Systematic Study of Widely Applicable N‐Doping Strategy for High‐Performance Solution‐Processed Field‐Effect Transistors

A specific design for solution‐processed doping of active semiconducting materials would be a powerful strategy in order to improve device performance in flexible and/or printed electronics. Tetrabutylammonium fluoride and tetrabutylammonium hydroxide contain Lewis base anions, F^? and OH^?, respectively, which are considered as organic dopants for efficient and cost‐effective n‐doping processes both in n‐type organic and nanocarbon‐based semiconductors, such as poly[[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)] (P(NDI2OD‐T2)) and selectively dispersed semiconducting single‐walled carbon nanotubes by π‐conjugated polymers. The dramatic enhancement of electron transport properties in field‐effect transistors is confirmed by the effective electron transfer from the dopants to the semiconductors as well as controllable onset and threshold voltages, convertible charge‐transport polarity, and simultaneously showing excellent device stabilities under ambient air and bias stress conditions. This simple solution‐processed chemical doping approach could facilitate the understanding of both intrinsic and extrinsic charge transport characteristics in organic semiconductors and nanocarbon‐based materials, and is thus widely applicable for developing high‐performance organic and printed electronics and optoelectronics devices.     

Dissolution Behaviors and Applications of Silicon Oxides and Nitrides in Transient Electronics

Silicon oxides and nitrides are key materials for dielectrics and encapsulation layers in a class of silicon‐based high performance electronics that has ability to completely dissolve in a controlled fashion with programmable rates, when submerged in bio‐fluids and/or relevant solutions. This type of technology, referred to as “transient electronics”, has potential applications in biomedical implants, environmental sensors, and other envisioned areas. The results presented here provide comprehensive studies of transient behaviors of thin films of silicon oxides and nitrides in diverse aqueous solutions at different pH scales and temperatures. The kinetics of hydrolysis of these materials depends not only on pH levels/ion concentrations of solutions and temperatures, but also on the morphology and chemistry of the films, as determined by the deposition methods and conditions. Encapsulation strategies with a combination of layers demonstrate enhancement of the lifetime of transient electronic devices, by reducing water/vapor permeation through the defects.     

Aptamer‐Functionalized Multidimensional Conducting‐Polymer Nanoparticles for an Ultrasensitive and Selective Field‐Effect‐Transistor Endocrine‐Disruptor Sensors

An endocrine disruptor (ED) is a type of xenobiotic compound that can cause serious diseases related to the estrous cycle, as well as various types of cancer. At low ED concentrations, estrogen receptors may respond as they would under physiological conditions. In this work, aptamer‐functionalized multidimensional conducting‐polymer (3‐carboxylate polypyrrole) nanoparticles (A_M_CPPyNPs) are fabricated for use in an FET sensor to detect bisphenol A (BPA). The multidimensional system, M_CPPyNPs, is first produced by means of dual‐nozzle electrospray of pristine CPPyNPs and vapor deposition polymerization of additional conducting polymer. The M_CPPyNPs are then immobilized on an amine‐functionalized (–NH₂) interdigitated‐array electrode substrate, through the formation of covalent bonds with amide groups (–CONH). The amine‐functionalized BPA‐binding aptamer is then introduced in the same way as that for M_CPPyNP immobilization. The resulting A_M_CPPyNP‐based FET sensors exhibit ultrasensitivity and selectivity towards BPA at unprecedentedly low concentrations (1 fm ) and among molecules with similar structures. Additionally, due to the covalent bonding involved in the immobilization processes, a longer lifetime is expected for the FET sensor.     

Study on Characteristics of Various RF Transmission Line Structures on PES Substrate for Application to Flexible MMIC

In this work, the coplanar waveguide is fabricated on a PES (poly[ether sulfone]) substrate for application to a flexible monolithic microwave integrated circuit, and its RF characteristics were thoroughly investigated. The quality factor of the coplanar waveguide on PES is 40.3 at a resonance frequency of 46.7 GHz. A fishbone‐type transmission line (FTTL) structure is also fabricated on the PES substrate, and its RF characteristics are investigated. The wavelength of the FTTL on PES is 5.11 mm at 20 GHz, which is 55% of the conventional coplanar waveguide on PES. Using the FTTL, an impedance transformer is fabricated on PES. The size of the impedance transformer is 0.318 mm × 0.318 mm, which is 69.2% of the size of the transformer fabricated by the conventional coplanar waveguide on PES. The impedance transformer showed return loss values better than –12.9 dB from 5 GHz to 50 GHz and an insertion loss better than –1.13 dB in the same frequency range.     

