Browsing by Subject "Electron Beam Lithography"

Now showing 1 - 3 of 3

Open Access
Design, fabrication, and applications of multi-mode nanoelectromechanical systems
(2017-07) Arı, Atakan Bekir
Miniaturization of systems allowed wide spread consumer use of microelectronics, integrated circuits and MEMS based sensors. Thanks to the advancement in microfabrication methods, it is possible to build structures with submicron dimensions. The integration of electronic control to these submicron structures started the NEMS eld. Due to their minuscule dimensions and very high frequency response, NEMS can sense external perturbations with unprecedented sensitivity. This made NEMS excellent candidates for sensor applications. NEMS are starting to evolve from academic research tools to become mass produced and large scale integrated sensing devices. Information extracted from the higher order modes further increase the capabilities of NEMS. In order to attain this extra information, we fabricated NEMS that can reach higher order mechanical modes. Every step of fabrication was done at Bilkent University research facilities such as UNAM and ARL. To pattern the submicron feature sizes, we relied on electron beam lithography. Thermal and electron beam evaporators were deployed for metallization of contacts and etch mask. In order to suspend the doubly clamped beams, we developed anisotropic silicon nitride and isotropic silicon dry etch recipes. At each step of the fabrication, tools such as SEM and stylus pro lometer was utilized for characterization. Fabricated NEMS were wirebonded to printed circuit boards for detection. Electrothermal actuation, an integrated method, was chosen to drive the nanomechanical resonator to its higher order modes. Piezoresistive down-mixing, another integrated method to complement the actuation, was used to detect the resulting nanomechanical motion. We used high frequency electronic equipment to detect RF range responses of our NEMS. Using these NEMS, we studied two novel applications on intermodal and mechanical coupling. First, we investigated intermodal coupling e ect of doubly clamped beams in order utilize this coupling e ect in higher order mode detection. When a doubly clamped beam is excited at its resonance frequency, every other mode of the device gets tuned. This occurs due to the clamping on both sides preventing longitudinal elongation and causing a stress on the beam. Using intermodal coupling method, we probed higher order modes of a nanomechanical resonator while tracking the fundamental frequency at the same time. We were able to detect mechanical modes up to 840 MHz, well out of the detection limit of our setup. We propose intermodal coupling as a novel detection method to acquire frequency response of NEMS at higher order modes which can not be detected with conventional methods. Finally, we studied nano scale energy sinks that absorb energy from a another structure. Energy sinks are linear oscillators that can trap the energy of a nearby structure within their phase space. When the natural frequency of these sinks are distributed optimally, nite number of sinks can mimic absorption of in nite sinks. We envisioned a real time dissipation controlled NEMS platform by deploying energy sinks. In order to test energy sink performance at nano scale, we devised an experimental setup, comparing identical nanomechanical resonators with and without energy sinks. We have shown that energy sinks successfully absorb energy of a resonator at nanoscale.
Open Access
Electron beam lithography designed silver nano-disks used as label free nano-biosensors based on localized surface plasmon resonance
(Optical Society of America, 2012-01-20) Cinel, N. A.; Butun, S.; Özbay, Ekmel
We present a label-free, optical nano-biosensor based on the Localized Surface Plasmon Resonance (LSPR) that is observed at the metaldielectric interface of silver nano-disk arrays located periodically on a sapphire substrate by Electron-Beam Lithography (EBL). The nano-disk array was designed by finite-difference and time-domain (FDTD) algorithm-based simulations. Refractive index sensitivity was calculated experimentally as 221-354 nm/RIU for different sized arrays. The sensing mechanism was first tested with a biotin-avidin pair, and then a preliminary trial for sensing heat-killed Escherichia coli (E. coli) O157:H7 bacteria was done. Although the study is at an early stage, the results indicate that such a plasmonic structure can be applied to bio-sensing applications and then extended to the detection of specific bacteria species as a fast and low cost alternative. © 2012 Optical Society of America.
Open Access
Synthesis and characterization of Van Der Waals heterostructures, and nanofabrication of electronic devices based on two-dimensional materials
(2017-11) Ramezani, Mehdi
Last two decades have seen a phenomenal shift of the dimensionality paradigm in materials processing, from zero-dimensional nanoparticles and quantum dots to one-dimensional nanowires and nanotubes, to two-dimensional materials. Each above-mentioned category of the nanomaterial can be manipulated exclusively, and mentored to drive special properties. However, for each of them, it may take time to discover their true potential and proper application in contemporary technology. The emergence of graphene in 2004 triggered the scienti c community to turn their vision toward investigation of two-dimensional materials. The impact of the discovery of graphene with its rare characteristics was such huge that no subject had been studied in the past as much as two-dimensional materials have. Nowadays, there are brand new two-dimensional materials with more intriguing properties which no one could imagine. However, our current technology had developed based on bulk material, and it is not ready yet to accept the use of nanomaterials. Recent advances in nanoscale characterization opened up new opportunities for nanomaterials to be investigated so delicately. The other face of the discovery of nanomaterial is the need for ingenious fabrication method. Integration of electronic and optoelectronic circuits in con ned space is one of the top paid objectives in research and development. The goal is providing a faster computational speed, lower energy consumption, and reducing the size of these systems. Although this is a long-term plan, it is not farfetched once we connect the dots and think outside the box.Herein, we address synthesis, characterization, and manipulation of various two-dimensional materials. A thorough report on chemical vapor deposition of molybdenum disul de and tungsten diselenide is provided in this study. Besides this two material we encountered some anomalies in the behavior of an unknown two-dimensional material which we synthesized it in our lab. The next step is to establish novel methods in order to fabricate electronic devices supporting atomically-thin structures. We could formulate a straightforward method to assemble atomically thin ake of material on transmission electron microscope grid, compatible for microscopy of thin materials and adjustable for various characterization method including Raman spectroscopy, and atomic force microscopy. Last but not least, we introduced a novel method to induce mechanical strain on the two-dimensional ake. This method allows a dynamic scanning electron microscopy of the strained structure, which could be utilized for versatile applications. It worth to mention that, a fabrication process is mainly based on mentoring wet-transfer, focused ion beam, and electron beam lithography.