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RISS 인기검색어
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- 저자 : Paul K. Chu (검색결과 8 건)
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SIMS AS A BULK ANALYTICAL TOOL
Chu, Paul K. 대한전자공학회 1989 ICVC : International Conference on VLSI and CAD Vol.1 No.1
Secondary ion mass spectrometry (SIMS) is traditionally regarded as strictly a depth profiling analysis technique. However, because of its high inherent sensitivity and capability to detect all elements and isotopes, SILLS also excels in the quantitative determination of bulk trace impurities and dopants in semiconductor substrates and metallization materials. Some recent applications, such as the determination of selected trace impurities in GaAs, carbon and oxygen in heavily-loped CZ-Si substrates, boron in N+ CZ-Si substrates, and radioactive (U & Th) and alkali elements in high purity metals (Al, W, etc.) are discussed. The production of advanced GaAs semiconductor devices with very high performance and/or reliability specifications requires the use of increasingly pure GaAs substrate materials. Presently, SIMS and glow discharge mass spectrometry (GDMS) are two of the most widely used techniques that can provide excellent detection limits. In general, CAMS is capable of providing quantitative survey impurity analysis of GaAs with 10^(14) atoms/㎤ level detection limits for most elements. However, SIMS detection limits are better for vacuum related species (H, C, O, N, etc.), some metallic iy cities (such as Cr and In), and certain n-type dopants (for instance, Se and Te). A combination of SIMS and GDMS will provide the best possible detection limits for most elements in the periodic table. Table 1 lists the detection limits obtained for a number of common impurity and dopant elements in GaAs using GDMS and high performance SIMS employing optimized analytical conditions. In VISI technology, radioactive alpda particle emitters like ^(238)U and ^(232)Th existing in packaging materials and metallic interconnects can induce soft errors in dynamic random access memory (DRAM) cells. As these memory cells shrink in size to submicron dimensions, they are more prone to small amount of alpha particles, even at the part-per-trillion level. The determination of these radioactive elements at the 10 part-per-trillion level is now routinely done by both SIMS 움 GDMS. The sensitivity offered by both techniques is comparable. SIMS is the preferred analytical technique when. sample size is constrained. However, the distribution of these elements may be nonuniform, especially at higher concentrations, and the large volume consumed in a typical CAMS analysis (milligrams versus micrograms or nanaograms) is a major advantage. In high purity metals used in MOS technology, mobile ions, such as Na arid K, can be very detrimental. Again, exploiting its high sensitivity, SIMS is frequently used to determine sodium concentrations in bulk solids or powders in the sub part-per-billion (ppb) range. In other applications, certain impurities are intentional, and their concentration must be carefully controlled. Many new types of devices are presently fabricated in lightly-doped epilayers grown on heavily-doped P+ or N+ CZ-Si substrates. In order to carefully control oxygen precipitation and Bettering, the oxygen contest must be well known. Fourier transform infrared spectroscopy (FTIR), which is the standard technique for determining the interstitial oxygen concentrationin lightly-doped silicon materials, is not suitable for P+ or N+ wafers because of free carrier absorption effects. Given the versatility of the technique, SIMS is capable of making the measurement when performed with homogeneous standards and rigorously executed analytical protocols. The precision currently attainable by SIMS using the load-line calibration method is better than ±2%. Carbon in Czochralski-grown silicon is also known to affect precipitation and impurity Bettering. The determination of carbon in N+ and P+ CZ-Si wafers and polysilicon starting materials poses a bigger challenge than that of oxygen, for the carbon concentration in these materials is typically much lower. At the present time, SIMS provides carbon detection limits in the range of 50-100 ppba for routine measurements. Based on some preliminary studies, the precision of the measurement is about ±10%. Even dopants that are oaly used in siliooci IC fabrication, such as boron, can be undesirable in the wrong places. Unintentional boroa doping in antimony doped N+ silio materials, for example, can cause deleterious effects in ICs by forniing phantan layers in the ntype epi or impeding the grorath of high resistivity n-type i. Because of its high sensitivity, S7MS is the best method for this analysis as well. By using double-focusing magnetic sector instrumentation, detection limits in the range of 10^(12) - 10^(13) atoms/㎤ are routinely achievable. Currently, this measurement can achieve a precision of better than ±8% at concentrations below 10^(14) atoms/cc. The applications described in this paper demonstrate the versatility of SIMS in the area of bulk analysis of electronics materials. Besides excellent sensitivity (sub-ppm), high precisions and accuracies can be achieved using refined protocols and standard statistical measurement approaches.
