5 results
Search Results
Now showing 1 - 5 of 5
- ItemMo-La2O3 multilayer metallization systems for high temperature surface acoustic wave sensor devices(Basel : MDPI AG, 2019) Menzel, S.B.; Seifert, M.; Priyadarshi, A.; Rane, G.K.; Park, E.; Oswald, S.; Gemming, T.Developing advanced thin film materials is the key challenge in high-temperature applications of surface acoustic wave sensor devices. One hundred nanometer thick (Mo-La2O3) multilayer systems were fabricated at room temperature on thermally oxidized (100) Si substrates (SiO2/Si) to study the effect of lanthanum oxide on the electrical resistivity of molybdenum thin films and their high-temperature stability. The multilayer systems were deposited by the magnetron sputter deposition of extremely thin (≤1 nm) La interlayers in between adjacent Mo layers. After deposition of each La layer the process was interrupted for 25 to 60 min to oxidize the La using the residual oxygen in the high vacuum of the deposition chamber. The samples were annealed at 800 °C in high vacuum for up to 120 h. In case of a 1 nm thick La interlayer in-between the Mo a continuous layer of La2O3 is formed. For thinner La layers an interlayer between adjacent Mo layers is observed consisting of a (La2O3-Mo) mixed structure of molybdenum and nm-sized lanthanum oxide particles. Measurements show that the (Mo-La2O3) multilayer systems on SiO2/Si substrates are stable at least up to 800 °C for 120 h in high vacuum conditions.
- ItemElectroless-deposited platinum antennas for wireless surface acousticwave sensors(Basel : MDPI AG, 2019) Brachmann, E.; Seifert, M.; Neumann, N.; Alshwawreh, N.; Uhlemann, M.; Menzel, S.B.; Acker, J.; Herold, S.; Hoffmann, V.; Gemming, T.In an effort to develop a cost-efficient technology for wireless high-temperature surface acoustic wave sensors, this study presents an evaluation of a combined method that integrates physical vapor deposition with electroless deposition for the fabrication of platinum-based planar antennas. The proposed manufacturing process becomes attractive for narrow, thick, and sparse metallizations for antennas in the MHz to GHz frequency range. In detail, narrow platinum-based lines of a width down to 40 μm were electroless-deposited on γ -Al2O3 substrates using different seed layers. At first, the electrolyte chemistry was optimized to obtain the highest deposition rate. Films with various thickness were prepared and the electrical resistivity, microstructure, and chemical composition in the as-prepared state and after annealing at temperatures up to 1100 °C were evaluated. Using these material parameters, the antenna was simulated with an electromagnetic full-wave simulation tool and then fabricated. The electrical parameters, including the S-parameters of the antenna, were measured. The agreement between the simulated and the realized antenna is then discussed.
- ItemSurface acoustic wave modulation of single photon emission from GaN/InGaN nanowire quantum dots(Bristol : IOP Publ., 2018) Lazić, S.; Chernysheva, E.; Hernández-Mínguez, A.; Santos, P.V.; van der Meulen, H.P.On-chip quantum information processing requires controllable quantum light sources that can be operated on-demand at high-speeds and with the possibility of in-situ control of the photon emission wavelength and its optical polarization properties. Here, we report on the dynamic control of the optical emission from core-shell GaN/InGaN nanowire (NW) heterostructures using radio frequency surface acoustic waves (SAWs). The SAWs are excited on the surface of a piezoelectric lithium niobate crystal equipped with a SAW delay line onto which the NWs were mechanically transferred. Luminescent quantum dot (QD)-like exciton localization centers induced by compositional fluctuations within the InGaN nanoshell were identified using stroboscopic micro-photoluminescence (micro-PL) spectroscopy. They exhibit narrow and almost fully linearly polarized emission lines in the micro-PL spectra and a pronounced anti-bunching signature of single photon emission in the photon correlation experiments. When the nanowire is perturbed by the propagating SAW, the embedded QD is periodically strained and its excitonic transitions are modulated by the acousto-mechanical coupling, giving rise to a spectral fine-tuning within a ~1.5 meV bandwidth at the acoustic frequency of ~330 MHz. This outcome can be further combined with spectral detection filtering for temporal control of the emitted photons. The effect of the SAW piezoelectric field on the QD charge population and on the optical polarization degree is also observed. The advantage of the acousto-optoelectric over other control schemes is that it allows in-situ manipulation of the optical emission properties over a wide frequency range (up to GHz frequencies).
