Bottom Contact Research Articles

Influence of Resonator Length on Performance of Nitride TJ VCSEL

This paper presents computer simulations of nitride-based tunnel-junction (TJ) vertical-cavity surface emitting lasers (VCSELs). The analyzed structures are non-polar continuous wave VCSELs with dielectric distributed Bragg reflectors (DBRs) emitting at around 405 nm. Both electric contacts are in the form of rings that surround the DBRs. The bottom electric contact also acts as a thermal contact between the laser and the heat sink, because the dielectric DBR is a thermal insulator. The results of our study show that the thickness of the laser's resonator and its absorption coefficient each have a very strong impact on both the threshold current and emitted power. A thick resonator reduces the thermal resistance of the device, but increases the optical absorption. The optimal resonator thickness depends on the absorption coefficient of the resonator material, different possible values for which are investigated here. Moreover, VCSELs with TJs has been compared with similar devices, with semi-transparent ITO contacts and without a TJ.

Improving device performance of p-type organic field-effect transistor using butterfly like triarylamines

Facile and economic strategy to create a controlled self-structured architecture of semiconducting molecules is very crucial in the accomplishment of carbon electronic devices. A series of new unsymmetrically functionalized butterfly type triarylamines with electron donating/withdrawing substituents were synthesized. Simple and efficient solution based method was used as a successful strategy for OFET with improved characteristics. Binary solvent system with chloroform and toluene (7:3) has improved inter/intra molecular communication in the active layer. The morphology of the films was analyzed by SEM reveals the uniform packing. In addition post thermal annealing has enhanced the crystallinity with minimal grain boundaries. HOMO values -5.1 to -5.4 eV obtained from cyclic voltammetry ensure that these molecules can efficiently transport holes. OFET devices were fabricated in bottom gate top contact (BGTC) architecture by spin coating. Molecules exhibited typical p -channel transistor behavior with mobility up to 1 cm 2 V −1 s −1 with 10 6 I on/off current ratio. Density functional theory (DFT) visualized the packing and interaction of molecules and supported the efficient mobility. Our investigation gives insight into the role of solvents to control the film architecture in solution processing OFET device construction. • New functionalized triarylamines are designed, synthesized and scrutinised for OFET applications. • HOMO level (-5.2–-5.4 eV) ensures efficient hole injection and transport. • Band gap tuned with respect to the electron donating and withdrawing substituents. • OFETs with bottom gate top contact architecture is fabricated by spin coating from a binary solvent mixture. • Exhibited higher melting points ensures the device durability with higher mobility up to 1 cm 2 V −1 s −1 with 10 6 I on/off current ratio.

Enhanced stability of piezoelectric nanogenerator based on GaN/V2O5 core-shell nanowires with capacitive contact

Enhanced stability of a piezoelectric nanogenerator (PNG) was demonstrated using c- and m-axis GaN/V2O5 core–shell nanowires (NWs) by analyzing the capacitive coupling of the PNG’s output. The NW array grown on GaN thin film was embedded in polydimethylsiloxane (PDMS) matrix, following which the matrix was transferred to an indium (In)-coated PET substrate for achieving superior flexibility of the PNG. The stability of the PNG was enhanced by holding the NW PDMS composite with a PDMS polymer as a bonding material on the PET substrate. The inserted PDMS layer improved the lifetime of the PNG, however, because of the insulating nature of PDMS, the piezoelectric output of GaN NWs was coupled capacitively to In contact on PET substrate and it resulted in a slight degradation of piezoelectric output due to the voltage drop across the bottom capacitive contact. The maximum piezoelectric current was 64 nA and output voltage was 11.9 V from the PNG with c-axis NWs. While the PNG with direct bottom contact exhibited 57% output reduction after 72 000 operation cycles, the PNG with capacitive contact did not show any degradation in stability even after 150 000 cycles.

