Conductance Imaging of the Depletion Region of Biased Silicon PN Junction Device

2001 ◽  
Vol 669 ◽  
Author(s):  
Jeong Young Park ◽  
R. J. Phaneuf ◽  
E. D. Williams
Keyword(s):  
Tunneling Current ◽  
Current Mode ◽  
Depletion Region ◽  
Constant Current ◽  
Band Bending ◽  
Pn Junction ◽  
Junction Device ◽  
Modulation Signal ◽  
Passivated Silicon ◽  
Lock In

ABSTRACTSimultaneous conductance imaging and constant current mode STM imaging have been used to delineate Si pn junction arrays over a range of reverse bias conditions. Conductance has been obtained by adding a modulation signal to voltages applied in the p and n regions of a model device, and by measuring the modulation signal of the tunneling current with a lock-in amplifier. Both constant current and conductance imaging ofthe electrically different regions (n, p, and depletion zone) show a pronounced dependence on applied pn junction bias. The conductance contrast is mainly due to electrically different behaviors of metal-gap-semiconductor junction which are determined by the tip-induced band bending of the oxide-passivated silicon surface.

Nontraditional techniques

1996 ◽  
Author(s):  
Wolfgang Schmickler
Keyword(s):  
Fermi Level ◽  
Electrode Surface ◽  
Electrochemical Techniques ◽  
Tunneling Current ◽  
Current Mode ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Electronic Density ◽  
Direction Parallel ◽  
Metal Tip

The traditional electrochemical techniques are based on the measurement of current and potential, and, in the case of liquid electrodes, of the surface tension. While such measurements can be very precise, they give no direct information on the microscopic structure of the electrochemical interface. In this chapter we treat several methods which can provide such information. None of them is endemic to electrochemistry; they are mostly skillful adaptations of techniques developed in other branches of physics and chemistry. The scanning tunneling microscope (STM) is an excellent device to obtain topographic images of an electrode surface . The principal part of this apparatus is a metal tip with a very fine point, which can be moved in all three directions of space with the aid of piezoelectric crystals. All but the very end of the tip is insulated from the solution in order to avoid tip currents due to unwanted electrochemical reactions. The tip is brought very close, up to a few Ångstroms, to the electrode surface. When a potential bias ΔV, usually of the order of a few hundred millivolts, is applied between the electrode and the tip, the electrons can tunnel through the thin intervening layer of solution, and a tunneling current is observed. The situation is illustrated in Fig. 15.2: A potential energy barrier exists between the tip and the substrate. Application of a bias potential shifts the two Fermi levels of the tip and of the substrate. Electrons can tunnel from the metal with the higher Fermi level through the barrier to empty states on the other metal. Roughly speaking, electrons with energies between the two Fermi levels can be transferred. A detailed calculation shows that the current is proportional to the electronic density of states at the Fermi level of the substrate. The tip is moved slowly in the yz direction parallel to the metal surface, and simultaneously the distance x from the electrode is adjusted in such a way that the tunneling current is constant (constant-current mode).

scholarly journals Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hai Le-The ◽  
Christian Küchler ◽  
Albert van den Berg ◽  
Eberhard Bodenschatz ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fluid Velocity ◽  
Current Mode ◽  
Constant Current ◽  
Small Scale ◽  
Turbulence Measurements ◽  
High Dynamic ◽  
Scale Turbulence ◽  
Constant Current Mode ◽  
Pt Nanowires

AbstractWe report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

Design and Implementation of Mid-Frequency Magnetron Sputtering Power Supply Based on TL494 and MCU

2013 ◽  
Vol 709 ◽  
pp. 408-412
Author(s):  
Yan Ling Zhao ◽  
Rong Xing Liu
Keyword(s):  
Magnetron Sputtering ◽  
Power Supply ◽  
Current Mode ◽  
Voltage Regulation ◽  
Control Circuit ◽  
Constant Current ◽  
Loop Control ◽  
Pulse Width Modulator ◽  
Digital Pulse ◽  
The Stability

Abstract. A mid-frequency magnetron sputtering (MFMS) power supply based on TL494 and MCU was introduced. A Buck Chopper and full bridge inverter were applied to the main circuit. The PWM controller TL494 was used in the Buck voltage-regulation control circuit to realize closed loop control. The drive signal of the IGBT in full bridge inverter was based on precise digital pulse width modulator (DPWM) signal produced by the MCU M30290. The DPWM can be set by potentiometer so the power supply can output the square wave with adjustable frequency and duty cycle. The power supply was operated in constant current mode. For micro or strong arcing of the target, different safeguards were adopted by the control circuit. At last, the system test and experimental results show that the stability, reliability and tuning range of the MFMS power supply can meet the requirements of the magnetron sputtering coating.

