Abstract: A radiation source includes a vacuum chamber, means for injecting an optical wave, a cold source for emitting electrons, a power supply, an anode for emitting X-rays, and at least one window through which the X-rays exit. A light source delivers the optical wave, and the cold source includes at least one substrate with a conducting surface and is subjected to an electric field. The cold further includes a photoconductive element in which the current is controlled approximately linearly by the illumination and at least one electron-emitting element, the photoconductive element electrically connected in series between an emitting element and a conducting surface. Current photogenerated in the photoconductive device is equal to that emitted by the emitter or the group of emitters with which it is associated, and the emitted stream of X-rays is approximately linearly dependent on the illumination.

Abstract: In an optically controlled cold-cathode electron tube, the emitters 1, of nanometer and/or micron size and of elongate shape, have a structure comprising a first material (4) of sp2-bonding carbon type and a metallic second material (3), said first material being in contact with and surrounding said second material at its top and over the entire length of the emitter or at least part of said length starting from its top toward the base (b). The second material has a plasma frequency substantially equal to or greater than the frequency of the optical control wave.

Abstract: In an array R of field-effect transistors for detecting analytes, each transistor of the array comprises a gate G, a semiconductor nanotube or nanowire element NT connected at one end to a source electrode S and at another end to a drain electrode D, in order to form, at each end, a junction J1, J2 with the channel. At least transistors FET1,1, FET1,2 of the array are differentiated by a different conducting material (m1, m2) of the source electrode S and/or drain electrode D.

Abstract: The invention relates to an optically-controlled field-emission cathode, comprising a substrate (10, 20, 30, 40, 50, 60, 70, 80, 90, 100) having at least one conducting surface (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) and at least one conducting emitter element (16, 26, 36, 46, 56, 66, 76, 86, 96, 106) in the vicinity of a conducting surface, characterized in that it also comprises at least one photoconducting element (13, 23, 33, 43, 53, 63, 73, 83, 93, 103) electrically connected in series between at least one emitter element and a conducting surface of the substrate. Another subject of the invention is an amplifier tube comprising such a cathode. The application is for Vacuum tubes, in particular for microwave amplification, with a view for example to applications in telecommunications.

Abstract: A radiation source includes a vacuum chamber, means for injecting an optical wave, a cold source for emitting electrons, a power supply, an anode for emitting X-rays, and at least one window through which the X-rays exit. A light source delivers the optical wave, and the cold source includes at least one substrate with a conducting surface and is subjected to an electric field. The cold further includes a photoconductive element in which the current is controlled approximately linearly by the illumination and at least one electron-emitting element, the photoconductive element electrically connected in series between an emitting element and a conducting surface. Current photogenerated in the photoconductive device is equal to that emitted by the emitter or the group of emitters with which it is associated, and the emitted stream of X-rays is approximately linearly dependent on the illumination.

Abstract: In an optically controlled cold-cathode electron tube, the emitters 1, of nanometer and/or micron size and of elongate shape, have a structure comprising a first material (4) of sp2-bonding carbon type and a metallic second material (3), said first material being in contact with and surrounding said second material at its top and over the entire length of the emitter or at least part of said length starting from its top toward the base (b). The second material has a plasma frequency substantially equal to or greater than the frequency of the optical control wave.

Abstract: The invention relates to an optically-controlled field-emission cathode, comprising a substrate (10, 20, 30, 40, 50, 60, 70, 80, 90, 100) having at least one conducting surface (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) and at least one conducting emitter element (16, 26, 36, 46, 56, 66, 76, 86, 96, 106) in the vicinity of a conducting surface, characterized in that it also comprises at least one photoconducting element (13, 23, 33, 43, 53, 63, 73, 83, 93, 103) electrically connected in series between at least one emitter element and a conducting surface of the substrate. Another subject of the invention is an amplifier tube comprising such a cathode. The application is for Vacuum tubes, in particular for microwave amplification, with a view for example to applications in telecommunications.

Abstract: The invention relates to a process for the growth of nanotubes or nanofibers on a substrate comprising at least an upper layer made of a first material, wherein: the formation, on the surface of the upper layer, of a barrier layer made of an alloy of the first material and of a second material, said alloy being stable at a first temperature; the formation of spots of catalyst that are made of the second material, on the surface of the alloy layer; and the growth of nanotubes or nanofibers at a second temperature below said first temperature. The alloy layer allows effective growth of nanotubes/nanofibers from catalyst spots on the surface of said alloy layer. This is because the alloy layer constitutes a diffusion barrier preventing the catalyst from diffusing into the growth substrate, which barrier is stable at the catalytic nanotube/nanofiber growth temperature.

