Solution processed zinc oxide thin film transistors with biocompatible dopants
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Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
Author
Date
2024-05-20
Department
Major/Subject
Functional Materials
Mcode
Degree programme
Master’s Degree Programme in International Design Business Management (IDBM)
Language
en
Pages
54
Series
Abstract
The solution processed ZnO thin film transistors (TFTs) is desirable to enable environmentally non toxic solutions, improved field effect mobility and low cost production for transient electronics. However, ZnO has polycrystalline structure and it might suffer from lower mobility due to scattering of mobile charge carriers at the grain boundaries. Insulating or electron-rich polymer doping might introduce amorphous phase in ZnO. The approach to achieve this through this research is ZnO TFT fabrication by spin coating and doping of various bio-based polymers including polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and polyethyleneimine (PEI) in order to enhance mobility by surpassing crystallinity. Different batch of samples prepared with varied spin coating parameters (spin time, spin speed, number of layers) and annealing methods (thermal and UV). Undoped ZnO TFT with spin speed of 8k rpm, spin time of 60 second and annealing at 300◦C is decided as the reference sample based on optimization of TFT fabrication. Among the doped samples, PVP doping with 0.75 weight percentage had better electrical performance. Therefore, materials characterization including TGA, GIXRD, AFM, FTIR, SEM is applied to these samples. It is observed that PVP doping increases surface roughness of ZnO thin films, decrease intensity of a peak position and introduces a new peak position in ZnO structure. To understand the effect of PVP doping in ZnO structure, TEM is needed. SEM revealed that the thickness of fabricated thin films of this study is in the 5 to 8 nm range. This might be the root cause of variability of transfer characteristics and poor electrical performances of the devices. Although ZnO TFTs fabricated in this research are not ready for performance tests and commercial use, future work might help address the issues challenged this study.Description
Supervisor
Vapaavuori, JaanaThesis advisor
Gillan, LiamKeywords
thin film transistor, polymer doping, zinc oxide, electrical characterization
