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Technology of MRAM (Magneto-resistive Random Access Memory) Using MTJ(Magnetic Tunnel Junction) Cell
Park, Wanjun,Song, I-Hun,Park, Sangjin,Kim, Teawan The Institute of Electronics and Information Engin 2002 Journal of semiconductor technology and science Vol.2 No.3
DRAM, SRAM, and FLASH memory are three major memory devices currently used in most electronic applications. But, they have very distinct attributes, therefore, each memory could be used only for limited applications. MRAM (Magneto-resistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. To be a commercially competitive memory device, scalability is an important factor as well. This paper is testing the actual electrical parameters and the scaling factors to limit MRAM technology in the semiconductor based memory device by an actual integration of MRAM core cell. Electrical tuning of MOS/MTJ, and control of resistance are important factors for data sensing, and control of magnetic switching for data writing.
Wanjun Park 한국자기학회 2002 Journal of Magnetics Vol.7 No.3
MRAM (Magnetoresistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. This paper is for testing the actual electrical parameters to adopt MRAM technology in the semiconductor based memory device. The discussed topics are an actual integration of MRAM core cell and its properties such as electrical tuning of MOS/MTJ for data sensing and control of magnetic switching for data writing. It will be also tested that limits of the MRAM technology for a high density memory.
Oxygen-induced p-type doping of a long individual single-walled carbon nanotube
Kang, Donghun,Park, Noejung,Ko, Ju-hye,Bae, Eunju,Park, Wanjun IOP Pub 2005 Nanotechnology Vol.16 No.8
<P>The effect of oxygen adsorption on a nanotube-based field effect transistor have been controversial as to whether it induces p-type doping of the nanotube body or the work function increase in the metal electrode. Here we report a transport measurement showing that a long individual single-walled nanotube can be doped as p-type upon oxygen adsorption. We discuss that, despite the fact that the charge transfer between the nanotube and O<SUB>2</SUB> adsorbator has not been agreed to date, the effect of oxygen adsorption should still be interpreted as inducing p-type doping in the nanotube body. The n-type doping by NH<SUB>3</SUB> adsorption is also measured for the purpose of comparison. Based on these observations, we suggest that, while the Schottky barrier management could be more effective for the transistor with a short nanotube, the doping effect could be more influential in devices with longer nanotubes. </P>
Bae, Giyeol,Park, Noejung,Park, Wanjun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>In this work, we study a basic mechanism for oxygen intercalation through defect sites due to possible imperfections, namely edges and grain boundaries, in graphene. From first-principles density functional theory calculations, graphene edge sites were found to be vulnerable to attack by oxygen, resulting in cleavage of the C-C sigma-bond and buckling of the sp(2)-bonded planar carbon sheet. This process weakens the interaction between graphene and underlying metal surface while creating an inflow path for external oxidants. The inevitable presence of graphene grain boundaries not only builds the channel in which intercalants move, but also considerably reduces the migration energy of atomic oxygen passing directly through the graphene sheet, thereby compromising the ability of graphene to protect the underlying</P>