High-performance thin-film transistor with 6,13-bis(triisopropylsilylethynyl) pentacene by inkjet printing

We have studied the performance improvement of organic thin-film transistor (OTFT) with a solution based TIPS pentacene (6,13-bis(triisopropylsilylethynyl)pentacene) by inkjet printing. The TIPS pentacene with 1.0 wt.% solution in 1,2-dichlorobenzene was used for printing of an active layer of OTFT. The OTFT printed at room temperature shows a shoulder-like behavior but it disappears for the OTFT printed at the substrate temperature of 60 °C. The OTFT on plastic exhibited an on/off current ratio of ∼10⁷, a threshold voltage of −2.0 V, a gate voltage swing of 0.6 V/decade and a field-effect mobility of 0.24 cm²/Vs in the saturation region.     

Dependence of annealing on stability of transparent amorphous InGaZnO thin film transistor

Bottom-gate transparent IGZO–TFT had been successfully fabricated at relatively low temperature (200 °C). The devices annealing for 4 h at 200 °C exhibit good electrical properties with saturation mobility of 8.2 cm²V^?1s^?1, subthreshold swing of 1.0 V/dec and on/off current ratio of 5×10⁶. The results revealed that the stability of TFT devices can be improved remarkably by post-annealing treatment. After applying positive gate bias stress of 20 V for 5000 s, the device annealing for 1 h shows a larger positive V_th shift of 4.7 V. However, the device annealing for 4 h exhibits a much smaller V_th shift of 0.04 V and more stable.     

Optical,electrical and sensing properties of In2O3 nanoparticles

In this work, various techniques such as differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible-near infrared (UV-vis-NIR), photoluminescence (PL), >as well as electrical and sensor techniques have been used for the characterization of indium oxide (In₂O₃₎ nanoparticles. Here, we also provide insight regarding the optical and electrical characteristics of In₂O₃ nanostructures. The impact of highly sensitive and fast responding gas sensors using In₂O₃ nanostructures is also discussed. It is found that the as-prepared In₂O₃ powder is a pure single phase and is stable up to 800 °C. The size of the particles is in the range of 12 nm as determined by transmission electron microscopy (TEM). The band gap was found to vary linearly with the annealing temperature. A good sensitivity up to 400 ppm was obtained for ethanol and a mechanism is proposed.     

Study of sensitivity and selectivity of α-Fe2O3 thin films for different toxic gases and alcohols

This paper presents a detailed study on the sensitivity and selectivity of α-Fe₂O₃ thin films produced by deposition of Fe and post-deposition annealed at two temperatures of 600 °C and 800 °C with flow of oxygen for application as a sensor for toxic gases including CO, H₂S, NH₃ and NO₂ and alcohols such as C₃H₇OH, CH₃OH, and C₂H₅OH. The crystallographic structure of the samples was studied by X-ray diffraction (XRD) method while an atomic force microscope (AFM) was employed for surface morphology investigation. The electrical response of the films was measured while they were exposed to various toxic gases and alcohols in the temperature range of 50–300 °C. The sample annealed at higher temperature showed higher response for different gases and alcohols tested in this work which can be due to the higher resistance of this sample. Results also indicated that the α-Fe₂O₃ thin films show higher selectivity to NO₂ gas relative to the other gases and alcohols while the best sensitivity is obtained at 200 °C. The α-Fe₂O₃ thin film post-deposition annealed at 800 °C also showed a good stability and reproducibility and a detection limit of 10 ppm for NO₂ gas at the operating temperature of 200 °C.     

Pyrene functioned diarylfluorenes as efficient solution processable light emitting molecular glass

In this paper, we described a new category of solution processable small molecule organic light emitting materials, the pyrene functioned diarylfluorenes: 2PE-PPF and DPE-PPF. They emit blue light in solution and green light in film, and show high thermal stability with the 5% weight loss temperature (T_d) over 400 °C. The glass transition temperature (T_g) for 2PE-PPF and DPE-PPF is 102 °C and 147 °C, respectively. These molecules are interesting molecular glass and they have good film forming abilities. Smooth and uniform film could be obtained by spin-coating. This character enables them able to be used in solution processed OLEDs by spin-coating or jet-printing. Single layered device using 2PE-PPF as the active material shows a turn-on voltage of 3.2 V, brightness over 8000 cd/m² and current efficiency up to 2.55 cd/A. Double layered device by inserting TPBI as the hole-blocking electron-transporting layer increases the maximum efficiency to 5.83 cd/A.     