Fast and Ultraclean Approach for Measuring the Transport Properties of Carbon Nanotubes

AbstractIn this work, a fast approach for the fabrication of hundreds of ultraclean field‐effect transistors (FETs) is introduced, using single‐walled carbon nanotubes (SWCNTs). The synthesis of the nanomaterial is performed by floating‐catalyst chemical vapor deposition, which is employed to fabricate high‐performance thin‐film transistors. Combined with palladium metal bottom contacts, the transport properties of individual SWCNTs are directly unveiled. The resulting SWCNT‐based FETs exhibit a mean field‐effect mobility, which is 3.3 times higher than that of high‐quality solution‐processed CNTs. This demonstrates that the hereby used SWCNTs are superior to comparable materials in terms of their transport properties. In particular, the on–off current ratios reach over 30 million. Thus, this method enables a fast, detailed, and reliable characterization of intrinsic properties of nanomaterials. The obtained ultraclean SWCNT‐based FETs shed light on further study of contamination‐free SWCNTs on various metal contacts and substrates.

Monolithic integration of high-voltage thin-film electronics on low-voltage integrated circuits using a solution process

The performance of silicon complementary metal–oxide–semiconductor integrated circuits can be enhanced through the monolithic three-dimensional integration of additional device layers. For example, silicon integrated circuits operate at low voltages (around 1 V) and high-voltage handling capabilities could be provided by monolithically integrating thin-film transistors. Here we show that high-voltage amorphous oxide semiconductor thin-film transistors can be integrated on top of a silicon integrated circuit containing 100-nm-node fin field-effect transistors using an in-air solution process. To solve the problem of voltage mismatch between these two device layers, we use a top Schottky, bottom ohmic contact structure to reduce the amorphous oxide semiconductor circuit switching voltage. These contacts are used to form Schottky-gated thin-film transistors and vertical thin-film diodes with excellent switching performance. As a result, we can create high-voltage amorphous oxide semiconductor circuits with switching voltages less than 1.2 V that can be directly integrated with silicon integrated circuits. High-voltage amorphous oxide semiconductor thin-film transistors can be integrated on top of a silicon integrated circuit containing 100-nm-node fin field-effect transistors using an in-air solution process.

One-step P2 scribing of organometal halide perovskite solar cells by picosecond laser of visible wavelength

Perovskite solar cells (PSC) have attracted attention by their unprecedented rise in device efficiency. However, the PSCs were mostly tested for the unit cells of small area, and it is important to upscale to solar modules. Laser scribing has great potential to this end. However, the key challenge identified in one-step P2 laser scribing is to remove film stack including the hole block layer (HBL) without damaging transparent conducting oxide (TCO) based bottom contact and thus to provide interconnecting paths with minimized contact resistance.In this study, we evaluate one-step P2 scribing performance of picosecond laser of 532 nm wavelength for mesoscopic perovskite architecture with the c-TiO2 (compact TiO2) as the HBL and fluorine doped tin oxide (FTO) as bottom contact. Despite anticipated challenge of low absorption selectivity, c-TiO2 layer could be efficiently removed without FTO damage over wide processing window enabling a self-terminating mechanism. Detailed parametric studies elucidate relevant scribing mechanisms such as layer-by-layer ablation mechanism or lift-off mechanism depending laser illumination direction. It is also revealed that the removal of c-TiO2 is triggered by ablation of upper layers, in particular, the mesoporous TiO2. Module level test is under way in conjunction with investigation of further scribing mechanisms.

Effect of Si Doping in Self-Assembled InAs Quantum Dots on Infrared Photodetector Properties

We investigate the characteristics of self-assembled quantum dot infrared photodetectors(QDIPs) based on doping level. Two kinds of QDIP samples are prepared using molecular beam epitaxy : n+-i(QD)-n+ QDIP with undoped quantum dot(QD) active region and n+-n−(QD)-n+ QDIP containing Si direct doped QDs. InAs QDIPs were grown on semi-insulating GaAs (100) wafers by molecular-beam epitaxy. Both top and bottom contact GaAs layer are Si doped at 2×1018/cm3. The QD layers are grown by two-monolayer of InAs deposition and capped by InGaAs layer. For the n+-n−(QD)-n+ structure, Si dopant is directly doped in InAs QD at 2×1017/cm3. Undoped and doped QDIPs show a photoresponse peak at about 8.3 μm, ranging from 6~10 μm at 10 K. The intensity of the doped QDIP photoresponse is higher than that of the undoped QDIP on same temperature. Undoped QDIP yields a photoresponse of up to 50 K, whereas doped QDIP has a response of up to 30 K only. This result suggests that the doping level of QDs should be appropriately determined by compromising between photoresponsivity and operating temperature.

