Study On Preparation And Properties Of ITO Flexible Transparent Conducitve Films Based On Copper

Transparent conductive oxides （TCO） are widely used in solar cells, flat panel displays,gas sensors, thin film resistors, and optoelectronic devices, ITO film is one of the focus. Withthe development of science, low-temperature preparation of TCO thin films on flexiblesubstrates has become a hot research topic.Because the surface of flexible substrate is not smooth, easily absorb moisture and gas,wepre-prepared SiO₂buffer layer to solve the above problems. ITO films are usually deposited ata temperature higher than250℃and annealed at a temperature higher than300℃in order toobtain high transmittance and conductivity. High temperature is not an effective processcondition when ITO films are deposited on a polymer substrate to be applied in flexibleoptoelectronic devices. One way to improve the optoelectronic properties of the ITO filmswithout substrate heating or post-annealing is to use ITO/Cu/ITO sandwich structure filmswhich have lower resistivity than ITO single layer films of the same thickness.Study found that the surface roughness of the ITO/Cu/ITO films is strongly affected by theunderlying SiO₂buffer layers. SiO₂buffer layers have little effect on the transmittance of allthe ITO/Cu/ITO films which has a positive effect on improving the electrical properties ofITO/Cu/ITO film. Introduction of a SiO₂buffer layer with proper thickness can lower theresistivity of the ITO/Cu/ITO films. The ITO/Cu/ITO film with a40nm SiO₂buffer layer hadthe lowest sheet resistance （143/sq） and the highest transmittance （65%） at550nm.We investigate the properties of the multilayer deposited at different Cu interlayerthickness with a40nm SiO₂buffer layer. The thickness of bottom ITO and upper ITO film iskept constant at40nm and35nm respectively. The SiO₂/ITO/Cu/ITO film with a3.8nm Culayer shows the transmission of68%and50%. The optical transmission mainly depends onthe Cu layer. The resistivity of the SiO₂/ITO/Cu/ITO films decreases rapidly when the Cuinterlayer thickness increases. The SiO₂（40nm）/ITO（40nm）/Cu（5nm）/ITO（35nm） film hassheet resistance of143/sq, transmittance of65%at550nm, φTCof9.4×10-5-1.There is no significant impact on the structure of the SiO₂/ITO/Cu/ITO film with thevariation of ITO thickness. Film is still amorphous. But the optical transmittance andabsorption is affected. In some case, the optical transmittance increase as the ITO thicknessincrease, which indicate that the optical transmission mainly depends on the Cu layer. Sheet resistance decrease as the ITO thickness increased. Sheet resistance showes a downward trend,when the ITO film increase from40nm to70nm.The electrical properties mainly depend onthe interlayer of the Cu, ITO play a secondary role.