EP0107686A1

EP0107686A1 - Method and device for producing photons in the ultraviolet wavelength range.

Info

Publication number: EP0107686A1
Application number: EP83901325A
Authority: EP
Inventors: Amand A Lucas
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-07
Filing date: 1983-05-05
Publication date: 1984-05-09
Also published as: EP0107686B1; JPS59500838A; US4574198A; LU84136A1; DE3366001D1; WO1983004099A1; JPS644307B2

Abstract

Procédé et dispositif de production de photons (7), dans la gamme des longueurs d'ondes ultraviolettes, comprenant l'implantation dans une matrice solide d'ions de gaz inerte ou respectivement insoluble vis-à-vis de la matrice, l'excitation du gaz emprisonné (2) dans la matrice solide, et l'émission desdits photons (7) par le gaz excité, ainsi que notamment le bombardement ionique d'une surface de la matrice solide par des ions à faible énergie d'au moins un gaz tel que précité, et le bombardement électronique (4) à faible énergie, de la matrice solide, avec émission des photons (7).Method and device for producing photons (7), in the range of ultraviolet wavelengths, comprising the implantation in a solid matrix of gas ions which are inert or respectively insoluble with respect to the matrix, the excitation gas trapped (2) in the solid matrix, and the emission of said photons (7) by the excited gas, as well as in particular the ion bombardment of a surface of the solid matrix by low energy ions of at least one gas as mentioned above, and electron bombardment (4) at low energy, of the solid matrix, with emission of photons (7).

Description

"Method and device for producing photons in the range of ultraviolet wavelengths".

The present invention relates to a process for the production of photons, in the range of ultraviolet wavelengths, comprising the implantation in a solid matrix of ions of inert gas or respectively insoluble with respect to the matrix, l excitation of the gas em trapped in the form of extended defects of the solid matrix, and the emission of said photons by the excited gas, as well as to a device for the implementation of this process.

Common light sources for the near, far, and extreme ultraviolet wavelength ranges are generally discharge sources where light is produced by passing an electrical discharge through a capillary containing noble or other gases at pressures between 10 and a few tens of thousands of Pa. For He, a commonly used gas, a continuous emission spectrum results from the formation in the discharge and the subsequent radiative decay, of excited helium molecules He _2.

Another important source of radiation in this spectrum range is the synchro. ton, which is a complicated and expensive installation, accessible only in a few places in the world.

It has also been envisaged to use the fluorescence of liquid helium as a source of radiation in the ultraviolet range, but this process requires cryogenic cooling, therefore at very low temperatures, as well as differential pumping, and its implementation is therefore very costly (see CM Surko, RE Packard, GJ Dick and F. Reif, Spectroscopic Study of the luminescence of liquid helium in the vacuum ultravidet, in Physical Review Letters, Vol. 24, N ° 12, (1970), p . 657 et seq.). I1 is also known to prepare solid matrices having wide defects, such as vacant agglomerates, or bubbles containing an inert gas or insoluble vis-à-vis the matrix. One obtains, for example, such a matrix with microbubbles of helium by bombardment by means of energetic He ions. The Al / He matrix has been the subject of spectro-copies of optical absorption and electronic energy loss (see JC Rife, SE Donnelly, AA Lucas, JM Gilles and JJ Ritsko, Optical absorption and electron -energy-loss spectra of helium microbubbles in Aluminum, Physical Review Letters, vol. 46, n ° 18 (1981), p. 1220 et seq.).

Finally, it has already been observed that a solid matrix bombarded by means of high-energy helium ions (200-600 keV) emits, from a certain dose of He, a continuous spectrum in the range of ultraviolet (v. RS Bhattacharya, KG Lang, A. Scharmann and KH Schartner, Continuous emission in the vacuum ultraviolet under energetic inert gas ion bombardment of aluminum, in J. Phys. D, vol. 11 (1978), p. 1935 and following.). It should be noted that the implantation of high energy helium ions is a relatively expensive process and that, since the helium ions are implanted at great depth in the matrix, the intensity of the emission of ultraviolet rays is low.

The object of the present invention is the development of a process and a device for producing photons in the range of ultraviolet wavelengths which sawing simple and inexpensive while giving results comparable to discharge sources.

To this end, according to the invention, ion bombardment of a surface of the solid matrix is carried out with low-energy ions of at least one gas as mentioned above, so as to obtain an implantation at a shallow depth of gas in the solid matrix, and then an electron bombardment, at low energy, of the solid matrix, with excitation of the trapped gas and emission of the abovementioned photons.

