ZnO nanorod arrays were fabricated in aqueous solutions under external voltages.The morphology and length of the nanorods could be readily controlled by varying such parameters as the voltage magnitude,growth time,solution concentration and substrate type.The external voltage,which made the adsorption of the Zn 2+ cation-containing complexes more possible,modified the growth behavior of the ZnO crystals and played a key role in guaranteeing the orderliness of the arrays.The increase in the nanorod length with the prolonged growth time gradually saturated due to the balance between the growth and the erosion.The ZnO nanorods respectively grown on the Zn and Si substrates differed considerably in both morphology and defect concentration.Field emission was extracted from arrays of nanorods with tapered ends.This field-assisted solution route for fabricating ZnO nanorods featured simplicity in manipulation,inexpensiveness in instrumentation,and effectiveness in controlling the morphology and length.
An increase of work function(0.3 eV) is achieved by irradiating poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) film in vacuum with 254-nm ultraviolet(UV) light. The mechanism for such an improvement is investigated by photoelectron yield spectroscopy, X-ray photo electron energy spectrum, and field emission technique. Surface oxidation and composition change are found as the reasons for work function increase. The UV-treated PEDOT:PSS film is used as the hole injection layer in a hole-only device. Hole injection is improved by UV-treated PEDOT:PSS film without baring the enlargement of film resistance. Our result demonstrates that UV treatment is more suitable for modifying the injection barrier than UV ozone exposure.
We describe a simple method to increase the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)film by exposure to ultraviolet(UV)light in vacuum.Up to four order of conductivity improvement(from 10 3to 50 S/cm)is achieved by irradiating PEDOT:PSS film with 254 nm ultraviolet(UV)light.Increased conductivity in UV treated PEDOT:PSS film is stable under ambient exposure.The mechanism for conductivity improvement is investigated by current-voltage measurement,atomic force microscopy,and absorption spectrum.Photo-cross-linking of PSS chains is determined as the reason for conductivity improvement.Our result demonstrates that UV treatment is capable of modifying the conductivity of PEDOT:PSS film independent of the process of film formation.
In this paper,configuration parameters of the waveguide are altered independently or simultaneously to control the cutoff frequencies of the guided band.The independent control range of the upper and lower cutoff frequencies is 55.0% and 63.9% of the photonic band gap(PBG),respectively.The regulating range of the simultaneous tuning can be as large as 28.6% in terms of the PBG,or 240% in terms of the bandwidth.This tuning cutoff frequency method provides an efficient way to tailor the guided band and further tune the optical properties of PhCWs.
Tungsten oxide(W 18 O 49) nanorods were grown by directly heating tungsten foils covered with potassium bromide(KBr) in low-pressure wet oxygen.The approach featured such advantages as convenient manipulation,low cost and rapid accessibility to high temperatures.A solid-liquid-solid(SLS) mechanism is believed to have dominated the growth process,in which the W 18 O 49 nanorods segregated from eutectic droplets of potassium tungstate and tungsten oxide.The ultraviolet photoelectron spectroscopy(UPS) analysis disclosed that the valence band maximum(VBM) of these nanorods was approximately 9 eV below the vacuum level.The feasibility of using the such-fabricated nanorods as field emitters was tested and the related mechanism was also discussed.
