# US 9,024,256 B2 · Electron microscope > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,024,256 B2 - Document ID: US9024256B2 - Status: Granted - Kind: B2 - Application number: 14/453,235 - Filed: 2014-08-06 - Published: 2014-11-27 - Granted: 2015-05-05 - Earliest claimed: 2012-02-07 - Assignees: Board of Trustees of Michigan State University - Applicants: Board of Trustees of Michigan State University - Inventors: Chong-Yu Ruan; Martin Berz; Zhensheng Tao - Web page: https://patentgrep.com/patent/US9024256B2 ## CPC - H01J 37/263: {Contrast, resolution or power of penetration} - H01J 37/045: {Beam blanking or chopping, i.e. arrangements for momentarily interrupting exposure to the discharge} - H01J 37/065: Construction of guns or parts thereof (H01J37/067 - H01J37/077 take precedence) - H01J 37/073: Electron guns using field emission, photo emission, or secondary emission electron sources - H01J 37/1471: {for centering, aligning or positioning of ray or beam} - H01J 37/228: {whereby illumination or light collection take place in the same area of the discharge} - H01J 37/26: Electron or ion microscopes; Electron or ion diffraction tubes - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J 2237/0432: High speed and short duration - H01J 2237/06333: Photo emission - H01J 2237/2802: Transmission microscopes - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract An electron microscope is provided. In another aspect, an electron microscope employs a radio frequency which acts upon electrons used to assist in imaging a specimen. Furthermore, another aspect provides an electron beam microscope with a time resolution of less than 1 picosecond with more than 105 electrons in a single shot or image group. Yet another aspect employs a super-cooled component in an electron microscope. ## Claims ### Claim 1 An electron microscope comprising: an electron gun operably emitting electrons; a radio frequency cavity within which a radio frequency is operably emitted to act upon the electrons; a pulse shaper adapted to shape a laser pulse received within the radio frequency cavity; and an imager operably using the electrons to at least one of: (a) create a magnified specimen image, or (b) produce diffraction patterns, after the electrons pass through the radio frequency cavity. ### Claim 2 (depends on 1) The electron microscope of claim 1, wherein the radio frequency cavity is adjacent the electron gun so as to act together in emitting the electrons, further comprising a bunching radio frequency cavity spaced away from and downstream of the electron gun. ### Claim 3 (depends on 2) The electron microscope of claim 2, further comprising a laser emitting a laser beam at the electron gun to assist in the emission of the electrons therefrom, and another laser beam also being emitted into a specimen chamber located downstream of the bunching radio frequency cavity. ### Claim 4 (depends on 1) The electron microscope of claim 1, further comprising an objective lens acting with the radio frequency cavity to control a density and focal distance of the electrons. ### Claim 5 (depends on 4) The electron microscope of claim 4, wherein the objective lens is an electromagnetic lens and the radio frequency cavity longitudinally compresses and widens at least a 105 quantity of the electrons per pulse. ### Claim 6 (depends on 1) The electron microscope of claim 1, further comprising shaping the laser pulse with the pulse shaper which is controlled by a computer. ### Claim 7 (depends on 6) The electron microscope of claim 6, further comprising a cooling member super-cooling the radio frequency cavity to 10 Kelvin or less, and the radio frequency cavity being a machinable and super-conducting material. ### Claim 8 (depends on 1) The electron microscope of claim 1, wherein a quantity of the electrons is more than 105 with a time resolution less than 1 picosecond, per pulse. ### Claim 9 (depends on 1) The electron microscope of claim 1, wherein the electron beam scans a specimen in a raster scan pattern, and the secondarily scattered electrons or beam-induced photons are collected to form an image. ### Claim 10 (depends on 1) The electron microscope of claim 1, wherein the image is created by transmission electron microscopy such that the electrons pass through a specimen and project onto the imager which is at least one of: (a) a fluorescent screen, or (b) a CCD camera. ### Claim 11 (depends on 1) The electron microscope of claim 1, wherein the radio frequency cavity is retrofit onto a previously assembled microscope electron beam column. ### Claim 12 (depends on 1) The electron microscope of claim 1, further comprising a microscope control circuit which comprises an amplifier and a phase shifter connected to the radio frequency cavity, and signals from a laser oscillator being synchronized to the amplifier in a phase-locked loop. ### Claim 13 (depends on 1) The electron microscope of claim 1, further comprising an electron beam column located between the radio frequency cavity and the electron gun, the radio frequency cavity bunching the electrons prior to imaging. ### Claim 14 (depends on 1) The electron microscope of claim 1, wherein the electron gun includes a DC gun. ### Claim 15 An electron microscope comprising: a radio frequency, femtosecond electron gun assembly operably emitting electrons within a radio frequency wave; a bunching cavity located downstream of the electron gun assembly and having a radio frequency wave in the bunching cavity for assisting in creating a group of at least a 105 quantity of the electrons with a time resolution of less than 1 picosecond, with a pattern of the electrons being wider than longer when they leave the bunching cavity; and a lens assisting in focusing the electrons. ### Claim 16 (depends on 15) The electron microscope of claim 15, wherein the electron gun assembly further comprises a super-conducting radio frequency cavity which is super-cooled to less than or equal to 10 Kelvin. ### Claim 17 (depends on 15) The electron microscope of claim 15, further comprising radio frequency waves of 400 MHz-3 GHz