电致变色器件中表面粗糙度，界面层检测方案(椭偏仪)

Application NoteOptical CoatingsUVISELSpectroscopic Ellipsometry SE17 Spectroscopic Ellipsometry Characterization of Electrochromic Devicesby Spectroscopic Ellipsometry Celine Eypert-Application Scientist - Thin Film Division Compounds that change colour visibly and reversibly when subjected to a change in their environ-ment (heat， light， pressure) are known as chromogenic materials. There are four major categoriesS：electrochromic， thermochromic， photochromic andpiezochromic. The change in opticall propertie：Scan be in the torm ot absorption， retlectance，or scattering. The change can be either in the visibleor beyond the visible spectrum. Electrochromic (EC) materials have been finding several ap-olications in smart windows，anti-dazzling rear view mirrors，switchable motorcycle helmet， tor contrast enhancement insome emissive display devices and in non-emissive largearea colour displays for information advertisement. The study of EC materials is an interdisciplinary field. In anelectrochemical cell of EC devices the discharged positiveons are free to diffuse into a thin solid film (electrode) of thehost material， modifying its electronic structure to create acoloured material. There are two major classes of materials，ion-insertion/extraction type such as tungsten trioxide， andnon-insertion groups such as the viologens. Tungsten trioxide WO3 is commonly used as it is one of thepest choices for the primary working electrode material forEC devices.It provides high charge capacity and has long-term cyclability. It goes blue in insertion of Li or other metals，nydrogen andguest atoms. Viologens are a family of halidesof quaternary bases that change from clear to bluish purple. The refractive index (n)， extinction coefficient (k)， and thick-ness (d) are important parameters for predicting the perform-ance of a film in an optical system. These optical parametersare also sensitive to the microstructure， and are often affect-ed by the deposition conditions and doping materials.Spectroscopic ellipsometry is the ideal technique to measurehese parameters simultaneously， very accurately and nondestructively for the samples under study. Basic Electrochromic Film Device Structures A micrometre-thick multilayer structure contains two trans-parent electrical conduction layers and two electrodes capa-ole of charge (ion) insertion/extraction. One of the electrodemust be electrochromic； and it usually consists of tungstenoxide. The other electrode can either be a complementarycolouring EC material or a material that remains transparentupon charge insertion (stock layer or ion storage layer). Ex-amples of ion storage materials are Nb2O5， V205， NiO，lrO2· Experimental Ellipsometric data were collected at an angle of incidence of70°using the UVISEL NIR (260-2100nm). The full electro-chromic device characterization was successfully carried outby spectroscopic ellipsometry in the spectral range 1-4 eV(1240-310nm). For multilayer samples it is always helpful and often neces-sary to characterize the structure step by step. The combination of phase modulation technology ofthe UVI-SEL and the advanced data analysis features included in theDeltaPsi2 software allows very hhigh accuracy for thin filmmeasurements on transparent substrates. Characterization of Glass/ITO/WO， device The following structure has been used to model the sample.The introduction of a very thin interface between the two lay-ers of WOx and ITO significantly improves the goodness offit parameter (x2=9.11→2.86). This interface is richer intungsten and is described by a mixture of 35.5% W + 64.5%WOx using the effective medium approximation. Roughness WOx 35.5%W + 64.5% WOinterface ITO Glass substrate Characterization of Glass/ITO/TiVO，device Characterization of Glass/ITO/TiVO，/Ta2O5device Characterization of Glass/ITO/TiVO/Ta2Os/WOx device Roughness WOx Ta205 TiVo， ITO The optical constants have been determined using： ·a combined Lorentz oscillator and Drude term for ITO an absorbing Lorentz oscillator for Ta205 the new amorphous dispersion formula for WOx andTiVO All these dispersion formulae are included in the DeltaPsi2software that allows accurate modelling of a large variety ofmaterials as well as describing complex behaviours such asgradient or anisotropy. ITO Optical Constants Conclusion The UVISEL Spectroscopic Ellipsometer is a powerful instru-ment for characterizing complete EC devices with high accu-racy and reliability， and provides information on surfaceroughness or interface layers along with their composition. HORIBAJOBIN YVONHORIBAExplore the future Find us at www.jobinyvon.com or telephone：China： + Other Countries： +() ORIBAExplore the future The UVISEL Spectroscopic Ellipsometer is a powerful instrument for characterizing complete EC devices with high accuracy and reliability, and provides information on surface roughness or interface layers along with their composition.