Intercalated Metal Oxide Superlattice Dielectrics (25092)
A family of intercalated metal oxide self-assembled superlattice dielectrics providing extraordinary insulative and capacitance properties for thin film transistor and organic electronic devices.
ADVANTAGE: Dielectric materials that enable low voltage operation of thin film transistors with wide potential for electronic, photonic and display applications.
SUMMARY: Integrated circuits (IC) fabricated from organic thin film transistors (OTFTs) offer the potential of cheap, logic circuits with applications as diverse as electronic price tags, postage stamps, rfid tags, and ‘smart’ cards. High-mobility, stable, and solution-processable organic semiconductor materials including both p-type (hole-transporting) and n-type (electron-transporting) semiconductors on SiO2 and plastic substrates have undergone significant advances for OTFT applications. However, there remains a need for alternative insulator materials in order to significantly reduce the OTFT operating voltage. Thus while the carrier mobilities of organic semiconductors now rival those of amorphous Si, this is generally achieved at very large source-drain/source-gate bias (30-50V). OTFT operation employing such large biases will incur excessive power consumption. A viable approach to increasing the drain current at low operating bias is to increase the capacitance of the gate dielectric, but at the low-cost/low-capital investment manufacture anticipated for organic electronics.
This invention demonstrates the intercalation of metal oxides into self-assembled superlattices (SASs) efficiently modulates the dielectric properties of the SAS dielectric and the resulting films are easily integrated into OTFT devices. These properties are also applicable to capacitative elements in LC displays, supercapacitors, and other insulated field-effect devices.
Thus, dielectric/insulating SAS films having the general structure in figure 1 were incorporated in MIS (metal-insulator-semiconductor) and OTFTs, a field-effect device. Solid-state leakage current-voltage measurements through the SAS films in the MIS device demonstrate the excellent dielectric properties of these materials. While Si/SiO2 native oxide substrates exhibit very large current densities of ~ 0.1 – 1.0 A/cm2 at 1.0 V, thin (~9 nm) SAS films reduce the leakage currents by ~ 9 orders of magnitude (~ 10-9 A/cm2).
The SAS-based dielectrics are effective in low-voltage OTFTs. Figure 2 exhibits the output plot of a SAS-Ti-based pentacene TFT compared to a pentacene TFT with a conventional 300 nm-thick SiO2 insulator (Ci = 10 nF/cm2). The SAS-based FET exhibits comparable carrier mobility (about 0.1 cm2/Vs) but with about two orders of magnitude reduction in operational voltage, essential to reduce OFET device power dissipation and enable high frequency operation.
The invention provides a family of unique thin film dielectrics with extraordinary capacitance suitable for a wide range of electronic applications.
Tobin Marks, Antonio Facchetti
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