Femtosecond laser processing of ceria-based micro actuators

In this paper we present a novel femtosecond laser micro-processing of gadolinium doped cerium oxide (CGO) taking advantage of the unique properties of the ultra-short laser pulse. The process can be extended to other materials which are incompatible with conventional deposition/patterning/etching processes. For example, CGO electrostrictive ceramics is lead-free and non-toxic, compatible with Si-microfabrication and exhibits large electrostriction effect at low frequencies. These qualities make CGO into a promising electroactive material for MEMS applications. However, conventional CGO lithography suffers from low yield due to metal shorts and due to damage during the etch and clean processes. Wet patterning of CGO is very difficult and often results in enhanced leakage or shorts between electrodes. These process compatibility issues can be avoided by using laser patterning. As a proof of concept, a precise patterning of electro-active ceramic Ce0.95Gd0.05O1.975 (CGO5) thin films (1.7 μm-thick) by femtosecond laser is demonstrated. The femtosecond laser patterning was used to fabricate double-clamped beam actuators made of CGO5 sandwiched between two metal contacts. The new process is studied and preliminary guide lines are presented. The process design rules are established; for example, a margin between the top contact edges and the CGO layer edges was defined prior to laser ablation to prevent a short-circuiting between top and bottom contacts due to metal ablation. Electro-mechanical testing of the resulting devices demonstrates the long-term mechanical and electrical endurance of 1.2 mm long beams. Using electrical excitation (voltage amplitude of 10 V with a carrier frequency of 10 MHz modulated at 10 Hz), actuation at 10 Hz induced an in-plane strain of 7×10−6 without any observable mechanical degradation for >800 k cycles. The processes presented in this work, therefore, provide a technological framework for integration of CGO into MEMS-devices.

Novel Tunnel-Contact-Controlled IGZO Thin-Film Transistors with High Tolerance to Geometrical Variability.

Thin insulating layers are used to modulate a depletion region at the source of a thin-film transistor. Bottom contact, staggered-electrode indium gallium zinc oxide transistors with a 3 nm Al2 O3 layer between the semiconductor and Ni source/drain contacts, show behaviors typical of source-gated transistors (SGTs): low saturation voltage (VD_SAT ≈ 3 V), change in VD_SAT with a gate voltage of only 0.12 V V-1 , and flat saturated output characteristics (small dependence of drain current on drain voltage). The transistors show high tolerance to geometry: the saturated current changes only 0.15× for 2-50 µm channels and 2× for 9-45 µm source-gate overlaps. A higher than expected (5×) increase in drain current for a 30 K change in temperature, similar to Schottky-contact SGTs, underlines a more complex device operation than previously theorized. Optimization for increasing intrinsic gain and reducing temperature effects is discussed. These devices complete the portfolio of contact-controlled transistors, comprising devices with Schottky contacts, bulk barrier, or heterojunctions, and now, tunneling insulating layers. The findings should also apply to nanowire transistors, leading to new low-power, robust design approaches as large-scale fabrication techniques with sub-nanometer control mature.

Focal cortical dysplasia II-related seizures originate from the bottom of the dysplastic sulcus: A stereoelectroencephalography study

