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Characterization and NO2 gas sensing performance of CdO:In2O3 polycrystalline thin films prepared by spray pyrolysis technique
摘要： Polycrystalline CdO:In2O3 thin films for gas sensor applications were prepared on glass and silicon substrates by using one-step spray pyrolysis technique from the aqueous solution of CdCl2 and InCl3 at a substrate temperature of 300 °C. The structure, surface morphology, and the optoelectronic properties of prepared films were characterized respectively by means of X-ray diffraction (XRD), atomic force microscope and UV–visible spectroscopy. Based on the XRD results, the polycrystalline nature of CdO films has been confirmed, and In2O3 films were found to exhibit a preferred orientation along (222) diffracted plane. The grain size varies between 9.0 and 28.4 nm. The results of Hall effect measurement of CdO:In2O3 thin films confirms that all films were an n-type semiconductor. The electrical properties of prepared thin films and their sensitivity to nitrogen dioxide (NO2) gas are also studied. The influence of the operating temperature and In2O3 concentration on the NO2 response were investigated. It is found that all films are sensitive to NO2 gas, and the ideal operating temperature for the film contented 20 vol% of In2O3 was found to be 200 °C at a gas concentration of 25 ppm. The sensing mechanism of the CdO:In2O3 thin film is discussed and attributed to electron transfer between the sensing element and NO2 molecules.
关键词： NO2 gas sensor,Sensitivity,Optoelectronic properties,Structural,Morphology,Metal-oxide semiconductors
更新于2025-09-19 17:15:36
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Influence of an Insulator Layer on the Charge Transport in a Metal/Insulator/n-AlGaN Structure
摘要： In this work, a parametric study revealing the impact of metal-insulator-semiconductor (MIS) structure in improving the electron injection between the n-AlGaN layer and the electrode metal is conducted. After inserting an insulator at the surface between the n-AlGaN layer and the electrode metal, the energy band bending of the thin insulator manipulates the conduction band barrier height between the electrode and the n-AlGaN layer, which enables the electrons to more efficiently tunnel through the thin insulator barrier. As a result, the electrical characteristics for the devices are significantly improved if the MIS structure is optimized. Furthermore, the impact of the affinity, the relative dielectric constant, and the bandgap for the insulator on the electron injection is investigated. Meanwhile, it is found that the electron injection is sensitive to the thickness and the length for the insulator. Detailed analysis regarding the electron transport and the device physics are reported in this work.
关键词： insulators,semiconductors,electrical characteristics,electron transport,n-AlGaN
更新于2025-09-19 17:15:36
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Facet-Dependent Optical Properties of Semiconductor Nanocrystals
摘要： Recent observations of facet-dependent electrical conductivity and photocatalytic activity of various semiconductor crystals are presented. Then, the discovery of facet-dependent surface plasmon resonance absorption of metal–Cu2O core–shell nanocrystals with tunable sizes and shapes is discussed. The Cu2O shells also exhibit a facet-specific optical absorption feature. The facet-dependent electrical conductivity, photocatalytic activity, and optical properties are related phenomena, resulting from the presence of an ultrathin surface layer with different band structures and thus varying degrees of band bending for the {100}, {110}, and {111} faces of Cu2O to absorb light of somewhat different wavelengths. Recently, it is shown that the light absorption and photoluminescence properties of pure Cu2O cubes, octahedra, and rhombic dodecahedra also display size and facet effects because of their tunable band gaps. A modified band diagram of Cu2O can be constructed to incorporate these optical effects. Literature also provides examples of facet-dependent optical behaviors of semiconductor nanostructures, indicating that optical properties of nanoscale semiconductor materials are intrinsically facet-dependent. Some applications of semiconductor optical size and facet effects are considered.
关键词： surface band bending,semiconductors,facet-dependent properties,cuprous oxide,nanocrystals
更新于2025-09-19 17:15:36
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Spectroscopic ellipsometry and morphological characterizations of nanocrystalline Hg1-xMnxO oxide diluted magnetic semiconductor thin films
摘要： The structural, optical spectroscopic ellipsometry and morphological properties of nanocrystalline Hg1-xMnxO (0 ≤ x ≤ 0.2) oxide diluted magnetic semiconductor thin films synthesized by electron beam deposition technique have been investigated by means of X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) techniques. All the deposited films crystallize in the form of a hexagonal crystal structure. The integration between X-ray and atomic force microscopy data shows a very good agreement for the nanosize nature of the deposited films. For the surface roughness, good matching between the results of SE and AFM measurements was observed. In the spectral range 200–1200 nm, the real part (ε1) and imaginary part (ε2) of the dielectric constant of nanocrystalline Hg1-xMnxO films have been extracted from SE measurements. At fixed energy value, the ε1, consequently the refractive index is found to decrease with increasing Mn2+ dopant. In contrary, the energy gap (Eg) of the deposited films determined from the ε2 is found to increase as the Mn2+ concentration increases. The variation of both the ε1 and Eg as a function of Mn2+ concentration is understood based on Lorentz-Lorenz relation and sp-d exchange interaction, respectively. The results reported here show that Mn-doped HgO nanocrystalline films could be employed in the fabrication of nanoscale optical and magneto-optical devices.
