Ammonia chemiresistor sensor based on poly-3-hexylthiophene film oxidized by nitrosonium hexafluorophosphate

An ammonia chemiresistor sensor is demonstrated on the basis of<br />poly(3-hexylthiophene) film oxidized by nitrosonium hexafluorophosphate. The sensor gave a good response to ammonia, while was insensitive to a variety of organic vapors. The detection limit was estimated to be ca. 0.22 ppm. The redox reaction between ammonia and bipolarons was attributed to the<br />sensor signals

Self-adaptive electronic contact between graphene and semiconductors

<div class="aip-paragraph">Understanding the contact properties of graphene on semiconductors is crucial to improving the performance of graphene optoelectronic devices. Here, we show that when graphene is in contact with a semiconductor, the charge carrier transport into graphene leads to a self-adaptive shift of the Fermi level, which tends to lower the barrier heights of the graphene contact to both <em class="emphitalic">n-</em> and <em class="emphitalic">p-</em>type semiconductors. A theoretical model is presented to describe the charge carrier transport mechanism and to quantitatively estimate the barrier heights. These results can benefit recent topical approaches for graphene integration in various semiconductor devices.</div

Layer-Controlled and Wafer-Scale Synthesis of Uniform and High-Quality Graphene Films on a Polycrystalline Nickel Catalyst

<div class="para"><p>Chemical vapor deposition (CVD) provides a synthesis route for large-area and high-quality graphene films. However, layer-controlled synthesis remains a great challenge on polycrystalline metallic films. Here, a facile and viable synthesis of layer-controlled and high-quality graphene films on wafer-scale Ni surface by the sequentially separated steps of gas carburization, hydrogen exposure, and segregation is developed. The layer numbers of graphene films with large domain sizes are controlled precisely at ambient pressure by modulating the simplified CVD process conditions and hydrogen exposure. The hydrogen exposure assisted with a Ni catalyst plays a critical role in promoting the preferential segregation through removing the carbon layers on the Ni surface and reducing carbon content in the Ni. Excellent electrical and transparent conductive performance, with a room-temperature mobility of &asymp;3000 cm² V^&minus;1 s^&minus;1 and a sheet resistance as low as &asymp;100 &Omega; per square at &asymp;90% transmittance, of the twisted few-layer grapheme films grown on the Ni catalyst is demonstrated.</p></div