Investigation Of Carrier Transport Of InSe FET And Its Application In Biosensor

Devices based on new semiconductor materials are one of the important development directions in the field of microelectronics,The successful preparation of graphene in 2004 brought two-dimensional(2D)materials to the forefront of attention.Graphene has a very high theoretical mobility,but its zero band gap nature limits its application in microelectronics and integrated circuits.In recent years,a variety of 2D semiconductor materials with suitable band widths such as MoS2,black scale,WS2,WSe2,and InSe.Due to the high specific surface area of 2D materials,they showed the very broad applications in gas,chemical and biomolecular sensing fields.Among them,InSe has a small electron effective mass and high electron mobility,and is extremely sensitive to surface scattering.The scattering sensitivity gives InSe devices a natural advantage for biomolecular sensing.At present,there are few investigations in biosensing based on InSe FET devices,as well as a lack of systematic and in-depth studies.In this thesis,the electron transfer mechanism of InSe field effect transistors is studied by uniform doping of bismuth elements in InSe and Bi as ohmic contact.The sensors of disease biomarker(mi)RNA and biomarker protein are constructed based on the InSe FETs,the biosensing mechanism of InSe FETs is explored.The high performance detection of miRNA、RNA and protein biomarkers using the constructed InSe FETs biosensor presents very promising applications in the biosensing fields.The main innovative research results of the thesis are as follows:(1)Mechanism of source-drain electrode contact materials effect on the performance of InSe FETs.InSe field effective transistor(FET)with different metal contacts were prepared using Bi,Ti,Cr,and Ni as source-drain electrode,and the effects of different metal contacts on the performance of InSe FETs were investigated.The semimetal Bi in contact with InSe twodimensional material,the orbital hybridization between Bi and InSe can effectively deplete the metal induced gap states,thus making the contact potential barrier at the metal-semiconductor interface greatly reduced.The contact resistance of the InSe FETs with Bi contact electrode is only 231 Ω/μm.The low contact resistance of the InSe FETs with Bi contact improves the electrical performance of the InSe FETs.The field-effect mobility of the InSe FETs can be up to 1250 cm2V-1 s-1,and the switching ratio of the transistor is greater than 106.(2)Bi-doped InSe based InSe field-effect transistors.The lattice structure defects were reduced by homogeneous Bi doping InSe crystals during the growth,and the high-resolution transmission electron microscopy images visually demonstrated that the InSe crystals were homogeneously doped at the Bi atomic level,achieved a more perfect periodic distribution of atoms and a complete lattice structure.The FETs based on Bi-doped InSe achieved a field-effect mobility of 1342 cm2V-1s-1.Bi doping suppressed the oxidation reaction caused by Se vacancies and the stability of InSe FETs is improved.The device performance of the FETs based on Bidoped InSe was essentially free of degradation after 2 weeks of storage at ambient temperature.The drift of the threshold voltage under electrical stress is about one-tenth of that of the FETs with non-doped InSe.The fatigue characteristics test results showed that the output current of the transistor with Bi-doped InSe remains essentially unchanged after 15000 repetitions of the test.In addition,the transistor with Bi-doped InSe exhibits excellent mechanical flexibility,and the transistor has a stable switching ratio within 100 bending(bending radius 7.5 mm)cycles.(3)InSe field-effect transistor biosensor for miRNA/RNA detection.High performance InSe field-effect transistors were integrated with PDMS-based microfluidic to construct InSe FET biomolecular sensors.The mechanism of miRNA/RNA biomolecular sensing in back-gate operation mode was investigated,and the specific detection of breast cancer miRNA biomarkers and Covid RNAs is performed.The whole detection time is 20 minutes and showed good linearity between target concentration and signal response in the range of 10 nM-1 fM,with a detection limit of 0.22 fM and the ability to identify single nucleotide mismatches.The standard mean squared deviation for the detection of multiple devices is 6.67%,and a single device can be reused three times.The InSe FETs biosensor in back gate mode overcomes the problems of easy electrolysis of aqueous samples at the operating voltage of the liquid grating mode.The back-gate operation mode of biosensor does not require separate liquid gate electrodes,and the sensor can be easily integrated,allowing the development of miniaturized sensing systems.The specific detection of the biomarker miRNA in clinical serum samples and the RNA in SARSCov-2 pseudovirus present good prospects for the InSe FET biosensors applications in the field of major disease screening and infectious disease prevention and control.(4)InSe field effect transistor biosensor for CA125 protein detection.InSe field effect transistor channel was functionalized using 3-aminopropyltriethoxysilane for immobilization of ovarian cancer biomarker C A125 antigen-specific capture antibody.The detection of CA125 antigen was performed using a back-gate mode of operation,where the surface charge of the protein macromolecule modulated gate voltage and the change in threshold voltage drifted with the change in concentration of the captured antigen.The results showed that the InSe FETs protein biosensor has excellent linearity in the antigen concentration range of 0.01~1000 U/mL,with a low detection limit of 0.01 U/mL for CA125 antigen and a standard deviation of 9.05%for multiple testing,and a total detection time in 1 hour.The detection results of ovarian cancer clinical samples are in high agreement with detection results using the Roche electrochemiluminescence(Cobas e601),reaching 95%.InSe FET based protein molecular biosensors have important applications in early screening of major diseases,efficacy assessment,and prognosis,etc.InSe FET biosensor devices can be integrated with signal processing IC chips to achieve miniaturization,and the biosignal is converted into an electrical signal during the sensing process.The detection of the electrical signal can overcome the limitations of external factors such as environment,vibration and high power needed,which makes it very promising for real-time,in-situ detection and home-based detection.