and 100 W-5 kW increase the width-to-length ratio of the at least 105 group of electrons between the electron gun and an imager, and the lens being an objective lens that laterally compresses the width of the group of electrons. ### Claim 18 (depends on 15) The electron microscope of claim 15, wherein a specimen image is created by scanning electron microscopy. ### Claim 19 (depends on 15) The electron microscope of claim 15, wherein a specimen image is created by transmission electron microscopy. ### Claim 20 (depends on 15) The electron microscope of claim 15, wherein the radio frequency cavity is retrofit onto a previously assembled microscope electron beam column. ### Claim 21 An electron microscope comprising: an electron gun operably emitting a series of electrons; a housing surrounding at least a portion of the electron gun, the housing being made from a super-conducting material; a super-cooler attached to the housing to operably cause an internal surface of the housing to have a temperature less than or equal to 10 Kelvin; and an imager operably using the electrons to create a specimen image. ### Claim 22 (depends on 21) The electron microscope of claim 21, further comprising a radio frequency wave emitted inside the housing. ### Claim 23 (depends on 22) The electron microscope of claim 22, further comprising a shaped laser beam pulse received within the housing, and the super-conducting material comprises niobium. ### Claim 24 (depends on 22) The electron microscope of claim 22, further comprising: a bunching radio frequency cavity spaced away from the housing; at least one condenser lens located between the bunching radio frequency cavity and the electron gun; and an adjustable objective lens located between the bunching radio frequency cavity and the imager. ### Claim 25 (depends on 21) The electron microscope of claim 21, wherein the super-cooler includes a cryo jacket which causes the internal surface of the housing to have a temperature less than 10 Kelvin. ### Claim 26 (depends on 21) The electron microscope of claim 21, wherein a quantity of the electrons is more than 105 with a time resolution less than 1 picosecond, per image. ### Claim 27 (depends on 21) The electron microscope of claim 21, wherein the electron beam scans a specimen in a raster scan pattern, and the secondarily scattered electrons or beam-induced photons are collected to form an image. ### Claim 28 (depends on 21) The electron microscope of claim 21, wherein the image is created by transmission electron microscopy such that the electrons pass through a specimen and project onto the imager which is at least one of: (a) a fluorescent screen, or (b) a CCD camera. ### Claim 29 An electron microscope comprising an electron gun and an imager, wherein a time resolution for at least 105 electrons emitted by the electron gun is less than 1 picosecond per image created by the imager. ### Claim 30 (depends on 29) The electron microscope of claim 29, further comprising radio frequency waves being emitted adjacent the electron gun. ### Claim 31 (depends on 30) The electron microscope of claim 30, further comprising a shaped laser beam pulse acting with the electron gun to emit the electrons in a beam toward the imager. ### Claim 32 (depends on 30) The electron microscope of claim 30, further comprising: a bunching radio frequency spaced away from the electron gun; at least one condenser lens located between the bunching radio frequency and the electron gun; and an adjustable objective lens located between the bunching radio frequency and the imager. ### Claim 33 (depends on 29) The electron microscope of claim 29, further comprising radio frequency waves of 400 MHz-3 GHz and 100 W-5 kW compress a longitudinal length of the at least 105 electrons between the electron gun and the imager. ### Claim 34 (depends on 29) The electron microscope of claim 29, further comprising super-cooling an internal surface of a radio frequency cavity to 10 Kelvin or less, and the radio frequency cavity being a machinable and super-conducting material. ### Claim 35 (depends on 29) The electron microscope of claim 29, wherein the image is created by the imager using scanning electron microscopy. ### Claim 36 (depends on 29) The electron microscope of claim 29, wherein the image is created by the imager using transmission electron microscopy. ### Claim 37 A method of using an electron microscope, the method comprising: (a) receiving a shaped laser beam in an upstream radio frequency cavity; (b) super-cooling the upstream cavity to a temperature less than or equal to 10 Kelvin; (c) generating an electron beam in the upstream cavity; (d) bunching the electron beam in a downstream radio frequency cavity; and (e) using the electron beam to create a specimen image. ### Claim 38 (depends on 37) The method of claim 37, further comprising using the downstream cavity to bunch a pulse of at least 105 electrons of the electron beam with a time resolution of less than 1 picosecond. ### Claim 39 (depends on 37) The method of claim 37, further comprising using a radio frequency wave of 500 MHz-3 GHz and 100 W-5 kW inside the downstream cavity. ### Claim 40 (depends on 37) The method of claim 37, further comprising receiving the shaped femtosecond laser pulse in a specimen chamber downstream of the cavities. ### Claim 41 (depends on 37) The method of claim 37, further comprising varying the electron beam with at least one condenser lens between the cavities, and varying the electron beam with an objective lens after the downstream cavity. ### Claim 42 (depends on 37) The method of claim 37, further comprising creating the magnified image with scanning electron microscopy. ### Claim 43 (depends on 37) The method of claim 37, further comprising creating the magnified image with transmission electron microscopy. ### Claim 44 (depends on 37) The method of claim 37, further comprising shaping pulses of the laser beam with a computer-controlled pulse shaper. ### Claim 45 (depends on 37) The method of claim 37, further comprising retrofitting the cavities onto a previously assembled microscope.