关键词： Atomic force microscope,Vapor deposition,Spectroscopic ellipsometry,Optical properties,Semiconductors,AFM,Optical materials,Nanostructured materials,Thin films,X-ray diffraction
更新于2025-09-19 17:15:36
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Theoretical study on the charge transport properties of three series dicyanomethylene quinoidal thiophene derivatives
摘要： It is very important to analyse the most advantageous connection style for quinoidal thiophene derivatives, which are used in n-type organic semiconductor transport materials. In the present work, the charge transport properties of three series of quinoidal thiophene derivatives, oligothiophene (series A), thienothiophene (series B) and benzothiophene (series C), are systematically investigated by employing the full quantum charge transfer theory combined with kinetic Monte-Carlo simulation. The single crystal structures of the molecules we constructed were predicted using the USPEX program combined with density functional theory (DFT) and considering the dispersion corrected. Our theoretical results expounded that how the different connection styles, including oligo-, thieno-, benzo- thiophene in the quinoidal thiophenes derivatives, effectively tune their electronic structures, and revealed that how their intermolecular interactions affect the molecular packing patterns and hence their charge transport properties by symmetry-adapted perturbation theory (SAPT). In the meanwhile we also elucidated the role of end-cyano groups in noncovalent interactions. Furthermore, it is clarified that the quinoidal thiophene derivatives show excellent carrier transport properties due to their optimal molecular stacking motifs and larger electronic couplings besides low energy gap. In addition, our theoretical results demonstrate that quinoidal oligothiophene derivatives (n=3~5) with more thiophene rings will have ambipolar transport properties, quinoidal thienothiophene and benzothiophene derivatives should be promising alternatives as n-type OSC. When we focused only on the electronic transport properties in the three series of molecules, quinoidal benzothiophene derivatives are slightly better than quinoidal oligothiophene and thienothiophene derivatives.
关键词： Crystal structure prediction,Dicyanomethylene quinoidal thiophene,N-type and ambipolar organic semiconductors,Charge transport property,Intermolecular interactions
更新于2025-09-19 17:15:36
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Novel I-doped Bi12O17Cl2 photocatalysts with enhanced photocatalytic activity for contaminants removal
摘要： Novel I-doped Bi12O17Cl2 photocatalysts have been synthesized using a facile chemical precipitation method and characterized by XRD, XPS, SEM, BET and UV–vis DRS etc. The corresponding results indicate that I- ions enter into the crystal lattices of Bi12O17Cl2 and replace partial Cl- ions form an impurity level over valence band and extend the visible light absorption ranges of Bi12O17Cl2. I-doped Bi12O17Cl2 exhibits much superior visible-light (λ > 420 nm) photocatalytic activity to that of the pure Bi12O17Cl2 in the methyl orange (MO) and phenol degradation, because a little amount of I- ions can boost the photocharges separation efficiency, which is ensured by photoluminescence spectra, transient photocurrent responses and electrochemical impedance spectra. It is expected that this work opens a new potential pathway to improve the photocatalytic activity of non-stoichiometric ratios bismuth oxyhalide via ions doping strategy.
关键词： B. Chemical synthesis,C. Electrochemical measurements,D. Catalytic properties,A. Semiconductors
更新于2025-09-19 17:15:36
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The role of cobalt doping on the optical and morphological properties of Mn3O4 nanostructured thin films obtained by SILAR technique
摘要： Cobalt doped manganese oxide thin films (Mn3O4:Co) were successfully deposited on soda lime glass substrates using SILAR technique. Mn3O4:Co thin films were characterized using XRD, SEM, Uv-VIS and Raman spectroscopy. The XRD spectra showed that thin films had substantially Hausmannite crystal structure. The preferential orientation of the pure and 0.5 at.% Co doped manganese oxide thin films (Mn3O4) was (002), but with increasing Co doping, it was detected that this preferential orientation shift towards the (211) plane. The absorbance, transmittance and optical band gap of the Mn3O4:Co thin films were determined using Uv-Vis spectroscopy and these properties of the thin films differed considerably due to cobalt doping. The optical band gap of pure Mn3O4 thin films was 2.00 eV, but on the other hand, due to the Co doping this value increased before and then decreased slightly. Optical transmittance of Mn3O4:Co films increased from 60 % to 70 % with the effect of Co doping. A1g mode, which is the characteristic vibration peak of Mn3O4 films, was confirmed for pure and doped Mn3O4 thin films at a wavelength of 658 nm.
