Effect Of Negative Bias Research Articles

Effect of DC negative bias on structure and properties of nitrogen doped diamond–like carbon films synthesized by HWP–CVD technique

In this paper, nitrogen doped diamond–like carbon (N–DLC) films are successfully prepared by helicon wave plasma (HWP) on silicon substrates in Ar/CH4/N2 gas mixtures at different DC negative bias voltages (–VDC). The surface morphology, structure and properties of N–DLC films have been studied by SEM, AFM, Raman and XPS. The deposition rate of the film decreases with increasing –VDC from 0 V to –50 V. The results of Raman spectra show that ID/IG decreases from 1.22 to 1.10 with increasing –VDC. The elemental surface composition of the N–DLC films has been analyzed by XPS. The results show that the N content and sp3/sp2 ratio of the N–DLC films increase with the increase of –VDC. Young's modulus values measured by AFM in SPM mode also show the expected increase with increasing –VDC. Moreover, the N–DLC electrode has been used to study the electrochemical reversibility.

Эксплицитная и имплицитная обработка негативных и нейтральных экспрессий лица при депрессии

The effect of negative bias in information processing in persons with depression is widely discussed in the literature. This perception bias is viewed as a possible mechanisms of the overall emotional decrease in patients with depression. However, most studies in this area were conducted using explicit processing of emotionogenic information. The results were ambiguous and sometimes showed the effects of positive bias in healthy respondents. In this study, an experimental design with both explicit and implicit processing of emotional stimuli was implemented. The face images of negative and neutral valence were shown in groups of healthy respondents and patients with depression. Among 106 participants there were 57 patients with moderate depression. The participants were presented with images of faces with neutral or angry expressions (Lundqvist et al., 1998) and instructed to count their number based on emotional valence in the explicit condition, or gender in the implicit condition (De Lyssnyder et al., 2012). A comparison of processing time by group, valence and task, showed complementary effects in tasks with explicit process- ing. The patients with depression took longer to process negative stimuli, and the healthy participants spent more time processing neutral stimuli. In the implicit processing condition, the healthy respondents did not display any significant differences in processing times for negative and neutral images, while the patients were still fixating on negative images. However, after statistically controlling the age-related effects, these differences were reduced to a strong fixation on neutral faces during explicit processing in the non-depressed group. The results suggest a possible preventative mechanism — preferential processing of positive information — providing protection from depressive symptoms. This view offers an alternative explanation to possible causes of depression onset in contrast with a pathogenic mechanism of fixation on negative information in patients with depression.

Mental health status of Chinese residents during the COVID-19 epidemic

BackgroundTo investigate the mental health status of Chinese residents during the epidemic of COVID-19, as well as to identify the positive and negative factors and regulatory effect of negative cognitive processing bias on mental health.MethodsA total of 60,199 residents in China were surveyed via an internet-based survey containing a general questionnaire, such as the self-rating depression scale, the state anxiety inventory, and the negative cognitive processing bias questionnaire. An ordered multiple logistic regression analysis model was used to analyze the collected data.ResultsThe survey revealed mild, moderate, and severe depressive symptoms in 62.65, 11.33, and 6.14% participants, respectively, and mild, moderate, and severe anxiety symptoms in 33.21, 41.27, and 22.99% participants, respectively. Multiple logistic regression analysis showed that factors, such as female gender, being older than 55 years, high school education level, medical staff, marital conflicts, negative attention bias, rumination, and death growth rate, positively affected depression and anxiety symptoms. The good family functionality, democratic working atmosphere, and a myriad of social activities negatively affected the level of depressive and anxiety symptoms.ConclusionChinese residents exhibited a high prevalence of anxiety and depressive symptoms during the epidemic. Thus, psychological interventions should focus on the vulnerable groups, and cognitive training should focus on reducing the negative cognitive processing bias. This might be an effective way to alleviate the mental stress of the general public during the COVID-19 pandemic.

Dysfunction in Automatic Processing of Emotional Facial Expressions in Patients with Obstructive Sleep Apnea Syndrome: An Event-Related Potential Study.