Abstract: In an array R of field-effect transistors for detecting analytes, each transistor of the array comprises a gate G, a semiconductor nanotube or nanowire element NT connected at one end to a source electrode S and at another end to a drain electrode D, in order to form, at each end, a junction J1, J2 with the channel. At least transistors FET1,1, FET1,2 of the array are differentiated by a different conducting material (m1, m2) of the source electrode S and/or drain electrode D.

Abstract: The invention relates to a process for the controlled growth of nanotubes or nanofibers on a substrate, characterized in that it furthermore comprises the production, on the substrate (11), of a bi-layer structure composed of a layer of catalyst material (71), for catalyzing the growth of nanotubes or nanofibers, and a layer of associated material, said associated material being such that it forms a noncatalytic alloy with the catalyst material at high temperature. The invention also relates to a process for fabricating a field-emission cathode using the above nanotube or nanofiber fabrication process. These processes allow very precise positioning of the catalyst spots from which the nanotubes and nanofibers can be grown and allow the fabrication of cathodes for which the nanotubes or nanofibers are self-aligned with the aperture in the extraction grid. Applications: electron tubes, nanolithography.

Abstract: The invention relates to a process for the growth of nanotubes or nanofibers on a substrate comprising at least an upper layer made of a first material, wherein: the formation, on the surface of the upper layer, of a barrier layer made of an alloy of the first material and of a second material, said alloy being stable at a first temperature; the formation of spots of catalyst that are made of the second material, on the surface of the alloy layer; and the growth of nanotubes or nanofibers at a second temperature below said first temperature. The alloy layer allows effective growth of nanotubes/nanofibers from catalyst spots on the surface of said alloy layer. This is because the alloy layer constitutes a diffusion barrier preventing the catalyst from diffusing into the growth substrate, which barrier is stable at the catalytic nanotube/nanofiber growth temperature.

Abstract: The invention relates to a process for the controlled growth of nanotubes or nanofibers on a substrate, characterized in that it furthermore comprises the production, on the substrate (11), of a bi-layer structure composed of a layer of catalyst material (71), for catalyzing the growth of nanotubes or nanofibers, and a layer of associated material, said associated material being such that it forms a noncatalytic alloy with the catalyst material at high temperature.

Abstract: A field-emission device includes at least one plane cathode made of conductive material with a low electron affinity located on a face of a substrate carrying a layer of a dielectric material, which layer has at least one cavity in which the cathode is located. A gate made of conductive material is located on the dielectric layer and has an aperture centered with respect to the cavity. The conductive material with a low electron affinity is a material deposited in amorphous form. Such a device may find particular application to electron guns or display devices.

Abstract: A drive system which makes it possible to drive a matrix of picture elements, each including a cathode made of a material with low electron affinity. Each of crossover-point circuits include a switching device associated with a cathode of a picture element and makes it possible, with the aid of memory circuits, to connect the cathode to a current source during a time necessary for the driving of all the rows of the matrix and to regulate the current conduction of the corresponding picture element. Such a drive system may find particular application to electron guns and display screens.

Abstract: Electron source made notably in the form of a micropoint cathode electrode in which a microcathode is located in a cavity (CA) of a dielectric (3). A first gate electrode (VG1) surrounds the cavity (CA) and a second gate electrode (VG2) surrounds the first gate electrode (VG1). The different electrodes are carried to potentials such that the first gate electrode (VG1) acts as an extraction electrode and the second gate electrode acts as a focusing electrode.

Abstract: A method according to which a layer of a semiconductor material is made on a substrate by growth in a confinement space defined by this substrate and by a confinement layer, this growth being achieved from a seed. The cross-section of the seed, substantially perpendicular to the general direction of growth, possesses a thick central part framed by two thinned lateral parts. The confinement space has the same cross-section as the seed.

Abstract: A method of growth according to which a layer of a material having apertures is made on the surface of a substrate. A material is deposited in each aperture. When this material is liquid, it can absorb the material to be grown. Then, the growth is done in vapor phase. The material of the layer is chosen in such a way that there is neither growth nor nucleation on its surface during the growth in vapor phase. The disclosed method can be applied to the making of crystal whiskers positioned with precision, and to the making of tip type microcathodes.

Abstract: Disclosed is a method for the growing of heteroepitaxial layers of monocrystalline semiconductor materials. To this end, on a substrate made of a material of a first type, there is made a seed of a second type of material. This seed is between a face of the substrate and a confinement layer which defines a confinement space with the face of the substrate. A vapor phase epitaxy of a material of the second type is then effected in the confinement space. This material of the second type grows from the seed in the confinement space. The method can be applied to the manufacture of heterogeneous semiconductor structures and to the three-dimensional integration of semiconductor components.