According to an embodiment of the invention, the method comprises the implantation at low depth of gas ions by one face of a solid matrix in mass and the electron bombardment of this same face with emission of the aforementioned photons induced from of this face. According to another mode of challenge of the invention, the method comprises the implantation at low depth of gas ions in a solid lamellar matrix with a thickness of less than 1 μm, and the above-mentioned electronic bombardment of one of the faces of this matrix with emission of the aforementioned photons induced from the other face of the matrix.

I1 is also provided, according to the invention, a device for implementing the method according to the invention, this device comprising a vacuum envelope, a solid matrix, in which are implanted shallow ions of at least one inert gas or insoluble gas respectively vis-à-vis the matrix, this matrix being mounted on a support inside the vacuum envelope, an electron production apparatus capable of subjecting the matrix to low electron bombardment energy and an electrical connection connecting the matrix to the outside, as well as an output for the photons produced, provided in the envelope.

Other details and particularities of the invention will emerge from the description given below, without implied limitation and with reference to the attached drawings.

FIG. 1 illustrates, diagrammatically, a device implementing a method for producing photons according to the invention, FIG. 2 illustrates, diagrammatically, a device implementing an alternative embodiment according to the invention. FIG. 3 shows, in more detail, a view partially in axial section through a device according to the invention.

FIG. 4 represents the fluorescence spectrum obtained by the use of a device according to the invention. The units plotted on the abscissa represent the wavelengths of the fluorescence spectrum and on the ordinate plots are arbitrary emission intensity units. In the figures, identical or analogous elements are designated by the same references.

The device illustrated in FIG. 1 comprises a solid matrix 1 which is prepared by implantation of low energy He ions in an Al sheet with a thickness of less than μm. A bombardment of low energy He ions, of the order of 5 keV, allows the implantation of a high concentration (locally greater than 10 atom%) of He over a depth of a few tens to a few thousand Å. Helium naturally agglomerates in the gaps in the matrix produced by bombardment and forms large defects, such as gap agglomerates or microbubbles 2 which remain stable at room temperature and can resist temperature increases up to at a few hundred ° C, for example up to 300 ° C.

The device illustrated in FIG. 1 also includes a device for producing low-energy electrons 3, such as an electron gun, this device projecting an electron beam 4 onto one of the faces 5, called the rear face, of the matrix 1. Electrons in the electro beam pic 4 advantageously have an energy less than or equal to 20 keV, preferably between 1 and 5 keV. In this case, fluorescence of the target is induced from the front face 6 of the matrix, the emission of photons being represented by the arrows in wavy lines 7.

There is shown in this figure 1, in dashed lines, an alternative embodiment, in which the lamellar matrix 1 is in the form of a continuous strip, wound at one end in a reserve roll 20 and at its other end in a discharge roller 21. In this way, if the part of the matrix subjected to electronic bombardment is accidentally altered, after a certain period of operation, the matrix can be moved in the direction of arrow 22, by rotating said rollers 20 and 21, and bring before the electron beam a new part of the matrix not yet subjected to electron bombardment. This movement can be carried out manually or automatically, and it can be continuous or intermittent during the operation of the device according to the invention.

In the device illustrated in FIG. 2, the matrix is a bulk substrate 8. The implantation of the He ions is carried out in the same way as for the lamellar matrix 1, proceeding so as to obtain a maximum concentration of microbubbles 2 of He below a depth, preferably less than 5,000 Å. In this case, the electron gun 3 projects a beam of low energy electrons onto the same surface as that by which the He ions have been implanted, and a fluorescence of the target is then induced through this surface 9, the emission of photons being represented by the arrows in wavy lines 10. We therefore have in this latter case what we will call an electronic bombardment of the front face of the matrix, as opposed to an electronic bombardment of the rear face of the matrix illustrated in FIG. 1. The device illustrated in FIG. 3 represents in a more detailed way a device implementing a electronic bombardment of the front face of the matrix.

This device according to FIG. 3 comprises an envelope 11 maintained under vacuum in which the matrix 8 is mounted on a support 12 which can be cooled by a cooling circuit 13, for example with water, in the event of use of the high intensity device. An electronic gun 3 emitting a beam of electrons with low energy and adjustable intensity is mounted on the envelope so as to direct this beam on the matrix. The angle of incidence between the beam and the plane of the matrix is calculated so that the emitted photons can propagate through the exit opening 14 formed at one of the front ends of the envelope 11. This end is provided with a flange 15 which is used to connect the device according to the invention to an apparatus in which ultraviolet light will be used.

An electrical connection 16 makes it possible in particular to measure the electronic current in the matrix. An electronic screen 17 can be provided in the outlet opening 14 intended to prevent any exit of electrons through this opening, this electronic screen 17 then also being connected to the outside by an electrical connection 18.

