Mean Pulse Widths Research Articles

Characterization of charge sharing induced by high LET heavy ions using inverter chains in a commercial bulk FinFET process

The inverter is one of the most important cell types in any standard cell library at each technology node, and it is also very important for single-event research. The distributions and cross-sections of single-event transients (SETs) and single-event multiple transients (SEMTs) were characterized using 14/16 nm bulk fin field-effect transistor (FinFET) inverters under heavy ion radiation. An inverter with double driving strength (INVX2) was used as an instantiate object to observe the SET and SEMT response. 181Ta with energies of 1891 GeV and 2000.5 MeV were used respectively in the experiments, of which the linear energy transfer (LET) values were 87.4 MeV cm2 mg−1 and 75.4 MeV cm2 mg−1. The test results indicated that: (a) the mean pulse widths of the SET and SEMT were less than 100 ps, and decreased with LET decreasing; (b) there was charge sharing between abutted INVX2 inverters placed horizontally, and the generation probability of SEMT induced by charge sharing was less than 1% even if the LET of heavy ion reached 87.4 MeV cm2 mg−1. The results were beneficial for a better understanding of SET and SEMT tolerance for inverters in FinFET technology.

Sulphur-fuelled Surface Arc Thruster for Propelling Nanosatellites

Pulsed electrothermal thrusters use kiloampere discharge currents for polytetrafluoroethylene (PTFE) ablation and sublimation. However, higher arc currents cause higher electromagnetic interference (EMI). A 10 J surface arc thruster (SAT), which adopts current regulating diodes (CRD), was developed that enables significant reduction in EMI. A CRD limits the discharge currents to 5 A in spite of the applied voltage. A low-melting-point sulphur propellant has been used that enables low-discharge currents to efficiently ablate it and accelerate it electrothermally. In this paper, the near-term potential for elemental sulphur propellant in SAT is investigated. The advantages of sulphur with respect to PTFE are presented. First, we measured the pulse width of the main discharge. Then sulphur propellant proved superior to PTFE propellant in discharge duration. The mean pulse widths of PTFE and sulphur are 3.38 and 22.1 ms, respectively. Second, we measured the pressure rise in the vacuum chamber after each discharge. The mean pressure rises of PTFE, sulphur powder and sulphur solid are 0.43, 0.94 and 1.9 mPa, respectively. Sulphur powder experienced the least intensity of discoloration in comparison with other propellants. The discharge initiator misfired frequently during PTFE ablation, but it ignited successively during sulphur ablation. Experimental results indicate sulphur is a suitable propellant for surface discharge propulsion, and for low arc currents is superior to PTFE.

5.0 GHz TMRT Observations of 71 Pulsars

Abstract We present integrated pulse profiles at 5 GHz for 71 pulsars, including eight millisecond pulsars (MSPs), obtained using the Shanghai Tian Ma Radio Telescope. Mean flux densities and pulse widths are measured. For 19 normal pulsars and one MSP, these are the first detections at 5 GHz—and for a further 19, including five MPSs, the profiles have a better signal-to-noise ratio than previous observations. Mean flux density spectra between 400 MHz and 9 GHz are presented for 27 pulsars and correlations of power-law spectral index are found with characteristic age, radio pseudo-luminosity, and spin-down luminosity. Mode changing was detected in five pulsars. The separation between the main pulse and interpulse is shown to be frequency independent for six pulsars, but a frequency dependence of the relative intensity of the main pulse and interpulse is found. The frequency dependence of component separations is investigated for 20 pulsars, and three groups are found: in seven cases, the separation between the outmost leading and trailing components decreases with frequency, roughly in agreement with radius-to-frequency mapping; in 11 cases, the separation is nearly constant; in the remaining two cases, the separation between the outmost components increases with frequency. We obtain the correlations of pulse widths with pulsar period and estimate the core widths of 23 multicomponent profiles and conal widths of 17 multicomponent profiles at 5.0 GHz using Gaussian fitting, and we discuss the width-period relationship at 5 GHz compared with the results at at 1.0 and 8.6 GHz.

Random telegraph signal noise in gate current of unstressed and reverse-bias-stressed AlGaN/GaN high electron mobility transistors

Random telegraph signal (RTS) fluctuations with relative amplitude up to 50% are observed in forward and reverse gate current of unstressed and reverse-bias-stressed AlGaN/GaN high electron mobility transistors. Measurements of RTS amplitude and mean pulse widths as a function of forward gate bias indicate that the RTS is due to modulation of current along an intrinsic or stress-induced percolation path across the AlGaN-barrier by electron capture and emission on a trap within the barrier. Processes of electron capture from GaN to trap and subsequent tunneling to metal gate or electron exchange between GaN channel and the trap are considered.

