Browsing by Subject "Probes"

Now showing 1 - 18 of 18

Open Access
Bismuth nano-Hall probes fabricated by focused ion beam milling for direct magnetic imaging by room temperature scanning Hall probe microscopy
(The Institution of Engineering and Technology (IET), 2001) Sandhu, A.; Masuda, H.; Kurosawa, K.; Oral, A.; Bending, S. J.
Bismuth nano-Hall probes fabricated by using focused ion beam (FIB) milling were studied. The nano-Hall probes were used for direct magnetic imaging of domain structures in low coercivity garnets and demagnetized strontium ferrite permanent magnets. The analysis was performed using room temperature scanning Hall probe microscopy and it was found that the Bi nano-probes could overcome limitations due to surface depletion and large series resistances.
Open Access
A chromogenic dioxetane chemosensor for hydrogen sulfide and pH dependent off-on chemiluminescence property
(Elsevier, 2014) Turan, I. S.; Sozmen, F.
In this paper, a rapid and highly selective chromogenic naked eye detection of hydrogen sulfide was achieved by a 1,2-dioxetane based chemiluminescent probe in aqueous media at pH 7.4. Chemiluminescence property of the probe can be modulated depending on the pH value of medium.
Open Access
Fabrication of 100 nm pMOSFETS With Hybrid AFW / STM lithography
(IEEE, 1997-06) Soh, H. T.; Wilder, K.; Atalar, Abdullah; Quate, C. F.
Scanning probe lithography (SPL) is an emerging area of research in which the scanning tunneling microscope (STM) or atomic force microscope (AFM) is used to pattern nanometer-scale features. Four factors will dictate the viability of SPL as a patterning technology for the semiconductor industry: 1) resolution, 2) alignment accuracy, 3) reliability, and 4) throughput. We present a new SPL technique-a hybrid between the AFM and STMto address these issues. We demonstrate its capabilities and its compatibility with semiconductor processing by fabricating a pMOSFET with an effective channel length (L,ff) of 100 nm and report the device characteristics.
Open Access
Gate bias characterization of CNT-TFT DNA sensors
(IEEE, 2009-12) Aktaş, Özgür; Töral, Taylan
This paper follows the approach in the works of Gui et al. (2007), that use the change in the current of carbon nanotube thin film transistors (CNT-TFT) with DNA attachment and DNA hybridization. The authors have studied the response of CNT-TFTs to DNA binding and hybridization. It was demonstrated for the first time that an increase in sensitivity is observed around the threshold voltage when sweeping the gate bias from negative to positive values. The results presented in this work suggest an improved approach to measuring the response of CNT-TFTs to DNA hybridization.
Open Access
Harmonic cantilevers for nanomechanical sensing of elastic properties
(IEEE, 2003-06) Şahin, O.; Yaralıoğlu, G.; Grow, R.; Zappe, S. F.; Atalar, Abdullah; Quate, C.; Solgaard, O.
We present a micromachined scanning probe cantilever, in which a specific higher order flexural mode is designed to be resonant at an exact integer multiple of the fundamental resonance frequency. We have demonstrated that such cantilevers enable sensing of nonlinear mechanical interactions between the atomically sharp tip at the free end of the cantilever and a surface with unknown mechanical properties in tapping-mode atomic force microscopy.
Open Access
High sensitivity and multifunctional micro-Hall sensors fabricated using InAlSb/InAsSb/InAlSb heterostructures
(2009) Bando, M.; Ohashi, T.; Dede, M.; Akram, R.; Oral, A.; Park, S.Y.; Shibasaki I.; Handa H.; Sandhu, A.
