Characterization Of Nanometer Thickness Conductive Organic Film Using Reflectance Spectroscopy

As the core component of micro-electronics,photoelectron,solar battery,biosensor and so on,organic thin film device has obtained widespread attention and remarkable achievement in recent years.There is no doubt that it is the key of the research since it can affect the current-illumination characteristic,stability,and working life of the device.While thin film usually prepare before electrode structure in the process of organic thin film device,electrical properties of thin film can't be tested under this kind of situation.So in this paper,based on the differential reflectance spectrum(DRS),we establish the DRS spectra by using the mathematical model with the thickness of each layer and the optical coefficient as parameters and propose an optimal fitting algorithm for determining the relevant parameters,and we analyze the revolution of the thin film and the thickness of the thin film and he growth rate of the thin film,and combining with electrical measurement data,we study the relationship between the effective conductive layer and the reflection spectrum.It provides a new method for monitoring the formation of the effective conductive layer of organic thin film when the electrical property test can't be carried out.The main works include the following aspects:1.In order to studying the approach for analyzing the form of the conductive layer during the organic thin film growth,and revealing the mechanism of the growth of the film included in DRS.We established the mathematical model in which optical coefficient of the material and the thickness of membrane serve as parameters and proposed a method of judgment of the fitting error.So we get simulation signal of differential reflectance spectrum(DRS)in the growth of thin film.2.We adopted Field Effect Transistor(FET)with a bottom-gate structure,on the basis of in-situ real-time measurement,using vacuum thermal evaporation deposited the pentacene organic thin film,as an electron transport layer,on the top of the transistor,i.e.an insulator substrate of Si/SiO2.And we test the signal of differential reflectance spectrum(DRS)and current signal between drain electrode and source electrode,and we repeated experiments many times.3.We find that simulation results of spectrum signal with four-phase model is an accurate indicator of spectrum signal tested,and come to a conclusion that the structure of thin film phase is the main existence of pentacene in its growth,calculating the equivalent growth rate of film.At the same time,using the method of judgement of the fitting error,we discussed the intrinsic relationship between differential reflectance spectrum(DRS)and the electrical properties of Field Effect Transistor(FET),finding that there is a obvious relativity between the trends of the fitting error with the growth and electrical properties of Field Effect Transistor(FET).The fact that the peak time of the fitting error are consistent with the formation of effective conductive layer provides a new way of studying the electrical properties of organic semiconductor thin film using reflectance spectroscop.