendement quantique est amélioré sur toute la gamme de longueur d'onde, et plus particulièrement aux grandes longueurs d'onde.Note that the quantum efficiency is improved over the entire wavelength range, and more particularly at long wavelengths.
Ainsi, pour λ~825nm, le rendement quantique de la photocathode selon l'invention est de l'ordre de 18% alors qu' il est de l'ordre de 10% dans le cas d' une photocathode sans réseau de diffraction, ce qui donne une amélioration de près de 80% du rendement quantique.Thus, for λ ~ 825nm, the quantum yield of the photocathode according to the invention is of the order of 18% whereas it is of the order of 10% in the case of a photocathode without a diffraction grating, which gives an improvement of nearly 80% in quantum efficiency.
La
Les références numériques identiques à celles de la
La photocathode 1 ne diffère du premier mode de réalisation préféré que par le fait que le réseau de diffraction 30 est dimensionné de sorte que tout photon arrivant sous incidence normale (α i =0), diffracté et non absorbé dans la couche photoémissive 20, soit réfléchi au niveau de la face aval 22 d'émission.The
Alternativement, le réseau de diffraction 30 est avantageusement dimensionné de sorte que l'angle de diffraction moyen
Ainsi, ces photons réfléchis restent localisés dans la couche photoémissive 20 jusqu'à leur absorption et la génération de paire électron-trou.Thus, these reflected photons remain localized in the
Cela permet de diminuer significativement le taux de transmission des photons de la couche photoémissive 20 en faveur du taux d'absorption.This makes it possible to significantly reduce the photon transmission rate of the
Le taux de transport des électrons restant inchangé, le rendement quantique de la photocathode est par conséquent encore amélioré, en particulier pour les photons d'énergie proche du seuil de photoémission.As the electron transport rate remains unchanged, the quantum yield of the photocathode is therefore further improved, in particular for photons of energy close to the photoemission threshold.
La
Les références numériques identiques à celles de la
La photocathode ne diffère du premier mode de réalisation préféré que par la présence d'un réseau de diffraction supplémentaire 40 dans la couche support 10.The photocathode differs from the first preferred embodiment only in the presence of an
Ce réseau supplémentaire 40 est disposé à proximité du premier réseau de diffraction 30, en amont de celui-ci suivant le sens de propagation des photons.This
Ces deux réseaux 30, 40 sont orientés selon des directions distinctes, de préférence orthogonales, et sont distants l'un de l'autre d'une distance négligeable par rapport à l'épaisseur de la couche support, par exemple d'une distance de l'ordre de λ/10 à 10λ.These two
Le réseau supplémentaire 40 est par exemple de même pas que le premier réseau de diffraction 30 précédemment décrit.For example, the
Selon une variante, le premier réseau de diffraction et le réseau supplémentaire sont réalisés dans un même plan selon un motif bidimensionnel dont la fonction de transmission est le produit des fonctions de transmission respectives du premier réseau et du réseau supplémentaire. Le motif bidimensionnel peut être obtenu par des techniques holographiques.According to a variant, the first diffraction grating and the additional grating are made in the same plane in a two-dimensional pattern whose transmission function is the product of the respective transmission functions of the first network and the additional network. The two-dimensional pattern can be obtained by holographic techniques.
Dans l'hypothèse de deux réseaux orthogonaux, la distribution angulaire des photons diffractés peut alors s'écrire sous la forme :
Ainsi, la distribution angulaire est davantage étalée que dans le premier mode de réalisation et l'épaisseur apparente de la couche photoémissive 20 pour les photons est plus importante, ce qui améliore le taux d'absorption.Thus, the angular distribution is more spread out than in the first embodiment and the apparent thickness of the
L'homme du métier comprendra que ce mode de réalisation n'est pas limité à deux réseaux de diffraction. Un plus grand nombre de réseaux de diffraction de directions distinctes peuvent être présents dans la couche support au niveau de la face arrière.Those skilled in the art will understand that this embodiment is not limited to two diffraction gratings. A greater number of diffraction gratings of different directions may be present in the backing layer at the back.
Par ailleurs, diverses modifications peuvent être apportées par l'homme du métier à l'invention qui vient d'être décrite uniquement à titre d'exemples non limitatifs.Moreover, various modifications may be made by those skilled in the art to the invention which has just been described solely by way of non-limiting examples.