IGZO thin film transistors with Al2O3 gate insulators fabricated at different temperatures

Thin film transistors (TFTs) with bottom gate and staggered electrodes using atomic layer deposited Al₂O₃ as gate insulator and radio frequency sputtered In–Ga–Zn Oxide (IGZO) as channel layer are fabricated in this work. The performances of IGZO TFTs with different deposition temperature of Al₂O₃ are investigated and compared. The experiment results show that the Al₂O₃ deposition temperature play an important role in the field effect mobility, I_on/I_off ratio, sub-threshold swing and bias stability of the devices. The TFT with a 250 °C Al₂O₃ gate insulator shows the best performance; specifically, field effect mobility of 6.3 cm²/Vs, threshold voltage of 5.1 V, I_on/I_off ratio of 4×10⁷, and sub-threshold swing of 0.56 V/dec. The 250 °C Al₂O₃ insulator based device also shows a substantially smaller threshold voltage shift of 1.5 V after a 10 V gate voltage is stressed for 1 h, while the value for the 200, 300 and 350 °C Al₂O₃ insulator based devices are 2.3, 2.6, and 1.64 V, respectively.     

High-performance diketopyrrolopyrrole-based organic field-effect transistors for flexible gas sensors

We demonstrate high-performance flexible polymer OFETs with P-29-DPP-SVS in various geometries. The mobilities of TG/BC OFETs are approximately 3.48 ± 0.93 cm²/V s on a glass substrate and 2.98 ± 0.19 cm²/V s on a PEN substrate. The flexible P-29-DPP-SVS OFETs exhibit excellent ambient and mechanical stabilities under a continuous bending stress of 1200 times at an R = 8.3 mm. In particular, the variation of μ_FET, V_Th and leakage current was very negligible (below 10%) after continuous bending stress. The BG/TC P-29-DPP-SVS OFETs on a PEN substrate applies to flexible NH₃ gas sensors. As the concentration of NH₃ increased, the channel resistance of P-29-DPP-SVS OFETs increased approximately 100 times from ∼10⁷ to ∼10⁹ Ω at V_SD = −5 V and V_GS = −5 V.     

Influences of annealing temperature on structural,magnetic and optical properties of Zn0.98V0.02O nanoparticles

The Zn_0.98V_0.02O nanoparticles were synthesized by the sol–gel method. The relationship between the annealing temperature (600 °C, 700 °C and 800 °C) and the structural, magnetic and optical properties of the obtained samples was studied. The results showed that Zn ions were partially substituted by V ions. The V doped ZnO nanoparticles annealed at 600 °C and 700 °C were single phase wurtize ZnO structure and they were ferromagnetic at room temperature. On the contrary, the sample annealed at 800 °C had a secondary phase of Zn₃V₃O₈. Therefore it was not saturated even in the field of 10,000 Oe due to the coexistence of ferromagnetic and paramagnetic materials. Photoluminescence results indicated that defects probably were the origin of ferromagnetism in V doped ZnO.     

Aging characteristics of ZnO–V2O5-based varistors for surge protection reliability

The effect of sintering temperature on clamping characteristics and pulse aging behavior of V₂O₅/MnO₂/Nb₂O₅ co-doped zinc oxide varistors was systematically investigated at 875–950 °C. Experimental results related to varistor effect showed that the breakdown field decreased dramatically from 6830 to 968 V/cm with the increase in the sintering temperature and the non-ohmic coefficient exhibited a maximum (49.5) at 900 °C in the sintering temperature. Varistors sintered at 900 °C exhibited the best clamp characteristics for the pulse current of 1–100 A, with the clamp voltage ratio of K = 1.86–2.77. Varistors sintered at 875 °C exhibited the strongest stability; variation rates for the breakdown field, for the non-ohmic coefficient, and for the leakage current density were −14.2%, −63.6%, and 59.0%, respectively, after application of a multi-pulse current of 100 A.     

Properties of high sensitivity ZnO surface acoustic wave sensors on SiO2/(1 0 0) Si substrates

The properties of ZnO/SiO₂/Si surface acoustic wave (SAW) Love mode sensors were examined and optimized to achieve high mass sensitivity. SAW devices A and B, were designed and fabricated to operate at resonant frequencies around 0.7 and 1.5 GHz. The ZnO films grown by pulsed laser deposition on SiO₂/Si demonstrated c-axis growth and the fabricated devices showed guided shear horizontal surface acoustic wave (or Love mode) propagation. Acoustic phase velocity in the ZnO layer was measured in both devices A and B and theoretical and experimental evaluation of the mass sensitivity showed that the maximum sensitivity is obtained for devices with ZnO guiding layer thicknesses of 340 nm and 160 nm for devices A and B, respectively. The performance of the SAW sensors was validated by measuring the mass of a well-characterized polystyrene–polyacrylic acid diblock copolymer film. For the optimized sensors, maximum mass sensitivity values were as high as 4.309 μm²/pg for device A operating at 0.7477 GHz, and 8.643 μm²/pg for device B operating at 1.5860 GHz. The sensors demonstrated large frequency shifts per applied mass (0.1–4 MHz), excellent linearity, and extended range in the femto-gram region. The large frequency shifts indicated that these sensors have the potential to measure mass two to three orders of magnitude lower in the atto-gram range.     

