直流反应磁控溅射制备的Mo掺杂TiO2薄膜的光电特性

通过直流反应磁控溅射制备了不同Mo掺杂量的Mo-TiO2薄膜.用原子力显微镜(AFM)、X射线衍射(XRD)仪、X射线光电子能谱(XPS)仪、紫外-可见(UV-Vis)分光光度计详细研究了Mo掺杂量对薄膜表面形貌、晶体结构、元素价态及吸收带边的影响.用瞬态光电流和循环伏安法考察了不同Mo含量ITO/Mo-TiO2电极的光电特性.结果表明:在TiO2薄膜中掺入的Mo以Mo6+和Mo5+两种价态存在;随着Mo掺杂量的增加,Mo-TiO2薄膜的晶粒尺寸逐渐减小,晶格畸变增大,吸收阈值显著红移;薄膜的禁带宽度先减小后增大,在Mo掺杂量为2.7%(n(Mo)/n(Ti))时禁带宽度最小;Mo掺杂量为0.9%的样品在氙灯下的光生电流最大,且随着所加阳极偏压的提高光生电流并未呈现出饱和的趋势.此后随着掺杂量的提高,薄膜的光生电流开始下降,当Mo掺杂量达到3.6%时,薄膜的光电流小于未掺杂的样品;说明适当浓度的Mo掺杂能够提高Mo-TiO2薄膜光电性能,光生电流最大可达未掺杂的2.4倍.

Photoelectric Properties of Mo Doped TiO2 Thin Films Deposited by DC Reactive Magnetron Sputtering

Nanocrystalline TiO2 thin films doped with different concentrations of Mo were deposited by direct current(DC) reactive magnetron sputtering.The influence of Mo on surfaces,crystal structures,the valence states of elements and the absorption band of Mo doped TiO2 films were characterized by means of atomic force microscopy(AFM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and Ultraviolet-visible spectroscopy(UV-Vis).To investigate the photoelectric characteristic of ITO(indium tin oxide)/Mo-TiO2 electrodes,a series of cyclic voltammetry experiments were conducted.The results indicate that an appropriate amount of Mo atoms,observed as Mo6+ and Mo5+ by XPS,could inhibit the crystal growth of particles,enhance the surface roughness of the Mo doped TiO2 thin film,and bring about a remarkable red shift of the absorption spectra.As the concentration of Mo increased,the energy gap declined at first until the amount of doped Mo eventually reached 3.6%(n(Mo)/n(Ti)),when a blue shift of spectra resulted and the energy gap grew wider.The sample doped with 0.9% Mo was irradiated with a Xe lamp and showed the highest photocurrent,which continued to increase with increasing voltage exerted on the anode.An increase in Mo concentration resulted in a decrease in photocurrent.Compared to the pure TiO2 film,the sample with 3.6% Mo had a much lower photocurrent.Our experiments demonstrate that Mo doping,when the concentration was controlled under a relatively low limit,brought about a significant improvement of the photoelectric properties of the TiO2 films.The highest photocurrent observed is 2.4 times that of the sample with no Mo doping.