AimObstructive sleep apnea syndrome (OSAS) is a prevalent chronic disease characterized by sleep fragmentation and intermittent hypoxemia. Several studies suggested that electrophysiological changes and neurocognitive abnormalities occurred in OSAS patients. In this study, we compared automatic processing of emotional facial expressions schematic in OSAS patients and matched healthy controls via assessing expression-related mismatch negativity (EMMN).MethodsTwenty-two OSAS patients (mean age 44.59 years) and twenty-one healthy controls (mean age 42.71 years) were enrolled in this study. All participants underwent Montreal Cognitive Assessment (MoCA) scale test and polysomnographic recording. An expression-related oddball paradigm was used to elicit EMMN and the electroencephalogram was recorded and analyzed. Furthermore, Pearson’s correlations were calculated to discuss the correlation between neuropsychological test scores, clinical variables and electrophysiological data.ResultsCompared with healthy controls, OSAS sufferers demonstrated significantly reduced EMMN mean amplitudes within corresponding time intervals, regardless of happy or sad conditions. Meanwhile, we observed that amplitude of sad EMMN was larger (more negative) than happy EMNN in healthy controls, while not in patients. Moderate correlations were found between MoCA test scores, sleep parameters and EMMN amplitudes.ConclusionOur findings suggested pre-attentive dysfunction of processing emotional facial expressions in patients with OSAS, without the existence of negative bias effect. Moreover, correlation analysis showed that clinical characteristics of OSAS patients could affect EMMN amplitudes. Further studies on the advantages of EMMN as clinical and electrophysiological indicators of OSAS are warranted.

Low-temperature deposition of large-grain polycrystalline Si thin films on polyethylene terephthalate

p-Si thin films with large grains have been fabricated on polyethylene terephthalate substrate by radio frequency plasma enahnced chemical vapor deposition under the assist of negative substrate bias. The micro-structural, optical and electrical properties of the as-deposited thin films are studied by X-ray diffraction, Raman scattering spectroscopy, scanning electron microscope, transmission electron microscopy, optical transmittance spectra and Hall measurement. The test results show that negative bias at moderate level promotes crystallization even at very low substrate temperature (100 ℃), and the large p-Si grain with the size of ~150–300 nm can be obtained at the negative of 100 V. Detailed analysis has been performed for illustrating the effect of negative bias on the growth of p-Si thin film.

Pre-attentive dysfunction of processing emotional faces in interictal migraine revealed by expression-related visual mismatch negativity

BackgroundSeveral investigations have indicated emotional processing impairment in migraineurs, while no report is available considering the automatic processing of emotional information. In this study, we aimed to characterize the pre-attentive processing of facial expressions in migraine sufferers by recording and analyzing expression-related visual mismatch negativity (EMMN). MethodsAltogether, 30 migraineurs (19 females) during the interictal period and 30 age-matched healthy controls (17 females) were recruited. An expression-related oddball paradigm was used to investigate automatic emotional processing, and a group of schematic emotional faces (neutral, happy, sad) unrelated to the participant’s task were employed in the experiment in order to avoid low-level processing. ResultsThere was no significant difference in behavioral performance (the response accuracy and reaction time) between migraine patients and healthy controls. Nevertheless, the mean EMMN amplitudes within the ranges of 150–250 ms and 250–350 ms were markedly attenuated in patients compared with controls, regardless of happy or sad condition (happy minus neutral or sad minus neutral), and sad EMMN was observed to be larger than happy EMMN only in healthy participants. Moreover, these electrophysiological data directly correlated with frequency and duration of migrainous attacks. ConclusionsOur findings implied that the pre-attentive dysfunction of processing both happy and sad expressions was demonstrated in interictal migraineurs, without the existence of negative bias (sad superiority) effect. Further studies on the availability of EMMN as an evaluative marker for migraine are warranted.

