SGS award for Pooja Thakkar

Pooja Thakkar received the Shoulders-Gray-Spindt award at the 34th Vacuum Nanoelectronics Conference (5-9 July, fully virtual, organized by Uni Lyon) for her paper "Voltage-controlled three-electron-beam interference by a three-element Boersch phase shifter with top and bottom shielding electrodes". The prize was created in 1998 to honor the founders of the field, Ken Shoulders (late), Henry Gray (late), and Capp Spindt, to promote young scientist (PhD students and early Postdocs) based on the criterion, if the work is novel, ingenious, and does it move the field forward.

Pooja contributed to the goal to manipulate electron waves to realize a novel electron diffraction imaging method. The project was a collaboration between the Paul Scherrer Institute (LNB and LMN) and the Forschungszentrum Jülich and was funded by the PhD School of the Swiss Nanoscience Institute (SNI).


(a) A cross section, and (b) 3d perspective view, show the schematic of five-layer Boersch phase shifter device with three elements along with three contact wires and a contact wire for grounding the top metal layer. (c) SEM image of three Boersch phase shifting elements. (d) A high magnification SEM image of the sidewall of one of the elements imaged at an angle of 20°.

Paper abstract: We report a three-element Boersch phase shifter for the wavefront manipulation of coherent electron beam. A device with five-layer structure is fabricated on a suspended silicon nitride membrane by the state-of-the-art lithography. By including the top-contact-shielding electrode in the design, the five-layer structure is adopted to minimize the parasitic beam deflection observed in a recently reported simplified three-layer device that poses a critical obstacle for device upscaling. Despite the mechanical stresses caused by the additional layers, we produced the five-layer device on a thin silicon nitride membrane and successfully tested its performance of the voltage-controlled phase shift of coherent electron beam. The experiment confirmed that the parasitic beam deflection was suppressed. Our work paves a way toward the realization of a multi-element Boersch phase shifter for a programmable holographic synthesis of electron waves in two- and threedimensions.