Kyunghoon Jeong

Self-assembled monolayer modified MoO3/Au/MoO3 multilayer anodes for high performance OLEDs

We control the work function and the surface energy of the MoO3/Au/MoO3 (MAM) anode of OLEDs by modifying the top MoO3 layer via vapor phase deposition. The performance and stability of the device are significantly altered depending on the dipole direction of the selfassembled monolayer (SAM) with permanent dipole moment inserted between N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) film and a MAM anode as well as on the interfacial wetting between the SAM and NPB layer. A CF3-terminated monolayer on a MAM electrode improved the performance and stability of the OLEDs relative to a reference device with only a MAM electrode, demonstrating that coating with SAMs via vapor phase deposition is an effective method to engineer the interface of MAM electrode optoelectronic devices.

Effects of Si interlayer on resistance switching of Pt/Si/TiO2/Pt structures

In order to improve the resistive switching reliability of devices made using TiO2 grown by atomic layer deposition at 130 °C, a thin Si layer was inserted between the Pt top electrode and the TiO2 thin films. The annealing of the Pt/Si(O)/TiO2/Pt structures at 300 °C in N2 ambient produced Pt/Pt3Si/PtSi particle-embedded SiO2/Ti-silicate/TiO2/Pt multistructures, as confirmed by x-ray diffraction, x-ray photoelectron spectroscopy, and high resolution transmission electron microscopy. The as-annealed multistructures showed enhanced adhesion properties and significantly improved resistive switching performances, especially in terms of the number of the switching cycles and device yield. Based on the analyses, the authors proposed that the interfacial formation of Pt3Si and Ti silicate is responsible for the enhanced adhesion and the improved resistive switching reliability of TiO2 devices result from the enhanced mechanical stability as well as the presence of Ti silicate, which acts as source and sink for ...

A simple process based on NH2- and CH3-terminated monolayers for low contact resistance and adherent Au electrode in bottom-contact OTFTs

An efficient process for the low contact resistance and adherent source/drain Au electrode in bottom-contact organic thin film transistors (OTFTs) was developed. This was achieved by using two different surface-functional groups of self-assembled monolayers, 3-aminopropyltriethoxysilane (APS), and octadecyltrichlorosilane (OTS), combined with atmospheric-pressure (AP) plasma treatment. Prior to the deposition of Au electrode, the aminoterminated monolayer self-assembles on SiO2 dielectrics, enhancing the adhesion of Au electrode as a result of the acid-base interaction of Au with the amino-terminal groups. AP plasma treatment of the patterned Au electrode on the APS-coated surface activates the entire surface to form an OTS monolayer, allowing the formation of a high quality pentacene layer on both the electrode and active region by evaporation. In addition, negligible damage by AP plasma was observed for the device performance. The fabricated OTFTs based on the two monolayers by AP plasma treatment showed the mobility of 0.23 cm2/Vs, contact resistance of 29 kΩ-cm, threshold voltage of −1.63 V, and on/off ratio of 9.8 × 105, demonstrating the application of the simple process for robust and high-performance OTFTs.

Effects of Solvent on the Formation of the MUA Monolayer on Si and Its Diffusion Barrier Properties for Cu Metallization

We investigated the effects of solvents, such as ethanol and isooctane, on self-assembly of the mercaptoundecanoic acid (MUA) monolayer on Si and its diffusion barrier properties for Cu metallization. The use of isooctane as a solvent produced MUA self-assembled monolayers (SAMs) (∼1.3 nm thick) on Si. These acted as an effective diffusion barrier against Cu diffusion up to 200°C. In contrast, the MUA SAMs produced by ethanol allowed the diffusion of Cu to a MUA-Si interface at 200°C, stimulating the out-diffusion of Si into Cu and thus resulting in the degraded diffusion barrier properties. This was possibly due to the partial formation of interplane hydrogen bonding between the terminal groups of the bound acid and free thiol groups. This provided less dense thiol surface groups, thus leading to poor adhesion of Cu to MUA SAMs. The fabricated Cu/isooctane-assisted MUA source/drain electrode a-Si:H thin film transistors with a channel length of 10 µm exhibited an excellent electron mobility of 0.74 cm2/V-s, threshold voltage of −0.51 V, Ion/Ioff ratio of 3.25 × 106, specific contact resistance of 4.24 Ω-cm2 after annealing at 200°C.

Effects of a Ni alloying element on Al?Ni metallization

The effect of the Ni content (2?18 at.% Ni) in Al thin films on their resistivity, hillock formation and Al3Ni compound formation was investigated. The as-deposited Al?Ni-alloy films showed high elastic strains which increased with increasing Ni content. In addition, the annealing of the supersaturated Al?Ni-alloy thin films yielded two phases: Al3Ni and Al with strong (2?2?0) and (1?1?1) textures, respectively, suggesting that the nucleation of (2?2?0) Al3Ni is closely associated with (1?1?1) Al. The resistivity of the as-annealed Al?Ni-alloy films varied as functions of the volume fraction and grain size of the two phases, which were determined by the Ni content and annealing temperature, respectively. The hillock formation was effectively suppressed when a small amount of Ni was added to the Al alloy. The results showed that a Ni content of less than approximately 4.5 at.% produced hillock-free Al-alloy thin films with a low resistivity of less than 6.0 ?? cm upon annealing at 350 ?C.