Back Channel Research Articles

EXPLICIT BACK-CHANNEL STRATEGY TRAINING AND IMPROVEMENT OF SPEAKING SKILL: CASE OF IRANIAN EFL LEARNERS

This study explores the effect of explicit back-channel strategy training on Iranian EFL language learners� success in speaking skill. Back-channels are turn taking responses uttered by the listeners. Forty homogenous learners (20 male, 20 female) were randomly assigned to four groups (2 experimental, 2 control). They were at intermediate level in terms of general English proficiency based on the results of Oxford Placement Test (OPT) and pre-test oral Proficiency Interview. After 18 sessions of treatment of back-channels for experimental groups, that were based on the methodological theory of English language teaching suggested by Doff (1990) and Harmer (1991), post- test oral proficiency test was administered for experimental and control groups. The findings of pretest and posttest oral exams revealed that EFL language learners� oral performance (speaking) in experimental groups improved. The result revealed that females employed back-channels more often than males when they were participating in a conversation. The type of back-channel both genders employed the most was short utterances, such as �yes�, and the most used function of back-channel was request for clarification. The results of this thesis will provide language teachers, EFL language learners, researchers, material developers, and readers, useful information about the types and functions of back channels that are needed to develop speaking ability appropriately through explicit teaching.Keywords: back channel strategy, communication strategy, explicit training

Numerical analysis of back pressure equal channel angular pressing of an Al-Mg alloy

Ultrafine grain size provides enhanced mechanical and/or physical properties such as strength and high ductility, superplasticity at relatively low temperatures and high strain rate and better corrosion resistance. Well-known as one of the most promising and effective structure refining method among other severe plastic deformation (SPD) techniques, equal channel angular pressing (ECAP) has been intensively investigated due to spectacular improvements in structure and therefore properties of bulk ultrafine grained/nanostructured materials. A successful ECAP requires surpassing two obstacles: the necessary load level which directly affects tools and a favourable stress distribution so the material withstanding the accumulated strain of repeated deformation. Materials could withstand more passes if a back pressure (BP) is applied. In traditional ECAP, tensile stress along the contact surface between the work piece and the upper wall of the outlet channel leads to crack initiation, while in the presence of BP, a negative (compressive) stress appears during the process balancing the tensile stress. In this study a comparative tridimensional finite element analysis (FEA) is performed to evaluate the flow of an Al-Mg alloy depending on different BP levels and process parameters. The results in terms of load level and strain distribution show the influence of BP on the material behaviour, opening opportunities for industrial applications.

Reducing the Peak-to-Average-Power-Ratio in Fusion Blankets

Breeding blankets with integrated first wall are one of the most critical components of nuclear fusion reactors. Blankets breeding zones are characterized by steep nuclear heating gradients due to the exothermic nuclear reaction 6Li(n, )T and the high intensity neutron flux in the proximity of the first wall. Non-uniformity in nuclear heating can generate sharp temperature gradients that deeply affect material properties. This conceptual study explores an original way to flatten nuclear heating profiles by proposing a blanket characterized by layers of different 6Li enrichment in the breeder region while maximizing Tritium Breeding Ratio (TBR) and power generation. Two types of fusion blanket are studied: (1) Helium Cooled Ceramic Reflector (HCCR) and (2) Dual Coolant Lead Lithium (DCLL). For HCCR, it is found in the optimal design case, that the power peak-to-average can be reduced by 47.85%, 42.45% and 54.13% in the front, middle and back channel respectively when compared to the reference design. On the other side, we found that this method of profile flattening is not appealing for DCLL, under the geometrical configuration and material selection in this particular blanket design, since most of nuclear heating is caused by photon heat deposition.

マレーシア人留学生と友人日本人大学生の接触場面における「規範」の違い : 「あいづち」の「規範」からの逸脱

マレーシア人留学生と友人日本人大学生の接触場面における「規範」の違い : 「あいづち」の「規範」からの逸脱

Improved Stability of $\alpha $ -InGaZnO Thin-Film Transistor under Positive Gate Bias Stress by Using Fluorine Plasma Treatment

The origin of positive-gate-bias-stress (PGBS)-induced instability and the effects of fluorine treatment on the instability of an InGaZnO thin-film transistor (TFT) are investigated. The fluorine treatments on the dielectric/InGaZnO interface and InGaZnO back channel of the device can effectively modulate their electrical properties. By characterizing the TFTs with various fluorine treatments, it is found that the back channel rather than the dielectric/InGaZnO interface dominates the PGBS instability. Electrons induced by moisture absorption near the back channel migrate from the back channel to the interface under PGBS at room temperature, thus resulting in a threshold-voltage decrease. Moreover, the fluorine treatment on the back channel effectively suppresses the PGBS instability due to reduced moisture absorption caused by the fluorine passivation.

