Negative photoconductance in 150 GHz transients from irradiated p-type Cz-Silicon

Boron doped (p-type) silicon wafers of the same type are irradiated with gamma, proton and chlorine ion beams. This causes radiation damage in the form of migration of vacancies, traps to photoelectrons. We use time-resolved millimeter wave pump-probe spectroscopy (150 GHz CW probe signal) and 532 nm ultrafast laser as pump source with variable fluence. Upon studying the transient response of the detector probe voltage as function of the pump-probe delay period we note a good positive (absorption) photoconductance peak and soon after recombination of photocarriers there occurs a negative photoconductance (NPC) transient. We consistently find that the NPC lasts for about 36 microseconds and this study points out that the positive to NPC peaks for each laser fluence varies with the type of radiation damaged samples.2 MeV proton beam damage create damage that trap carriers very effectively, and enhances the resistivity of the silicon wafer from 15 Ohms to 150 Ohms. The Chlorine ion damaged silicon responds consistently to the 150 GHz probe beam and correlates strongly with the laser fluence.

Negative photoconductance in 150 GHz transients from irradiated p-type Cz-Silicon

Boron doped (p-type) silicon wafers of the same type are irradiated with gamma, proton and chlorine ion beams. This causes radiation damage in the form of migration of vacancies, traps to photoelectrons. We use time-resolved millimeter wave pump-probe spectroscopy (150 GHz CW probe signal) and 532 nm ultrafast laser as pump source with variable fluence. Upon studying the transient response of the detector probe voltage as function of the pump-probe delay period we note a good positive (absorption) photoconductance peak and soon after recombination of photocarriers there occurs a negative photoconductance (NPC) transient. We consistently find that the NPC lasts for about 36 microseconds and this study points out that the positive to NPC peaks for each laser fluence varies with the type of radiation damaged samples.2 MeV proton beam damage create damage that trap carriers very effectively, and enhances the resistivity of the silicon wafer from 15 Ohms to 150 Ohms. The Chlorine ion damaged silicon responds consistently to the 150 GHz probe beam and correlates strongly with the laser fluence.

Conductivity inversion of unidirectional CFRP laminate based on ECT using neural network

For the electrical anisotropy of carbon fiber reinforced polymer (CFRP), conductivity of unidirectional CFRP laminate in three directions was inverted in this paper. The three-dimensional eddy current electromagnetic model of unidirectional composites was constructed by ANSYS software, and the influence of the electrical conductivity of the material on the detection signal of the probe in the longitudinal, transverse and thickness directions was studied. In order to improve the amplitude of the probe output signal induced by the change of conductivity, the optimal detection angle of the eddy current probe was determined. On this basis, the relationship between the conductivity and the detection signal was studied to estimate the initial values of the conductivity based on the experimental data obtained by the eddy current testing (ECT). According to the forward model, the theoretical probe voltage under the estimated conductivity were calculated. The database consisting of conductivity and corresponding theoretical results was built for the neural network to construct the mapping that can estimate conductivity by experimental results. Using neural network for iteration, the conductivity was inverted quickly and precisely.

Effects of Filler Wire Intervention on Gas Tungsten Arc: Part II - Dynamic Behaviors of Liquid Droplets

In gas tungsten arc welding (GTAW), the filler wire in-creases the deposition efficiency and influences the welding stability. Its interactions with the gas tungsten arc (GTA) are significant to better understand the welding process and to monitor and control weld quality. In view of this, the first part of the work, Effects of Filler Wire Intervention on Gas Tungsten Arc: Part I — Mechanism, explained the inter-action mechanisms between the filler wire and the gas tungsten arc based on the proposed arc-sensing method of detecting probe voltage (i.e., the voltage signal between the filler wire and the tungsten electrode/workpiece). In this second part of the work, experiments were designed to make the filler wire melt in different areas of the arc to study the dynamic behaviors of the droplet and its effect on the arc. Typical metal transfer modes are discussed, and droplet oscillation is geometrically characterized through image processing and then analyzed in the time domain and time-frequency domain. The results show that the liquid droplet affects the arc through its transfer to the weld pool, its oscillation, and occupying the arc space. Information about these dynamic behaviors can be easily reflected in the probe voltage, which would be a valuable signal to monitor the process stability in GTAW with filler wire. This work shows the potential of the proposed sensing method for monitoring and controlling weld quality in all welding positions, GTA-based additive manufacturing, etc.