The casing 11 is maintained under vacuum, either by a pumping device, not shown, connected to the casing by the flange connection 19, or by the pumping device now holding the vacuum device, not shown, connected to the flange 15 .

The matrix material must meet two main conditions: the insolubility of the gas in the matrix and relatively low absorption by the matrix of the gas emission continuum. The material of the matrix must preferably have optical properties such that the depth of escape of the photons produced is compatible with the depth of implantation. Therefore, the electron beam penetration depth need not exceed this photon escape depth and electron energies in the range of 0.1 to 20 keV are sufficient, even for surface bombardment before, with a relatively grazing incidence. This property of the photon source makes it possible to avoid the high costs necessary for carrying out high energy ionic and electronic bombardments, such as those used in known methods and devices. Excitement can be produced in particular by the use of a low energy electronic gun.

As matrix material one can use advantageously materials chosen from the group comprising metals, such as Sn, Mg, Al, semiconductors, such as Si, Ge or certain insulators. Since the emission depth of the source is very small, the source is substantially planar and the surface and the shape of the source can be simply adjusted by structuring the electron beam. By concentrating the beam, an effectively point source can be obtained; by scanning or spreading the beam, it is possible to obtain an extended source compatible, for example, with the slit geometry used in certain spectroscopic work. In addition, a time-varying fluorescence intensity can easily be obtained by modulating the electron beam in pulses, which allows the use of the source in servo-control techniques (of the "lock in" type). The duration of existence of the fluorescence is less than 10 nsec.

According to a nonlimiting example of implementation of the method according to the invention, a source of Al / He-based photons is prepared in the manner described above and implemented according to the invention under an electron bombardment having an energy of 3800 V. This source produces, as shown in FIG. 4, a continuous spectrum of fluorescence which extends from 580 to 900 Å, which is similar to what is obtained with conventional discharge sources. The production of photons from the matrix was compared with the synchrotron source SURF II and this compa reason indicates an efficiency greater than or equal to 10 ^-4 photons per electron. With sufficient electronic current, the brightness can reach that obtained by discharge lamps. Unlike conventional discharge sources, there is the possibility, using the method according to the invention, of developing a multi-gas composite source in order to extend the width of the spectral band from 580 to 3,000 AT. In fact, it is obvious that in addition to helium, other gases inert with respect to the matrix can be used, for example rare gases or others, such as

Ne, Ar, ...., H ₂ , N ₂ , .... If we implant in the matrix of ions of several of these gases, we can thus obtain said composite multi-gas source.

The applications of a photon source according to the invention are numerous. It can be used in any application where discharge sources are now used, for example for photoelectronic spectroscopy in the ultraviolet, for studies of reflectivity, absorption and photoconductivity, etc.

In addition to the use of the device according to the invention as a simple means of producing photons in the range of near, far and extreme ultraviolet rays, the source according to the invention can be incorporated into a large number of new, more complex systems. Among others, we can cite: a) particle detectors, by detecting the fluorescence induced in the device by the passage of charged particles. b) contact lithography in the ultraviolet, by implantation of an integrated circuit by means of a beam of inert gas ions on a mask in the form of thin film and by subsequent printing of the circuit, by placing the film in contact with a photoresist coating, sensitive to UV photons, and by bombardment with an electron beam to activate ultraviolet fluorescence; c) source of stimulated emission of extreme ultraviolet light (excimer laser), thanks to the choice of an appropriate pumping mechanism and an appropriate resonant cavity.

The methods and devices according to the invention have the advantage of not requiring differential pumping, gas replacement and cryogenic cooling. In addition, they are very easy to implement and flexible in operation. The source according to the invention offers the advantage of a brightness, which can vary by six orders of magnitude or differentiation, by modification of the intensity of the electron beam. It allows a specific geometry by concentration. Finally, its implementation is relatively inexpensive. It should be understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made thereto without departing from the scope of this patent.

Claims

CLAIMS.

1. A method of producing photons (7), in the range of ultraviolet wavelengths, comprising implantation in a solid matrix of ions of inert gas or respectively insoluble with respect to the matrix, excitation of gas trapped (2) in the solid matrix, and the emission of said photons (7) by the excited gas, characterized in that it comprises an ion bombardment of a surface of the solid matrix by ions with low energy d '' at least one gas as mentioned above, so as to obtain a shallow implantation of gas (2) in the solid matrix, and then an electron bombardment (4), at low energy, of the solid matrix, with excitation of the gas imprisoned and emission of the above photons (7).

