Study On Preparation And Properties Of ZrN_x/Ag/ZrN_x Low-e Coating

Low-e coatings are, nowadays, deposited onto architectural windows to be employed in commercial and residential buildings for the purpose of saving energy. These show a high spectral selectivity, giving high visible transmittance and high far-infrared (IR) reflectance. In satisfies the natural lighting under the demand, they can save the heating and air conditioning expense. Low-e systems based on single or double silver films are the most popular in world. A large variety of different designs already exists, for example, TiO₂,ZnO,SnO₂ and so on. Zirconium nitrides have extreme physical and chemical properties, and reveal interesting optical and electrical properties which highly depend on the nitrogen stoichiometry. Indeed, the material exhibits a transition from the stable metallic ZrN to the metastable semi-transparent insulating Zr3N4. Due to its character, there is interest in film of zirconium nitride for use in Low-E coatings. The worth of these multilayer films is that all the thin films are prepared under the non-oxygen environment, so the barrier layer is not need, simplify the preparation craft, effective avoid the silver film oxidation.In this work, all films have been prepared by r.f. magnetron sputtering, using N2 as the reaction gas. The films were characterized by means of XRD, SEM, XPS, UV-VIS-NIR spectroscopy, ellipsometer and so on.The results showed that the nano-ZrN films are amorphous, have high transmission and low reflection in the visible light scope. With the increase of N/Zr increase, the quantity of free electrons and reflectivity of films decrease. STS spectra of ZrN indicates that the band gap is 2.99eV and the free electrons of the films are small, which lead to nearly no absorption of visible light. XPS spectra showed that there is a lot of ZrO₂ molecule in surface which influences the optical property of nano-ZrN films.The optical property and the moisture durability of low-e coatings were investigated. With the thickness of ZrN_x coating increasing, at visible region, the transmittance peak position move to infrared, and the peak value and width increases. While the thickness of ZrN_x coating came to 40nm, the peak position is almost unchanged and the peak value decreased. The results showed that the best structure of low emission coating glass is 30nm ZrN_x/10nm Ag /30nm ZrN_x, the visual transmission is about 78 % in the wavelength of 610nm, the average visual transmission is over 70% and the infrared reflection is about 72%in the wavelength of 2500nm. A multilayer stack film of ZrN_x /Ag/ZrN_x has revealed clear interference spectra with spectra selectivity. The moisture test showed that with the thickness of ZrN_x increasing the ZrN_x /Ag/ZrN_x coatings had a better moisture resistance.