High Performance Millimeter‐Wave Image Reject Low‐Noise Amplifier Using Inter‐stage Tunable Resonators

A Q‐band pHEMT image‐rejection low‐noise amplifier (IR‐LNA) is presented using inter‐stage tunable resonators. The inter‐stage L‐C resonators can maximize an image rejection by functioning as inter‐stage matching circuits at an operating frequency (F_OP) and short circuits at an image frequency (F_IM). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L‐C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR‐LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and F_IM/F_OP of the reported millimeter/quasi‐millimeter wave IR‐LNAs.     

Gas Diffusion,Energy Transport,and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

The thermal conductivity of gas‐permeated single‐walled carbon nanotube (SWCNT) aerogel (8 kg m^?3 density, 0.0061 volume fraction) is measured experimentally and modeled using mesoscale and atomistic simulations. Despite the high thermal conductivity of isolated SWCNTs, the thermal conductivity of the evacuated aerogel is 0.025 ± 0.010 W m^?1 K^?1 at a temperature of 300 K. This very low value is a result of the high porosity and the low interface thermal conductance at the tube–tube junctions (estimated as 12 pW K^?1). Thermal conductivity measurements and analysis of the gas‐permeated aerogel (H₂, He, Ne, N₂, and Ar) show that gas molecules transport energy over length scales hundreds of times larger than the diameters of the pores in the aerogel. It is hypothesized that inefficient energy exchange between gas molecules and SWCNTs gives the permeating molecules a memory of their prior collisions. Low gas‐SWCNT accommodation coefficients predicted by molecular dynamics simulations support this hypothesis. Amplified energy transport length scales resulting from low gas accommodation are a general feature of CNT‐based nanoporous materials.     

Adaptive modulation and coding for Long Term Evolution‐based mobile satellite communication system

The adaptive modulation and coding (AMC) scheme is mandatory for modern wireless communication systems to overcome inevitable channel impairments. Many of the limitations using AMC are due to the long round‐trip delay of a satellite system. This paper proposes an efficient AMC scheme with power control and symbol interleaving that can be effectively applied to satellite systems. In particular, we focus on mobile satellite systems that have maximum compatibility in a Long Term Evolution system. Simulations reveal that the proposed scheme can provide a maximum 10.2% increase of average beam spectral efficiency and a maximum of 8‐dB power gain compared with a conventional AMC scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Adaptive TCX Windowing Technology for Unified Structure MPEG‐D USAC

The MPEG‐D unified speech and audio coding (USAC) standardization process was initiated by MPEG to develop an audio codec that is able to provide consistent quality for mixed speech and music contents. The current USAC reference model structure consists of frequency domain (FD) and linear prediction domain (LPD) core modules and is controlled using a signal classifier tool. In this letter, we propose an LPD single‐mode USAC structure using an adaptive widowing‐based transform‐coded excitation module. We tested our system using official test items for all mono‐evaluation modes. The results of the experiment show that the objective and subjective performances of the proposed single‐mode USAC system are better than those of the FD/LPD dual‐mode USAC system.     

A 3 Gb/s transmitter with a tapless pre-emphasis CML output driver

A 3 Gb/s wireline transmitter (Tx) with a tapless pre-emphasis current-mode logic output driver is presented in this paper. The proposed output driver can support 2.5, 6 and 10 dB pre-emphasis without any additional current tap. It can reduce the current consumption of the output driver by 30 %. The 1.5 GHz phase-locked loop (PLL), multi-phase generator, and 26-to-1 serializer are utilized to serialize 26-bit parallel data to 1-bit 3 Gb/s serial data stream. The rms and peak-to-peak jitters of PLL are 2.97 and 22.5 ps, respectively. The eye opening of the proposed output driver at 3 Gb/s is 0.8UI with a 10 dB loss channel. The current consumption of the output driver is only 5.14 mA, and the Tx is 9 mA. The area of the Tx is 0.72 mm² using the 0.11 μm CMOS process.