Dae Kyu Kim

Study on copper phthalocyanine and perylene-based ambipolar organic light-emitting field-effect transistors produced using neutral beam deposition method

The neutral cluster beam deposition (NCBD) method has been applied to the production and characterization of ambipolar, heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, multi-digitated, long-channel geometry. Organic thin films of n-type N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide and p-type copper phthalocyanine were successively deposited on the hydroxyl-free polymethyl-methacrylate (PMMA)-coated SiO2 dielectrics using the NCBD method. Characterization of the morphological and structural properties of the organic active layers was performed using atomic force microscopy and X-ray diffraction. Various device parameters such as hole- and electron-carrier mobilities, threshold voltages, and electroluminescence (EL) were derived from the fits of the observed current-voltage and current-voltage-light emission characteristics of OLEFETs. The OLEFETs demonstrated good field-effect characteristics, well-balanced ambipolarity, and substantial EL unde...

Low-voltage pentacene thin-film transistors using Hf-based blend gate dielectrics

High-performance pentacene thin-film transistors operating at low voltages were fabricated using hafnium (Hf)-based blend gate dielectrics. Crosslinked HfOx/1,6-bis(trimethoxysilyl)hexane blend (CLHB) dielectric films were prepared by varying the ratio of HfOx and 1,6-bis(trimethoxysilyl)hexane (BTMH), and the resulting films were deposited by solution-processed sol–gel chemistry. p-Type pentacene was deposited on the dielectric films using the neutral cluster beam deposition method. The dielectric properties and morphologies of the films were systematically investigated with respect to the relationship between the compositions of blend dielectrics and device performance. In comparison to the pristine HfOx-based OFETs, as the BTMH molar ratio increased, the leakage current, capacitance, dielectric constant and trap density of the interface states decreased, leading to an increase in the CLHB-based transistor performance such as increased hole-carrier mobility and current on/off ratio and a decrease in subthreshold swing. The OFETs demonstrated similar device performance at high HfCl4 : BTMH molar ratios of 1 : 0.5 and 1 : 0.8. At the molar ratio of 1 : 0.5, the OFETs operating under −4 V had μh,avgeff = 1.6 cm2 V−1 s−1 and Ion/Ioff = 2 × 105 with the corresponding leakage current and capacitance of ∼2 × 10−7 A cm−2 at 2 MV cm−1 and ∼137 nF cm−2. The performance enhancement was found to be closely correlated with the blend dielectrics.

ZrO2 dielectric-based low-voltage organic thin-film inverters

In this paper, the authors first report ZrO2-dielectric based low-voltage organic thin-film complementary metal-oxide semiconductor inverters. Two active layers of p-type pentacene and n-type N,N′-dioctyl-3,4,9,10-perylenedicarboximide were successively deposited on the thermally stable, transparent ZrO2 using the neutral cluster beam deposition method. Based on the good balance between p- and n-type transistors, the complementary inverters exhibited ideal characteristics including sharp inversions, complete switching, high gains, and large voltage swings at low operating voltage levels.

Low-voltage organic devices based on pristine and self-assembled monolayer-treated HfTiOx gate dielectrics

Low-voltage organic field-effect transistors (OFETs) and complementary metal oxide semiconductor (CMOS) inverters based on pentacene and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) were fabricated on HfTiOx gate dielectrics. Both pristine dielectrics and substrates passivated with self-assembled monolayers (SAMs) of n-dodecylphosphonic acid (PA-C12) were employed. The high capacitance and low leakage current of the HfTiOx-based dielectrics enabled the devices to operate at |V| < 3 V. Passivation with PA-C12 was highly effective in improving the device characteristics. In particular, an electron mobility of 0.72 cm2 V−1 s−1 was measured for the device fabricated with the passivated HfTiOx dielectric, which represents the best performance reported to date for perylene-based OFETs prepared with thin, high-k gate dielectrics. The CMOS inverters exhibited fast switching and high gain characteristics, which were attributed to good coupling between the optimized p- and n-type OFETs.