AZO Thin Film Transistor Performance Enhancement by Capping an Aluminum Layer

Coplanar bottom-gate aluminum-zinc-oxide (AZO) thin film transistors (TFTs) with aluminum (Al) capping layers were fabricated in this work. The influences of the Al capping layer thickness and the post-annealing condition on the performance of the AZO-TFTswere investigated. Results show that the performance of the AZO-TFTs are enhanced significantly by introducing the Al capping layer on back channel, with saturation mobility increasing dramatically from 0.128 to 12.6 cm2/ $\text {V}\cdot \text {s}$ . The enhancement is ascribed to the diffusion of Al atoms into the AZO thin film and thus induced crystallization improvement.

28‐1: Invited Paper: Effect of Channel Defining Layer on the Vertical Oxide TFTs for the Application to the Ultra High Resolution Display

We investigated the effect of back channel material which plays as a channel defining layer in vertical TFT for the application to the TFT of ultra‐high resolution display. Although the IGZO vertical TFT with polyimide back channel has low mobility, it shows good on/off ratio higher than 107 , low gate leakage current, and hard saturation behavior with channel length of 1 um.

P‐137: Vt Behaviors of LTPS‐TFT Fabricated on PI substrate for Flexible Applications

In this paper, one of goals is to elucidate Vt behaviors of a top gate LTPS‐TFT fabricated on the PI substrate exposed to the negative bias temperature stress (NBTS), hot carrier injection (HCI) and breakdown voltage (BV). Physical and device characterization intend to comprehend the structural dependency of LTPS‐TFT on Vt stability and reliability in comparison to the glass substrate. It is found that turn‐over Vt behaviors of a top gate LTPS‐TFT on the polyimide (PI) substrate depends on negative bias temperature stress (NBTS) conditions. Vt behaviors are attributed to LTPS‐TFT structure dependent intrinsic negative charges at the interface between the barrier and PI substrate, causing the accumulation of positive charges at the poly‐Si back channel. In fact, intrinsic process parameters, such as barrier thickness and PI cure conditions, play important roles to control interfacial charges at the interface. Finally, streamlined barrier process enables LTPS‐TFT on PI substrate to expand advanced flexible applications without compromising luminescence and reliability.

P‐10: High‐Density Plasma Sputtered InZnSnO Thin‐Film Transistors Fabricated by Back Channel Etching Method on Flexible Polyimide Substrate

We demonstrate the fabrication of high performance InZnSnO thin‐film transistors (TFT) with the field‐effect mobility of 25 cm2/Vs on about 10 um‐thin polyimide substrate. Back‐channel etch (BCE) process in the bottom gate configuration is employed for easy implementation of devices with shorter channel length and smaller parasitic capacitance and cost‐effective fabrication compared with devices with etch‐stop layer (ESL). For highly uniform electrical characteristics with high field‐effect mobility, InZnSnO are deposited by high density plasma (HDP) sputtering which is assisted by microwave in order to enable the thin‐film more densified compared with conventional sputtering method. The combination of HDP sputtering method for oxide deposition and BCE process provides highly uniform electrical characteristics of TFTs with high mobility and cost‐effective method for their fabrication in large area flexible substrate.

P‐14: Prevention of Indium Segregation in BCE Type InGaZnO TFTs with Titanium Source/Drain

Electrical properties of back channel etching type amorphous Indium‐gallium‐zinc oxide thin film transistors with pure titanium and two titanium alloy electrodes were compared. Among the three electrodes, new titanium alloy shows the best TFT performance both in terms of mobility and threshold voltage and pure titanium electrode shows the worst performance. In cases of titanium electrode, indium protrusions were observed on the surface of IGZO semiconductor after source/drain back channel etching. The poor electrical performance of titanium source/drain is attributed to indium protrusions acting as electron trap sites. In this study, a new mechanism on indium segregation is proposed and effective prevention method is suggested.

Improvement of Electrical Characteristics and Stability of Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using Nitrocellulose Passivation Layer.