ObjectivesFocal cortical dysplasia (FCD) II is a frequently observed histopathological substrate in epilepsy surgery. In the present study, we explored the spatial distribution of epileptogenic activities across FCD II lesions using stereoelectroencephalography. MethodsPatients with histopathologically confirmed type II FCDs and who had at least one depth electrode that go through the wall of the dysplastic sulcus from the surface to the bottom were included. The dysplastic sulci were divided into the bottom and non-bottom parts manually, and contacts were defined as bottom or non-bottom contacts according to their locations. Factors (bottom location, pathological subtype, magnetic resonance imaging manifestation, and presence of bottom-of-sulcus dysplasia) potentially associated with earliest onset identified by conventional visual analysis, epileptogenicity index (EI), and standardized number of high-frequency oscillations (HFOs) were analyzed. Linear regression analyses between distance (from the location of the analyzed contact to the bottom of the sulcus) and EI value and HFO number were performed. ResultsSixteen patients with 19 depth electrodes containing 112 valid contacts were included. Bottom location was the sole factor significantly associated with earliest onset (P < 0.001), EI value (P < 0.001), and HFO number (P < 0.001). Most earliest onsets were recorded by the bottom contacts, bottom contacts had higher EI value (0.81 ± 0.28 vs. 0.31 ± 0.24, P < 0.001) and more HFOs (0.78 ± 0.28 vs. 0.35 ± 0.31, P < 0.001) than non-bottom contacts. Moreover, the EI value (R = −0.72, P < 0.001) and HFO number (R = −0.64, P < 0.001) were significantly negatively correlated with distance, regardless of histopathological subtype, MRI manifestation, or absence of bottom-of-sulcus dysplasia. ConclusionSeizure onsets and interictal HFOs most often arise from the bottom part of a sulcus with type II FCD. SignificanceThe findings of the present study contribute to intracranial electrode selection, trajectory planning, and, later on, resection of this kind of malformation.

Signal amplification with patterned conducting polymer electrodes based organic thin film transistor circuit

Organic thin film transistors (OTFTs) fabricated with non-destructive patterning techniques are the building blocks in realizing flexible electronic interface for sensing applications. In this study, a single stage differential amplifier is demonstrated with flexible OTFTs. The OTFTs were fabricated with thermally evaporated Pentacene as the semiconducting layer. The electrodes of the OTFTs were realized using a conductive polymer composite, poyaniline:polystyrene sulphonic acid (PANi-PSS), patterned by a modified Parylene lift-off process. Electrical characteristics of bottom contact TFTs with polymeric PANi-PSS electrodes is superior to those with conventional metal electrodes due to a lower charge injection barrier and resultant lower contact resistance. The measurement of the transistor characteristics and the amplifier response reported has been carried out with a wafer probing test jig set up. The differential amplifier realized with p-type Pentacene transistors with mobility, 0.5 cm2/Vs, exhibited a voltage gain of 10 dB in a frequency bandwidth of 1 kHz.

Analysis and simulation of the multiple resistive switching modes occurring in HfOx-based resistive random access memories using memdiodes

In this work, analysis and simulation of all experimentally observed switching modes in hafnium oxide based resistive random access memories are carried out using a simplified electrical conduction model. To achieve switching mode variation, two metal-insulator-metal cells with identical stack combination, but varying oxygen stoichiometry of the hafnia layer, namely, stoichiometric vs highly deficient, are considered. To access the individual switching modes, the devices were subjected to a variety of cycling conditions comprising different voltage and current ranges. For modeling the device behavior, a single or two antiserially connected memdiodes (diode with memory) were utilized. In this way, successful compact simulation of unipolar, bipolar, threshold, and complementary resistive switching modes is accomplished confirming the coexistence of two switching mechanisms of opposite polarity as the basis for all observable switching phenomena in this material. We show that only calibration of the outer current–voltage loops with the memdiode model is necessary for predicting the device behavior in the defined region revealing additional information on the switching process. The correspondence of each memdiode device with the conduction characteristics of the individual top and bottom metal-oxide contacts allows one to assess the role played by each interface in the switching process separately. This identification paves the path for a future improvement of the device performance and functionality by means of appropriate interface engineering.

