Effects of Gd doping on band gap, band offset, oxygen vacancies, and electrical properties of amorphous HfO2 film have been studied. The results show that Gd incorporation helps increase band gap, conduction band offset and conduction band minimum, and reduce oxygen vacancies simultaneously. Kept at the same physical thickness of 5 nm, Gd-doped HfO2 gate dielectric has a leakage current density of 9.0×10−4 A/cm2 at 1 V gate voltage, one and a half orders of magnitude lower than that of the pure HfO2. Gd doping also enhances the dielectric constant. The capacitance equivalent thicknesses of 0.98 nm and 0.81 nm for HfO2 and Gd-doped HfO2 films, respectively, have been obtained.
In this work, a series of molecules TPE-PA-n (n = 3−11) were designed with classic aggregation-induced emission (AIE) 1,1,2,2-tetraphenylethene (TPE) for self-assembled monolayers (SAMs), which are applied for the detection of trace nitroaromatic compound (NAC) explosives. Phosphoric acid that acts as an anchor is used to connect with TPE through alkyl chains of various lengths. It is found that the alkyl chains play a role in pulling TPE luminogens to aggregate for light emission, which can affect the fluorescence and sensing performance of the SAMs. Ulteriorly, a model is built to explore the influence of the alkyl chain length on the device performance, which is determined by the three effects of the alkyl chain: flexibility, the coupling effect, and the odd−even effect. By comparison, the functional molecules with the chain length of 8 were finally selected and further applied for NAC sensors. By means of fluorescence spectra, the SAM sensor was proved to have good stability, reversibility, selectivity, and sensitivity, and its detection limits for trinitrotoluene, dinitrotoluene, and nitrobenzene were 1.2, 6.0, and 35.7 ppm, respectively. This work provides new ideas for the design and preparation of flexible sensors for trace NAC detection with high performance, low cost, and easy operation.
This work has prepared polymeric self-assembled monolayer (SAM) sensors for the detection of trace volatile nitroaromatic compound (NAC) explosives by fluorescence quenching. A typical aggregation-induced emission (AIE) luminogen 1,1,2,2-tetraphenylethene (TPE) polymerizes into PTPE to increase the fluorescence intensity in the SAMs, and the phosphoric acid acts as the anchor group to form stable covalent bonds with the Al 2 O 3 substrate. This design takes advantage of the high sensitivity and good stability of SAMs, and high fluorescence intensity, and "wire effect" of the conjugated polymers. The polymeric SAM sensors are prepared on the Al 2 O 3 silicon wafer and testing paper. Both of them show good response speed, reversibility, selectivity, and sensitivity. The detection limits down to 0.07, 0.35, and 4.11 ppm for TNT, DNB, and NB, respectively, are achieved on the inorganic testing paper. Furthermore, due to the higher fluorescence intensity by interlacing and overlapping of fibers, the detection of the paper can be distinguished by naked eyes even with a low-power handheld UV lamp, which provides an experimental basis for the development of cheap and easy trace NAC explosive sensors.
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