Effect of DC negative bias on microstructure and surface morphology of amorphous silicon carbide films prepared by HWP-CVD

The effect of DC negative bias (− Vs) on microstructure and surface morphology of amorphous silicon carbide thin films prepared by helicon wave plasma chemical vapor deposition is reported. Microstructure and surface morphology were obtained by scanning electron microscope (SEM) and atomic force microscope (AFM). The results show that the increase of − Vs on the substrate make a more compact film and lower surface roughness, which can reach 0.56 nm. The XRD analysis reveals that the SiC thin films are of an amorphous structure. Percentages of carbon and silicon atoms (C/Si) were measured by energy dispersive spectrometer (EDS), and the C/Si ratio can reach 1.45. The structural properties of the films were studied by Raman spectroscopy techniques and Fourier transform infrared (FTIR). It is found that the films contain not only Si–C bonds but also Si–CHx bonds. Raman spectra results show that the proportion of disordered carbon in the films decreases with the increase of − Vs. The results of ultra-microhardness tester show that the hardness of the films increases with the increase of − Vs and the maximum mechanical hardness can reach 18.5 GPa at − Vs = − 60 V.

Effect of Substrate Bias Voltage on the Structure and Properties of Mos2-Ti Composite Films on Titanium Alloy Surface

In order to discuss the effect of negative bias on the structure and properties of MoS2-Ti composite films on titanium alloy surface. In this paper, MoS2-Ti solid lubrication films were deposited on titanium alloy surface by unbalanced magnetron sputter. The effects of negative bias on the structure and properties of MoS2-Ti solid lubrication films were discussed. The morphology, phase, hardness, friction and wear resistance and wear mark morphology of solid lubricating film were analyzed and tested by scanning electron microscope, XRD, microhardness tester, friction and wear tester and surface profilometer. The results shows that wwhen the negative bias voltage was -150V and -200V, the structure of MoS2-Ti films is compact and the bonding with the substrate is compact. With the increase of negative bias voltage, the hardness of the film increases gradually. The wear rate of the films prepared at -150V bias voltage is the lowest, which is 2.2×10−17mm3/(N×m). The MoS2-Ti composite films deposited on the surface of titanium alloy exhibit excellent tribological properties with low friction and wear resistance, which effectively improves the surface friction and wear properties of titanium alloy.

A comprehensive evaluation of radiation hardening by applying negative body bias and back-gate bias in 130 nm PDSOI technology

This paper comprehensively evaluates the effects of negative body bias and negative back-gate bias on the total ionizing dose (TID) effects in 130 nm partially-depleted (PD) SOI technology. We studied the T-gate/H-gate nMOSFETs and pMOSFETs, and found that the negative body bias is ineffective for radiation hardening. However, the negative back-gate bias is an effective method for hardening the nMOSFETs. When the back-gate is biased at −2.5 V during irradiation and measurement, the TID tolerance can be improved from below 50 krad(Si) to up 100 krad(Si) while the performance of pMOSFETs is not degraded. 3D TCAD simulations are performed to analyze the failure of the negative body bias and the effective mechanism of the negative back-gate bias.

The effect of negative substrate bias on the electrical characteristics of InAlN/GaN MIS-HEMTs

The effect of the negative substrate bias (Vsub) on the device performance of the InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) is studied. When the Vsub decreased from 0 V to −40 V, the two-dimensional electron gas (2DEG) electron density (n2D) under the gate region decreased, while the 2DEG electron mobility (µ2DEG) under the gate region was significantly improved. Due to the InGaN back barrier layer and the thin GaN channel layer (15 nm), the 2DEG electrons in the channel are injected into the InGaN back barrier layer with negative Vsub, leading to the decreased n2D. The decrease of the n2D caused the decrease of the collision probability between the polar optical phonon (POP) and the 2DEG electrons, and the enlarged distance between the 2DEG electrons and the AlN/GaN interface, resulting in the weaker POP and interface roughness scatterings and higher µ2DEG. This provides a possible way to increase 2DEG electron mobility and further improve the device performance of InAlN/GaN MIS-HEMTs.

