• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.207-209
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• 2009

This paper describes the characteristics of poly 3C-SiC micro resonators with $3{\times}10^{17}{\sim}1{\times}10^{19}cm^{-3}$ doping concentrations. The 1.2 ${\mu}m$ thick cantilever and the 0.4 ${\mu}m$ thick doubly clamped beam resonators with different lengths were fabricated using poly 3C-SiC thin films. The characteristics of poly 3C-SiC micro resonators were evaluated by quartz and a laser vibrometer in vacuum at room temperature. The resonant frequencies of micro resonators decreased with doping concentrations owing to reduction in the Young's modulus of poly 3C-SiC thin films. It was confirmed that the resonant frequencies of poly 3C-SiC resonators are controllable by doping concentrations. Therefore, poly 3C-SiC resonators could be applied to MEMS devices and bio/chemical sensor applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.468-473
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• 2003

In this paper, for enhancement of property on a-Si:H TFTs We measure interface characteristics of ferroelectrics thin film and a-Si:H thin film. First, SrTiO$_3$ thin film is deposited bye-beam evaporation. Deposited films are annealed for 1 hour in N2 ambient at $150^{\circ}C∼600^{\circ}C$. Dielectric characteristics of deposited SrTiO$_3$ films are very good because dielectric constant shows 50∼100 and breakdown electric field are 1 ∼ 1.5 MV/cm. a-SiN:H,a-Si:H(n-type a-Si:H) are deposited onto SrTiO$_3$ film to make MFNS(Meta1/ferroelectric/a-SiN:H/a-Si:H) by PECVD. After the C-V measurement for interface characteristics, MFNS structure shows no difference with MNS(Metal/a-SiN:H/a-Si:H) structure in C-V characteristics but the insulator capacitance value of MFNS structure is much higher than the MNS because of high dielectric constant of ferroelectric.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.389-393
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• 2003

The effect of antireflection layer on the reduction of optical loss has been investigated in Si photodiodes detecting red light with central wavelength of 670 nm. The theoretical analysis showed minimum reflection loss of 6% for the $SiO_2$thickness of about $1100∼1200\AA$ in the $SiO_2$-Si system with the single antireflection layer and no reflection loss for the X$N_3$N$_4$$SiO_2$thickness of $2000\AA$/$1200\AA$ in the $Si_3$$N_4$$SiO_2$-Si system with double antireflection layer. In our experiments, Si photodiodes with the web-patterned $p^{＋}$-shallow diffusion region were fabricated by bipolar IC process technology and the devices were classified into three kinds according to the structure of $Si_3$$N_4$/$SiO_2$antireflection layer. The fabricated devices showed maximum spectral response in the optical spectrum of 650∼700 nm. The average photocurrents of the devices with the $Si_3$$N_4$$SiO_2$thickness of $1000\AA$/X$SiO\AA$, and $2000\AA$$1800\AA$ under the incident power, of -17 dBm were 3.2 uA, 3.5 uA and 3.1 uA, respectively.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.956-956
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• 1990

A nitrogenation of coal ash in the presence of carbon was carried out to examine the effects of reaction temperature, reaction time and carbon composition on the formation of AlN, SiC and Si3N4. Decreasing the particle size increased the formation of AlN and its maximum composition in the product was obtaiend under 1450∼1500℃, 2 hours of reaction time and about 30% of carbon addition(on the basis of sample weight). Compositions of SiC and Si3N4 were distributed to the opposite so that SiC showed a higher composition compared with Si3N4 at a lower temperature, a shorter reaction time and a greater carbon addition.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.166-168
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• 2006

$Si_3N_4/SiC$ composite ceramics was sintered in order to investigate their bending strength behavior after crack healing. $Y_2O_$ and $TiO_2$ power was added as sintering additives to enhance it's sintering property. A three-point bending specimen was cut out from sintered plates. About $100\;{\mu}m$ semi-circular surface cracks were made on the center of the tension surface of the three-point bending specimen using Vickers indenter. After the crack-healing processing from $500^{\circ}C$ to $1300^{\circ}C$, for 1 h, in air, the bending strength behavior of these crack-healed specimen coated with $SiO_2$ colloidal were determined systematically at room temperature. $Si_3N_4/SiC$ ceramics using additive powder ($Y_2O_3+TiO_2$) was superior to that of additive powder $Y_2O_3$. The additive powder $TiO_2$ exerted influence at growth of $Si_3N_4$. The optimum crack healing conditions coated $SiO_2$ colloidal were $1000^{\circ}C$ at $Si_3N_4/SiC$ using additive powder ($Y_2O_3+TiO_2$), and $1300^{\circ}C$ at $Si_3N_4/SiC$ using additive powder $Y_2O_3$.

• Korean Journal of Materials Research
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• v.8 no.1
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• pp.27-32
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• 1998

In-Sit반응소결에의해 Si과 AI금속분말을 이용하여 Si$_{3}$N$_{4}$-AIN 복합세라믹스를 합성하였다. 합성된 Si$_{3}$N$_{4}$-AIN복합세라믹스의 미세조직과 결정구조를 해석하기 위해, OM, TEM, XRD및 EDX를 이용하였으며, Si$_{3}$N$_{4}$-AIN -20wt.%AIN복합세라믹스에서 Si의 질화율은 97%로 가장 높았다. Si$_{3}$N$_{4}$-AIN 복합세라믹스에서 Si의 질화율은 AI첨가량 증가에 따라 감소하였다. 대부분의 AI입자들은 다결정 AI입자들은 다결정 AIN(4-H구조)로 완전질화되었으며, 따라서 잔류 AI상은 반응소결체내에서 관찰되지 않았다. Si$_{3}$N$_{4}$의 결정구조는 $\alpha$와 $\beta$구조가 혼재된 상태이며, 잔류 Si입자내에서는 미소균열 및 전위가 관찰되었다. AI/Si$_{3}$N$_{4}$와 Si$_{3}$N$_{4}$ 두계면에서 이들은 거친 형상을 보이지만, 계면반응상은 관찰되지 않았다.

