Wetting Angles on Illuminated Ta2O5 Thin Films with Controlled Nanostructure
Wetting Angles on Illuminated Ta2O5 Thin Films with Controlled Nanostructure
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DOI：
10.1021/jp805708w
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发表时间：
2009-03-05
影响因子：
3.7
通讯作者：
Gonzalez-Elipe, Agustin R.
中科院分区：
文献类型：
--
作者：
Rico, Victor;Borras, Ana;Gonzalez-Elipe, Agustin R.
通过改变蒸发源与衬底的夹角，采用电子蒸发法制备了不同纳米结构和表面粗糙度的Ta 2 O 5薄膜。通过改变蒸发的几何形状和/或通过在高达1000摄氏度的升高温度下退火蒸发的膜以使其结晶，获得折射率（n）从1.40到1.80的大变化。非常平坦和紧凑的薄膜（n = 2.02），也得到了通过轰击与O-2（+）离子的动能为800 eV的辅助生长。已经发现了一个类似的相关性之间的润湿接触角的水和膜的粗糙度的蒸发和蒸发+退火的样品，无论其程序的制备和其他微观结构特征。当用It > E-g = 4.2eV（E-g，Ta 2 O 5的带隙能量）的UV光照射薄膜时，它们的表面以与报道的照射的TiO 2薄膜非常相似的方式变得超亲水（接触角< 10度）。转化成超亲水状态的速率是较小的结晶比非晶薄膜，这表明在Ta 2 O 5的晶体域在表面的大小是一个重要的参数，用于控制这种动力学。当用动能为800 eV的N2（+）离子注入可见光照射的薄膜时，也发现水接触角发生变化。这种光活性的起源进行了讨论，在与氮注入原子的电子带隙状态。讨论了制备Ta_2O_5增透自清洁膜的可能性。
Ta2O5 thin films with different nanostructure and surface roughness have been prepared by electron evaporation at different angles between the evaporation source and the substrates. Large variation of refraction indexes (n) from 1.40 to 1.80 were obtained by changing the geometry of evaporation and/or by annealing the evaporated films at increasing temperatures up to 1000 degrees C to make them crystalline. Very flat and compact thin films (n = 2.02) were also obtained by assisting the growth by bombardment with O-2(+) ions of 800 eV kinetic energy. A similar correlation has been found between the wetting contact angle of water and the roughness of the films for the evaporated and evaporated + annealed samples, irrespective of their procedure of preparation and other microstructural characteristics. When the films were illuminated with UV light of It > E-g = 4.2 eV (E-g, band gap energy of Ta2O5), their surface became superhydrophilic (contact angle < 10 degrees) in a way quite similar to those reported for illuminated TiO2 thin films. The rate of transformation into the superhydrophilic state was smaller for the crystalline than for the amorphous films, suggesting that in Ta2O5 the size of crystal domains at the surface is an important parameter for the control of this kinetics. Changes in the water contact angle on films illuminated with visible light were also found when they were subjected to implantation with N-2(+) ions of 800 eV kinetic energy. The origin of this photoactivity is discussed in terms of the electronic band gap states associated with the nitrogen-implanted atoms. The possibility of preparing antireflective and self-cleaning coatings of Ta2O5 is discussed.