关键词： RAMAN,SILAR,semiconductors,doping effect,Hausmannite
更新于2025-09-19 17:15:36
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Morphology Controlling of ZnO Sub-Micron- and Micro-Structures from Sub-Micron Zinc Citrate Precursor
摘要： A wet-chemical route has been demonstrated to investigate the morphology evolution of high crystalline ZnO sub-micron- and micro-structures created from a zinc citrate precursor consisted of zinc citrate nanoparticles. The concentrations of precursor zinc citrate and the addition of trisodium citrate were key factors in the controlling of ZnO micro-morphology. Assembled growth resulted in the formation of ZnO sub-micron- and micro-structure with twin-cone and flower-like morphologies. The ZnO flower was consisted of cone petals. The shape of ZnO microstructures was further adjusted using trisodium citrate to created thin and thick hexagonal-plates. In the case of a high Zn concentration, thick hexagonal-plates were split into a flower-like morphology. The investigation of morphological evolution indicated that trisodium citrate is critical to control the growth rate of polar (0001) plane. The formation of a flower-like structure is ascribed to the assembly of crystal units with a high zinc citrate concentration.
关键词： Semiconductors,Morphology,Sub-Micron- and Micro-Structures,ZnO
更新于2025-09-19 17:15:36
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Polymer semiconductors incorporating head-to-head linked 4-alkoxy-5-(3-alkylthiophen-2-yl)thiazole
摘要： Polymer semiconductors incorporating head-to-head linked 4-alkoxy-5-(3-alkylthiophen-2-yl) thiazole? Xin Zhou,?ab Peng Chen,?a Chang Woo Koh,c Sheng Chen,a Jianwei Yu,a Xianhe Zhang,a Yumin Tang,a Luca Bianchi,a Han Guo,*a Han Young Woo and Xugang Guo *a *c Head-to-head linked bithiophenes with planar backbones hold distinctive advantages for constructing organic semiconductors, such as good solubilizing capability, enabling narrow bandgap, and e?ective tuning of frontier molecular orbital (FMO) levels using minimal thiophene numbers. In order to realize planar backbone, alkoxy chains are typically installed on thiophene head positions, owing to the small van der Waals radius of oxygen atom and accompanying noncovalent S/O interaction. However, the strong electron donating alkoxy chains on the electron-rich thiophenes lead to elevated FMO levels, which are detrimental to material stability and device performance. Thus, a new design approach is needed to counterbalance the strong electron donating property of alkoxy chains to bring down the FMOs. In this study, we designed and synthesized a new head-to-head linked building block, 4-alkoxy-5-(3-alkylthiophen-2-yl)thiazole (TRTzOR), using an electron-de?cient thiazole to replace the electron-rich thiophene. Compared to previously reported 3-alkoxy-30-alkyl-2,20-bithiophene (TRTOR), TRTzOR is a weaker electron donor, which considerably lowers FMOs and maintains planar backbone through the noncovalent S/O interaction. The new TRTzOR was copolymerized with benzothiadiazoles with distinct F numbers to yield a series of polymer semiconductors. Compared to TRTOR-based analogous polymers, these TRTzOR-based polymers have broader absorption up to 950 nm with lower-lying FMOs by 0.2–0.3 eV, and blending these polymers with PC71BM leads to polymer solar cells (PSCs) with improved open-circuit voltage (Voc) by ca. 0.1 V and a much smaller energy loss (Eloss) as low as 0.59 eV. These results demonstrate that thiazole substitution is an e?ective approach to tune FMO levels for realizing higher Vocs in PSCs and the small Eloss renders TRTzOR a promising building block for developing high-performance organic semiconductors.
关键词： solar cells,thiazole,head-to-head linked,Polymer semiconductors,energy loss
更新于2025-09-19 17:15:36
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Solution and on-surface synthesis of structurally defined graphene nanoribbons as a new family of semiconductors
摘要： Graphene nanoribbons (GNRs) are quasi-one-dimensional subunits of graphene and have open bandgaps in contrast to the zero-bandgap graphene. The high potential of GNRs as a new family of carbon-based semiconductors, e.g. for nanoelectronic and optoelectronic applications, has boosted the research attempts towards fabrication of GNRs. The predominant top-down methods such as lithographical patterning of graphene and unzipping of carbon nanotubes cannot prevent defect formation. In contrast, bottom-up chemical synthesis, starting from tailor-made molecular precursors, can achieve atomically precise GNRs. In this account, we summarize our recent research progress in the bottom-up synthesis of GNRs through three different methods, namely (1) in solution, (2) on-surface under ultrahigh vacuum (UHV) conditions, and (3) on-surface through chemical vapour deposition (CVD). The solution synthesis allows fabrication of long (>600 nm) and liquid-phase-processable GNRs that can also be functionalized at the edges. On the other hand, the on-surface synthesis under UHV enables formation of zigzag GNRs and in situ visualization of their chemical structures by atomic-resolution scanning probe microscopy. While the on-surface synthesis under UHV is typically costly and has limited scalability, the industrially viable CVD method can allow lower-cost production of large GNR films. We compare the three methods in terms of the affordable GNR structures and the resulting control of their electronic and optical properties together with post-processing for device integration. Further, we provide our views on future perspectives in the field of bottom-up GNRs.
关键词： semiconductors,CVD,on-surface synthesis,UHV,Graphene nanoribbons,optoelectronics,bottom-up synthesis,solution synthesis
更新于2025-09-19 17:15:36