Subthreshold characteristics of pentacene field-effect transistors influenced by grain boundaries.

Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs

Alignment of liquid crystal/carbon nanotube dispersions for application in unconventional computing

We demonstrate the manipulation of single-walled carbon nanotube/liquid crystal composites using in-plane electric fields. The conductivity of the materials is shown to be dependant on the application of a DC bias across the electrodes. When the materials are subjected to this in-plane field, it is suggested that the liquid crystals orientate, thereby forcing the SWCNTs to follow in alignment. This process occurs over many seconds, since the SWCNTs are significantly larger in size than the liquid crystals. The opportunity for applying this material to unconventional computing problems is suggested

Enhanced THz transmission apertures through sub-wavelength annular apertures

We report on the development of a surface micromachined process for the fabrication of coaxial apertures surrounded by periodic grooves. The process uses a combination of copper electroforming and the negative epoxy based resist, SU8, as a thin flexible substrate. The device dimensions are suitable for the implementation of filters at THz frequencies, and measurements show a pass band centred around 1.5 THz. These devices could form the basis of the next generation of THz biosensors

Diodos orgánicos emisores de luz: estrategias para la optimización de dispositivos y la obtención de un oled blanco

III Encuentro sobre Nanociencia y Nanotecnología de Investigadores y Tecnólogos Andaluce

Zinc oxide thin-film transistors fabricated at low temperature by chemical spray pyrolysis

We report the electrical behavior of undoped zinc oxide thin-film transistors (TFTs) fabricated by low-temperature chemical spray pyrolysis. An aerosol system utilizing aerodynamic focusing was used to deposit the ZnO. Polycrystalline films were subsequently formed by annealing at the relatively low temperature of 140°C. The saturation mobility of the TFTs was 2 cm2/Vs, which is the highest reported for undoped ZnO TFTs manufactured below 150°C. The devices also had an on/off ratio of 104 and a threshold voltage of −3.5 V. These values were found to depend reversibly on measurement conditions

Effects of hydrogen plasma treatment on the electrical behavior of solution-processed ZnO transistors

The effects of hydrogen plasma treatment on the active layer of top-contact zinc oxide thin film transistors are reported. The transfer characteristics of the reference devices exhibited large hysteresis effects and an increasing positive threshold voltage (VTH) shift on repeated measurements. In contrast, following the plasma processing, the corresponding characteristics of the transistors exhibited negligible hysteresis and a very small VTH shift; the devices also possessed higher field effect carrier mobility values. These results were attributed to the presence of functional groups in the vicinity of the semiconductor/gate insulator interface, which prevents the formation of an effective channel

Evolution of Electronic Circuits using Carbon Nanotube Composites

Evolution-in-materio concerns the computer controlled manipulation of material systems using external stimuli to train or evolve the material to perform a useful function. In this paper we demonstrate the evolution of a disordered composite material, using voltages as the external stimuli, into a form where a simple computational problem can be solved. The material consists of single-walled carbon nanotubes suspended in liquid crystal; the nanotubes act as a conductive network, with the liquid crystal providing a host medium to allow the conductive network to reorganise when voltages are applied. We show that the application of electric fields under computer control results in a significant change in the material morphology, favouring the solution to a classification task

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease