The preparation of PT/PEK c films is reported as well as their dielectric and optical properties. The c axis orientation ratio of the films is 68%. Dielectric constant and loss factor at 10 kHz is about 4.023 F/m and ...The preparation of PT/PEK c films is reported as well as their dielectric and optical properties. The c axis orientation ratio of the films is 68%. Dielectric constant and loss factor at 10 kHz is about 4.023 F/m and 0.003, respectively. The refractive indices of the films, n e and n o, are 1.657 3 and 1.627 8 at 0.63 μm wavelength, respectively. The optical band gap of the film with a thickness of 2.33 μm is found to be 3.06 eV.展开更多
The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittan...The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittance （T%）, wide band gap energy （Eg） and high electrical conductivity （σ）. Modifying titanium oxide films with metal nanoparticles would increase electrical conductivity but reduce optical band gap energy. We developed the sol-gel derived titanium suboxide （TiOx） films modified with silver （Ag） or gold （Au） or copper （Cu） nanoparticles （NPs）. This study explores a tradeoff between narrowing optical band gap and enhancing electrical conductivity of nanostructured TiOx films by controlling the Au- or Ag- or Cu-NPs loading concentrations （mol%） in titania. The Au- and Cu-NPs loading concentration of 4 mol% should meet a tradeoff which yields the higher T%, wider Eg and higher compared to those of pure TiOx films. In addition, since the pure Cu is not thermodynamically stable in ambience as compared to Au and Ag, the stability of as-obtained colloidal CuNPs is also examined. A careful examination of the time evolution of surface plasmon resonance （SPR） bands of CuNPs indicates that their stability is only up to 4 h.展开更多
Reflective and transmissive film interference colors were calculated for DLC films on the Si and SiO 2 substrates.The calculated interference colors were compared with photographed colors of the prepared DLC samples.T...Reflective and transmissive film interference colors were calculated for DLC films on the Si and SiO 2 substrates.The calculated interference colors were compared with photographed colors of the prepared DLC samples.The observed film colors were found to match reasonably well with the corresponding calculated colors,indicating that DLC film colors come from interference instead of color center effects.Color charts for DLC films on the Si and SiO 2 substrates with various optical gaps were constructed,and the relationship between interference color and film properties such as optical gap,thickness and substrate were investigated.Usefulness of the calculated color charts in estimating optical gap or thickness of DLC films were demonstrated.展开更多
The ability to fine-tune band gap and band inversion in topological materials is highly desirable for the development of novel functional devices. Here we propose that the electronic properties of free-standing nanome...The ability to fine-tune band gap and band inversion in topological materials is highly desirable for the development of novel functional devices. Here we propose that the electronic properties of free-standing nanomernbranes of the topological crystalline insulators （TCI） SnTe and Pb1-xSnx（Se,Te） are highly tunable by engineering elastic strain and membrane thickness, resulting in tunable band gap and giant piezoconductivity. Membrane thickness governs the hybridization of topological electronic states on opposite surfaces, while elastic strain can further modulate the hybridization strength by controlling the penetration length of surface states. We propose a frequency-resolved infrared photodetector using force-concentration induced inhomogeneous elastic strain in TCI nanomembranes with spatially varying width. The predicted tunable band gap accompanied by strong spin-textured electronic states will open new avenues for fabricating piezoresistive devices, infrared detectors and energy-efficient electronic and spintronic devices based on TCI nanomembrane.展开更多
One polythiophene derivative PT3T and two low band gap copolymers,PBTT-T3T and PBTT,with different ratios of 5,6-dini-trobenzothiadiazole as the acceptor unit in the polymer backbone have been synthesized by Pd-cataly...One polythiophene derivative PT3T and two low band gap copolymers,PBTT-T3T and PBTT,with different ratios of 5,6-dini-trobenzothiadiazole as the acceptor unit in the polymer backbone have been synthesized by Pd-catalyzed Stille-coupling polymerizations.Thermal stability,X-ray diffraction analyses,UV-vis absorption spectra,photoluminescence spectra and electrochemical properties of the copolymers were investigated.The band gap estimated from UV-vis-NIR spectra of the copolymers films varied from 1.39 to 1.94 eV.Among these copolymers,the films of PBTT-T3T and PBTT,which contain the 5,6-dinitrobenzothiadiazole unit,cover a broad wavelength range in the visible and near-infrared region from 400 to 1000 nm with the maximal peak absorption around 700 nm,which is exactly matched with the maximum in the photon flux of the sun.展开更多
Indium oxide(In_2O_3) films were prepared on Al_2O_3(0001) substrates at 700 °C by metal-organic chemical vapor deposition(MOCVD).Then the samples were annealed at 800 °C,900 °C and 1 000 °C,respec...Indium oxide(In_2O_3) films were prepared on Al_2O_3(0001) substrates at 700 °C by metal-organic chemical vapor deposition(MOCVD).Then the samples were annealed at 800 °C,900 °C and 1 000 °C,respectively.The X-ray diffraction(XRD) analysis reveals that the samples were polycrystalline films before and after annealing treatment.Triangle or quadrangle grains can be observed,and the corner angle of the grains becomes smooth after annealing.The highest Hall mobility is obtained for the sample annealed at 900 °C with the value about 24.74 cm^2·V^(-1)·s^(-1).The average transmittance for the films in the visible range is over 90%.The optical band gaps of the samples are about 3.73 e V,3.71 e V,3.70 eV and 3.69 eV corresponding to the In_2O_3 films deposited at 700 °C and annealed at 800 °C,900 °C and 1 000 °C,respectively.展开更多
文摘The preparation of PT/PEK c films is reported as well as their dielectric and optical properties. The c axis orientation ratio of the films is 68%. Dielectric constant and loss factor at 10 kHz is about 4.023 F/m and 0.003, respectively. The refractive indices of the films, n e and n o, are 1.657 3 and 1.627 8 at 0.63 μm wavelength, respectively. The optical band gap of the film with a thickness of 2.33 μm is found to be 3.06 eV.
文摘The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittance （T%）, wide band gap energy （Eg） and high electrical conductivity （σ）. Modifying titanium oxide films with metal nanoparticles would increase electrical conductivity but reduce optical band gap energy. We developed the sol-gel derived titanium suboxide （TiOx） films modified with silver （Ag） or gold （Au） or copper （Cu） nanoparticles （NPs）. This study explores a tradeoff between narrowing optical band gap and enhancing electrical conductivity of nanostructured TiOx films by controlling the Au- or Ag- or Cu-NPs loading concentrations （mol%） in titania. The Au- and Cu-NPs loading concentration of 4 mol% should meet a tradeoff which yields the higher T%, wider Eg and higher compared to those of pure TiOx films. In addition, since the pure Cu is not thermodynamically stable in ambience as compared to Au and Ag, the stability of as-obtained colloidal CuNPs is also examined. A careful examination of the time evolution of surface plasmon resonance （SPR） bands of CuNPs indicates that their stability is only up to 4 h.
基金supported in part by the National Basic Research Programof China (Grant No. 2012CB933502)
文摘Reflective and transmissive film interference colors were calculated for DLC films on the Si and SiO 2 substrates.The calculated interference colors were compared with photographed colors of the prepared DLC samples.The observed film colors were found to match reasonably well with the corresponding calculated colors,indicating that DLC film colors come from interference instead of color center effects.Color charts for DLC films on the Si and SiO 2 substrates with various optical gaps were constructed,and the relationship between interference color and film properties such as optical gap,thickness and substrate were investigated.Usefulness of the calculated color charts in estimating optical gap or thickness of DLC films were demonstrated.
文摘The ability to fine-tune band gap and band inversion in topological materials is highly desirable for the development of novel functional devices. Here we propose that the electronic properties of free-standing nanomernbranes of the topological crystalline insulators （TCI） SnTe and Pb1-xSnx（Se,Te） are highly tunable by engineering elastic strain and membrane thickness, resulting in tunable band gap and giant piezoconductivity. Membrane thickness governs the hybridization of topological electronic states on opposite surfaces, while elastic strain can further modulate the hybridization strength by controlling the penetration length of surface states. We propose a frequency-resolved infrared photodetector using force-concentration induced inhomogeneous elastic strain in TCI nanomembranes with spatially varying width. The predicted tunable band gap accompanied by strong spin-textured electronic states will open new avenues for fabricating piezoresistive devices, infrared detectors and energy-efficient electronic and spintronic devices based on TCI nanomembrane.
基金support from the National Natural Science Foundation of China (50933003 & 50903044)MOST of China (2009AA032304)
文摘One polythiophene derivative PT3T and two low band gap copolymers,PBTT-T3T and PBTT,with different ratios of 5,6-dini-trobenzothiadiazole as the acceptor unit in the polymer backbone have been synthesized by Pd-catalyzed Stille-coupling polymerizations.Thermal stability,X-ray diffraction analyses,UV-vis absorption spectra,photoluminescence spectra and electrochemical properties of the copolymers were investigated.The band gap estimated from UV-vis-NIR spectra of the copolymers films varied from 1.39 to 1.94 eV.Among these copolymers,the films of PBTT-T3T and PBTT,which contain the 5,6-dinitrobenzothiadiazole unit,cover a broad wavelength range in the visible and near-infrared region from 400 to 1000 nm with the maximal peak absorption around 700 nm,which is exactly matched with the maximum in the photon flux of the sun.
基金supported by the National Natural Science Foundation of China(Nos.6127411311204212 and 61404091)+5 种基金the Program for New Century Excellent Talents in University(No.NCET-11-1064)the Tianjin Natural Science Foundation(Nos.13JCYBJC1570013JCZDJC2610014JCZDJC31500 and 14JCQNJC00800)the Tianjin Science and Technology Developmental Funds of Universities and Colleges(Nos.2010070320130701 and 20130702)
文摘Indium oxide(In_2O_3) films were prepared on Al_2O_3(0001) substrates at 700 °C by metal-organic chemical vapor deposition(MOCVD).Then the samples were annealed at 800 °C,900 °C and 1 000 °C,respectively.The X-ray diffraction(XRD) analysis reveals that the samples were polycrystalline films before and after annealing treatment.Triangle or quadrangle grains can be observed,and the corner angle of the grains becomes smooth after annealing.The highest Hall mobility is obtained for the sample annealed at 900 °C with the value about 24.74 cm^2·V^(-1)·s^(-1).The average transmittance for the films in the visible range is over 90%.The optical band gaps of the samples are about 3.73 e V,3.71 e V,3.70 eV and 3.69 eV corresponding to the In_2O_3 films deposited at 700 °C and annealed at 800 °C,900 °C and 1 000 °C,respectively.