COMPLEX DYNAMICS AND FAST-SLOW SCALE INSTABILITY IN CURRENT-MODE CONTROLLED BUCK CONVERTER WITH CONSTANT CURRENT LOAD

2013 ◽  
Vol 23 (04) ◽  
pp. 1350062 ◽  
Author(s):  
GUOHUA ZHOU ◽  
BOCHENG BAO ◽  
JIANPING XU
Keyword(s):  
Complex Dynamics ◽  
Period Doubling ◽  
Current Mode ◽  
Input Voltage ◽  
Second Order ◽  
Buck Converter ◽  
Constant Current ◽  
Current Load ◽  
Time Model ◽  
Conduction Mode

The complex dynamics and coexisting fast-slow scale instability in current-mode controlled buck converter with constant current load (CCL), operating in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM), are investigated in this paper. Via cycle-by-cycle computer simulation and experimental measurement of current-mode controlled buck converter with CCL, it is found that a unique fast-slow scale instability exists in the second-order switching converter. It is also found that a unique period-doubling accompanied by Neimark–Sacker bifurcation exists in this simple second-order converter, which is different from period-doubling or Neimark–Sacker bifurcations reported previously. Based on a nonlinear discrete-time model and the corresponding Jacobian, the effects of CCL and input voltage on the dynamics of current-mode controlled buck converter are investigated and verified theoretically. Fixed point analysis for slow-scale low-frequency oscillation is also given to verify the dynamics and the coexisting fast-slow scale instability.

Research on the Type of Electrical Contact at Metal-Insulator Interface

2011 ◽  
Vol 383-390 ◽  
pp. 5154-5157
Author(s):  
Qian Peng ◽  
Li Ren Zhou
Keyword(s):  
Electrical Contact ◽  
Depletion Region ◽  
Energy Band Structure ◽  
Metal Insulator ◽  
Band Bending ◽  
Whole Process ◽  
Insulator Interface ◽  
Metal Insulator Metal ◽  
Electrode Metal ◽  
Nor Band

This paper takes metal-insulator-metal system as example and investigates the main types of electrical contact through the view of energy band structure, to analyze the whole process of the transition from ohm contact to barrier contact. Ohm contact, which promotes charges injection from electrode (metal) to insulator, can be used as storage of charge carrier, which is body limited; it can also be regarded as a type of contact that forms an accumulation layer extending from the interface to the interior of the insulator. Whereas, barrier contact is a type of contact which forms a depletion region extending from the interface to the interior of insulator. As for this type of contact, electron injection from metal tends to the state of saturation. The characteristic of neutral contact is that there is no space charge in the insulator, nor band bending, which means the boundary of conduction band and valence band up to the interface is flat.

ZERO-CROSS INSTANTANEOUS STATE SETTING FOR CONTROL OF A BIFURCATING H-BRIDGE INVERTER

2007 ◽  
Vol 17 (10) ◽  
pp. 3571-3575 ◽  
Author(s):  
SATOSHI AKATSU ◽  
HIROYUKI TORIKAI ◽  
TOSHIMICHI SAITO
Keyword(s):  
Pulse Width Modulation ◽  
Control Method ◽  
Period Doubling ◽  
Current Mode ◽  
Nonlinear Phenomena ◽  
Unstable Periodic Orbits ◽  
Bifurcation And Chaos ◽  
Zero Crossing ◽  
Modulation Signal ◽  
A Current

This paper studies stabilization of low-period unstable periodic orbits (UPOs) in a simplified model of a current mode H-bridge inverter. The switching of the inverter is controlled by pulse-width modulation signal depending on the sampled inductor current. The inverter can exhibit rich nonlinear phenomena including period doubling bifurcation and chaos. Our control method is realized by instantaneous opening of inductor at a zero-crossing moment of an objective UPO and can stabilize the UPO instantaneously as far as the UPO crosses zero in principle. Typical system operations can be confirmed by numerical experiments.

scholarly journals The Use of Electrodialysis to Prepare Aqueous Bread Extracts for Bromate Determination by Chemiluminescence