Electrical characterization and TCAD simulations of multi-gate bulk nMOSFET

A multi-gate nMOSFET in bulk CMOS process has been fabricated by integration of polysilicon-filled trenches. We have simulated its electrical characteristics by using TCAD software and compared them with results obtained from electrical measurements. The threshold voltage and the subthreshold slope of the top gate have been extracted and we found a good accordance, for both parameters, between the measurements (V_TH=0.59 V, S=90 mV/dec) and simulations (V_TH=0.50 V, S=92 mV/dec). The surface channel effective mobility of this multi-gate MOSFET was extracted and evaluated with both effective length and surface. The studies revealed that mobility degraded towards smaller dimensions of the MOS channel. At last, the Si/SiO₂ interface quality studies were carried out. We noticed that the injected donor traps have a larger influence on the current–voltage characteristics than acceptor-like traps. With its good electrical performances, this low-cost multi-gate MOSFET technology presents interesting perspective in CMOS image sensors and more generally in analog application taking benefit of the multi-threshold for example.     

Effect of substrate temperature on indium tin oxide (ITO) thin films deposited by jet nebulizer spray pyrolysis and solar cell application

This study focused on the effect of substrate temperature (350 °C, 400 °C, and 450 °C) on morphological, optical, and electrical properties of indium tin oxide (ITO) films deposited onto porous silicon/sodalime glass substrates through jet nebulizer spray pyrolysis for use in heterojunction solar cells. X-ray diffraction analysis confirmed the formation of pure and single-phase In₂O₃ for all the deposited films whose crystallinity was enhanced with increasing substrate temperature, as shown by the increasing (222) peak intensity. Morphological observations were conducted using scanning electron microscopy to reveal the formation of continuous dense films composed of nanograins. The UV–vis spectra revealed that the transmittance increased with increasing substrate temperature, reaching a value of over 80% at 450 °C. The photoelectric performance of the solar cell was studied using the I–V curve by illuminating the cell at 100 mW/cm². A high efficiency (η) of 3.325% with I_sc and V_oc values of 14.8 mA/cm² and 0.60 V, respectively, was attained by the ITO solar cell annealed at 450 °C.     

Characterization of scaled MANOS nonvolatile semiconductor memory (NVSM) devices

We have modeled and characterized scaled Metal–Al₂O₃–Nitride–Oxide–Silicon (MANOS) nonvolatile semiconductor memory (NVSM) devices. The MANOS NVSM transistors are fabricated with a high-K (K_A = 9) blocking insulator of ALD deposited Al₂O₃ (8 nm), a LPCVD silicon nitride film (8 nm) for charge-storage, and a thermally grown tunneling oxide (2.2 nm). A low voltage program (+8 V, 30 μs) and erase (?8 V, 100 ms) provides an initial memory window of 2.7 V and a 1.4 V window at 10 years for an extracted nitride trap density of 6 × 10¹⁸ traps/cm³ eV. The devices show excellent endurance with no memory window degradation to 10⁶ write/erase cycles. We have developed a pulse response model of write/erase operations for SONOS-type NVSMs. In this model, we consider the major charge transport mechanisms are band-to-band tunneling and/or trap-assisted tunneling. Electron injection from the inversion layer is treated as the dominant carrier injection for the write operation, while hole injection from the substrate and electron injection from the gate electrode are employed in the erase operation. Meanwhile, electron back tunneling is needed to explain the erase slope of the MANOS devices at low erase voltage operation. Using a numerical method, the pulse response of the threshold voltages is simulated in good agreement with experimental data. In addition, we apply this model to advanced commercial TANOS devices.     

