Ultrafast Dynamics Of Nanocrystalline SnSe₂ Films

Biosensors are developing rapidly and are widely used in many fields such as food safety and health care.Nanotechnology is the key to promote the further development of biosensors.Therefore,it has become a hot research topic in the world to promote the development of biosensors and improving the performance of biosensors by finding more suitable nanomaterials.SnSe2 is a new two-dimensional material with good electrical and thermal conductivity,which has potential for applications in sensors,photocatalysis and energy storage.This paper focuses on the study of ultrafast carrier and ultrafast energy dynamics in SnSe2 materials to promote the application of SnSe2 materials in biosensors and other applications.This article uses pulsed laser deposition(PLD)experiments to prepare multiple sets of SnSe2 thin films,and uses X-ray diffraction spectroscopy(XRD)and X-ray photoelectron spectroscopy(XPS)experiments to characterize the thin film samples.The experimental results confirm the film's quality and suitable experimental conditions for film preparation.Subsequently,the linear transmission spectrums of the films are obtained by measurement.Finally,the ultrafast carrier dynamics related to pulse energy and wavelength and transient absorption(TA)spectroscopy in SnSe2 films with deposition times of 20 min and 30 min are investigated using femtosecond pump-probe experiments using TA spectroscopy.The TA spectrum of the SnSe2 film with deposition time of 20 min show that a bleaching signal caused by the state filling effect appears at the 611 nm and excited state absorption(ESA)signal associated with free carrier absorption appears in the region of 680 nm-780 nm.An ESA signal related to free carrier absorption appears at 649 nm in the TA spectrum of the SnSe2 film with a deposition time of 30 min.The 3e exponential model is used to fit the ultrafast carrier dynamics,and it is found that the carrier experienced three different relaxation processes of the carrier scattering process,recombination process and diffusion process.Furthermore,it is found that the TA spectrum and ultrafast kinetic process of the film are affected by the pulse energy.Due to the band gap recombination effect,the peaks are red-shifted with the increase of pulse energy.Because the effect of the pulse energy on the temperature difference between the electron and the crystal lattice and the carrier concentration,the lifetime of carrier are increases with the increase of pulse energy.The results of this paper reveal the relaxation process of carriers in SnSe2 thin films and the modulation of pulse energy on ultrafast carrier dynamics,which greatly promotes the application of SnSe2 thin films in the fields of biosensors and optoelectronic devices.