• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.631-636
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• 2017

The degradation mechanism of $Mo_xW_{1-x}Si_2$ ultrahigh-temperature heating elements fabricated by self-propagating high-temperature synthesiswas investigated. The $Mo_xW_{1-x}Si_2$ specimens (with and without post-annealing) were subjected to ADTs (accelerated degradation tests) at temperatures up to $1,700^{\circ}C$ at heating rates of 3, 4, 5, 7, and $14^{\circ}C/min$. The surface loads of all the specimen heaters were increased with the increase in the target temperature. For the $Mo_xW_{1-x}Si_2$ specimens without annealing, many pores and secondary-phase particles were observed in the microstructure; the surface load increased to $23.9W/cm^2$ at $1,700^{\circ}C$, while the bending strength drastically reduced to 242 MPa. In contrast, the $Mo_xW_{1-x}Si_2$ specimens after post-annealing retained $single-Mo_xW_{1-x}Si_2$ phases and showed superior durability after the ADT. Consequently, it is thought that the formation of microcracks and coarse secondary phases during the ADT are the main causes for the degraded performance of the $Mo_xW_{1-x}Si_2$ heating elements without post-annealing.

• Polymer(Korea)
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• v.25 no.3
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• pp.435-440
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• 2001

The objective of this study was to examine the effect of oxidation inhibitor contents on the work of adhesion, fracture toughness, and impact strength of the unidirectional carbon-carbon composites (C/C composites). The molybdenum disilicide ($MoSi_2$) used as an oxidation inhibitor was impregnated with phenolic resins to improve the anti-oxidation properties of the composites in different concentrations of 4, 12 and 20 wt%. Based on Wilhelmy equation, the work of adhesion of C/C composites was calculated by contact angle methods. Fracture toughness and impact strength were pressured by three-point bending test for the critical intensity factor ($K_IC$) and Izod test method, respectively. As a result, the composites made with $MoSi_2$ resulted in an increasing of both fracture toughness and impact strength. Especially, the composites made with 12 wt% $MoSi_2$ content showed the highest value of London dispersive component, $W_A\;^L$, in work of adhesion, resulting from improving the interfacial adhesion force among fibers, filler, and matrix in this system.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.256-262
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• 1999

Sputter deposited CoCr(Mo)/Si film were studied with emphasis on the correlation between magnetic properties and crystallographic orientation. The perpendicular coercivities of CoCr films decreased with Si underlayer thickness, whereas those of CoCrMo films increased with Si underlayer thickness. It has been explained that additions of the larger atomic radius Mo atoms in CoCr films impedes crystal growth resulting in a decrease in grain size, thus this small grain size may induce high perpendicular coercivity. The c-axis alignment of CoCrMo film was improved due to addition of 2at.%Mo. It means CoCrMo layer grow self-epitaxial directly from orientation and structure of Si underlayer when the main layer grow on underlayer.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.653-657
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• 2012

In this study, a molybdenum disilicide ($MoSi_2$) coating process was investigated by hydrogen reduction and Si-pack cementation. At first, the metallic Mo coating was carried out by hydrogen reduction of $MoO_3$ powder at $750^{\circ}C$ for various holding times (1, 2, 3 h) in hydrogen atmosphere. A $4.3{\mu}m$ thick metallic molybdenum thin film was formed at 3 h. $MoSi_2$ was obtained by Si-pack cementation on molybdenum thin film through hydrogen reduction processing. It was carried out using $Si:Al_2O_3:NH_4Cl=5:92:3$ (wt%) packs at $900^{\circ}C$ for various holding times (30, 60, 90 min) in Ar atmosphere. When the holding time was 90 min, a $MoSi_2$ layer was coated successfully and a $15.4{\mu}m$ thickness was observed.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.938-944
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• 1998

$MoSi_2$/W composites were fabricated by vacuum hot press at $1600^{\circ}C$ under 30MPa for 3 hrs. The effects of the amount of tungsten in the composites was explained in terms of the microstructure and mechanical properties. Although tungsten was mainly substituted to Mo atoms forming a complete solid solution of (Mo.W).Si, (x= 1, 5, y=2, 3). the grain size of composites became smaller with the increase of tungsten added. Vickers hardness was increased with the increase of tungsten content due to the solid-solution hardening. On the other hand, toughness of composites decreased sharply by increasing the amount of tungsten. Optimum tungsten amount was determined to be a 10 vol% of composite. Indentation fracture toughness was calculated to be 4.5MPa\sqrt{m}$ in this composites, compared with $2.7MPa\sqrt{m}$ in pure $MoSi_2$.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.240-244
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• 2006