A study on MIS Schottky diode based hydrogen sensor using La2O3 as gate insulator

In this work, a Metal–Insulator–Semiconductor (MIS) based Schottky-diode hydrogen sensor was fabricated with La₂O₃ as a gate insulator. The electrical properties (current–voltage characteristics, change in barrier height and sensitivity) and hydrogen sensing performance (dynamic response and response time) were examined from 25 °C to 300 °C and towards H₂ with different concentrations. The conduction mechanisms were explained in terms of Fowler–Nordheim tunneling (below 120 °C) and the Poole–Frenkel effect at temperatures (above 120 °C). The results show that at an operating temperature of 260 °C, the sensitivity of the device can reach a maximum value of 4.6 with respect to 10,000-ppm hydrogen gas and its response time was 20 s.     

A methodology for projecting SiO2 thick gate oxide reliability on trench power MOSFETs and its application on MOSFETs VGS rating

In this work, a methodology based on the E-model for the reliability projection of a thick (> 20 nm) SiO₂ gate oxide on a vertical trench power MOSFET, is presented. Experimental results suggest that a Logic Level (LL) trench MOSFET with 35 nm of gate oxide can be rated at V_GS = + 12 V if one assumes continuous DC Gate-Source bias of V_GS = + 12 V at T = 175 °C for 10 years at a defect level of 1 Part Per Million (PPM). We will demonstrate that if we take into account MOSFET device lifetime as dictated by the Automotive Electronics Council (AEC Q101) mission profile, then devices can be rated higher to V_GS = + 14.7 V at T = 175 °C for the same PPM level (1 PPM). The application of the methodology for establishing the oxide thickness, t_ox, for any required voltage rating, is discussed.     

Growth temperature dependence of epitaxial Gd2O3 films on Si(1 1 1)

This article reports on the epitaxy of crystalline high κ oxide Gd₂O₃ layers on Si(1 1 1) for CMOS gate application. Epitaxial Gd₂O₃ thin films have been grown by Molecular Beam Epitaxy (MBE) on Si(1 1 1) substrates between 650 and 750 °C. The structural and electrical properties were investigated depending on the growth temperature. The C–V measurements reveal that equivalent oxide thickness (EOT) equals 0.7 nm for the sample deposited at the optimal temperature of 700 °C with a relatively low leakage current of 3.6 × 10^?2 A/cm² at |V_g ? V_FB| = 1 V.     

Integration of a graphene ink as gate electrode for printed organic complementary thin-film transistors

We demonstrate a new electrode gate based on graphene ink for complementary printed organic metal oxide semiconductor (CMOS) technology on flexible plastic substrates. The goal is to replace the standard silver electrode gate. Devices made with graphene were enhanced and showed a high field-effect mobility of 3 cm² V⁻¹ s⁻¹ for P-type and 0.9 cm² V⁻¹ s⁻¹ for the N-type semiconductors. The improvement is attributed to the increase of the electrical capacitance of the organic dielectric (CYTOP) due to the graphene layer. A seven-stage ring oscillator was made with high oscillation frequencies of 2.1 kHz at 40 V corresponding to a delay/gate value of 34 μs. These performances are promising for use of low cost printed electronic applications.     

Low-operating-voltage polymeric transistor with solution-processed low-k polymer/high-k metal-oxide bilayer insulators

We have successfully demonstrated a polymeric semiconductor-based transistor with low-k polymer/high-k metal-oxide (TiO₂) bilayer as gate dielectric. The TiO₂ layers are readily processable from solution and cured at low temperature, instead of traditionally sputtering or high temperature sintering process, thus may suitable for a low-cost organic field effect transistors (FETs) manufacture. The low-k polymer capped on TiO₂ layer could further smooth the TiO₂ dielectric surface and suppress the leakage current from grain boundary of TiO₂ films. The resulting unpatented P3HT-OFETs could operate with supply voltage less than 10 V and the mobility and threshold voltage were 0.0140 cm²/V s and 1.14 V, respectively. The on/off ratio was 1.0 × 10³.     

Characteristics of ZnOV2O5MnO2Nb2O5Er2O3 semiconducting varistors with sintering processing

The effects of sintering temperature on the microstructure, electrical properties, and dielectric characteristics of ZnOV₂O₅MnO₂Nb₂O₅Er₂O₃ semiconducting varistors have been studied. With increase in sintering temperature the average grain size increased (4.5–9.5 μm) and the density decreased (5.56–5.45 g/cm³). The breakdown field decreased with an increase in the sintering temperature (6214–982 V/cm). The samples sintered at 900 °C exhibited remarkably high nonlinear coefficient (50). The donor concentration increased with an increase in the sintering temperature (0.60×10¹⁸–1.04×10¹⁸ cm^?3) and the barrier height exhibited the maximum value (1.15 eV) at 900 °C. As the sintering temperature increased, the apparent dielectric constant increased by more than four-fold.