We investigate the effects of ambient atmosphere on the electrical performance of p-type tin monoxide (SnO) thinfilm transistors (TFTs), and present the effective method for the passivation of SnO TFTs using a SU-8 organic layer. The experimental data shows that the SnO TFTs without a passivation layer suffer from the electrical performance degradation under humid environments, which implies that the formation of the passivation layer is necessary in p-type SnO TFTs for the stable operation of the devices. The SU-8 organic layer was successfully incorporated as a passivation layer of SnO TFTs. The SnO TFTs with a SU-8 passivation layer exhibit very similar transfer characteristics with those without a passivation layer, and show much improved long-term durability and bias stress stability compared with the SnO TFTs without a passivation layer under air environments.Index Terms-P-type SnO TFTs, SU-8 passivation layer, humidity, long-term durability, bias stress stability.

We investigate the effects of environmental water and oxygen on the electrical stability of p-type tin monoxide (SnO) thin-film transistors (TFTs). Under negative gate bias stresses, there was a larger threshold voltage shift ( V th ) in the devices that had been exposed to water than that for the devices that remained unexposed. However, under positive gate bias stresses, devices that had been exposed to water exhibited approximately the same V th as what was observed in devices that had not been exposed. This phenomenon is attributed to the generation of residual-water-related hole traps near the valence band edge in SnO TFTs. In addition, we observed that the environmental oxygen partial pressure had very little effect on the electrical stability of p-type SnO TFTs under either negative or positive gate bias stresses. The weak chemisorption of oxygen molecules caused by high ionization energy can be a plausible mechanism for the oxygen insensitivity of negative gate bias-stress-induced instabilities, and the low electron concentration near the exposed back-channel of p-type SnO TFTs can possible explain the oxygen insensitivity of positive gate bias-stress-induced instabilities.Index Terms-P-type SnO TFTs, environmental water, environmental oxygen, negative gate bias stresses, positive gate bias stresses, electrical stability.

The permeable pavement is one of Low Impact Development technics that allows stormwater to infiltrate through the pavement surface and the underlying base layer, thereby reducing surface runoff and preventing water contamination. For permeable base layers of permeable pavements, open-graded aggregates are often used to infiltrate and store stormwater in the pore of aggregate base layers. The mechanical behavior of open-graded aggregates has not been a major interest of pavement industry and society, and therefore there is much less information known for behavior of compacted open-graded aggregates comparing to dense-graded materials. This study aims at investigating the mechanical behavior of compacted permeable or open-graded aggregate base materials based on field experiments. Five different open-graded aggregates were selected, and they were compacted in the field up to 12 passes with a 10-ton vibratory compaction roller. The mechanical behaviors of aggregates were evaluated by conducting plate load tests at 2, 4, 8, and 12 passes of roller. For the test conditions considered herein, the strain modulus at the first loading seems to provide more consistent results with respect to aggregate types and level of compaction than other stiffness measures from plate load tests.

This paper experimentally investigates the subgap density of states (DOS) in p-type tin monoxide (SnO) thin-film transistors (TFTs) for the first time by using temperature-dependent field-effect measurements. As the temperature increases, the turn-on voltage moves in the positive direction, and the off-current and subthreshold slope continuously increase. We found that the conductivity of the SnO TFT obeys the Meyer-Neldel (MN) rule with a characteristic MN parameter of 28.6 eV −1 in the subthreshold region, from which we successfully extracted the subgap DOS by combing the field-effect method and the MN relation. The extracted subgap DOS from fabricated p-type SnO TFTs are exponentially distributed in energy, and exhibit around two orders of magnitude higher values compared to those of the n-type amorphous indium-gallium-zinc oxide TFTs.

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