Abstract
The photodesorption kinetics of graphene with various UV laser power is studied by conductance response. Analytical expressions of the power-dependent photodesorption kinetics of graphene in ambience are derived. The photodesorption time constant τd, steady current, and magnitude of modulation current, can be expressed as functions of the adsorption time constant τa, desorption cross section σ, and photon flux density. Under illumination the steady occupation ratio of adsorbed O2 on graphene is equal to τd/τa. It is suggested that the photodesorption of O2 on graphene is attributed the injection of photogenerated hot electrons and is restricted by the density of antibonding states of O2.
Highlights
Graphene [1], few atomic carbon layers in a honeycomb lattice, is the ultimate twodimensional surface material without bulk effect
The conductance response of graphene can be utilized to monitor the molecular adsorption and desorption, making graphene an ideal system to study the kinetics of adsorption and desorption
The UV-laser photodesorption of chemical vapor deposition (CVD) graphene in air is studied by the current response
Summary
Graphene [1], few atomic carbon layers in a honeycomb lattice, is the ultimate twodimensional surface material without bulk effect. The conductance response of graphene can be utilized to monitor the molecular adsorption and desorption, making graphene an ideal system to study the kinetics of adsorption and desorption. O2 molecules act as electron acceptors for graphene and are the dominant species of adsorbates that influences the conductivity of graphene. We studied the UV-power-dependent photodesorption kinetics of graphene in ambience by monitoring the response current of graphene. In order to investigate the underlying mechanism, the photodesoprtion is performed by the lasers of various Eph. From the dependence of σ on Eph, it is suggested that the photodesorption of graphene involves the injection of photogenerated hot electrons and is restricted by the density of antibonding states of O2
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