Zn2+ to probe voltage-gated proton (Hv1) channels

Cherny and coworkers use zinc ion as a probe to identify different conformational states of voltage-gated proton (Hv1) channels.

Effects of Filler Wire Intervention on Gas Tungsten Arc: Part I - Mechanism

For gas tungsten arc welding (GTAW), the effects of filler wire on the GTA are worth being clarified, which will help deepen the understanding of arc characteristics and in-spire new ideas for the real-time monitoring of weld quality. To this end, this work proposed a novel sensing method of detecting probe voltages (i.e., the voltage signals between a filler wire and tungsten electrode/workpiece). Based on this method, in this first part of the work, a tungsten probe was used to replace the filler wire and to interact with the arc in the specific experiments to elucidate the static and dynamic interaction mechanisms between the GTA and filler wire. The results showed that the filler wire intervention deflects the arc to various degrees and will change the volt-age signals. As a metal conductor, the filler wire will in-crease the arc voltage by increasing the average electric field strength. However, its effects on the different areas of the arc are not always consistent, which makes the change trend of the probe voltages not always the same. Moreover, due to thermal inertia, the probe voltage does not strictly change synchronously with the arc voltage under the dynamic disturbance. This work lays a theoretical foundation for monitoring the stability of the GTAW process.

Emission portrait of surface of reinforcing structural material

Atoms on the surface of solids are in the form of negative ions. To analyze the emission portrait of the crystal surface with scanning tunnel microscope with tungsten probe, voltage of not more than 2 V should by applied. Studied autoelectronic emission in scanning tunnel microscope is realized from one emission center. In scanning tunnel microscope, ponderomotor forces significantly distort of the surface structure of solid. Autoelectronic emission from the surface of solid is performed together with negative ions and Fermi level.

Локальное анодное окисление слоев графена на SiC

A method of local anodic oxidation has been used to obtain graphene-oxide regions on SiC. The change of the surface properties was confirmed by atomic-force microscopy and Raman spectroscopy. Experimental data were obtained on the conductivity, potential, and topography of the oxidized regions. It was shown that the oxidation leads to a rise in the surface potential. A relationship was found between oxidation parameters, such as the scanning velocity and the probe voltage. The method of local anodic oxidation was used to obtain by lithography an ~20-nm-wide nanoribbon and an ~10-nm-wide nanoconstriction.

CURRENT VOLTAGE CHARACTERISTIC OF PLANAR LANGMUIR PROBE IN IONOSPHERIC MAXWELLIAN PLASMA

Frequently used geometries of Langmuir probes are planar, spherical, and cylindrical shapes. The geometry is chosen depending on the purpose of the measurements and the platform configuration. Planar Langmuir Probes have been installed on satellites and sounding rockets to observe the general characteristics of thermal plasma in the ionosphere for more than five decades. Because of its simplicity and convenience, the Langmuir probe is one of the most frequently installed scientific instruments on spacecraft. The Planar Langmuir Probe is the key plasma diagnostic used by scientists interested in plasma characterization to measure the internal parameters of the bulk of the plasma. This research explores the theoretical study of Planar Langmuir Probe I-V Characteristics. The relationship between first derivative of current verses applied probe voltage is also computed. With the help of the (volt–ampere curves) of Planar Langmuir probes, the different parameters of plasma can be determined such as plasma potential, floating potential, probe currents in different probe voltage and so on. Planar Langmuir probe geometry is easy to construct and equally suitable for plasma characterization.