Ultrafast carrier trapping of a metal-doped titanium dioxide semiconductor revealed by femtosecond transient absorption spectroscopy

Ultrafast carrier trapping of a metal-doped titanium dioxide semiconductor revealed by femtosecond transient absorption spectroscopy

Ultrafast carrier trapping of a metal-doped titanium dioxide semiconductor revealed by femtosecond transient absorption spectroscopy
Jingya Sun, Yang Yang, Jafar I. Khan, Erkki Alarousu, Zaibing Guo, Xixiang Zhang, Qiang Zhang, and Omar F. Mohammed
ACS Appl Mater Inter, 6(13), pp 10022-10027, (2014)
Jingya Sun, Yang Yang, Jafar I. Khan, Erkki Alarousu, Zaibing Guo, Xixiang Zhang, Qiang Zhang, and Omar F. Mohammed
Metal-doped titanium dioxide, Transient absorption spectroscopy
2014
We explored for the first time the ultrafast carrier trapping of a metal-doped titanium dioxide (TiO2) semiconductor using broadband transient absorption (TA) spectroscopy with 120 femtosecond (fs) temporal resolution. The titanium dioxide was successfully doped layer-by-layer with two metals ions namely Tungsten (W) and Cobalt (Co). The time-resolved data demonstrate clearly that the carrier trapping time decreases progressively as the doping concentration increases. A global fitting procedure for the carrier trapping suggests the appearance of two time components: a fast one that is directly associated with carrier trapping to the defect state in the vicinity of the conduction band and a slow component that is attributed to carrier trapping to the deep level state from the conduction band. With a relatively long doping deposition time on order of 30 seconds, a carrier lifetime of about 1 picosecond is obtained. To confirm that the measured ultrafast carrier dynamics are associated with electron trapping by metal doping, we explored the carrier dynamics of the un-doped TiO2. The findings reported here may be useful to the implementation of high-speed optoelectronic applications and fast switching devices.
 
DOI: 10.1021/am5026159