O_2流量对磁控溅射N掺杂TiO_2薄膜成分及晶体结构的影响

Composition and crystal structure of N doped TiO_2 film deposited with different O_2 flow rates

利用直流脉冲磁控溅射方法在室温下通过改变O2流量制备具有不同晶体结构的N掺杂TiO2薄膜,利用台阶仪、X射线光电子能谱仪、X射线衍射仪、紫外-可见分光光度计等设备对薄膜沉积速率、化学成分、晶体结构、禁带宽度等进行分析.结果表明:所制备的薄膜元素配比约为TiO1.68±0.06N0.11±0.01,N为替位掺杂,所有样品退火前后均未形成Ti—N相结构,N掺杂TiO2薄膜的沉积速率、晶体结构等主要依赖于O2流量.在O2流量为2sccm时,N掺杂TiO2薄膜沉积速率相对较高,薄膜为非晶态结构,但薄膜内含有锐钛矿(anatase)和金红石(rutile)相晶核,退火后薄膜呈anatase和rutile相混合结构,禁带宽度仅为2.86eV.随着O2流量的增加,薄膜沉积速率单调下降,退火后样品禁带宽度逐渐增加.当O2流量为12sccm时,薄膜为anatase相择优生长,退火后呈anatase相结构,禁带宽度为3.2eV.综合本实验的分析结果,要在室温条件下制备晶态N掺杂TiO2薄膜,需在高O2流量(>10sccn)条件下制备.

N doped TiO2films were deposited in direct current pulsed magnetron sputtering system at room temperature. We have studied the influence of O2 flow rate on the crystal structure of deposited films by using stylus profilometer,X-ray photoelectron spectroscope,X-ray diffractometer,and ultraviolet-visible spectrophotometer. The results indicate that the growth behavior and crystal structure of N doped TiO2 film is dominated by the O2 flow rate. It was found that the chemical stiochiometry is close to TiO1. 68 ±0. 06 N0. 11 ±0. 01 for all film samples,in which the N mainly exists in substitutional doped state. When O2 flow rate is 2 sccm （1 sccm = 1 mL /min）,N doped TiO2 film has amorphous structure with high growth rate,which contains both anatase phase and rutile phase crystal nucleuses. In this case,the film displays the mix-phase of anatase and rutile and the band gap is 2. 86 eV after annealing treatment. The film growth rate decreases with increasing O2 flow rate. After annealing treatment,the band gap of N doped TiO2 films decreases with increasing O2 flow rate. While N doped TiO2 film is anatase phase when O2 flow rate is 12 sccm. In this case,the band gap is 3. 2 eV after annealing treatment. It should be noticed that no TiN phase appears for all samples before and after annealing treatment.