Increase In Effective Mobility Research Articles

Hiring and Separation Rates Before and after the Arab Spring in the Tunisian Labour Market

AbstractWe seek to explore the hiring and separation rates in Tunisia before and after the Arab Spring based on quarterly business level data for 503 firms over the span of January 2007 to December 2012. Furthermore, we examine whether employers are willing to dismiss older workers to trigger an effective increase in mobility that will open new opportunities for the youth community. We build our analysis upon six main empirical models to study employment decisions reflected by major indicators such as the number of hiring, number of separations, total employment effects, male‐female ratio, age cohorts, labour mobility and net employment. The results show that the Arab Spring has created structural unemployment trends. In addition, we note that the 2008 global turmoil has fostered the firing level of employment. Our conclusions also indicate that the response of Tunisia's government to high unemployment rates caused by the financial meltdown in 2008 and the events in 2011 was not sufficient to remove the attached lingering effects that still distress the country's labour market. In addition, our findings emphasize the significant challenges faced by Tunisian youth that could be mitigated by efficient policy actions to incentivize training and development geared towards the private sector.

Electrical transport and EPR investigations: A comparative study for d.c. conduction mechanism in monovalent and multivalent ions doped polyaniline

A detailed comparative study of electron paramagnetic resonance (EPR) in conjunction with d.c. electrical conductivity has been undertaken to know about the charge transport mechanism in polyaniline (PANI) doped with monovalent and multivalent protonic acids. This work is in continuation of our previous work for further understanding the conduction mechanism in conducting polymers. The results reveal that the polarons and bipolarons are the main charge carriers formed during doping process and these cause increase in electrical conductivity not only by increase in their concentration but also because of their enhanced mobility due to increased inter-chain transport in polyaniline at high doping levels. EPR line asymmetry having Dysonian line shape for highly doped samples shows a marked deviation of amplitudes A/B ratio from values close to one to much high values as usually observed in metals, thereby support the idea of high conductivity at higher doping levels. The nature of dopant ions and their doping levels control the charge carriers concentration as well as electrical conductivity of polyaniline. The electrical conductivity has also been studied as a function of temperature to know the thermally assisted transport process of these charge carriers at different doping levels which has been found to follow the Mott’s variable range hopping (VRH) conduction model for all the three dopants used. The charge carriers show a change over from 3D VRH to quasi 1D VRH hopping process for multivalent ions at higher doping levels whereas 1D VRH has been followed by monovalent ion for full doping range. These studies collectively give evidence of inter-chain percolation at higher doping levels causing increase in effective mobility of the charge carriers which mainly seems to govern the electrical conduction behaviour in this system.

Circular Geometry Transistors Fabricated on Germanium-on-Alumina Bonded Substrates

Germanium (Ge) has been bonded to fine grain alumina (Al2O3) by means of a polished polycrystalline silicon interface layer. After room temperature bonding and subsequent bond strength annealing at 150 oC for 24 hrs, the germanium layer was ground and polished to 100µm. Low temperature Tungsten (W) gate circular geometry devices, W/L = 9, fabricated on this layer exhibited effective mobility values of 150 cm2/Vs. This is much lower than results obtained on equivalent devices on bulk Ge. Improvement in the germanium polish process resulted in transistors with an effective mobility of 415 cm2/Vs, comparable to that of the bulk Ge devices. Low temperature measurement, down to temperatures of 173 K, showed an improvement in device performance resulting in both an increase in effective mobility to 591 cm2/Vs and a decrease in sub threshold slope from 180 mV/dec to 60 mV/dec indicating a reduction in leakage current.

Increase in electron mobility of InGaAs/InP composite channel high electron mobility transistor structure due to SiN passivation

The influence of silicon nitride passivation on electron mobility of InGaAs/InP composite channel high electron mobility transistor structure has been studied. Different from the structures with single InGaAs channel, an increase in effective mobility μ e with a negligible change of sheet carrier density n s after SiN deposition is clearly observed in the composite channel structures. The enhancement of μ e could be explained under the framework of electrons transferring from the InP sub-channel into InGaAs channel region due to the energy band bending at the surface region caused by SiN passivation, which is further confirmed by low temperature photoluminescence measurements.

