Ranju Jung
Samsung
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Publication
Featured researches published by Ranju Jung.
Applied Physics Letters | 2007
Seok-Woon Lee; Kookrin Char; Dong-Chan Kim; Ranju Jung; Sun-Kyoung Seo; Xiang-Shu Li; Gyeong-Su Park; I. K. Yoo
Epitaxial NiO films have been fabricated on SrRuO3 films prepared on SrTiO3 single-crystal substrates. The x-ray diffraction spectra and transmission electron microscopy confirm the epitaxial growth of NiO with atomically flat surfaces on the SRO electrode. The I-V measurements of epitaxial NiO show the resistive memory switching behavior with a change in the polarity of the voltage bias, in contrast with the switching behavior of polycrystalline NiO by a single polarity. The I-V characteristics of epitaxial NiO prepared under various synthesis conditions and electrodes are presented, which suggests an important role of interfaces between NiO and electrodes on the resistive switching behavior.
Applied Physics Letters | 2009
S. H. Phark; Ranju Jung; Yoosoo Chang; T. W. Noh; Dong-Wook Kim
Ag/NiO/Pt structures did (did not) exhibit reproducible resistive switching when a positive bias was applied to the Pt (Ag) electrode. X-ray photoemission spectra revealed that ultrathin NiO films on Pt (Ag) layers did (did not) undergo reversible chemical state change during heat treatment in a vacuum and oxygen ambient. Such differences in interfacial chemical interaction may affect filament formation and rupture processes near the electrode and hence alter the resistive switching behaviors.
Japanese Journal of Applied Physics | 2008
Dong-Wook Kim; Ranju Jung; Bae Ho Park; Xiang-Shu Li; Chanwoo Park; Seongmo Shin; Dong-Chirl Kim; Chang-won Lee; Sunae Seo
We investigated the structural and electrical properties of polycrystalline NiO thin films on Pt electrodes formed by thermal oxidation. A Ni–Pt alloy phase was found at the interface, which could be explained by the oxidation kinetics and reactions of Ni, NiO, and Pt. An increase in the oxidation temperature decreased the volume of the alloy layer and improved the crystalline quality of the NiO thin films. Pt/NiO/Pt structures were fabricated, and they showed reversible resistance switching from a high-resistance state (HRS) to a low-resistance state (LRS) and vice versa during unipolar current–voltage measurements. The oxidation temperature affected (did not affect) the HRS (LRS) resistance of the Pt/NiO/Pt structures. This indicated that the transport characteristics of HRS and LRS should be different.
Japanese Journal of Applied Physics | 2007
Dong-Wook Kim; Bae Ho Park; Ranju Jung; Sunae Seo
We report on studies of the resistance switching behaviors of Pt/NiO/Pt structures, whose 60-nm-thick NiO thin films were formed by the thermal oxidation of Ni films. X-ray diffraction studies showed that a single-phase NiO film was obtained and that its lattice constant was very close to that of the bulk. Current–voltage characteristics exhibited reproducible resistance switching under a unipolar bias voltage. The switching voltage and current for the thermally grown NiO thin films did not show large variation in the oxidation temperature range, 350–550 °C.
Journal of The Electrochemical Society | 2006
Yong-Jin Kim; Chel-Jong Choi; Ranju Jung; Soon-Young Oh; Jang-Gn Yun; Won-Jae Lee; Hee-Hwan Ji; Jin-Suk Wang; Hi-Deok Lee
The effects of a triple capping layer (Ti/Ni/TiN) on the electrical and structural properties of nickel monosilicide (NiSi) have been investigated as a function of rapid thermal annealing temperature. It is shown that thesamples with the triple capping layer produce lower sheet resistances than the samples with double (Ti/TiN) or single (TiN) capping layers across the whole annealing temperature range. Scanning transmission electron microscopy results show that, after annealing, interfacial layers consisting of Ni, Ti, and Si elements are formed in the samples with the triple and double capping layers. It is further shown that the triple-capped samples are more thermally stable than the double- and single-capped samples. This could be attributed to the segregation of Ti atoms in grain boundaries of NiSi film, which reduces grain boundary energy. The simple model is presented to explain the influence of Ti reaction flux on the surface morphology and the interface uniformity between the silicide and Si substrate.
Japanese Journal of Applied Physics | 2007
Chel-Jong Choi; Moongyu Jang; Yarkyueon Kim; Myungsim Jun; Tae-Youb Kim; Byoungchul Park; Seongjae Lee; Hyundoek Yang; Ranju Jung; Man Chang; Hyunsang Hwang
We have investigated the effect of high-pressure hydrogen postannealing (HPHA) on the effective metal work function (Φm,eff) of a Pt–Er alloy metal gate on a HfO2 film. By considering the presence of an interfacial layer (IL) between the HfO2 film and a Si substrate and a negative charge at the HfO2/IL interface, the Φm,eff values of the Pt–Er alloy metal gate before and after HPHA, extracted from the relations of equivalent oxide thickness versus flat-band voltage, are determined to be ~5.1 and ~4.8 eV, respectively. The increase in the density of interface dipole caused by the reduction of PtOx during HPHA could be responsible for the decrease in Φm,eff.
Electrochemical and Solid State Letters | 2006
Chel-Jong Choi; Moongyu Jang; Yarkyeon Kim; Myungsim Jeon; Byoungchul Park; Seongjae Lee; Ranju Jung; Hyundoek Yang; Man Chang; Hyunsang Hwang
High-pressure hydrogen postannealing effects on the electrical and structural properties of the Pt-Er alloy metal gate on HfO 2 film have been investigated. It is shown that high-pressure hydrogen postannealing causes the removal of microvoids formed near the interface between Pt-Er alloy and HfO 2 film, resulting in the increase of gate electrode contact areas, causing the decrease of equivalent oxide thickness. It is further shown that high-pressure hydrogen postannealing plays a role in the reduction of PtO x and the interface trap density, leading to the negative shift of flatband voltage and the improvement of the HfO 2 interface quality.
Applied Physics Express | 2015
Ranju Jung; Soo-hyon Phark; Dong-Wook Kim; M. H. Upton; D. Casa; T. Gog; Jungho Kim
We present observations of the Ni K-edge resonant inelastic X-ray scattering (RIXS) in NiOx thin films showing unipolar resistive switching (RS). The RIXS spectra of RS NiOx thin films can be described in terms of crystal field (dd) and charge transfer (CT) excitations. We found distorted dd excitations in the films’ pristine state before electroforming, and identical excitations for high and low resistance states after electroforming. This suggests that the RS property of NiOx thin film is related to defects in pristine NiOx films, and RS occurs in local nanosized spots too small to be detected by RIXS.
Advanced Materials | 2007
Myoung-Jae Lee; Young-soo Park; Dongseok Suh; Eun-hong Lee; Sunae Seo; Dong-Chirl Kim; Ranju Jung; Bo-Soo Kang; Seung-Eon Ahn; Chang Bum Lee; David H. Seo; Young-Kwan Cha; In-kyeong Yoo; Jin-Soo Kim; Bae Ho Park
Current Applied Physics | 2012
Seok-Woon Lee; Hwan Kim; Kookrin Char; Jin-Young Jang; Myungshin Kim; Myung Rae Cho; YungWoo Park; Ranju Jung; Dong-Chan Kim; Sun-Kyoung Seo