Research Of Scanning Imaging Based On Bottom Illumination TERS

Tip-enhanced Raman spectroscopy(TERS)as a non-destructive and label-free imaging method that provides molecular-scale information with high sensitivity and nano-scale spatial resolution and thus has wide application in nanomaterials and biochemical analysis and characterization.Its high sensitivity and spatial resolution mainly come from the local surface plasmon resonance(LSPR)at apex of the probes,and its performance depends crucially on the tip size and shape.,and the high detection sensitivity comes from Hybrid coupling effect between the tip vertex position probe and the excitation beam.Most of the original probes required are based on some commercial AFM probes.The raw materials used in commercial AFM tips are silicon or silicon nitride,Its difficult to directly apply them for effective TERS studies.It is often necessary to perform some special processing on these AFM probes to improve the TERS characteristics of the tip.In order to study a stable TERS enhanced probe used for Raman Imaging work.This thesis firstly investigates the most widely used probe processing method.On the basis of common AFM probes,a precious metal film such as gold or silver is coated on the surface of the tip to obtain an effective TERS probe for specific experimental work..For vacuum thermal evaporation method,the quality of the metal film layer is directly related to the actual coating process,including the type of coating equipment,vacuum,evaporation rate,and temperature.The optimization of relevant experimental parameters directly determines the tip of TERS.Based on the bottomil uminated transmissive AFM-TERS imaging system,the TERS enhancement of the probe was theoretically and experimentally analyzed.Combined with the application of metal ized "tilt ed " nanoprobes,we studied the effects of probe tip parameters on the enhancement,Including the effect of simulating the probe cone angle and the tilt angle relative to the substrate on the electric field enhancement,and the effect thickness of the tip coating cladding.the experimental parameters of the probe can be optimized to obtain a TERS probe for better effect,and the enhanced Raman spectra of different nanoscale samples were accurately measured.The local continuous mapping based on the stable single-point Raman spectroscopy acquisition enables nano-level highresolution imaging.At the same time,the experimental system has strong flexibility,the experimental operation can easily be repeated,and more samples can be measured.It will help us to further study the characteristics and applications of this particular metal nanostructure imaging,and it also has a certain prospect in super-resolution bioimaging..