Large Area Printing of Organic Electronics

Organic electronic systems offer the possibility of lightweight, flexibility and large area coverage, properties not easily achievable with standard silicon technology, and at potentially lower manufacturing costs. DuPont has focused on the development of conducting and semiconducting organic materials that allow for the printing of active and passive electronic devices. A number of groups have focus in improving device performance by designing organic semiconducting materials of higher mobility. We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The method, based on creating subpercolating conducting networks, would enable the printing of submicron features with conventional commercial engines. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in effective mobility without reduction of the on/off ratio.These conducting and semiconducting composites are compatible with various large area printing processes such as thermal and ink jet. However, the manufacturing of complex multi-layer circuits over large areas in a reel-to-reel configuration has been one of the driving forces in the organic electronics field. We are currently evaluating the feasibility of micro-contact printing as a path to high-resolution reel-to-reel electronics. Thus extending flexography into the high-resolution arena. Unlike conventional lithography, micro-contact printing; not requiring sacrificial resists, developers, and etchants; maybe compatible with a wider range of materials and substrates currently utilized in plastic electronics.

Structure and electrical transport properties of pure and Li 2O-doped CuO/MgO solid solution

The different electrical properties, σ, ɛ′, tan δ and E σ of pure and Li 2O-doped CuO/MgO solid solution were investigated. The mole fraction of CuO (MF) was varied between 0.048 and 0.2. Pure and doped samples were subjected to heat treatments at 673 and 1073 K. The results revealed that the amount of CuO dissolved in MgO lattice increases progressively by increasing the MF as evidenced from the progressive decrease in the intensity of all diffraction lines of undissolved CuO phase. The dissolution process of copper ions in MgO lattice was accompanied by progressive increase in its lattice parameter. This process being conducted at 1073 K was accompanied by a significant progressive increase in the values of σ, ɛ′ and tan δ with subsequent decrease in the value of E σ . The increase in the MF value of CuO from 0.048 to 0.2 led to a significant increase in the value of σ DC, measured at room temperature, from 6.33 × 10 −12 to 9.9 × 10 −10 Ω −1 cm −1 and E σ decreases from 0.76 to 0.58 eV. Li 2O doping of the investigated system followed by calcination at 1073 K resulted in a measurable increase in values of σ, ɛ′ and tan δ with subsequent decrease in E σ . These results were discussed in the light of the possible effective increase in the charge carriers concentration (Cu 2+ions dissolved in MgO lattice) and also to an effective increase in mobility of these charge carriers by Li 2O doping.

Thermodynamic characterization of the oriented state of bisphenol A polycarbonate as it pertains to enhanced physical aging

It has recently been demonstrated that hot-drawn samples of bisphenol A polycarbonate (PC) have a 50% higher volume relaxation rate than their isotropic counterpart even though the oriented samples have a lower initial free volume (i.e., higher density). 1 In an attempt to better understand this paradox, samples of unaged, hot-drawn PC were characterized thermodynamically and kinetically as a function of orientation. Heat capacity, hole energy, and T g data indicate that the chain mobility is actually decreasing slightly with orientation, possibly due to the hindered motion brought about by tighter packing, stronger intermolecular bonding, and reduced free volume. Nonetheless, this decrease in localized mobility is in contradiction to the enhanced volume relaxation rates observed for the oriented samples. In contrast, dynamic mechanical data indicate an increase in the relaxation strength of the β-transition (-100°C at 1 Hz) upon stretching for both the stretch and transverse directions. This implies that more segments are actively participating in the relaxation process for the oriented samples even though their individual localized mobility might be slightly lower. The net result is an increase in effective mobility for the oriented samples. It is conjectured that the enhanced relaxation strength of the oriented samples is a result of the stretching process somehow activating more of the chains into a higher energy state, and may be related to the physical aging concept of stress-induced rejuvenation/ acceleration.