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The properties of porous silicon as a therapeutic agent <i>via</i> the new photodynamic therapy
Lee, Chongmu,Kim, Hojin,Cho, Youngjoon,Lee, Wan In Royal Society of Chemistry 2007 Journal of materials chemistry Vol.17 No.25
<P>Photodynamic therapy (PDT) is a very useful approach for cancer treatment, but it has a few short-term and long-term side effects arising from reactive oxygen species (ROS) generation. Recently a new photodynamic therapy (PDT) based not on the ROS generation capability of photosensitizers but on the heat generation capability of carbon nanotubes (CNT) combined with a near-infrared (NIR) light irradiation technique has received significant attention. Our experimental results show that PSi can also be utilized as a therapeutic agent that generates sufficient heat to kill cancer cells without toxicity. The surface temperature of PSi increases as high and as quickly as that of CNT, but PSi was found to produce a smaller amount of ROS than CNT during NIR light irradiation. In addition, we developed a new method to effectively measure the amount of the ROS produced by nanomaterial photosensitizers including porous silicon (PSi) and CNT. The analysis results show that this method is reliable and reproducible.</P> <P>Graphic Abstract</P><P>Porous silicon can be utilized as a therapeutic agent that generates sufficient heat to kill cancer cells with minimal reactive oxygen species generation upon exposure to near-infrared light. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b700892a'> </P>
ECR plasma pretreatment for ZnO epitaxy
Jongmin Lim,Chongmu Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
The eects of precleaning the substrate on the epitaxial growth of ZnO were investigated. Dry cleaning techniques employing argon, oxygen, and hydrogen ECR plasmas were employed, respectively, to remove organic contaminants and native oxides on sapphire and silicon substrates prior to the growth of the ZnO lm by atomic layer epitaxy. The incubation period for ZnO nucleation was measured by using scanning electron microscopy (SEM) and Auger electron emission spectroscopic analysis (AES) to investigate the incubation period for ZnO nucleation. ECR plasma pretreatment reduced the cleaning eciency. Oxygen ECR plasma pretreatment was more eective than any other plasma pretreatment because oxygen ECR plasma treatment increased the hydroxyl packing density at the substrate surface, and its eects on sapphire substrates were especially prominent.
ECR plasma precleaning for RuO2 MOCVD
Taejong Eom,Chongmu Lee,Hyounwoo Kim 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
RuO2 is widely studied as a lower electrode material for high dielectric capacitors in dynamic random access and ferroelectric random access memories. Precleaning of the underlying TiN lm surface is essential to enhance RuO2 nucleation in RuO2 metal organic chemical vapor deposition (MOCVD). In this study, the eects of hydrogen, oxygen, and argon electron cyclotron resonance (ECR) plasma precleaning on RuO2 nucleation were investigated using X-ray diraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses. Argon ECR plasma pretreatment was found to oer the highest RuO2 nucleation density among these three pretreatments. The mechanism through which RuO2 nucleation is enhanced by ECR plasma pretreatment may be that the argon or the hydrogen plasma removes nitrogen and oxygen atoms at the TiN lm surface so that the underlying TiN lm surface is changed to Ti-rich TiN
Comparison of the Properties of Cu Films Deposited on four Different Types of TiN Substrates
Shin, Young Hoon,Lee, Chongmu 대한금속재료학회(대한금속학회) 1997 METALS AND MATERIALS International Vol.3 No.2
Cu is now widely accepted as the premier replacement for Al in ULSI interconnect metalliztion. However, it cannot be used without a diffusion barrier since it diffuses through a SiO, layer into the Si substrate very easily. TiN is one of the potential candidates for the barrier. In this paper the properties of the Cu films deposited on four different kinds of TiN films were compared. The properties of the CVD-Cu film strongly depend upon the type of the TiN substrate. The Cu film with the highest quality from the viewpoint of surface roughness and thickness uniformity on the four different kinds of the TiN substrate are obtained at 180, 220, 200℃ and 200℃ for the TiN(TDEAT), TiN(TDEAT+NH₃), TiN(TDMAT), and TiN (sputtered) substrates, respectively. The Cu deposition temperatures at which the Cu films with the lowest electrical resistivity are deposited 200$quot;C on TiN(TDEAT), at 220℃ on TiN(TDEAT+NH,) and TiN(TDEAT) and 180℃ on TiN(sputtered), respectively. The smoothest and flattest surface morphology of the Cu film is obtained on TiN(TDMAT), the next on TiN(TDEAT), the third on TiN(sputtered), and the last on TiN(TDEAT+NH₃) as a descending order at the Cu deposition temperatures of 200℃.