Negative bias effects on deposition and mechanical properties of ultrananocrystalline diamond/amorphous carbon composite films deposited on cemented carbide substrates by coaxial arc plasma

Ultrananocrystalline diamond/amorphous carbon composite (UNCD/a-C) films were deposited on negatively biased cemented carbide (WC-Co) substrates by coaxial arc plasma deposition. The deposition rate is increased to be 0.9 nm/s, which is approximately 3 times larger than that of films deposited under no bias condition. In addition, the critical load in scratch tests was enhanced to be 31 N, which is 4 times more than that of the no bias films. On the other hand, the hardness was slightly degraded by employing the negative bias. From electrical diagnostics of the bias application, it was found that the negative bias is immediately compensated by the arrival of highly-dense positive carbon ions at the substrate and the substrate is weakly positively charged after the compensation. This might be the main reason for the degraded hardness by the bias application, Since the positive bias deaccelerate carbon ions, which facilities the formation of sp2 bonds.

Negative magnetization and the sign reversal of exchange bias field in Co(Cr1-xMnx)2O4 (0≤x≤0.6)

A series of Co(Cr1-xMnx)2O4 (0 ≤ x ≤ 0.6) ceramic samples have been synthesized by using the sol-gel method. The magnetic properties of the ceramics are experimentally studied through different protocols of dc magnetization measurements. It is found that Mn-doping continuously decreases the total magnetization for x in the range of 0 ≤ x ≤ 0.2 and the net magnetization becomes negative in the range of 0.3 ≤ x ≤ 0.5. The net magnetization reverses and becomes positive upon further increasing x to 0.6. This unusual magnetic phenomenon in the system for x = 0.3–0.5 can be called as negative magnetization. It is regarded as arising from the competition of the two magnetic sublattices at different crystallographic sites. For the sample x = 0.3, the magnetic switching effect near the compensation temperature Tcomp has been studied, and it shows potential applications in the spintronic devices. The magnetic configuration of the sample could be changed under a high magnetic field, and the spin is reoriented at TSR. Both positive and negative exchange bias effects are observed, which are ascribed to the pinning force of uncompensated spins on ferromagnetic moments and the magneto-structural transition, respectively.

Changes in Global Trade Patterns and Women's Employment in Manufacturing, 1995–2011

ABSTRACTThis study investigates the feminization and defeminization trends in manufacturing employment in thirty countries from 1995 to 2011. Utilizing two separate methods, structural decomposition analysis (SDA) and factor content analysis (FCA), the study identifies the major industries and trade partners behind the structural shifts in trade that have induced changes in employment and thus in the rates of women’s employment. The findings highlight that, as a general trend, defeminization in manufacturing has persisted in the Global North, led by a negative trade impact in low-technology industries. In the Global South, feminization and defeminization trends are not as straightforward. Despite positive changes in women’s share of employment in medium-high- and high-technology industries, negative gender bias effects of trade changes are found particularly in high-technology industries, where occupations are notably gendered.

The effect of positive and negative memory bias on anxiety and depression symptoms among adolescents.

To examine the interaction effect of anxiety and depression on the intentional forgetting of positive and negative valence words. One hundred fifty-five grade 7 to grade 10 students participated in the study. The item-method directed forgetting paradigm was used to examine the intentional forgetting of positive-valence, negative-valence, and neutral-valence words. Negative-valence words were recognized better than either positive-valence or neutral-valence words. The results revealed an anxiety main effect (p=.01, LLCI=-.09, and ULCI=-.01) and a depression main effect (p=.04, LLCI=.00, and ULCI=.24). The anxiety score was negative, whereas the depression score was positively related to the directed forgetting of negative-valence words. Regression-based moderation analysis revealed a significant anxiety×depression interaction effect on the directed forgetting of positive-valence words (p=.02, LLCI=.00, and ULCI=.01). Greater anxiety was associated with more directed forgetting of positive-valance words only among participants with high depression scores. With negative-valence words, the anxiety×depression interaction effect was not significant (p=.15, LLCI=- .00, and ULCI=.01). Therapeutic strategies to increase positive memory bias may reduce anxiety symptoms only among those with high depression scores. Interventions to reduce negative memory bias may reduce anxiety symptoms irrespective of levels of depression.

