Ultrahigh-frequency silicon acousto-electronics

Host: University of Twente (TWENTE)
Supervisor: W.G. van der Wiel (TWENTE), Co-supervisor: P. V. Santos (PDI)


NanoLab, University of Twente, Enschede

Robert Ukropec

Robert Ukropec comes from Slovakia, where he first obtained his Bachelor of Science in Physics at the Comenius University in Bratislava. Much recently, he finished his Master of Science in Physics at the RWTH University in Aachen with a specialization in nanoelectronics. His Master’s Thesis topic dealt in local conductance characterizations of contacted InAs nanowires with scattering infrared near-field optical microscopy. Most of the primary research, including fabrication and first characterization of samples, was achieved at the Forschungszentrum Jülich under supervision of Prof. Thomas Schäpers. Optical measurements were obtained under the supervision of Prof. Thomas Taubner at the I. Institute of Physics (IA) at the RWTH. Robert’s research interests are in novel nanoelectronic devices, specializing in surface phenomena. In his free time, he was active in AEGEE-Aachen, the Aachen local branch of the European Student’s Forum, through which he helped organize many activities for visiting international students. His hobbies are skiing, traveling, dancing and reading.


Generation of ultrahigh-frequency (UHF) SAWs on Si multilayers with mesoscopic structures such as quantum point contacts (QPCs), acoustic switches (AS) and NIP (n-type/intrinsic/p-type) regions for acoustic charge pumping, switching and photon generation/detection. TWENTE (with NTD and SolMateS) has demonstrated a CMOS-compatible nano-imprint lithography (NIL) process for UHF IDTs with record frequencies (up to 24 GHz).

The acoustic current through QPCs pumped at these frequencies should reach 1-20 nA even in the single-electron/SAW-cycle regime, thus providing a very precise current-standard measurement for metrological applications. Electrically induced electrons can be picked up by a SAW and transported to a p-doped region leading to electron-hole recombination. Photon generation can be enhanced by quantum confinement in the silicon, which is known to enable a direct band gap. There are strong links with WP1-2 and WP1-3.

Expected Results

The PhD student will develop and fabricate NIL IDTs (with NTD) for UHF SAWs on different substrates, but focus on Si-based multilayer systems. The PhD student will use simulation tools to design, optimise, produce masks, and fabricate IDTs, thereby learning several cleanroom processes. IDTs will be combined with on-chip electronic or optical micro/nano devices. Acousto-(opto) electronic measurements will be partially carried out at PDI.

Pulsed laser deposition (PLD) of piezoelectric films will be learned during an internship at SolMateS. Knowledge about integration of NIL-fabricated IDTs with graphene devices will be learned from the collaboration with UPM and PDI, and integration with Lamb-wave sensors from the collaboration with CNR. Many other WPs will try out NIL developed in this WP as it will make the lithography of small-period transducers much easier.