Mark Field

Terahertz vacuum electronic circuits fabricated by UV lithographic molding and deep reactive ion etching

The 0.22 THz vacuum electronic circuits fabricated by UV lithography molding and deep reactive ion etching processes are under investigation for submillimeter wave applications. Eigenmode transient simulations show that, accounting for realistic values of our currently achievable fabrication tolerances, the transmission, and dispersion properties of the operation modes of a TE-mode, staggered, double grating circuit are maintained within less than 1 dB and 2% deviation, respectively. Scanning electron microscopy and atomic force microscopy analyses of the fabricated circuit samples demonstrate that both of the microelectromechanical system fabrication approaches produce circuits with ±3–5 μm dimensional tolerance and ∼30 nm surface roughness.

Detection of single magnetic bead for biological applications using an InAs quantum-well micro-Hall sensor

Room-temperature detection of a single commercial superparamagnetic bead (1.2μm in diameter) suitable for biological applications has been realized using an InAs quantum-well micro-Hall sensor. The detection was demonstrated using phase-sensitive detection on a single Hall cross as well as in a Hall gradiometry setup. The high signal to noise ratio, obtained in both configurations, promises detection of single nanometer-size particles by further miniaturization of the device to submicron dimensions.

Magnetic characterization of a single superparamagnetic bead by phase-sensitive micro-Hall magnetometry

Employing phase sensitive micro-Hall magnetometry at room temperature, we map the susceptibility of a single superparamagnetic bead, 1.2μm in diameter, as a function of magnetic field. We find that the dependence can be explained by modeling the bead as an ensemble of noninteracting superparamagnetic nanoparticles with log-normal distribution of magnetic moments. We also discuss the effect of possible dipolar interactions between the nanoparticles on the obtained results.

The detection of specific biomolecular interactions with micro-Hall magnetic sensors

The detection of reagent-free specific biomolecular interactions through sensing of nanoscopic magnetic labels provides one of the most promising routes to biosensing with solid-state devices. In particular, Hall sensors based on semiconductor heterostructures have shown exceptional magnetic moment sensitivity over a large dynamic field range suitable for magnetic biosensing using superparamagnetic labels. Here we demonstrate the capability of such micro-Hall sensors to detect specific molecular binding using biotin-streptavidin as a model system. We apply dip-pen nanolithography to selectively biotinylate the active areas of InAs micro-Hall devices with nanoscale precision. Specific binding of complementarily functionalized streptavidin-coated superparamagnetic beads to the Hall crosses occurs via molecular recognition, and magnetic detection of the assembled beads is achieved at room temperature using phase sensitive micro-Hall magnetometry. The experiment constitutes the first unambiguous demonstration of magnetic detection of specific biomolecular interactions with semiconductor micro-Hall sensors, and the selective molecular functionalization and resulting localized bead assembly demonstrate the possibility of multiplexed sensing of multiple target molecules using a single device with an array of micro-Hall sensors.

Temperature dependent nucleation and annihilation of individual magnetic vortices

We studied the temperature dependence of the magnetization reversal in individual submicron permalloy disks with micro-Hall and bend-resistance magnetometry. The nucleation field exhibits a nonmonotonic dependence with positive and negative slopes at low and high temperatures, respectively, while the annihilation field monotonically decreases with increasing temperature, but with distinctly different slopes at low and high temperatures. Our analysis suggests that at low temperatures vortex nucleation and annihilation proceeds via thermal activation over an energy barrier, while at high temperatures they are governed by a temperature dependence of the saturation magnetization.

8.3: A high aspect ratio, high current density sheet beam electron gun

A beamstick for demonstration of a 25∶1 aspect ratio, 750 A/cm² current density sheet beam for DARPAs HiFIVE project will be described.

InAs quantum well Hall devices for room-temperature detection of single magnetic biomolecular labels

Hall sensors with cross width of ∼1μm were fabricated from InAs∕AlSb quantum well semiconductor heterostructures containing two-dimensional electron gas. The room-temperature device characteristics were examined by Hall effect and electronic noise measurements along with analytical calculations. In the low-frequency range, from 20Hzto1.6kHz, the noise-equivalent magnetic field resolution was found to be limited by 1∕f and generation-recombination noise from 22to3.5μT∕Hz. The corresponding noise-equivalent magnetic moment resolution reached 106μB∕Hz at ∼700Hz and was even lower at higher frequencies. Using a phase-sensitive measurement technique, detection of a single 1.2μm diameter bead, suitable for biological applications, was achieved with a signal to noise ratio of ∼33.3dB, as well as detection of six 250nm beads with a signal to noise of ∼2.3dB per bead. The work demonstrates the efficacy of InAs quantum well Hall devices for application in high sensitivity detection of single magnetic biomolecular l...

An ultra-low loss millimeter-wave solid state switch technology based on the metal - insulator - transition of vanadium dioxide

A new ultra-low-loss and broad band millimeter wave switch technology based on the reversible metal / insulator phase transition of vanadium dioxide has been developed. We report having fabricated series configured, single-pole single-throw (SPST) switches having measured S-parameters from DC to 110 GHz. The on-state insertion loss is 0.2 dB and off-state isolation is 21 dB at 50 GHz. The resulting impedance contrast ratio, ZOFF/ZON, is greater than 500:1 at 50GHz (i.e. cut-off frequency fc ~ 40 THz). As a demonstration of the technologys utility, we also present the results of a 2-bit real time delay phase shifter incorporating a pair of VO2 SP4T switches. This switch technologys high impedance contrast ratio combined with its compactness, ease of integration, and low voltage operation make it an enabler of previously unachievable high-performance millimeter wave FPGAs.

A 180mW InP HBT Power Amplifier MMIC at 214 GHz

A solid state power amplifier MMIC is demonstrated with 180mW of saturated output power at 214GHz, from an unthinned die, and a small signal S21 gain of 22.0dB. 3-dB bandwidth extends from below 210GHz to 230GHz. PDC is 12.9W. PA Cell design uses a 250nm InP HBT process and a novel three-port tuning network. Three levels of on-wafer power combining in 5μm BCB microstrip are used to combine 16 PA cells in a power amplifier MMIC. The result is a 4x increase in output periphery versus the previous state-of-the-art for InP HBT power amplifier MMICs designed for 220GHz.

Development of a 220 GHz 50 W sheet beam travelling wave tube amplifier

We report on progress in developing a travelling wave tube amplifier with significant gain and power at 220 GHz. This paper provides an overview of the program, describing fabrication and test of slow-wave structures with bandwidths exceeding 50 GHz centered at 220 GHz, the production of a sheet electron beam, development of a solid state preamplifier delivering 50 mW to the tube with > 17 dB of gain and beam-wave simulation of the entire circuit leading to expected output powers of over 50 W. Two further papers from the group are also submitted to IVEC: from UC Davis describing the interaction structure fabrication and hot test, and from CPI describing the sheet electron beam, TWT design and beam - wave simulations. The tube is currently under test and results will be reported in this paper.