Further diversification of Hall sensor technology requires development of materials with high electron mobility and an ultrathin conducting layer very close to the material's surface. Here, we describe the magnetoresistive properties of micro-Hall devices fabricated using InAlSb/InAsSb/InAlSb heterostructures where electrical conduction was confined to a 30 nm-InAsSb two-dimensional electron gas layer. The 300 K electron mobility and sheet carrier concentration were 36 500 cm2 V-1 s-1 and 2.5× 1011 cm-2, respectively. The maximum current-related sensitivity was 2 750 V A-1 T-1, which was about an order of magnitude greater than AlGaAs/InGaAs pseudomorphic heterostructures devices. Photolithography was used to fabricate 1 μm×1 μm Hall probes, which were installed into a scanning Hall probe microscope and used to image the surface of a hard disk. © 2009 American Institute of Physics.
Open Access
High-speed transparent indium-tin-oxide based resonant cavity Schottky photodiode with Si/sub 3/N/sub 4//SiO/sub 2/ top Bragg mirror
(IEEE, Piscataway, NJ, United States, 2000) Bıyıklı, Necmi; Kimukin, I.; Aytur, O.; Özbay, Ekmel; Gokkavas, M.; Unlu, S.
Photodetectors demonstrating high bandwidth-efficiency (BWE) products are required for high-performance optical communication and measurement systems. For conventional photodiodes the BWE product is limited due to the bandwidth-efficiency trade-off. A resonant cavity enhanced (RCE) photodetection scheme offers the possibility to overcome this limitation. Very high BWE products are achieved using Schottky and p-i-n type RCE photodiodes, which could not be reached with conventional detector structures. Even better performances should be possible for RCE Schottky photodiodes if one can get rid of the optical losses and scattering caused by the Schottky metal, Au, which also serves as the top mirror of the resonant cavity. The transparent, low resistivity material indium-tin-oxide (ITO) is a potential alternative to thin semi-transparent Au as a Schottky-barrier contact material. We report our work on high-performance ITO-based RCE Schottky photodiodes.
Open Access
Imaging capability of pseudomorphic high electron mobility transistors, AlGaN/GaN, and Si micro-Hall probes for scanning Hall probe microscopy between 25 and 125 °c
(American Vacuum Society, 2009) Akram, R.; Dede, M.; Oral, A.
The authors present a comparative study on imaging capabilities of three different micro-Hall probe sensors fabricated from narrow and wide band gap semiconductors for scanning hall probe microscopy at variable temperatures. A novel method of quartz tuning fork atomic force microscopy feedback has been used which provides extremely simple operation in atmospheric pressures, high-vacuum, and variable-temperature environments and enables very high magnetic and reasonable topographic resolution to be achieved simultaneously. Micro-Hall probes were produced using optical lithography and reactive ion etching process. The active area of all different types of Hall probes were 1×1 μ m2. Electrical and magnetic characteristics show Hall coefficient, carrier concentration, and series resistance of the hall sensors to be 10 mG, 6.3× 1012 cm-2, and 12 k at 25 °C and 7 mG, 8.9× 1012 cm-2 and 24 k at 125 °C for AlGaNGaN two-dimensional electron gas (2DEG), 0.281 mG, 2.2× 1014 cm-2, and 139 k at 25 °C and 0.418 mG, 1.5× 1014 cm-2 and 155 k at 100 °C for Si and 5-10 mG, 6.25× 1012 cm-2, and 12 k at 25 °C for pseudomorphic high electron mobility transistors (PHEMT) 2DEG Hall probe. Scan of magnetic field and topography of hard disc sample at variable temperatures using all three kinds of probes are presented. The best low noise image was achieved at temperatures of 25, 100, and 125 °C for PHEMT, Si, and AlGaNGaN Hall probes, respectively. This upper limit on the working temperature can be associated with their band gaps and noise associated with thermal activation of carriers at high temperatures.
Open Access
Local electric fields in aqueous electrolytes
(American Chemical Society, 2021-07-27) Drexler, C. I.; Cracchiolo, O. M.; Myers, R. L.; Okur, Halil İbrahim; Serrano, A. L.; Corcelli, S. A.; Cremer, P. S.