Enfin la photocathode décrite ci-dessus peut être intégrée dans un système optique de détection de photons. Un tel système optique comprend un dispositif de sortie adapté à convertir les photoélectrons en un signal électrique. Ce dispositif de sortie peut comprendre une matrice CCD, le système optique étant connu sous l'acronyme EB-CCD (Electron Bombarded CCD). Alternativement, le dispositif de sortie peut comprendre une matrice CMOS sur substrat aminci et passivé, le système optique étant alors connu sous l'acronyme EBCMOS (Electron Bombarded CMOS).Finally, the photocathode described above can be integrated into an optical photon detection system. Such an optical system comprises an output device adapted to convert the photoelectrons into an electrical signal. This output device may comprise a CCD matrix, the optical system being known by the acronym EB-CCD (Electron Bombarded CCD). Alternatively, the output device may comprise a CMOS matrix on thinned and passivated substrate, the optical system then being known by the acronym EBCMOS (Electron Bombarded CMOS).
Claims (15)
- A semi-transparent photocathode (1) for a photon detector, including:- a transparent support layer (10) having a front face (11) to receive said photons and an opposite back face (12), and- a photoemissive layer (20) provided on said back face (12) and having an opposite emitting face (22), intended to receive said photons from said support layer (10) and to responsively emit photoelectrons from said emitting face (22),characterized in that it includes a transmission diffraction grating (30) able to diffract said photons, provided in the support layer (10) and located at said back face (12).
- The photocathode (1) according to claim 1, characterized in that said diffraction grating (30) is etched in the back face (12) of the support layer (10).
- The photocathode (1) according to claim 1 or 2, characterized in that said diffraction grating (30) is formed of a periodical arrangement of patterns (31) filled with a material having an optical index different from the material of the support layer (10).
- The photocathode (1) according to claim 3, characterized in that said diffraction grating (30) is provided so as to bound at least partly the back face (12) of the support layer (10) by being flush with the same.
- The photocathode (1) according to claim 3, characterized in that a layer of said material is directly provided on the back face, in continuity with said patterns.
- The photocathode (1) according to claim 4 or 5, characterized in that a diffusion barrier is provided between the diffraction grating and the photoemissive layer.
- The photocathode (1) according to any of claims 1 to 6, characterized in that it includes at least a further diffraction grating (40) able to diffract said photons, which is located in the support layer (10) and provided in the vicinity of said first diffraction grating (30), formed of a periodical arrangement of patterns (41) along a direction distinct from that of the patterns of the first grating.
- The photocathode (1) according to claim 7, characterized in that the first grating and the further diffraction grating (40) are located in a same plane and made by means of two-dimensional patterns.
- The photocathode (1) according to any of claims 1 to 8, characterized in that the photoemissive layer (20) comprises antimony and at least one alkaline metal.
- The photocathode (1) according to claim 8, characterized in that the photoemissive layer (20) is made of a material selected from SbNaKCs, SbNa2KCs, SbNaK, SbKCs, SbRbKCs, or SbRbCs.
- The photocathode (1) according to any of claims 1 to 8, characterized in that the photoemissive layer (20) is formed of AgOCs.
- The photocathode (1) according to any of claims 1 to 11, characterized in that the photoemissive layer (20) has a substantially constant thickness.
- The photocathode (1) according to claim 12, characterized in that the photoemissive layer (20) has a thickness lower than or equal to 300nm.
- A photon detection optical system including a photocathode (1) according to any of claims 1 to 13, and an output device for emitting an output signal in response to the photoelectrons emitted by said photocathode (1).
- The optical system according to claim 14, being an image intensifier tube or a photomultiplier tube, of the EB-CCD or EBCMOS type.