Temperature-Controlled Fabrication of Crystalline $\beta$-Bi2O3 Nanowires through an MOCVD Process
Hyoun Woo Kim,Chongmu Lee,Jong Woo Lee 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I
We have investigated the effect of growth temperature on the resultant -Bi2O3 nanostructures. Scanning electron microscopy (SEM) images indicated that the substrate temperature in the range of 400 – 500 C affected the sample morphology on Au-coated Si substrates. While we prepared cluster- or film-like structures at 500 C, we obtained one-dimensional structures at a lower temperature of 400 C with a diameter of 30 – 90 nm. We discuss the possible growth mechanism of -Bi2O3 nanowires with respect to temperature effects. Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) analyses coincidentally revealed that the as-grown nanowires had a tetragonal -Bi2O3 structure. The photoluminescence (PL) spectrum of the -Bi2O3 nanowires, obtained by using a He-Cd laser (3.82 eV) as the excitation source, showed a blue emission centered at around 2.8 – 3.1 eV.
Dukryel Kwon,Hyunah Park,Chongmu Lee,H. T. Jeon,S Ghosh,Sudipta Roy 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
Cu seed layers deposited by magnetron sputtering onto tantalum nitride barrier lms were treated with an electron cyclotron resonance (ECR) plasma to enhance Cu nucleation prior to Cu electroplating. Then, the copper lms were electroplated and annealed by rapid thermal annealing (RTA) or rapid thermal nitridation (RTN) at various temperatures ranging from 200 to 500 C. The eects of annealing on the copper lms electroplated on the hydrogen ECR plasma cleaned copper seed layers were investigated using X-ray diraction (XRD), electron back-scattered diraction (EBSD), and atomic force microscopy (AFM). It appears that the copper lm undergoes complete recrystallization during annealing at a temperature higher than 400 C. The resistivity of the Cu lm tends to decrease and the degree of (111) preferred orientation tends to increase as the annealing temperature increases. The optimum annealing condition for obtaining the lm with the lowest resistivity, the smoothest surface, and the highest degree of the (111) preferred orientation is rapid thermal nitriation (RTN) at 400 C for 120 s. The resistivity and the surface roughness of the electroplated copper lm annealed under this condition are 1.98 -cm and 17.77 nm, respectively.
Dependence of the physical properties DLC films
Jae Bun Kim,Chongmu Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Diamond like carbon lms have been deposited using CH4/Ar gas mixtures with various CH4 concentrations by the rf-plasma enhancement chemical vapor deposition technique. It has been found that the deposition rate initially increases with the Ar dilution, but nally drops due to the pronounced etching eect of Ar ion sputtering and the reduced amount of CH4 present to sustain the growth of the lms. The hardness and the integrated intensity ratio (ID/IG) of the Raman D-line and G-line, respectively, tend to increase with increase in the Ar fraction in the precursor gas mixture. FTIR spectra show that the amount of hydrogen in the lms decreases with increasing Ar dilution. This may be due to the small amount of carbon-supplying gas (CH4) at a high Ar fraction and disruption of weak sp2 CHn bonds by Ar ions. All these results show that the sp3 fraction in the lms increases with an increase in the Ar fraction in the precursor.