Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

A Simple Non-Invasive Biomarker Can Reflect Both the Acute and Chronic Pulmonary Impact of Patent Ductus Arteriosus (PDA) Shunting

The SFR (Sp02/Fi02 ratio) offers a continuous, non-invasive reflection of pulmonary function regardless of whether the baby is ventilated or breathing spontaneously. We hypothesized that significant PDA shunting would impair pulmonary oxygen diffusion, in turn, reflected by decreased SFR; and that early PDA related decreases in SFR will predict subsequent chronic lung disease (CLD). Methods: We retrospectively examined records from preterm neonates <30 weeks gestational age. Ductal shunting was graded for severity by first week echocardiogram. SFR was calculated as SpO2/Fi02 and recorded on day 7 of life and at 36 weeks postmenstrual age (PMA). Results: We studied 104 infants: 65 with closed duct; 17 with hemodynamically insignificant PDA and 22 with hemodynamically significant (hsPDAs). CLD developed in 9 (14%) of those with closed ducts; 6 (35%) of those with hisPDA; and in 12 (55%) of those with hsPDA (p=0.005). Babies with hsPDA had significantly lower SFR values at both time points. SFRs in babies with hisPDA were decreased at 1 week postnatally, but were similar to those of babies with closed ducts at 36 weeks. SFR at 36 wks. was decreased only in infants with hsPDA [[467[461,467] vs. 467[413,471] vs. 369[262,436] respectively; p=0.000148]. Using ROC curve analysis, week 1 SFR was strongly associated with hsPDA (AUC=0.770; p<0.0001) and highly predictive (AUC=0.801; p<0.0001) of CLD at 36 weeks PMA. Conclusion: Early decreases in SFR reflect both the acute and chronic pulmonary impact of PDA shunting, possibly providing the missing link supporting an association between hemodynamically significant PDA and subsequent CLD.

Nanostructured gas diffusion layer to improve direct oxygen reduction reaction in Air-Cathode Single-Chamber Microbial Fuel Cells

The aim of this work is the development of new nanostructured-gas-diffusion-layer (GDL) to improve the overall behaviour of Air-Cathode Single-Chamber-Microbial-Fuel-Cells (SCMFCs). The design of new nanostructured-GDL allowed exploiting all nanofibers ’intrinsic properties, such as high surface ratio to volume, high porosity, achieving thus a good oxygen diffusion into the proximity of catalyst layer, favouring thus the direct oxygen-reduction-reaction (ORR). Nanostructured-GDLs were prepared by electrospinning process, using a layer-by-layer deposition to collect 2 nanofibers’ mats. The first layer was made of cellulose nanofibers able to promote oxygen diffusion into SCMFC. The second layer, placed outwards, was based on polyvinyl-fluoride (PVDF) nanofibers to prevent the electrolyte leakage. This nanostructured-GDL plays a pivotal role to improve the overall performance of Air-Cathode-SCMFCs. A maximum current density of 20 mA m-2 was obtained, which is higher than the one reached with commercial-GDL, used as reference material. All results were analysed in terms of energy recovery parameter, defined as ratio of generated power integral and the internal volume of devices, evaluating the overall SCMFC performance. SCMFCs with a nanostructured-GDL showed an energy recovery equal to 60.83 mJ m-3, which was one order of magnitude higher than the one obtained with commercial-GDL, close to 3.92 mJ m-3.