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Analysis of Local Surface Plasmon Resonance in Multilayered Au/Ag/Graphene Nanoshells
Chao Liu,Zhaoting Liu,Jingwei Lv,Tao Sun,Qiang Liu,Haiwei Mu,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5
"The localized surface plasmon resonance (LSPR) properties of Au/Ag/graphene nanoshells are studied by discrete dipole approximation (DDA). The coupled resonance wavelengths show a remarkable dependence on the graphene thickness as well as refractive index of the surrounding medium. The resonance wavelengths of Au/Ag/graphene nanoshells red-shift as the thickness of the graphene layer is increased, when the radii of the Au core and Ag interlayer are 40 nm and 45nm, respectively. Specifically, the longer wavelength red-shifts from 540 nm to 740 nm when the refractive index varies from 1.25 to 2.05. "
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Chao Liu,Jingwei Lv,Famei Wang,Qiang Liu,Haiwei Mu,Tao Sun,Qiang Liu,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.8
Multilayered nanoshells have attracted much attention due to their unique optical, electronic and magnetic properties. In this work, numerical calculation using discrete dipole approximation (DDA) is conducted to investigate the quad-layered metal nanoshell consisting of a particle with a dielectric silica (SiO2) core, inner cadium sulfide (CdS) shell, middle indium tin oxide (ITO) shell and outer metal silver (Ag) shell. The phenomenon is interpreted by plasmon hybridization theory and the Ag–ITO–CdS–SiO2 multilayered nanoshells are studied by extinction spectra of localized surface plasmon resonance. The variation in the spectrum peak with nanoparticle thickness and refractive index of the surrounding medium is derived. The electric field enhancement contour around the nanoparticles under illumination is analyzed at the plasmon resonance wavelength. The |ω-->, |ω+->, and |ω-+> modes red-shift with the refractive index of the surrounding medium and increase in the layer thickness causes either blue-shift or red-shift as shown by the extinction spectra. The mechanism of the red-shift or blue-shift is discussed. The |ω--> blue-shifts and furthermore, the |ω-+> and |ω+-> modes of the Ag coated multilayered nanostructure are noticeable by comparing the extinction efficiency spectra of the Au–ITO–CdS–SiO2 and Ag–ITO–CdS–SiO2 multilayered nanoshells.
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Localized Surface Plasmon Resonance Properties of Concentric Dual-Ring Nanodisk
Haiwei Mu,Jianxin Wang,Qiang Liu,Wei Liu,Xianli Li,Jingwei Lv,Chao Liu,Famei Wang,Tao Sun,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.6
The extinction spectral properties based on localized surface plasmon resonance (LSPR) of the concentric dual-ring nanodisk (CDRN) structure are investigated by discrete dipole approximation (DDA) and plasmon hybridization theory. The CDRN nanostructure shows flexible tunable multipole resonances in the near-infrared regime and the coupled resonance wavelengths depend on the structural parameters of the nanostructure, which has great potential in multichannel LSPR-based bio-sensing applications.
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Honghui Tong,Qinchuan Chen,LiLu Shen,Yanfeng Huo,Ke Wang,Tanmin Feng,Lilan Mu,Jun Zha,Paul K. Chu 한국진공학회(ASCT) 2002 Journal of Korean Vacuum Science & Technology Vol.6 No.2
Hydraulic pumps are used to control the landing wheels of aircrafts, and their proper operation is vital to plane safety. It is well known that adhesive wear failure is a major cause of pump failure. A dual nitrogen plasma immersion ion implantation process calling for the implantation of nitrogen at two different energies and doses has been developed to enhance the surface properties of the disks in the pumps. The procedures meet the strict temperature requirement of <200℃, and after the treatment, the working lifetime of the pumps increases by more than a factor of two. This experimental protocol has been adopted by the hydraulic pump factory as a standard manufacturing procedure.
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Wen, Xin,Chen, Xuecheng,Tian, Nana,Gong, Jiang,Liu, Jie,Rü,mmeli, Mark H.,Chu, Paul K.,Mijiwska, Ewa,Tang, Tao American Chemical Society 2014 Environmental science & technology Vol.48 No.7
<P>The catalytic carbonization of polyolefin materials to synthesize carbon nanotubes (CNTs) is a promising strategy for the processing and recycling of plastic wastes, but this approach is generally limited due to the selectivity of catalysts and the difficulties in separating the polyolefin mixture. In this study, the influence of nanosized carbon black (CB) and Ni<SUB>2</SUB>O<SUB>3</SUB> as a novel combined catalyst system on catalyzing carbonization of polypropylene (PP), polyethylene (PE), polystyrene (PS) and their blends was investigated. We showed that this combination was efficient to promote the carbonization of these polymers to produce CNTs with high yields and of good quality. Catalytic pyrolysis and model carbonization experiments indicated that the carbonization mechanism was attributed to the synergistic effect of the combined catalysts rendered by CB and Ni<SUB>2</SUB>O<SUB>3</SUB>: CB catalyzed the degradation of PP, PE, and PS to selectively produce more aromatic compounds, which were subsequently dehydrogenated and reassembled into CNTs via the catalytic action of CB together with Ni particles. Moreover, the performance of the synthesized CNTs as the electrode of supercapacitor was investigated. The supercapacitor displayed a high specific capacitance as compared to supercapacitors using commercial CNTs and CB. This difference was attributed to the relatively larger specific surface areas of our synthetic CNTs and their more oxygen-containing groups.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-7/es404646e/production/images/medium/es-2013-04646e_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es404646e'>ACS Electronic Supporting Info</A></P>
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