2005 ◽  
Vol 88 (3) ◽  
pp. 794-799
Author(s):  
Katsuichi Himata ◽  
Charles Warner ◽  
Douglas Currie ◽  
Qian Graves ◽  
Gregory Diachenko
Keyword(s):  
Current Mode ◽  
Sulfate Solution ◽  
Oxidation Products ◽  
Constant Current ◽  
Semipermeable Membranes ◽  
Anode Oxidation ◽  
Cleanup Procedure ◽  
Collection Period ◽  
Hot Dog ◽  
Hydroxylamine Sulfate

Abstract A cleanup procedure based on electrodialysis is described for the preparation of aqueous bread extracts for bromate determination by chemiluminescence. The technique utilizes electrophoresis with 3 chambers separated by semipermeable membranes. The relative merits of reverse osmosis (RO), ultrafiltration, and nanofiltration membranes with various molecular weight cutoffs were evaluated. The best results were obtained with an RO membrane manufactured from thin-film (composite) polysulfone as support for polyamide. A 0.14M sodium sulfate solution in the center or collection chamber provides optimum conductivity. Aqueous hydroxylamine sulfate (30mM) was selected for the anode compartment as a reductant for the anode oxidation products. The constant current mode at 150 mA with a potential of ca 100 volts was used. After electrophoretic separation, the bromate concentration in the collection chamber was typically 2 to 3 times greater than the concentration in the bread extract. The chemiluminescent reaction of bromate with sulfite with hydrocortisone as the enhancer was selected for detection of bromate. The emission, with a wavelength maximum at 575 nm, was found to “glow” rather than “flash” after the reagents were mixed; therefore, it was possible to optimize the light collection period. The method was validated with a variety of commercial bread products. White bread, hot dog buns, hamburger rolls, and a multigrain bread from 7 different manufacturers were studied.

scholarly journals New Current-Mode Integrated Ternary Min/Max Circuits without Constant Independent Current Sources

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Mona Moradi ◽  
Reza Faghih Mirzaee ◽  
Keivan Navi
Keyword(s):  
Integrated Circuit ◽  
Power Dissipation ◽  
Field Effect Transistors ◽  
Current Source ◽  
Integrated Design ◽  
Current Mode ◽  
Constant Current ◽  
Constant Current Source ◽  
Static Power ◽  
Current Flows

Novel designs of current-mode Ternary minimum (AND) and maximum (OR) are proposed in this paper based on Carbon NanoTube Field Effect Transistors (CNTFET). First, these Ternary operators are designed separately. Then, they are combined together in order to generate both outputs concurrently in an integrated design. This integration results in the elimination of common parts when both functions are required at the same time. The third proposed current-mode integrated circuit generates both ternary operators with the usage of only 30 transistors. The new designs are composed of three main parts: (1) the part which converts current to voltage; (2) threshold detectors; and (3) the parallel paths through which the output current flows. Unlike the previously presented structure, there is no need for any constant current source within the new designs. This elimination leads to less static power dissipation. The second proposed current-mode segregated Ternary minimum operates 43% faster and consumes 40% less power in comparison with a previously presented structure.

Bulk Carbon Nanotubes for Micro Anemometry (Invited Paper)

2003 ◽  
Author(s):  
Victor T. S. Wong ◽  
Wen J. Li
Keyword(s):  
Current Mode ◽  
Constant Current ◽  
Experimental Measurements ◽  
Dynamic Characterization ◽  
Temperature Coefficient Of Resistance ◽  
Micro Electro Mechanical Systems ◽  
Mode Configuration ◽  
Multi Walled Carbon Nanotube ◽  
Constant Current Mode ◽  
Bulk Carbon

We have successfully developed a process to manipulate post-growth multi-walled carbon nanotube (MWNT) by AC electrophoresis to form resistive elements and showed that these elements can potentially served as novel sensing elements for micro/nano thermal and anemometry sensing. We have measured the temperature coefficient of resistance (TCR) of these MWNT bundles and integrated them into constant current mode configuration for dynamic characterization. Preliminary experimental measurements showed that the devices could be operated in micro-watt power range for micro thermal and anemometry sensing. This operation range is three orders of magnitude lower than conventional Micro-Electro-Mechanical Systems (MEMS) polysilicon sensors in constant current (CC) mode configuration. In addition, the devices exhibited very fast frequency response (> 100 kHz) in CC mode. Based on these results, we are currently developing polymer-based MWNT embedded sensor for various micro/nano fluidic applications.

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