研究目的
Investigating the anomaly in the electrical characteristics of thin film transistors with multi-layered sol-gel processed ZnO, specifically the kink/hump effects observed in transconductance and capacitance-voltage characteristics.
研究成果
The anomaly (kink/hump effect) in multi-layered ZnO TFTs is attributed to the formation of depletion layers at ZnO-ZnO interlayer-interfaces due to oxygen chemisorption during fabrication. As the number of layers increases, the effects become more apparent, with Coulomb scattering causing local declines in transconductance. This provides insight into defect-related issues in solution-processed TFTs and suggests methods like oxygen plasma treatment to suppress these effects.
研究不足
The study is limited to sol-gel processed ZnO TFTs fabricated in ambient conditions, which may introduce variability due to chemisorption of ambient gases. The number of layers and specific fabrication parameters might not cover all possible variations, and the effects could be influenced by local density of active sites and annealing conditions.
1：Experimental Design and Method Selection:
The study involved fabricating bottom-gate ZnO TFTs with varying numbers of spin-coated layers (1, 4, and 8 layers) to analyze electrical characteristics. The sol-gel spin-coating technique was used for film fabrication, with calcination and annealing processes to form nanocrystalline ZnO thin films. Electrical measurements included current-voltage (I-V) and capacitance-voltage (C-V) analyses.
2：Sample Selection and Data Sources:
Highly conductive boron-doped silicon wafers were used as substrates. Three samples were prepared with different numbers of ZnO layers (1L, 4L, 8L), with thicknesses measured using a profilometer.
3：List of Experimental Equipment and Materials:
Equipment includes a spin coater, calcination furnace, annealing furnace, DC sputtering system for contact deposition, photolithography setup for mesa structure formation, X-ray diffractometer (Bruker D2 Phaser), Raman spectrometer (Jobin Yvon), Keithly 2400 SourceMeter for I-V measurements, and Keithly 590CV analyzer for C-V measurements. Materials include ZnO precursor, titanium, palladium, hydrochloric acid for etching, and silicon wafers.
4：Experimental Procedures and Operational Workflow:
Precursors were spin-coated at 3000 rpm for 30 s, calcined at 300°C for 5 minutes, and repeated for multi-layered samples. Annealing was done at 800°C for 1 hour. Source and drain contacts were deposited via DC sputtering, and mesa structures were formed using photolithography and wet etching. Electrical measurements were performed on representative devices.
5：Data Analysis Methods:
Data analysis included calculating carrier concentration using the 1/C^2 vs. V_G method, built-in potential, Schottky barrier width, and Debye length. XRD and Raman spectroscopy were used for structural characterization.
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