REVERBERATION IN THE UV-OPTICAL CONTINUUM BRIGHTNESS FLUCTUATIONS OF MACHO QUASAR 13.5962.237

We examine the nature of brightness fluctuations in the UV-Optical spectral region of an ordinary quasar with 881 optical brightness measurements made during the epoch 1993 - 1999. We find evidence for systematic trends having the character of a pattern of reverberations following an initial disturbance. The initial pulses have brightness increases of order 20% and pulse widths of 50 days, and the reverberations have typical amplitudes of 12% with longer mean pulse widths of order 80 days and pulse separations of order 90 days. The repeat pattern occurs over the same time scales whether the initial disturbance is a brightening or fading. The lags of the pulse trains are comparable to the lags seen previously in reverberation of the broad blue-shifted emission lines following brightness disturbances in Seyfert galaxies, when allowance is made for the mass of the central object. In addition to the burst pulse trains, we find evidence for a semi-periodicity with a time scale of 2 years. These strong patterns of brightness fluctuations suggest a method of discovering quasars from photometric monitoring alone, with data of the quality expected from large brightness monitoring programs like Pann-Stars and LSST.

Impact of carbon concentration on 1∕f noise and random telegraph signal noise in SiGe:C heterojunction bipolar transistors

The influence of carbon concentration on the low-frequency noise (LF noise) of Si∕SiGe:C∕Si heterojunction bipolar transistors (HBTs) is investigated. When carbon is incorporated into these HBTs, representative noise spectra of the input current spectral density SIB show significant generation-recombination (GR) components. On the other hand, for transistors without carbon incorporation, no GR components were observed. When only 1∕f noise component is observed, the 1∕f noise level is found to be independent of the carbon concentration and the associated figure of merit of the normalized noise magnitude KB has a very good value of ∼4×10−10μm2. In order to relate the 1∕f noise and the high-frequency performance of the transistor, we studied and modeled the figure of merit defined as the ratio fc∕fT (fc is the low-frequency corner frequency and fT the unity current-gain frequency). Then we performed a detailed analysis of the GR components associated with the presence of the carbon. We found that the observed Lorentzian spectra are associated with random telegraph signal (RTS) noise. However, no RTS noise was measured in carbon-free devices. It is believed that the RTS noise is due to electrically active defects formed by the addition of carbon, typically observed for concentrations above the bulk solid solubility limit in silicon. The RTS amplitude (ΔIB) is found to scale with the base current, to decrease exponentially with temperature, and to be independent of the carbon concentration. The mean pulse widths (tH,tL) of the RTS are found to decrease rapidly with bias voltage, as 1∕exp(qVBE∕kT) or stronger. Our results confirm that electrically active C-related defects are located in the base-emitter junction, and the RTS amplitude is explained by a model based on voltage barrier height fluctuations across the base-emitter junction induced by trapped carriers in the space charge region. The observed bias dependence of mean pulse widths seems to indicate that two capture processes are involved, electron and hole capture. These C-related defects behave like recombination centers with deep energy levels rather than electron or hole traps involving trapping-detrapping processes.

Radio emission from AXP and XDINS

The result of the search for, and the observations of radio emission from two groups of isolated neutron stars: AXP 1E 2259+586 and XDINS 1RXS J1308.6+212708 and 1RXS J214303.7+065419 are reported. The observations were carried out on two sensitive transit radio telescopes at a few frequencies in the range 42–112 MHz. The flux densities, mean pulse profiles, as well as, the estimation of the dispersion measures, distances and integrated radio luminosities of all objects are presented. Comparison with X-ray data shows large differences in the mean pulse widths and luminosities.

Radio Emission from Anomalous X-ray Pulsars

Observations of AXP 1E 2259+586 and XDINS 1RXS J1308.6+212708 at 111, 87, 61 and 42 MHz are reported. Mean pulse profiles, as well as, the estimation of the dispersion measures, distances, spectral indices, and integrated radio luminosities of both objects are presented. Comparison with X-ray data shows large differences in the mean pulse widths and luminosities. The detection of radio emission from these two X-ray pulsars, together with other data, suggests the need to revise the radio-emission mechanisms in the magnetar model or the magnetar model itself.

Radio emission from two anomalous X-ray pulsars

Observations of the anomalous X-ray pulsar (AXP) 1E 2259+586 and the AXP candidate 1RXS J1308.6+212708 at 111, 87, and 61 MHz are reported. The observations were carried out on two high-sensitivity radio telescopes of the Pushchino Radio Astronomy Observatory. Mean pulse profiles are presented, and the dispersion measures, distances, spectral indices, and integrated radio luminosities of both objects are estimated. Comparison with X-ray data shows large differences in the mean pulse widths and luminosities. The detection of radio emission from these two AXPs, together with other data, suggests the need to revise the radio-emission mechanisms in the magnetar model or the magnetar model itself.