Dimethylacetamide-promoted Direct Arylation Polycondensation of 6,6′-Dibromo-7,7′-diazaisoindigo and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene toward High Molecular Weight n-Type Conjugated Polymers

A highly efficient and eco-friendly protocol for the synthesis of an alternating copolymer poly(7,7′-diazaisoindigo-alt-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene) (PAIID-4FTVT) via direct arylation polycondensation (DArP) is presented. Through detailed study, we found that the inhibitory effect of 7,7′-diazaisoindigo on DArP stemmed from the coordination of N atom with catalyst can be overcome by using dimethylacetamide (DMAc) as the co-solvent. Thus, PAIID-4FTVT with number-average molecular weight (Mn) > 100 kDa was synthesized via DArP by optimizing the content of DMAc. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy revealed that PAIID-4FTVT was defect-free. Top gate and bottom contact (TG/BC) organic thin-film transistors (OTFTs) were fabricated to characterize the semiconducting properties of the polymers. PAIID-4FTVT displayed unipolar n-type characteristics with the electron mobility (µe) strongly dependent on Mn. The highest µe up to 0.25 cm2·V−1·s−1 was achieved with the high molecular weight sample.

Influence of corium composition on ex-vessel steam explosion

The worst event that could happen in a nuclear power plant is a severe accident. If during such accident the corium melt comes into contact with the coolant water, a steam explosion may occur. At some stage of the accident progression, the primary system and the containment integrity of the nuclear power plant are jeopardized.In the article, the material influence of the oxide and metal corium on the ex-vessel steam explosion is investigated. The main purpose of the research work was a comparative analysis of different scenarios of steam explosion in the flooded reactor cavity. The purpose was to determine the influence of the material properties of the melt (comparison of oxide and metallic melt) and the oxidation of the metallic melt on the steam explosion strength. A PWR ex-vessel steam explosion study was carried out with the MC3D computer code. A premixing simulation and an explosion simulation were performed for each type of the corium. The explosion was triggered at the time of melt bottom contact. The global jet breakup model was used to simulate the premixing simulations.In the first part comparative calculations with oxide corium and oxide corium with prescribed thermal properties of metal corium are presented to find the isolated influence of thermal properties. The analysis of PWR ex-vessel steam explosion with oxide corium was already performed in the past (Leskovar and Uršič, 2014), but in this paper the comparative calculations with oxide corium and oxide corium with prescribed thermal properties of metal corium are presented for the first time. The purpose was to determine the differences in premixing and the steam explosion strength at simulations considering solely the different thermal properties of the oxide and metal corium.In the second part of the paper the influence of the metal corium oxidation on the ex-vessel steam explosion is presented. Due to the focusing effect the reactor vessel would most likely fail at the side and the outflow of metal corium would occur. First of all it was necessary to collect material properties of metal corium. The ex-vessel steam explosion was investigated and discussed by varying the metal corium oxidation rate. Additionally, based on experimental findings, the hydrogen film hypothesis for oxidation is presented. In this paper the calculations with properties of metal corium are presented for the first time. With the comparison of the simulation results the influence of the corium composition on the strength of the steam explosion is analysed. The simulation results revealed that with metal corium the strength of the steam explosion is in some cases higher than with oxide corium.

Design and implementation of bound-to-quasibound GaN/AlGaN photovoltaic quantum well infrared photodetectors operating in the short wavelength infrared range at room temperature

In this paper, we discuss the design of photovoltaic quantum well infrared photodetectors (QWIPs) based on polar GaN/AlGaN multiquantum wells (MQWs). Getting a reasonable escape probability of the excited electron requires adjusting the bound-to-quasibound intersubband transition in the absorbing quantum well and engineering the polarization-related internal electric field in the barriers. This can be achieved with a MQW period that consists of 3 layers, namely, the active quantum well, an extraction barrier, and an injection barrier, the latter being thin enough to allow tunneling transport. Following this design scheme, we demonstrate bound-to-quasibound GaN/AlGaN QWIPs with peak photocurrent response at 2.3 μm, operating at room temperature in both photovoltaic and photoconductive modes. Based on high-resolution x-ray diffraction measurements, the entire detector structure, which included a 40-period MQW with 30 nm-thick barriers, along with top and bottom contact layers of combined thickness above 900 nm, was grown pseudomorphically on an AlGaN-on-sapphire template. A room-temperature responsivity of 88 μA/W was measured at zero bias, increasing up to 302 μA/W at −1.0 V bias. The responsivity reached its maximum at 150–200 K, where it was approximately a factor of 2 higher than at room temperature. Ideas for a new device structure to improve the QWIP response in the photovoltaic mode are proposed.