Effect of negative bias on TiAlSiN coating deposited on nitrided Zircaloy-4

TiAlSiN coatings were deposited on the nitrided Zircaloy-4 by multi-arc ion plating at −100 V, −200 V and −300 V. In this study, the high temperature oxidation behavior of coatings was tested by a box-type resistance furnace in air for 3 h at 800 °C; the macro-morphology of coatings was observed and analyzed by a zoom-stereo microscope; the micro-morphology of coatings was analyzed by a scanning electron microscopy (SEM), and the chemical elements of samples were analyzed by an energy dispersive spectroscopy(EDS); the adhesion strength of the coating to the substrate was measured by an automatic scratch tester; and the phases of coatings were analyzed by an X-ray diffractometer(XRD). Results show that the coating deposited at −100 V shows better high temperature oxidation resistance behavior, at the same time, Al elements contained in the coating is of the highest amount, meanwhile, the adhesion strength of the coating to the substrate is the highest, which is 33N. As the bias increases, high temperature oxidation resistance behavior of the coating weakens first and then increases, the amount of large particles on the surface of the coating increases first and then decreases whereas the density of the coating decreases first and then increases, and adhesion strength of the coating to the substrate increases first and then weakens. The coating's quality is relatively poor when the bias is −200 V.

Effect of deposition parameters and heat-treatment on the microstructure, mechanical and electrochemical properties of hydroxyapatite/titanium coating deposited on Ti6Al4V by RF-magnetron sputtering

Functionally graded HA/Ti coatings were deposited on silicon and Ti6Al4V substrate by radio-frequency (RF) magnetron sputtering. The effect of RF-power, negative bias and heat-treatment on the microstructure, mechanical and electrochemical properties of the coatings were characterized by SEM, XRD, FTIR, AFM Nanoindentation and electrochemical workstation. The obtained results showed that the as-deposited HA/Ti coatings were characteristic of amorphous structure, which transformed into a crystal structure after heat-treatment, and reformed O–H peak. The content of crystallization was increasing with the increase of negative bias. A dense, homogenous, smooth and featured surface, and columnar cross-section structure was observed in SEM observation. AFM results showed that the surface roughness became higher after heat-treatment, and increased with increasing RF-power. The mechanical test indicated that the coating had a higher nanohardness (9.1 GPa) in the case of −100 V and 250 W than that of Ti6Al4V substrate, and a critical load as high as 17 ± 3.5 N. The electrochemical test confirmed the HA/Ti coating served as a stable protecting barrier in improving the corrosion resistance, which the corrosion current density was 1.3% of Ti6Al4V, but it was significantly influenced by RF-power and negative bias. The contact angle test demonstrated that all the coatings exhibited favorable hydrophilic properties, and it decreased by 20–25% compared to that untreated samples. Thus all results indicated that magnetron sputtering is a promising way for fabricating a better biocompatible ceramic coating by adjusting deposition parameters and post-deposition heat treatments.

The effect of negative bias on the preparation conditions and structural changes in boron-doped nanocrystalline silicon thin films prepared on PET

In this work, the fabrication of boron-doped nanocrystalline silicon (nc-Si) deposited on PET substrate at room temperature are reported. Negative substrate bias is applied during deposition for improving the crystallinity of samples. The effects of negative bias on the structural, electrical and optical properties of B-doped nc-Si thin films prepared on PET are systemically studied through various characterizations. XRD and Raman results show that a phase transition from amorphous phase to crystalline phase takes place at negative bias=80V. By using moderate negative bias, the crystalline volume fraction can be effectively improved. The electrical properties have been found related to the crystalline volume fraction. At negative bias=120V, the maximum values of dark conductivity (1.94S/cm) and carrier concentration (7.4×1019cm−3) are obtained for the sample which has the largest crystalline volume fraction. Furthermore, the promotion mechanism on B-doping was illustrated in this paper.

