Broadband radio-frequency TEM specimen holders for in situ biasing excitation and 100-ps-scale electron beam control
Broadband electrical excitation inside a transmission electron microscope (TEM) is required to investigate electrically driven nanodevices at their actual operating frequencies and to develop fully electrical time-resolved experiments at a sub-nanosecond range. Here, we report the performances of homemade two- and four-channel radio-frequency (RF) TEM specimen holders based on a hybrid architecture combining coaxial transmission lines with miniaturized impedance-controlled printed circuit boards (PCB). Removable mechanical contacts provide direct electrical connection to interchangeable TEM chips without wire bonding. Vector network analyzer measurements demonstrate broadband transmission through the complete electrical path up to the specimen. With a representative TEM chip, the two-channel holder exhibits a -3 dB bandwidth of 7.9 GHz, while insertion losses remain below 12 dB up to 18 GHz. The same RF holder architecture was used to drive a miniaturized electrostatic electron-beam deflector. The measured temporal response indicates that the holder deflector assembly remains compatible with electrical pulse durations approaching 100 ps, with the shortest accessible times presently limited by the available waveform generator. High-resolution TEM imaging with a 200 ps probe window does not show detectable degradation of spatial resolution, while off-axis electron holography is successfully performed for probe durations down to 0.5 ns under conditions representative of operando measurements. These results establish a versatile broadband platform combining GHz electrical excitation and sub-nanosecond electron-beam control. The dual-stage configuration of our Hitachi HF3300 microscope further provides the basis for a future fully electrical pump-probe TEM approach using independently driven RF holders for specimen excitation and electron-probe control.