A Scanned Perturbation Technique For Imaging Electromagnetic Standing Wave Patterns of Microwave Cavities

We have developed a method to measure the electric field standing wave distributions in a microwave resonator using a scanned perturbation technique. Fast and reliable solutions to the Helmholtz equation (and to the Schrodinger equation for two dimensional systems) with arbitrarily-shaped boundaries are obtained. We use a pin perturbation to image primarily the microwave electric field amplitude, and we demonstrate the ability to image broken time-reversal symmetry standing wave patterns produced with a magnetized ferrite in the cavity. The whole cavity, including areas very close to the walls, can be imaged using this technique with high spatial resolution over a broad range of frequencies.Comment: To be published in Review of Scientific Instruments,September, 199

Measurement of Wave Chaotic Eigenfunctions in the Time-Reversal Symmetry-Breaking Crossover Regime

We present experimental results on eigenfunctions of a wave chaotic system in the continuous crossover regime between time-reversal symmetric and time-reversal symmetry-broken states. The statistical properties of the eigenfunctions of a two-dimensional microwave resonator are analyzed as a function of an experimentally determined time-reversal symmetry-breaking parameter. We test four theories of onepoint eigenfunction statistics and introduce a new theory relating the one-point and two-point statistical properties in the crossover regime. We also find a universal correlation between the one-point and twopoint statistical parameters for the crossover eigenfunctions. PACS numbers: 05.45. Mt, 03.65.Sq, 11.30.Er, 84.40.Az Many complex quantum systems whose underlying classical behavior is chaotic can be described by treating their Hamiltonian matrix elements as random numbers which fluctuate around zero with a Gaussian distribution. There are universal statistical properties of the eigenvalues and eigenfunctions of these random matrices which depend only on the symmetries of the Hamiltonian. For instance, random matrix theory has been shown to be consistent with the statistical properties of nuclei [1], molecules [2], and two-dimensional quantum dots When time-reversal symmetry is present, wave chaotic systems have statistical properties described by a Gaussian orthogonal ensemble (GOE) of random matrices Here we address the evolution of eigenfunctions of semiclassical wave chaotic systems from the TRS to the TRSB limits. A considerable theoretical literature has developed proposing detailed descriptions of eigenvector statistics in the crossover regime, although little experimental data are available to test these theories. These theories treat only the evolution of the one-point statistical property of eigenfunction distribution, P͑jCj 2 ͒, which quantifies the degree of probability density, jCj 2 , fluctuations in the eigenfunctions The experimental arrangement used to create and measure the wave chaotic eigenfunctions has been described previously We have found that the nonreciprocal property of the ferrite, hence the degree of TRSB, is a function of frequency of the eigenmode in a relatively narrow range of frequency 2482 0031-9007͞00͞85(12)͞2482(4)$15.0

Ultra Narrow Silicon FETs Integrated With Microfluidic System for Serial Sequencing of Biomolecules Based on Local Charge Sensing

Ultra-narrow channel silicon field effect transistors (FET) with suspended gates, integrated with on-chip micro-fluidic delivery system are demonstrated. These devices are designed to be used for serial sequencing of DNA, RNA and proteins, by detecting the local charge variations along these molecules as they are passed between the gate and the channel of the FETs in an aqueous solution. Devices are fabricated with down to 5 nm high tunnels passing between the gate and the channel of the FETs, integrated with larger scale micro-fluidic delivery system. The smallest fabricated active area width is less than 10 nm. A silicon nitride based shallow trench isolation (STI) scheme is developed in order to accommodate fabrication of the tunnels going through the FET, through removal of sacrificial silicon dioxide in HF. A device architecture with an independently controlled side-gate, surrounding the active area, is developed to suppress the edge related leakage currents and allow further scaling of the device width while achieving high sensitivity. The side-gated devices are fabricated as nFET prototypes using thermally grown silicon dioxide gate insulator and silicon nitride STI. The leakage currents are suppressed below 50 fA down to 70 nm gate length with the application of a negative side-gate bias. Side-gated sub-10 nm wide devices exhibit threshold voltage tunability in a range exceeding 2.5 V and with a maximum sensitivity of ?Vt/?Vside > 2 V/V. Wider channel devices with gate lengths less than 70 nm retain Ion/Ioff ratios exceeding 109 and achieve drive currents exceeding 1.5 mA/?m. Narrow channel devices with 150 nm gate length show less than 5 mV/V drain induced barrier lowering. With these performance parameters, side-gated device geometry is a promising candidate for future generation low-power, and higher performance circuits. The possibility of using this device geometry as a side-trapping FLASH memory structure is also demonstrated. A capacitance measurement technique is developed to achieve aF resolution using an instrument with 0.1 fF resolution at 1 MHz utilizing the random fluctuations. These capacitance measurements, performed on the small scale devices, are used to extract effective device dimensions, carrier density and effective carrier mobilities