National University of Singapore

Institute of Materials Research and Engineering

Anjam Khursheed

Hung Quang Hoang

Jacob C Phang

Jacob Chee Hong Phang

Thiam Leong Thong

John Thiam Leong Thong

Xiuyuan Shao

John Thiam Thong

A cathode structure for cold field electron emission and method of fabricating a single-tip cathode structure for cold field electron emission. The cathode structure comprises a pointed cathode wire; and a graphene-based coating on at least a tip of the pointed cathode wire. In a preferred embodiment, graphene is coated on nickel tips by chemical vapour deposition wherein nickel functions as a catalyst for growth of graphene. The cathode structure provides stable cold field emission for electron microscopy and lithography applications and exhibits an ultralow work function value of about 1.1 eV.

Cathode structure for cold field electron emission and method of fabricating the same

According to embodiments of the present invention, an aberration correction apparatus is provided. The aberration correction apparatus includes an aberration correction unit including a first conductive element, and a second conductive element arranged rotationally symmetrical about the first conductive element, wherein the aberration correction unit is arranged to propagate an annular beam having charged particles in between the first conductive element and the second conductive element such that propagation of the annular beam through the aberration correction unit is rotationally symmetrical about the first conductive element, and wherein the aberration correction unit is configured to generate, between the first conductive element and the second conductive element, a magnetic field force and an electric field force directed in opposite directions and superimposed on each other to act on the charged particles to change a trajectory of the charged particles, and an annular aperture optically coupled to the aberration correction unit.

Aberration correction apparatus, device having the same, and method for correcting aberration of charged particles

A gun configured to generate charged particles, comprising a ring-cathode () electrically configured to generate a charged particle beam; a lens arranged to focus the charged particle beam on a specimen; and at least one correction focusing electrode () arranged to generate at least one electrostatic/magnetic field to further divergently/convergently focus the charged particle beam for correcting in-plane geometric aberrations associated with the lens, the focusing being based on the in-plane geometric aberrations associated with the lens. A related method is also disclosed.

Gun configured to generate charged particles

A parallel radial mirror analyzer (PRMA) () for facilitating rotationally symmetric detection of charged particles caused by a charged beam incident on a specimen is disclosed. The PRMA comprises a zero-volt equipotential grid (), and a plurality of electrodes () electrically configured to generate corresponding electrostatic fields for deflecting the charged particles in accordance with respective energy levels of the charged particles to exit through the grid () to form corresponding second-order focal points on a detector (). The detector () is disposed external to the corresponding electrostatic fields. A related method is also disclosed.

Parallel radial mirror analyser with an angled zero-volt equipotential exit grid for scanning electron microscopes

A sequential radial mirror analyzer (RMA) () for facilitating rotationally symmetric detection of charged particles caused by a charged beam incident on a specimen () is disclosed. The RMA comprises a 0V equipotential exit grid (), and a plurality of electrodes () electrically configured to generate corresponding electrostatic fields for deflecting at least some of the charged particles of a single energy level to exit through the exit grid () to form a second-order focal point on a detector (). The second-order focal point is associated with the single energy level, and the detector () is disposed external to the corresponding electrostatic fields. A related method is also disclosed.

Sequential radial mirror analyser

An apparatus for spectrometry that includes a spectrometer configured for second order focusing and capable of 2&#x3c0; azimuthal collection.

Electrostatic electron spectrometry apparatus

This invention is a multi-beam charged particle instrument that can simultaneously focus electrons and a variety of positive and negative ions, such as Gallium, Oxygen and Cesium ions, onto the same material target. In addition, the instrument has provision to simultaneously capture the spectrum of both secondary electrons and ions. The highly dispersive, high resolution mass spectrometer portion of the instrument is expected to detect and identify secondary ion species across the entire range of the periodic table, and also record a portion of their emitted energy spectrum. The electron energy spectrometer part of the instrument is designed to acquire the entire range of scattered electrons, from the low energy secondary electrons through to the elastic backscattered electrons.