Vibrational Stark shifts were explored in aqueous solutions of organic molecules with carbonyl- and nitrile-containing constituents. In many cases, the vibrational resonances from these moieties shifted toward lower frequency as salt was introduced into solution. This is in contrast to the blue-shift that would be expected based upon Onsager’s reaction field theory. Salts containing well-hydrated cations like Mg2+ or Li+ led to the most pronounced Stark shift for the carbonyl group, while poorly hydrated cations like Cs+ had the greatest impact on nitriles. Moreover, salts containing I– gave rise to larger Stark shifts than those containing Cl–. Molecular dynamics simulations indicated that cations and anions both accumulate around the probe in an ion- and probe-dependent manner. An electric field was generated by the ion pair, which pointed from the cation to the anion through the vibrational chromophore. This resulted from solvent-shared binding of the ions to the probes, consistent with their positions in the Hofmeister series. The “anti-Onsager” Stark shifts occur in both vibrational spectroscopy and fluorescence measurements.
Open Access
Nanoscale tribology of graphene grown by chemical vapor deposition and transferred onto silicon oxide substrates
(Cambridge University Press, 2016) Demirbaş, T.; Baykara, M. Z.
We present a comprehensive nanoscale tribological characterization of single-layer graphene grown by chemical vapor deposition (CVD) and transferred onto silicon oxide (SiO2) substrates. Specifically, the nanotribological properties of graphene samples are studied via atomic force microscopy (AFM) under ambient conditions using calibrated probes, by measuring the evolution of friction force with increasing normal load. The effect of using different probes and post-transfer cleaning procedures on frictional behavior is evaluated. A new method of quantifying lubrication performance based on measured friction coefficient ratios of graphene and SiO2 is introduced. A comparison of lubrication properties with mechanically-exfoliated graphene is performed. Results indicate that CVD-grown graphene constitutes a very good solid lubricant on SiO2, reducing friction coefficients by ∼ 90% for all investigated samples. Finally, the effect of wrinkles associated with CVD-grown graphene on measured friction values is quantitatively analyzed, with results revealing a substantial increase in friction on these structural defects.
Open Access
On-chip characterization of THz Schottky diodes using non-contact probes
(IEEE Computer Society, 2016) Khan, T. M.; Ghobadi, A.; Celik, O.; Caglayan, C.; Bıyıklı, Necmi; Okyay, Ali Kemal; Topalli, K.; Sertel, K.
We present non-contact characterization of GaAs Schottky contacts in the 140-220 GHz band. The non-contact probing technique utilizes planar on-chip antennas that are monolithically integrated with the coplanar waveguide environment housing the Schottky diode under test. The diode contact is fabricated through a 6 mask lithographic process with a 5 μm deep-trench under the contact to minimize parasitics and extend operation into the THz band. A quasi-optical link between the VNA ports and on-chip probe antennas enables efficient signal coupling into the test device. The non-contact probe station is calibrated using on-chip quick-offset-short method and the effectiveness of this approach is demonstrated for integrated diodes for under various bias conditions.
Open Access
Optical bistability in one-dimensional doped photonic crystals with spontaneously generated coherence
(2013) Aas, S.; Müstecaplioǧlu O.E.
We investigate optical bistability in a multilayer one-dimensional photonic crystal where the central layer is doped with Λ-type three-level atoms. We take into account the influence of spontaneously generated coherence when the lower atomic levels are sufficiently close to each other, in which case Kerr-type nonlinear response of the atoms is enhanced. We calculate the propagation of a probe beam in the defect mode window using the numerical nonlinear transfer matrix method. We find that Rabi frequency of a control field acting on the defect layer and the detuning of the probe field from the atomic resonance can be used to control the size and contrast of the hysteresis loop and the threshold of the optical bistability. In particular we find that at the optimal spontaneously generated coherence, a three orders of magnitude lower threshold can be achieved relative to the case without the coherence. © 2013 American Physical Society.
Open Access
Repetition rate tuning of an ultrafast ytterbium doped fiber laser for terahertz time-domain spectroscopy
(IEEE, 2013) Keskin H.; Altan H.; Yavaş, Seydi; İlday, F. Ömer; Yagci, M.E.; Aydin O.; Eken, K.; Sahin, B.