Surface Catalytic Modification of Conjugated Polymer on Low‐Cost Bottom Contact for Improved Injection Efficiency of Organic Transistors

AbstractTheir mismatched energy alignment with organic semiconductors limits the application of low‐cost metals in organic electronics. A novel surface catalytic low‐temperature chemical vapor deposition (CVD) based on the Ullmann reaction is applied to selectively modify patterned Ag/Cu electrodes. The work functions of Ag and Cu are tuned from 4.3 and 4.5 eV to 4.8 and 4.9 eV, respectively, after modification with conjugated polymers. Owing to the change in work function and pentacene morphology, the contact resistance decreases by several orders of magnitude compared with that of devices with pristine Ag or Cu electrodes, and the correspond mobilities of pentacene bottom‐contact field effect transistors increase to 0.66 cm2 V−1 s−1 (Ag) and 0.64 cm2 V−1 s−1 (Cu). This mobility is one of the highest values demonstrated with pentacene organic field‐effect transistors with Cu or Ag electrodes. This simple, clean, and low‐temperature modification method paves the way for the application of low‐cost metals in organic electronics.

Electrically Tunable Metal–Semiconductor–Metal Terahertz Metasurface Modulators

We propose metal-semiconductor-metal cavity arrays as active elements of electrically tunable metasurfaces operating in the terahertz spectrum. Their function is based on reverse biasing the Schottky junction formed between top metal strips and the n-type semiconductor buried beneath. A gate bias between the strips and a back metal reflector controls the electron depletion layer thickness thus tuning the Drude permittivity of the cavity array. Using a rigorous multiphysics framework which combines Maxwell equations for terahertz waves and the drift-diffusion model for describing the carrier behavior in the semiconductor, we find a theoretically infinite extinction ratio, insertion loss of around 10%, and picosecond intrinsic switching times at 1 THz, for a structure designed to enter the critical coupling regime once the depletion layer reaches the bottom metal contact. We also show that the proposed modulation concept can be used for devices operating at the higher end of the terahertz spectrum, discussing the limitations on their performance.

(Invited) Compact Modeling of I-V and C-V Characteristics in OTFTs from 125K to 350K

Organic TFTs (OTFs) are very promising devices for flexible, wearable and printed electronics. Nowadays OTFT performances are already comparable to a-Si:H TFTs. In order to design OTFT circuits, physically-based compact models for the OTFT DC, AC and transient characteristics are needed. This requires a correct understanding of the physical effects affecting OTFT behavior. Despite a number of compact I-V models have been presented, only a few C-V models have been published [1-4]. Besides, very few models have considered the temperature dependence, even though temperature analysis is instrumental to identify relevant physical effects. Moreover, most of those temperature studies have been carried out only for I-V characteristics at high temperatures [5] and the very few analysis at low temperatures have not targeted all parameters [6]. In this work, we present a complete study of both current and gate capacitance in OTFTs for temperatures ranging from 150K to 350K. Parameters were extracted using a unified model and extraction method specific to OTFTs, based on assuming an exponential DOS and variable range hopping [7-8]. The dependences of model parameters with the temperature are analyzed. In order to carry out the temperature study of C-V characteristics, we improved an analytical capacitance model [1, 3] for OTFTs in order to be valid from the depletion to the accumulation regime with continuous and smooth regime transitions as well as for the first order gate capacitance derivative. The key parameters used in the capacitance model are the same as those of I-V characteristics and were extracted from them [4, 7]. Furthermore, we show that from the first order gate capacitance model derivative, we can identify the different operating regimes and obtain the threshold voltage () and band-flat voltage ( at different temperatures. We performed measurements on small-molecule OTFTs manufactured in CEA-Liten (Grenoble- France). The OTFTs under study were top gate bottom contact multifingers with and. Our model shows good agreement with the experimental I-V (Fig. 1) and C-V (Fig. 2) characteristics, and the first order capacitance model derivative (Fig. 3) from for temperatures ranging from 120K to 350K, and for frequencies up to 10 kHz. [1] Castro-Carranza, A., et al., (2012). Organic thin-film transistor bias-dependent capacitance compact model in accumulation regime. IET circuits, devices & systems, 6(2), 130-135 [2] Li, L., Marien, et al.,, “Compact Model for Organic Thin-Film Transistors” IEEE Electr Dev Let, vol. 31, no. 3, pp. 210-212, Mar. 2010. [3] Fadlallah, M., et al. “Modeling and characterization of organic thin film transistors for circuit design” J. Appl. Phys, vol. 99, no.104504, May 2006. [4] Estrada, M., et al.,(2013). Frequency and voltage dependence of the capacitance of MIS structures fabricated with polymeric materials. IEEE Transactions on Electron Devices, 60(6), 2057-2063. [5] Estrada, et al., (2010). Modeling the behavior of charge carrier mobility with temperature in thin-film polymeric transistors. Microelectronic Engineering, 87(12), 2565-2570. [6] Haddad, C., et al., Organic Electronics (2018), https://doi.org/10.1016/j.orgel.2018.06.037[7] Estrada, M., at al., (2005). Accurate modeling and parameter extraction method for organic TFTs. Solid-state electronics, 49(6), 1009-1016. [8] Estrada, M.,et al., . (2008). Mobility model for compact device modeling of OTFTs made with different materials. Solid-State Electronics, 52(5), 787-794. Figure 1

