Glen Gronniger

Electron diffraction from free-standing, metal-coated transmission gratings

Electron diffraction from a free-standing nanofabricated transmission grating was demonstrated, with energies ranging from 125 eV to 25 keV. Observation of 21 diffraction orders highlights the quality of the gratings. The image charge potential due to one electron was measured by rotating the grating. These gratings may pave the way to low-energy electron interferometry.

A three-grating electron interferometer

We report the observation of fringes from a three-grating electron interferometer. Interference fringes have been observed at low energies ranging from 6 to 10?keV. Contrasts of up to 25% are recorded and exceed the maximal contrast of the classical equivalent Moir? deflectometer. This type of interferometer could serve as a separate beam Mach?Zehnder interferometer for low-energy electron interferometry experiments.

A measurement of electron-wall interactions using transmission diffraction from nanofabricated gratings

Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50to900eV. The interaction time is of the order of typical metal image charge response times and in principle allows the investigation of image charge formation. In addition to the image charge interaction there is a dephasing process reducing the transverse coherence length of the electron wave. The dephasing process causes broadening of the diffraction peaks and is consistent with a model that ascribes the dephasing process to microscopic contact potentials. Surface structures with length scales of about 200nm observed with a scanning tunneling microscope, and dephasing interaction strength typical of contact potentials of 0.35eV support this claim. Such a dephasing model motivated the investigation of different metallic coatings, in particular Ni, Ti, Al, and different thickness Au–Pd coatings. Improved quality of diffraction patterns was found for Ni. This coating made electron diffraction possible at energies as low as 50eV. This energy was limited by our electron gun design. These results are particularly relevant for the use of these gratings as coherent beam splitters in low energy electron interferometry.Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50to900eV. The interaction time is of the order of typical metal image ch...

An electron Talbot-Lau interferometer and magnetic field sensing

We present a demonstration of a three grating Talbot-Lau interferometer for electrons. As a proof of principle, the interferometer is used to measure magnetic fields. The device is similar to the classical Moire deflectometer. The possibility to extend this work to build a scaled-up electron deflectometer or interferometer for sensitive magnetic field sensing is discussed.

Phase and Absorption Gratings for Electrons

In matter optics with atoms many analogies between light and matter waves have been explored. In matter optics with electrons the same does not appear to hold to the same extent. Although electron microscopy in use far supersedes any tool developed in atom optics, this technique is based on only a few optics elements [2]: electron lenses [3], beam splitters (biprisms) [4] and coherent sources [5]. In atom optics, apart from these elements [6,7,8,9,10], mirrors [11], polarizing beam splitters [12], fibers [13], modulators [14], and gratings [15] are a few examples of the many analogies that have been explored. It may be possible to develop some of these techniques for electron optics and find useful applications for them. Here, we would like to present our work on phase and absorption gratings for electrons. For completeness we should mention that absorption gratings for electrons were demonstrated decades ago [16]. The near field diffraction pattern was observed using 50 keV electrons for a grating made from individually deposited wires. We observe the far-fields diffraction pattern at 500 eV for a nano-fabricated grating. Given the ever improving capabilities in nano-fabrication and the variation of patterns that can be made, we feel it is interesting to revisit this field.