Random telegraph signal noise mechanisms in reverse base current of hot carrier-degraded submicron bipolar transistors: Effect of carrier trapping during stress on noise characteristics

We investigate physical mechanisms of random telegraph signal (RTS) noise in reverse base current of hot carrier-degraded polysilicon emitter bipolar junction transistors. RTS noise, analyzed in the time domain, is studied as a function of reverse base-emitter bias, temperature, and additional reverse-bias stress. Two-level RTS with a relative amplitude as high as 100% is observed at room temperature. The RTS amplitude varies exponentially with the applied reverse base-emitter voltage and depends weakly on temperature. The additional hot carrier stress is observed to induce changes in RTS amplitude and mean pulse widths (independent or correlated), and a disappearance/reappearance of the RTS fluctuations. The results are interpreted by a model where the RTS noise is caused by fluctuations of generation-recombination (g-r) parameters (i.e., capture cross sections and energy position in the gap) of a stress-induced complex bistable defect (CBD) at the Si/SiO2 interface. The complex defect is assumed to be either a two-state fast interface state or an interacting pair of a fast interface state with a slow neighboring border trap. The RTS amplitude is well explained by fluctuations in a single-defect electric-field-enhanced g-r rate between a finite value and naught. The RTS amplitude-bias characteristics and their temperature dependence are satisfactorily accounted for by an expression for a phonon-assisted tunneling current via a single deep-level state. The model parameters are the g-r parameters of the defect and its spatial position in the base-emitter p–n junction. The stress-induced changes in the RTS noise are attributed to the influence of log-time trapping of hot carriers on border states laying in the vicinity of a CBD center. The charged border traps interact with a CBD, changing both its g-r parameters and the RTS switching behavior. The variations in RTS parameters are related to the microscopic nature of the interaction and are discussed for the two types of the CBDs.

Random telegraph noise and leakage current in smart power technology DMOS devices

Random telegraph signal (RTS) noise, analyzed in time and frequency domains, and leakage current are studied in smart power technology double-diffused metal oxide semiconductor (DMOS) field effect transistors. The RTS noise is strongly correlated with the presence of an excess leakage current in the device. The observed drain current (gate bias) dependencies of relative (absolute) RTS amplitude and gate voltage dependence of RTS mean pulse widths suggest that the RTS noise sources are located under the gate and in the drain-body region. A model, where the multicell DMOS structure is considered as parallel connection of submicron MOSFETs, is proposed to account for the results.

Pulsatile growth hormone release in normal women during the menstrual cycle.

We sought to characterize pulsatile growth hormone (GH) release in normal women during the menstrual cycle and to document possible relationships between such characteristics and concentrations of 17 beta-oestradiol and progesterone. Fifteen women with ostensibly normal menstrual function were studied during the early follicular phase, 15 during the late follicular phase and 15 during the mid-luteal phase of the menstrual cycle. The phase of the menstrual cycle having been documented, blood samples were obtained from each woman every 10 minutes for 24 hours. Serum GH was measured in each sample by immunoradiometric assay. Pulsatile GH release was appraised utilizing the objective, statistically-based pulse detection algorithm Cluster. The mean (+/- SEM) integrated serum GH concentration (mU/l min) in late follicular phase women (5335 +/- 848) was higher than that observed in early follicular phase women (3156 +/- 322; P = 0.032). The integrated GH concentration calculated for mid-luteal phase women (3853 +/- 788) was intermediate between but not statistically different from that observed in early follicular (P = 0.48) and late follicular (P = 0.14) phase women. No differences in GH pulse frequency (pulses/24 hours) were found among early follicular (8.27 +/- 0.55), late follicular (7.93 +/- 0.91) or mid-luteal (8.47 +/- 0.66) phase women. Mean maximal GH pulse amplitude (mU/l) was higher in late follicular phase (8.93 +/- 1.00) than early follicular phase (5.74 +/- 0.67; P = 0.008) and mid-luteal phase (5.76 +/- 0.74; P = 0.008) women. Similarly, incremental GH pulse amplitude (mU/l) was higher in late follicular phase (7.33 +/- 0.83) than early follicular phase (4.68 +/- 0.58; P = 0.005) and mid-luteal phase (4.36 +/- 0.39; P = 0.002) women. No differences in mean pulse widths or in the interpeak valley mean GH concentrations were found among the groups. Multiple regression of each pulse parameter against serum concentrations of testosterone, 17 beta-oestradiol and progesterone revealed a significant (P = 0.045) positive correlation between maximum GH pulse amplitude and oestradiol and a significant (P = 0.04) negative correlation between maximal GH pulse amplitude and progesterone (r = 0.41). These results suggest that late follicular phase concentrations of oestradiol may enhance circulating GH via an amplitude-modulated rather than a frequency-modulated effect on the endogenous GH pulse. Progesterone may blunt this oestrogen-associated effect, thus resulting in the observed mid-luteal phase concentrations of GH. Whether these gonadal hormones act primarily at the hypothalamus and/or anterior pituitary gland remains to be clarified, but the present observations indicate that pulsatile GH release throughout the normal menstrual cycle is significantly amplitude regulated.