• Journal of Korea Foundry Society
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• v.13 no.4
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• pp.350-358
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• 1993

Aluminum base composites reinforced with various amount of SiC particles and Mg contents have been investigated by different fabrication method for twenty-years. In this paper, how the decomposition and dissolution behaviors of $SiCp(20{\mu}m)$ in the melt of Al composites arised was studied. As the results, the decomposition and dissolution of SiCp into the melt of Al composites increased with increase of the temperature above $720^{\circ}C$, and holding time at a given melting temperature. Because SiC is thermodynamically unstable in this Al-SiCp composite at temperature above the liquidus, SiCp dissolves and reacts with Al in matrix to form $Al_4C_3$ according to following chemical equation $4Al+3SiC{\rightarrow}Al_4C_3+3Si$, Si decomposed and dissolved from SiCp increases Si content of matrix, while liquidus temperature of matrix decrease with increase of SiC content in matrix. The hardness of SiCp decreased with increase of the melting temperature, the hardness of the matrix /particle interface increased with increase of the melting temperature due to increase of the $Mg_2Si$ and $Al_4C_3$ intermetallic compounds, etc.

• Journal of Powder Materials
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• v.6 no.1
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• pp.103-110
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• 1999

Different sizes of Si powder and milling medium materials (steel and partially stabilized zirconia (PSZ)) were used to synthesize $Ti_3Si$ and $TiSi_2$ by mechanical aollying (MA) of Ti-25.0.at.%Si and Ti-66.7at.% Si powder mixtures. the formation of each titanium silicide did not occur even after 360 min of MA of as-re-ceived Si and Ti powder mixtures due to the lack of homogeneity. $Ti_3Si$, however, was synthesized after 240 min of MA of Ti and 60 min-premilled Si powder mixture. ${\alpha}-TiSi_2$ and $TiSi_2$ were produced by jar milling of Ti and 60 min-premilled Si powder mixture for 48 hr and high -energy PSZ ball-milling in a steel vial for 360 min. The formation of each titanium silicide was characterized by a slow reaction rate as the reactants and product(s) coexisted for a certain period of time. The formation of $Ti_3Si$ and $TiSi_2$ and the reaction rates appeared to be influenced by the Si particle size, the homogeneity of the powder mixtures and the milling medium materials.

• Journal of the Korean Ceramic Society
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• v.37 no.11
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• pp.1039-1043
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• 2000

$\alpha$-Si$_3$N$_4$가 20vol% 혼합된 SiC/Si$_3$N$_4$혼합물에서 $\alpha$-SiC의 일부를 SiC whisker로 치환하여 첨가한 후 180$0^{\circ}C$, 25MPa의 압력으로 hot pressing하여 SiC/Si$_3$N$_4$/SiCw 복합체를 제조하였다. SiC whisker의 첨가 함량이 증가할수록 상대밀도, 꺽임강도, 마모 저항성은 감소되었으나, 파괴인성은 크게 향상되었다. $\alpha$-SiC의 일부를 SiC whisker로의 치환은 치밀화를 억제하였으나 파괴인성의 증가는 마모 저항성을 향상시키지 않았다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.109-109
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• 2010

$Er^{3+}$ ion shows a stable and efficient luminescence at 1.54mm due to its $^4I_{13/2}\;{\rightarrow}\;^4I_{15/2}$ intra-4f transition. As this corresponds to the low-loss window of silica-based optical fibers, Er-based light sources have become a mainstay of the long-distance telecom. In most telecom applications, $Er^{3+}$ ions are excited via resonant optical pumping. However, if nanocluster-Si (nc-Si) are co-doped with $Er^{3+}$, $Er^{3+}$ can be excited via energy transfer from excited electrical carriers in the nc-Si as well. This combines the broad, strong absorption band of nc-Si with narrow, stable emission spectra of $Er^{3+}$ to allow top-pumping with off-resonant, low-cost broadband light sources as well as electrical pumping. A widely used method to achieve nc-Si sensitization of $Er^{3+}$ is high-temperature annealing of Er-doped, non-stoichiometric amorphous thin film with excess Si (e.g.,silicon-rich silicon oxide(SRSO)) to precipitate nc-Si and optically activate $Er^{3+}$ at the same time. Unfortunately, such precipitation and growth of nc-Si into Er-doped oxide matrix can lead to $Er^{3+}$ clustering away from nc-Si at anneal temperatures much lower than ${\sim}1000^{\circ}C$ that is necessary for full optical activation of $Er^{3+}$ in $SiO_2$. Recently, silicon-rich silicon nitride (SRSN) was reported to be a promising alternative to SRSO that can overcome this problem of Er clustering. But as nc-Si formation and optical activation $Er^{3+}$ remain linked in Er-doped SRSN, it is not clear which mechanism is responsible for the observed improvement. In this paper, we report on investigating the effect of separating the nc-Si formation and $Er^{3+}$ activation by using hetero-multilayers that consist of nm-thin SRSO or SRSN sensitizing layers with Er-doped $SiO_2$ or $Si_3N_4$ luminescing layers.