Interface-induced spontaneous positive and conventional negative exchange bias effects in bilayer La0.7Sr0.3MnO3/Eu0.45Sr0.55MnO3 heterostructures

We report zero-field-cooled spontaneous-positive and field-cooled conventional-negative exchange bias effects in epitaxial bilayer composed of La0.7Sr0.3MnO3 (LSMO) with ferromagnetic (FM) and Eu0.45Sr0.55MnO3 (ESMO) with A-type antiferromagnetic (AF) heterostructures respectively. A temperature dependent magnetization study of LSMO/ESMO bilayers grown on SrTiO3 (001) manifest FM ordering (TC) of LSMO at ~320 K, charge/orbital ordering of ESMO at ~194 K and AF ordering (TN) of ESMO at ~150 K. The random field Ising model has demonstrated an interesting observation of inverse dependence of exchange bias effect on AF layer thickness due to the competition between FM-AF interface coupling and AF domain wall energy. The isothermally field induced unidirectional exchange anisotropy formed at the interface of FM-LSMO layer and the kinetically phase-arrested magnetic phase obtained from the metamagnetic AF-ESMO layer could be responsible for the spontaneous exchange bias effect. Importantly, no magnetic poling is needed, as necessary for the applications. The FM-AF interface exchange interaction has been ascribed to the AF coupling with sum {J}_{ex}vec{{S}_{{rm{FM}}}}cdot vec{{S}_{{rm{AF}}}} ({J}_{ex}approx {J}_{AF}, coupling constant between AF spins) for the spontaneous positive hysteresis loop shift, and the field-cooled conventional exchange bias has been attributed to the ferromagnetically exchanged interface with {J}_{ex}approx {J}_{F} (coupling constant between FM spins).

Improvement of crystallinity for poly-Si thin film by negative substrate bias at low temperature

Polycrystalline silicon (p-Si) thin films are fabricated by plasma enhanced chemical vapor deposition (PECVD) at low substrate temperature (180°C) with high-hydrogen dilution. Negative DC substrate bias is applied during the deposition process for improving the crystallinity of thin films. It is found that there is a phase transition from nanocrystalline phase to polycrystalline phase at negative bias=50V, as identified by scanning electron microscopy (SEM). The optimized p-Si thin film with large grains (~480nm) are obtained at negative bias=100V. The deconvoluted Raman spectra reveal that the p-Si thin film is a mixture including amorphous silicon (a-Si), nanocrystalline silicon (nc-Si) and p-Si, and the crystalline volume fraction gradually increases with the substrate negative bias in the range of 0–100V. The impacts of negative bias on the optical and electrical properties of p-Si thin films have been investigated. The growth mechanism of the p-Si grains has been discussed in detail. A grain-merging model is proposed for explaining the effect of negative bias on the formation of large p-Si grains at low temperature.

Positive and negative exchange bias effects from magnetization reversal in Ho3+ doped YFe0.5Cr0.5O3

The polycrystalline ceramics of Y1−xHoxFe0.5Cr0.5O3 (x=0, 0.05 and 0.1) are synthesized by a sol-gel method. The magnetization reversal and exchange bias effect are investigated in single phase bulk Y1−xHoxFe0.5Cr0.5O3. Magnetic Ho3+ ion as a dopant is introduced into the system to confirm the influence of A-site ion on the magnetic interactions. The dual reversal of exchange bias field for x=0.05 is observed, and its characteristic temperatures are corresponding to the compensation temperatures of magnetization reversal. The exchange bias field of x=0.1 is found to be ∼10.03kOe at 4K, revealing a large value compared with that of x=0. A schematic diagram based on the competition between the single ion anisotropy and Dzyaloshinsky-Moriya interaction, and the antiparallel coupling between the Ho3+ moments and the canted Cr3+/Fe3+ moments, is used to understand the dual reversal phenomenon of magnetization and exchange bias effect.