The density functional theory is performed to investigate the energy band structure, effective mass and carrier mobility of Graphene/ZnO (G/ZnO) heterojunction. The intrinsic G/ZnO heterojunction has higher electron mobility (4.323 m2/V⋅s) as compared to Graphene and ZnO. The adsorption of H2O and O2 molecules significantly reduces the carrier mobility of the G/ZnO heterojunction. Then, the number of H2O and O2 molecules is changed from 1 to 4. The results show that electron mobility of the G/ZnO heterojunction increase with increasing number of H2O, but the opposite is true for O2. Therefore, both strain and external electric field (Eext) are used to regulate the electronic properties. The carrier mobility are significantly enhanced under appropriate Eext. In this work, under the strain and Eext, the calculation about the adsorption of H2O and O2 will play an important role in monitoring the stability of G/ZnO heterojunction based microelectronic devices in the external environment.
The heterostructure consisting of zinc oxide and reduced graphene oxide (ZnO/rGO/ZnO) is prepared on cotton fabric by repeated immersion and magnetron sputtering. In addition, the gas selectivity of the sample is analyzed based on I-V characteristics under different gas atmospheres (air, methanal, ethanol, acetone and toluene). Compare with that in air atmosphere, the I-V characteristic curve under toluene gas atmosphere changes significantly, and the current decreased significantly. The experimental results show that the samples exhibit high selectivity. In order to study the intrinsic physical characteristics of the heterostructure after gas adsorption, the band structures, density of states (DOS), adsorption energy (Ead) and charge density difference (CDD) are calculated based on density function theory (DFT). The existence of rGO results in a high electrical conductivity, which is consistent with the experimental results. Meanwhile, toluene has the highest Ead (-0.85 eV) and charge transfer (0.67 e). The charge transfer results prove that a large number of electrons are transferred from the surface of the heterostructure to the vicinity of toluene molecules, which leads to a change in the electrical conductivity of the heterostructure. Based on the excellent gas selectivity, the application of cotton-based ZnO/rGO/ZnO structure in gas sensing field is promoted.
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