2. Method according to claim 1, characterized in that it comprises the implantation at low depth of gas ions by a face (9) of a solid matrix in mass (8) and the electronic bombardment (4) of this same face with emission of the aforementioned photons (10) induced from this face (9). 2. Method according to claim

1, characterized in that it comprises the implantation at low depth of gas ions in a solid lamellar matrix (1) with a thickness of less than 1 μm, and the above-mentioned electronic bombardment (4) of one of the faces (5,6) of this matrix (1) with emission of the aforementioned photons (7) induced from the other side of the matrix (1).

4. Method according to any one of claims 1 to 3, characterized in that it comprises the intermittent or continuous displacement of the matrix (1, 8), in which the gas ions have been implanted, from a position of reserved for a bombardment position, where it undergoes said electronic bombardment, then for a discharge position, the matrix (1, 8) being in the form of a continuous substrate.

5. Method according to any one of claims 1 to 4, characterized in that the ion bombardment is carried out with ions of said one or more gases having an energy making it possible to obtain a high concentration of gas in the form of extended defects (2) of the matrix (1,8), over a depth not exceeding a few thousand Å.

6. Method according to claim 5, characterized in that the energy of the aforesaid gas ions is of the order of 5 keV.

7. Method according to any one of claims 1 to 6, characterized in that it comprises the implantation at shallow depth in the matrix (1,8) of ions of several inert gases or respectively insoluble vis-à-vis of the matrix.

8. Method according to any one of claims 1 to 7, characterized in that it comprises the implantation of ions of rare gases, in particular helium.

9. Method according to any one of claims 1 to 8, characterized in that the electron bombardment (4) is carried out with electrons having an energy less than or equal to 20 keV, preferably between 1 and 5 keV.

10. Method according to any one of claims 1 to 9, characterized in that it comprises, during the electron bombardment (4), the concentration of an electron beam on the matrix (1,8) so as to produce a point source of photons (7,10).

11. Method according to any one of claims 1 to 9, characterized in that it comprises, during the electron bombardment (4), the scanning of the matrix by an electron beam, so as to produce an extended source of photons ( 7, 10).

12. Method according to any one of claims 1 to 9, characterized in that it comprises, during the electron bombardment (4), the spreading of an electron beam, so as to produce an extended source of photons (7 , 10)

13. Method according to any one of claims 1 to 12, characterized in that it comprises, during the electron bombardment (4), a modulation of the intensity of the electron beam, so as to produce a source of variable intensity of photons (7, 10).

14. Method according to any one of claims 1 to 13, characterized in that the matrix (1, 8) used is made of a material exhibiting low absorption of the continuous emission spectrum of the excited gas contained in the matrix.

15. The method of claim 14, characterized in that the matrix (1,8) used is made of a material chosen from the rump comprising metals, such as Sn, Mg, Al, semiconductors, such as Si, Ge, or insulators, such as LiF, NaCl.

16. Device for implementing the method according to any one of claims 1 to 15, characterized in that it comprises an envelope (11) under vacuum, a solid matrix (1,8) in which are implanted at low depth of the ions of at least one inert gas or one which is respectively insoluble with respect to the matrix, this matrix being mounted on a support (12) inside the vacuum envelope, an apparatus for producing electrons (3) capable of subjecting the matrix to low energy electron bombardment and an electrical connection (16) connecting the matrix to the outside, as well as an output (14) for the photons produced, provided in the envelope.

17. Device according to claim 16, characterized in that it comprises a solid mass matrix (8), one surface of which contains implanted gas ions, the electron production apparatus (3) being arranged so as to carrying out the above-mentioned electronic bombardment of this surface, with emission of the aforementioned photons induced from this surface.

18. Device according to claim 16, characterized in that it comprises a lamellar solid material (1) with a thickness of less than 1 μm, the electron production apparatus being arranged so as to carry out the above-mentioned electronic bombardment of one of the faces of this matrix with emission of the aforementioned photons induced from the other face of the matrix.

19. Device according to any one of claims 16 to 18, characterized in that it comprises a matrix (1,8) in the form of a continuous substrate, movable in the envelope of intermittent or continuous material between a position of reserve, a bombardment position of the matrix and an evacuation position.

20. Device according to any one of claims 16 to 19, characterized in that it comprises a cooling circuit (13) of the support (12) of the matrix.

21. Device according to any one of claims 16 to 20, characterized in that the envelope (11) has a connection flange (15) around the outlet (14) for the photons produced, for mounting a vacuum device on the device, and in that optionally the device has across this output an electronic screen (17) connected to the outside.

22. Device according to any one of claims 16 to 21, characterized in that the electron production apparatus (3) to low energy is an electron gun producing electrons with an energy less than or equal to 5 keV.

23. Device according to any one of claims 16 to 22, characterized in that it comprises a vacuum pump connected to the vacuum envelope.