Ozone oxidation methods for aluminum oxide formation: Application to low-voltage organic transistors

Abstract

a b s t r a c tFour atmospheric pressure ozone oxidation methods were used to produce ultra-thin layers of aluminum oxide for organic thin-film transistors. They are UV/ozone oxidation in ambient (UV-AA) and dry (UV-DA) air, UV/ozone oxidation combined with high-voltage discharge-generated ozone in dry air (UV+O 3 -DA), and discharge-generated ozone in dry air (O 3 -DA). The lack of the high-energy UV photons during the O 3 -DA oxidation led to low relative permittivity and high leakage current density of the AlO x layer that rendered this method unsuitable for transistor dielectrics. Although this oxidation method led to the incorporation of oxygen into the film, the FTIR confirmed an increased concentration of the subsurface oxygen while the XPS showed the highest portion of the unoxidized Al among all four methods. The remaining three oxidation methods produced AlO x films with thicknesses in excess of 7 nm (2-h oxidation time), relative permittivity between 6.61 and 7.25, and leakage current density of (1-7) Â 10 À7 A/cm 2 at 2 MV/cm, and were successfully implemented into organic thin-film transistors based on pentacene and DNTT. The presence of -OH groups in all oxides is below the detection limit, while some carbon impurities appear to be incorporated.

1 Volt organic transistors with mixed self-assembled monolayer/Al2O3 gate dielectrics

“…the leakage current density J G was below 10 À7 A/cm 2 at 1.5 MV/cm in all cases, confirming the formation of dense monolayers for all SAM compositions [7,35]. The value [21,36,37]. The shift in the threshold voltage of these OFETs is dependent on the composition of the applied SAM.…”

Establishing a Field-Effect Transistor Sensor for the Detection of Mutations in the Tumour Protein 53 Gene (TP53)—An Electrochemical Optimisation Approach

“…Whilst this change is small, it is indeed measurable. Possible methods to increase the FET potential change have been hypothesised, including the use of thin-film transistors such as organic FETs or organic thin-film transistors (OTFTs) [22][23][24]. Such devices feature significantly smaller feature sizes with channel lengths in the micron range enabling greater charge carrier mobility and hence potential change.…”

“…This method is simpler than electrochemical techniques such as EIS, which requires circuit fitting to an equivalent circuit to interpret results, and is ultimately more amenable to a PoC setting. FETs, and particularly organic semiconductor variants which feature inherent advantages such as low-cost production and compatibility with flexible substrates [21,22], can also be mass produced via processes such as vacuum thermal evaporation [23,24] and printing [25], which results in high-volume/low-cost production.…”

Optimizing the plasma oxidation of aluminum gate electrodes for ultrathin gate oxides in organic transistors

“…This work focuses on ultrathin hybrid gate dielectrics. The first component of these dielectrics is a thin metal oxide that can be produced by atomic layer deposition 8 , 24 , 25 , anodic oxidation 26 – 28 , UV/ozone-assisted oxidation 29 – 31 , or plasma-assisted oxidation of the surface of the gate electrode 13 . Among the advantages of the plasma-oxidation process are the fact that it does not require electrical contact to the gate metal during the oxidation process 32 (which greatly simplifies the fabrication process), that the oxide is formed only where needed for the TFTs (which eliminates the need for subtractive patterning to open vias for interconnects 22 ) and that the high quality of the native interface between the gate metal and the gate oxide minimizes the hysteresis in the current–voltage characteristics and the subthreshold swing of the TFTs 33 , 34 .…”