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RS20170179A RS55724B1 (en) | 2012-10-12 | 2012-10-12 | Semi-transparent photocathode with improved absorption rate |
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PCT/EP2012/070313 WO2014056550A1 (en) | 2012-10-12 | 2012-10-12 | Semi-transparent photocathode with improved absorption rate |
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US (1) | US9960004B2 (en) |
EP (1) | EP2907154B1 (en) |
JP (1) | JP6224114B2 (en) |
KR (1) | KR101926188B1 (en) |
CN (1) | CN104781903B (en) |
AU (1) | AU2012391961B2 (en) |
BR (1) | BR112015007210B1 (en) |
CA (1) | CA2887442C (en) |
IL (1) | IL237874B (en) |
PL (1) | PL2907154T3 (en) |
RS (1) | RS55724B1 (en) |
RU (1) | RU2611055C2 (en) |
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US9734977B2 (en) | 2015-07-16 | 2017-08-15 | Intevac, Inc. | Image intensifier with indexed compliant anode assembly |
RU185547U1 (en) * | 2017-02-20 | 2018-12-14 | Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" | PHOTOCATODE FOR PULSE PHOTOELECTRONIC INSTRUMENTS |
RU2686063C1 (en) * | 2018-07-02 | 2019-04-24 | Общество с ограниченной ответственностью "Катод" | Semitransparent photocathode |
CN112908807B (en) * | 2021-01-13 | 2024-07-02 | 陕西理工大学 | Photocathode and application thereof |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL235195A (en) * | 1958-01-18 | |||
US3697794A (en) | 1969-03-19 | 1972-10-10 | Rca Corp | Photocathode comprising layers of tin oxide, antimony oxide, and antimony |
US3688145A (en) * | 1970-10-08 | 1972-08-29 | Donald K Coles | Light detector having wedge-shaped photocathode and accelerating grid structure |
US3700947A (en) * | 1971-04-08 | 1972-10-24 | Bendix Corp | Increased sensitivity photocathode structure |
US4999211A (en) | 1989-09-22 | 1991-03-12 | Itt Corporation | Apparatus and method for making a photocathode |
JPH0668947B2 (en) | 1990-01-08 | 1994-08-31 | 浜松ホトニクス株式会社 | Method for forming photocathode |
JPH07321358A (en) | 1994-05-27 | 1995-12-08 | Sanyo Electric Co Ltd | Photovoltaic device and its manufacture |
GB9620037D0 (en) * | 1996-09-26 | 1996-11-13 | British Tech Group | Radiation transducers |
US6054718A (en) | 1998-03-31 | 2000-04-25 | Lockheed Martin Corporation | Quantum well infrared photocathode having negative electron affinity surface |
US6759800B1 (en) | 1999-07-29 | 2004-07-06 | Applied Materials, Inc. | Diamond supported photocathodes for electron sources |
JP4926504B2 (en) | 2006-03-08 | 2012-05-09 | 浜松ホトニクス株式会社 | Photocathode, electron tube provided with the photocathode, and method for producing photocathode |
FR2925218B1 (en) | 2007-12-13 | 2010-03-12 | Photonis France | IMAGE INTENSIFIER TUBE WITH REDUCED SIZE AND NIGHT VISION SYSTEM EQUIPPED WITH SUCH A TUBE |
JP5563869B2 (en) * | 2009-04-02 | 2014-07-30 | 浜松ホトニクス株式会社 | Photocathode, electron tube and photomultiplier tube |
FR2961628B1 (en) | 2010-06-18 | 2012-08-31 | Photonis France | ELECTRON MULTIPLIER DETECTOR FORMED OF A HIGHLY DOPED NANODIAMANT LAYER |
CN102136519A (en) * | 2010-11-26 | 2011-07-27 | 中国科学院上海技术物理研究所 | Optical coupling unit of quantum well long-wave infrared detector grating waveguide micro-cavity |
CN202167452U (en) | 2011-07-13 | 2012-03-14 | 重庆大学 | Transmission-type GaN photocathode based on double-faced concave hole substrate |
CN102280343B (en) * | 2011-07-13 | 2013-01-23 | 重庆大学 | Transmission-type GaN ultraviolet photocathode based on two-sided patterned substrate |
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AU2012391961A1 (en) | 2015-04-02 |
CN104781903B (en) | 2017-05-24 |
US20150279606A1 (en) | 2015-10-01 |
CA2887442A1 (en) | 2014-04-17 |
JP2015536522A (en) | 2015-12-21 |
AU2012391961B2 (en) | 2017-12-07 |
EP2907154A1 (en) | 2015-08-19 |
KR101926188B1 (en) | 2018-12-06 |
PL2907154T3 (en) | 2017-05-31 |
JP6224114B2 (en) | 2017-11-01 |
KR20150086472A (en) | 2015-07-28 |
RU2015113428A (en) | 2016-10-27 |
SG11201501814QA (en) | 2015-05-28 |
IL237874A0 (en) | 2015-05-31 |
RU2611055C2 (en) | 2017-02-21 |
IL237874B (en) | 2020-04-30 |
BR112015007210A2 (en) | 2017-08-08 |
CA2887442C (en) | 2019-08-06 |
CN104781903A (en) | 2015-07-15 |
BR112015007210B1 (en) | 2021-08-03 |
US9960004B2 (en) | 2018-05-01 |
WO2014056550A1 (en) | 2014-04-17 |
RS55724B1 (en) | 2017-07-31 |
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