Study On Ultrafast Processes Using The Pump-probe Technique

Pump-probe technique is an ultra-fast time-resolved measurement technology.It is often used to detect the transient processes of physical and chemical changes inside the material such as the transfer of energy,the generation of chemical bonds.The most important application is the study on the dynamics of the excited state carrier.Graphene is a new type of material that has been developing rapidly over the past decade.Due to its two-dimensional structure and zero band gap characteristics,graphene has ultra-fast electron mobility,excellent electrical and thermal conductivity,and unique optical properties.In order to prepare versatile graphene materials,the researchers adjusted and doped its structure.Through the introduction of oxygen-containing functional groups,the scientists obtain graphene oxide.The doping process changes the structure of graphene.In order to understand the influence of doping process on its properties,the photo excitation kinetics of graphene oxide was studied.In the experiment,the transient absorption characteristics of the graphene oxide samples were tested by a self-built pump-probe system,and we studied the dynamic processes of graphene oxide under different excitation intensity.With low pumping energy,the relaxation time constants of the sample are 0.22ps and 1.98ps.The proportion of the two relaxation time is about 66.8%and 33.2%.In this condition,the excitation kinetics of graphene oxide is similar to that of pure graphene,and the~2 hybrid region plays a major role in the relaxation process of carriers,While with high pumping energy,the relaxation time constants are 1.42ps and8.61ps,which accounts for approximately 35.6%and 64.4%of the total.Under this condition,the~3 hybrid region has an influence on its kinetic process and prolongs the recovery time of carriers.