Fast Development of Self‐Assembled, Highly Oriented Polymer Thin Film and Observation of Dual Sensing Behavior of Thin Film Transistor for Ammonia Vapor

AbstractThe technological demand for polymer thin film transistors (PTFTs) is continuously increasing because of their potential applications in various kinds of sensor designs. Despite this, there is need for development of a facile technique that can produce high performance low cost PTFTs. Therefore, a facile method is presented for ultrafast formation of large area self‐assembled, highly orientated, crystalline polymer thin films at high surface free energy mobile air–liquid interface named “floated polymer thin film over fluid substrate.” The grown thin film over different solid substrates is studied by multiple‐characterization techniques viz. high resolution‐transmission electron microscopy, grazing incident X‐ray diffraction, absorption spectroscopy, and cyclic voltammetry. Finally, the PTFTs having bottom gate and top contact configuration with the variations in source‐drain (S/D) electrode is fabricated for ammonia sensing. A synergistic enhanced ammonia vapor sensing performance with dual sensing characteristics through Pd‐electrode based PTFTs is observed when it is operated in two different modes of operation, that is, ON state to OFF state and vice‐versa. However, this transition is absent in Au‐electrode based PTFTs. Further, the observation of high gas response and dual sensing phenomena for ammonia vapor is argued by the evidence from a higher (approximately threefold) mobility, scanning electron microscopy (SEM), and atomic force microscopy (AFM) images.

Occurrence and distribution of the coral Dendrophyllia ramea in Cyprus insular shelf: Environmental setting and anthropogenic impacts

Occurrence and abundance of deep-water corals in the Levantine Mediterranean Sea is still largely unknown. This is the first attempt to quantitatively describe a Dendrophyllia ramea population discovered in June 2015 during the CYCLAMEN expedition on board the Research Vessel Aegaeo. This population is the deepest ever described until now in the Mediterranean and was found on the outer insular shelf off eastern Cyprus (Protaras, 35°02′N; 34°05′E). Video transects conducted by means of a remotely operated vehicle revealed a well-developed population of D. ramea located on a sandy seabed at 125–170 m depth. The highest density was 6 colonies m−2 and on average 1.6 ± 1.4 (SD) colonies m−2. The population consists of isolated or piled up branches of various sizes and large colonies, some ∼50 cm max width. The corals thrive on soft bottoms, representing a rather novel aspect of the research on D. ramea, since the species is still considered to be mostly associated with rocky substrates. The occurrence of the species in sedimentary grounds makes it especially vulnerable to bottom contact fishing gears as bottom trawling. Spatial distribution of the coral population, as well as a first attempt to characterize its habitat, are explored as an approach to describe the habitat's suitability and the vulnerability for the species in the area.