In this research, nitrocellulose is proposed as a new material for the passivation layers of amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The a-IGZO TFTs with nitrocellulose passivation layers (NC-PVLs) demonstrate improved electrical characteristics and stability. The a-IGZO TFTs with NC-PVLs exhibit improvements in field-effect mobility (μFE) from 11.72 ± 1.14 to 20.68 ± 1.94 cm2/(V s), threshold voltage (Vth) from 1.85 ± 1.19 to 0.56 ± 0.35 V, and on/off current ratio (Ion/off) from (5.31 ± 2.19) × 107 to (4.79 ± 1.54) × 108 compared to a-IGZO TFTs without PVLs, respectively. The Vth shifts of a-IGZO TFTs without PVLs, with poly(methyl methacrylate) (PMMA) PVLs, and with NC-PVLs under positive bias stress (PBS) test for 10,000 s represented 5.08, 3.94, and 2.35 V, respectively. These improvements were induced by nitrogen diffusion from NC-PVLs to a-IGZO TFTs. The lone-pair electrons of diffused nitrogen attract weakly bonded oxygen serving as defect sites in a-IGZO TFTs. Consequently, the electrical characteristics are improved by an increase of carrier concentration in a-IGZO TFTs, and a decrease of defects in the back channel layer. Also, NC-PVLs have an excellent property as a barrier against ambient gases. Therefore, the NC-PVL is a promising passivation layer for next-generation display devices that simultaneously can improve electrical characteristics and stability against ambient gases.

Oxygen Adsorption Effect of Amorphous InGaZnO Thin-Film Transistors

The effect of oxygen adsorption at the back channel of a-IGZO thin-film transistors (TFTs) is investigated. It is shown that for TFTs with the channel layer sputter-deposited at a high O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Ar flow rate ratio (RO/Ar), the threshold voltages in vacuum and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambient do not show any difference; for devices fabricated at a low RO/Ar, the threshold voltages in vacuum are lower than those in O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . In addition, the devices in O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> show a more significant threshold voltage shift than those in vacuum do under a positive gate bias stress. The surface-state model is used to explain this observation. It is inferred that the oxygen adsorptions are physical and chemical, respectively, in the high-and low-RO/Ar cases, and the transition from physical to chemical adsorption occurs when a positive gate bias stress is applied.

Improvement of Stress Stability in Back Channel Etch-Type Amorphous In-Ga-Zn-O Thin Film Transistors with Post Process Annealing

The electronic structures and electronic states near the back channel surfaces in amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) were investigated. The X-ray photoelectron spectroscopy (XPS) analysis revealed that, due to insufficient wet-etching of source/drain (S/D) of Mo metal, continuous sub-gap states formed throughout the bandgap, which induced degradation of the subthreshold swing of the TFTs with a back channel etch (BCE) structure. The stability under the negative bias thermal illumination stress (NBTIS) in the a-IGZO BCE-type TFTs was worse than that of conventional etch stop layer (ESL)-type TFTs. The Vth shift (ΔVth) increased from −2.5 V to −4.0 V with a hump-shaped variation. According to photoinduced transient spectroscopy (PITS) analysis, a broader shoulder of around 160 K clearly appeared in PITS spectra from the a-IGZO thin films with the BCE structure. The effect of post process annealing applied as the final process step of the TFT fabrication (post-annealing) was also examined against the a-IGZO BCE-TFTs. As the post-annealing temperature was increased, the peak at around 160 K which is associated with the hydrogen-related traps in a-IGZO thin film was markedly decreased. The results for the post-annealing at 300°C suggested a decrease in density of trap states which originated from depletion of Zn. A marked improvement of the stress stabilities under the positive bias, thermal stress (PBTS) was also observed as well as NBTIS.

Enhanced Radiation Hardness in SOI MOSFET with Embedded Tunnel Diode Layer

This paper presents an improved body tie structure for partially depleted silicon-on-insulator (SOI) MOSFETs. Inspired by tunneling current of degenerated p-n-junction at low forward bias, a tunnel diode layer is inserted at back channel forming a new type of body tie. The tunnel diode layer can be prepared either by ion implantation or in situ silicon deposition, which is fully compatible with present commercial SOI processes. The introduced body contact serves as an additional current flowing path for accumulated majority carriers generated by impact ionization or heavy-ion radiation, reducing critical floating body effects. The heavily doped tunnel diode layer extending from source to drain improves total dose radiation hardness and suppresses front-back channel coupling of SOI MOSFET for increasing back-gate threshold voltage and reduced width of space charge region. Experimental and simulation results validate the usefulness of the introduced body tie in enhancing radiation hardness of SOI transistor comparing with the conventional floating body devices. Therefore, SOI device with embedded tunnel diode layer can be considered as a promising candidate in spaceborne applications.