- ItemBlood platelet enrichment in mass-producible surface acoustic wave (SAW) driven microfluidic chips(Cambridge : RSC, 2019) Richard, Cynthia; Fakhfouri, Armaghan; Colditz, Melanie; Striggow, Friedrich; Kronstein-Wiedemann, Romy; Tonn, Torsten; Medina-Sánchez, Mariana; Schmidt, Oliver G.; Gemming, Thomas; Winkler, AndreasThe ability to separate specific biological components from cell suspensions is indispensable for liquid biopsies, and for personalized diagnostics and therapy. This paper describes an advanced surface acoustic wave (SAW) based device designed for the enrichment of platelets (PLTs) from a dispersion of PLTs and red blood cells (RBCs) at whole blood concentrations, opening new possibilities for diverse applications involving cell manipulation with high throughput. The device is made of patterned SU-8 photoresist that is lithographically defined on the wafer scale with a new proposed methodology. The blood cells are initially focused and subsequently separated by an acoustic radiation force (ARF) applied through standing SAWs (SSAWs). By means of flow cytometric analysis, the PLT concentration factor was found to be 7.7, and it was proven that the PLTs maintain their initial state. A substantially higher cell throughput and considerably lower applied powers than comparable devices from literature were achieved. In addition, fully coupled 3D numerical simulations based on SAW wave field measurements were carried out to anticipate the coupling of the wave field into the fluid, and to obtain the resulting pressure field. A comparison to the acoustically simpler case of PDMS channel walls is given. The simulated results show an ideal match to the experimental observations and offer the first insights into the acoustic behavior of SU-8 as channel wall material. The proposed device is compatible with current (Lab-on-a-Chip) microfabrication techniques allowing for mass-scale, reproducible chip manufacturing which is crucial to push the technology from lab-based to real-world applications. © The Royal Society of Chemistry.
- ItemMultiharmonic Frequency-Chirped Transducers for Surface-Acoustic-Wave Optomechanics(College Park, Md. [u.a.] : American Physical Society, 2018) Weiß, Matthias; Hörner, Andreas L.; Zallo, Eugenio; Atkinson, Paola; Rastelli, Armando; Schmidt, Oliver G.; Wixforth, Achim; Krenner, Hubert J.Wide-passband interdigital transducers are employed to establish a stable phase lock between a train of laser pulses emitted by a mode-locked laser and a surface acoustic wave generated electrically by the transducer. The transducer design is based on a multiharmonic split-finger architecture for the excitation of a fundamental surface acoustic wave and a discrete number of its overtones. Simply by introducing a variation of the transducer's periodicity p, a frequency chirp is added. This combination results in wide frequency bands for each harmonic. The transducer's conversion efficiency from the electrical to the acoustic domain is characterized optomechanically using single quantum dots acting as nanoscale pressure sensors. The ability to generate surface acoustic waves over a wide band of frequencies enables advanced acousto-optic spectroscopy using mode-locked lasers with fixed repetition rate. Stable phase locking between the electrically generated acoustic wave and the train of laser pulses is confirmed by performing stroboscopic spectroscopy on a single quantum dot at a frequency of 320 MHz. Finally, the dynamic spectral modulation of the quantum dot is directly monitored in the time domain combining stable phase-locked optical excitation and time-correlated single-photon counting. The demonstrated scheme will be particularly useful for the experimental implementation of surface-acoustic-wave-driven quantum gates of optically addressable qubits or collective quantum states or for multicomponent Fourier synthesis of tailored nanomechanical waveforms.