Repetition rate tuning enables the fast acquisition of THz pulse profiles [1]. By using this method we demonstrate a compact and broadband terahertz time domain spectroscopy system (THz TDS) driven by ytterbium doped fiber laser source. The importance of this method is realized in that Yb:doped fiber lasers can be amplified to sub-millijoule pulse strengths more easily than other types of fiber lasers [2]. Hence, it has the potential to be used in excite-THz probe experiments. Furthermore, the repetition rate-tuning adds flexibility in the excite-probe techniques. These attributes as well as THz generation and detection are investigated with the laser that was developed. © 2013 IEEE.
Open Access
Self immolative dioxetane based chemiluminescent probe for H2O2 detection
(Elsevier, 2017) Seven, O.; Sozmen, F.; Simsek Turan, I.
Chemiluminescent detection of H2O2 has been achieved by using self immolative dioxetane based probe which enables the signal amplification via disassembly of two chemiluminogenic modules at the same time in response to single analyte. Upon treatment of the probe with H2O2, boronate ester was deprotected subsequently to trigger the decomposition of 1,2-dioxetane ring via CIEEL mechanism which results in light emission as a selective sign of H2O2. ï¿½ 2016 Elsevier B.V.
Open Access
A sensitive and selective chemiluminogenic probe for palladium
(Royal Society of Chemistry, 2015) Turan, I. S.; Yilmaz, O.; Karatas, B.; Akkaya, E. U.
Palladium triggered removal of a propargyl group leads to the cleavage of the 1,2-dioxetane ring, leading to bright chemiluminescence. The reaction of the probe is highly specific for the Pd species, thus the probe described here has considerable potential for practical utility.
Open Access
Wireless monitoring of a structural beam to be used for post-earthquake damage assessment
(IEEE, 2018-05-06) Özbey, B.; Kurc, O.; Demir, Hilmi Volkan; Ertürk, Vakur B.; Altıntaş, Ayhan
Wireless monitoring of a standard reinforced concrete beam is shown in a simply supported beam experiment. The passive nested split-ring resonator (NSRR) probes are attached on the reinforcing bars (rebars) within the beam, and an antenna interrogates the probes from outside the beam. The results of the experiment show that the plastic deformation region strain/displacement can be detected by the wireless sensing system. The data collected by the system constitutes an important input for the assessment of the damage that can be observed after earthquakes.
Open Access
A wireless passive sensing system for displacement/strain measurement in reinforced concrete members
(MDPI AG, 2016) Ozbey B.; Erturk V.B.; Demir H.V.; Altintas, A.; Kurc O.
In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range. © 2016 by the authors; licensee MDPI, Basel, Switzerland.
Open Access
Wireless sensing in complex electromagnetic media: construction materials and structural monitoring
(Institute of Electrical and Electronics Engineers Inc., 2015) Özbey, B.; Demir, Hilmi Volkan; Kurc, O.; Ertürk, V. B.; Altıntaş, A.
In this paper, wireless sensing in the presence of complex electromagnetic media created by combinations of reinforcing bars and concrete is investigated. The wireless displacement sensing system, primarily designed for use in structural health monitoring (SHM), is composed of a comb-like nested split-ring resonator (NSRR) probe and a transceiver antenna. Although each complex medium scenario is predicted to have a detrimental effect on sensing in principle, it is demonstrated that the proposed sensor geometry is able to operate fairly well in all scenarios except one. In these scenarios that mimic real-life SHM, it is shown that this sensor exhibits a high displacement resolution of 1 μm, a good sensitivity of 7 MHz/mm in average, and a high dynamic range extending over 20 mm. For the most disruptive scenario of placing concrete immediately behind NSRR, a solution based on employing a separator behind the probe is proposed to overcome the handicaps introduced by the medium. In order to obtain a one-to-one mapping from the measured frequency shift to the displacement, a numerical fit is proposed and used. The effects of several complex medium scenarios on this fit are discussed. These results indicate that the proposed sensing scheme works well in real-life SHM applications. © 2001-2012 IEEE.