Time-domain charge pumping on silicon-on-insulator MOS devices

Time-domain charge pumping, which monitors transient currents during the charge pumping process, was applied to silicon-on-insulator (SOI) MOS gated p–i–n diodes. We found that the transient electron current is strongly dependent on the polarity of the back (substrate) gate. Specifically, when the back gate is positively biased, the current peak caused by the electron trap to the interface defects was found to disappear (or significantly weaken), which was attributed to the charging effects of the trapped electrons. The present results reveal the importance of the formation of the back channel and provide important information for further detailed analysis of the charge pumping process in SOI MOS devices.

Analytical subthreshold current modeling of nanoscale ultra-thin body ultra-thin box SOI MOSFETs with a vertical gaussian doping profile

Based on the evanescent-mode analysis, an insightful study of the channel potential is performed for the nanoscale ultra-thin body ultra-thin box SOI MOSFETs with a vertical Gaussian doping. And a two-dimensional (2D) analytical subthreshold current model is presented. The front and the back channel subthreshold currents are effectively derived using the inversion layer current density model which takes the Gaussian doping into account. The accuracy of the model has been verified by 2D numerical device simulations using Sentaurus Technology Computer-Aided Design (TCAD) from Synopsys. The model provides a deep understanding and can be instrumental for the nanoscale ultra-thin body ultra-thin box SOI MOSFETs with a non-uniform doping profile operating in the subthreshold regime.

Back Channel to Cuba: The Hidden History of Negotiations between Washington and Havana ‐ by LeoGrande, William M. and Kornbluh, Peter

Back Channel to Cuba: The Hidden History of Negotiations between Washington and Havana ‐ by LeoGrande, William M. and Kornbluh, Peter

A novel nondestructive testing method for amorphous Si–Sn–O films

Traditional methods to evaluate the quality of amorphous silicon-substituted tin oxide (a-STO) semiconductor film are destructive and time-consuming. Here, a novel non-destructive, quick, and facile method named microwave photoconductivity decay (μ-PCD) is utilized to evaluate the quality of a-STO film for back channel etch (BCE) thin-film transistors (TFTs) by simply measuring the D value and peak reflectivity signal. Through the μ-PCD method, both optimum deposition procedure and optimal annealing temperature are attained to prepare a-STO film with superior quality. The a-STO TFTs are fabricated by the obtained optimum procedure that exhibits a mobility of 8.14 cm2 V−1 s−1, a Ion/Ioff ratio of 6.07 × 109, a Von of -1.2 V, a steep subthreshold swing of 0.21 V/decade, a low trap density (Dt) of 1.68 × 1012 eV−1 cm−2, and good stability under the positive/negative gate-bias stress. Moreover, the validity of the μ-PCD measurement for a-STO films is verified by x-ray photoelectron spectroscopy, Hall effect measurement, and the performance of STO TFTs measured by traditional methods. The non-destructive μ-PCD method sheds light on the fast optimization of the deposition procedure for amorphous oxide semiconductor films with excellent quality.

Two-dimensional numerical modelling of sediment and chemical constituent transport within the lower reaches of the Athabasca River.

Flows and transport of sediment and associated chemical constituents within the lower reaches of the Athabasca River between Fort McMurray and Embarrass Airport are investigated using a two-dimensional (2D) numerical model called Environmental Fluid Dynamics Code (EFDC). The river reach is characterized by complex geometry, including vegetated islands, alternating sand bars and an unpredictable thalweg. The models were setup and validated using available observed data in the region before using them to estimate the levels of cohesive sediment and a select set of chemical constituents, consisting of polycyclic aromatic hydrocarbons (PAHs) and metals, within the river system. Different flow scenarios were considered, and the results show that a large proportion of the cohesive sediment that gets deposited within the study domain originates from the main stem upstream inflow boundary, although Ells River may also contribute substantially during peak flow events. The floodplain, back channels and islands in the river system are found to be the major areas of concern for deposition of sediment and associated chemical constituents. Adsorbed chemical constituents also tend to be greater in the main channel water column, which has higher levels of total suspended sediments, compared to in the flood plain. Moreover, the levels of chemical constituents leaving the river system are found to depend very much on the corresponding river bed concentration levels, resulting in higher outflows with increases in their concentration in the bed sediment.

William M. LeoGrande and Peter Kornbluh, Back Channel to Cuba: The Hidden History of Negotiations between Washington and Havana. Chapel Hill: University of North Carolina Press, 2014. 524 pp. $25.00.

William M. LeoGrande and Peter Kornbluh, <i>Back Channel to Cuba: The Hidden History of Negotiations between Washington and Havana</i>. Chapel Hill: University of North Carolina Press, 2014. 524 pp. $25.00.