Multi-beam ion/electron spectra-microscope

An electron microscope and a method of imaging objects. The method including the steps of: generating at least one electron pulse, each electron pulse including a plurality of electrons with the electrons having a kinetic energy spread; demagnifying each electron pulse using one or more lenses, each lens having a focal strength; dynamically varying said focal strength of at least one of said one or more lenses to compensate for said kinetic energy spread; and forming an image of said object based on interactions at said object resulting from each demagnified pulse. The electron microscope comprising: an electron source adapted to produce a plurality of electron pulses, each electron pulse including a plurality of electrons with the electrons having a kinetic energy spread; one or more lenses adapted to demagnify each of said electron pulses at said object, each lens having a focal strength; compensation means for dynamically varying said focal strength of at least one of said one or more lenses to compensate for said kinetic energy spread; and a detector for forming an image of said object based on interactions at said object resulting from each of said demagnified pulses

Electron microscope and a method of imaging objects

In a scanning electron microscope, an emitted primary electron beam is diverted by an angle of at least about 45 degrees prior to incidence with a specimen. The beam may be bent by a magnetic separator. The separator may also serve to deflect secondary electron and back scattered electrons. As the angle of emissions and reflections from the specimen is close to the angle of incidence, bending the primary electron beam prior to incidence, allows the electron source to be located so as not to obstruct the travel of emissions and reflections to suitable detectors.

Scanning electron microscope

A lens () for a scanning electron microscope is adapted to be removably mounted on a specimen stage (). The lens () includes a magnetic circuit () having a first magnetic pole piece () and a second magnetic pole piece (), and a specimen holder (). The specimen holder () is located between the first and second magnetic pole pieces (). The magnetic circuit () also includes a lens bore () to permit an electron beam () to strike a surface of a specimen mounted on the specimen holder (), in use. The lens bore () has a width of greater than 1 mm.

Lens for a scanning electron microscope

An imaging device, such as an EEM, includes an electric/magnetic lens used to focus pulsed electrons emitted from an object on to a target plane. Before a pulse of emitted electrons reaches the lens, electrons are spatially separated in dependence on their respective kinetic energies and are then subject to a time varying electric field that keeps the final focal plane constant for a wide variety of different energy electrons. The electric field compensates for variations in the image focal length caused by a spread in kinetic energies, causing the electrons to be focused proximate the target plane, reducing chromatic aberration. The varying electric field may be provided by varying an electric potential at the lens by, for example, varying a voltage supplied to an electrode at the lens. This potential effectively varies the focal strength of the lens in time, in order to compensate for variations in kinetic energies of electrons arriving at the lens, effectively keeping the image plane position constant.

Reducing chromatic aberration in images formed by emmission electrons

A device for converting a scanning electron microscope (SEM) to a scanning transmission electron microscope (STEM) is adapted to be mounted on a conventional SEM. The device has a casing mountable on the SEM and provides support for a specimen to be scanned by a beam of primary electrons exiting the objective lens of the SEM. The casing defines a pathway allowing transmission electrons that have passed through the specimen to be detected. The device may have a magnet mountable on the casing for generating a transverse magnetic field to deflect the transmission electrons within the casing. A magnetic lens may be mounted within the casing for focusing the beam of primary electrons onto the specimen. The secondary electron detector of the SEM may be used to detect secondary electrons emitted from a target excited by the transmitted electrons. Alternatively, an electron detector may be mounted within the casing for detecting the transmitted electrons.

Converting scanning electron microscopes

A detachable, portable SEM column that is easily disconnected from the electron gun assembly and specimen chamber of the system, allowing different column designs to be used in a given SEM system. As an alternate design, the electron gun and column are configured as a single detachable, portable assembly. The column of the present invention contains a condenser lens and an objective lens, both designed employing permanent magnet elements for primary field generation. Relatively small coils are used for scanning and precise adjustment of focus.

Growing community of inventors

Singapore, Singapore

Anjam Khursheed