In this paper, magnetic properties and annealing behavior of spin valve structures using Mo(MoN) layers as underlayers were studied varying the thickness of the underlayers. The spin valve structure was consisted of Si substrate/$SiO_2(2,000{\AA})/Mo(MoN)(t{\AA})/NiFe(21\;{\AA})/CoFe(28\;{\AA})/Cu(22\;{\AA})/CoFe(18\;{\AA})/IrMn(65\;{\AA})/Ta(25\;{\AA})$. Also, MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The resistivity of the MoN film increased as the $N_2$ gas flow rate was increased. After annealing at $600^{\circ}C$, XRD results did not show peaks of silicides. XPS results indicated MoN film deposited with 5 sccm of $N_2$ gas flow rate was more stable than the film deposited with 1 sccm of $N_2$ gas flow rate. The variations of MR ratio and magnetic exchange coupling fold were small for the spin valve structures using Mo(MoN) underlayers up to thickness of45 ${\AA}$. MR ratio of spin valves using MoN underlayers deposited with various $N_2$ gas flow rate was about 7.0% at RT and increased to about 7.5% after annealing at $220^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased to about 3.5%. Variation of $N_2$ gas flow rate up to 5 sccm did not change the MR ratio and $H_{ex}$ appreciably.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.417-423
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• 2010

A dense nanostructured MoSi$_{2}$-SiC composite was synthesized by a pulsed current activated combustion synthesis method within 2 min of one step from mechanically activated powders of Mo$_{2}$C and Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense MoSi$_{2}$-SiC with a relative density of up to 98% was produced under simultaneous application of an 80 MPa pressure and pulsed current. The average grain size and mechanical properties of the composite were investigated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1325-1326
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• 2006

Tungsten-molydiside $W_xMo_{1-x}Si_2$ was synthesized by self-propagating high temperature synthesis (SHS). The SHS product with the initial composition of (0.5Mo+0.5W+2Si) contains 23.9% $MoSi_2$, 40.89% $WSi_2$ with remaining 9.11% Mo, 9.16% Si and 16.94%W. Lattice parameters of the $MoSi_2$ and $WSi_2$ determined by Rietvelt analysis were a=0.3206 nm, c=0.7841 nm and a=0.3212 nm, c=0.7822 nm, respectively.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.484-488
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• 2007

Mo(Ti) alloy and pure Cu thin films were subsequently deposited on $SiO_2-coated$ Si wafers, resulting in $Cu/Mo(Ti)/SiO_2$ structures. The multi-structures have been annealed in vacuum at $100-600^{\circ}C$ for 30 min to investigate the outdiffusion of Ti to Cu surface. Annealing at high temperature allowed the outdiffusion of Ti from the Mo(Ti) alloy underlayer to the Cu surface and then forming $TiO_2$ on the surface, which protected the Cu surface against $SiH_4＋NH_3$ plasma during the deposition of $Si_3N_4$ on Cu. The formation of $TiO_2$ layer on the Cu surface was a strong function of annealing temperature and Ti concentration in Mo(Ti) underlayer. Significant outdiffusion of Ti started to occur at $400^{\circ}C$ when the Ti concentration in Mo(Ti) alloy was higher than 60 at.%. This resulted in the formation of $TiO_2/Cu/Mo(Ti)\;alloy/SiO_2$ structures. We have employed the as-deposited Cu/Mo(Ti) alloy and the $500^{\circ}C-annealed$ Cu/Mo(Ti) alloy as gate electrodes to fabricate TFT devices, and then measured the electrical characteristics. The $500^{\circ}C$ annealed Cu/Mo($Ti{\geq}60at.%$) gate electrode TFT showed the excellent electrical characteristics ($mobility\;=\;0.488\;-\;0.505\;cm^2/Vs$, on/off $ratio\;=\;2{\times}10^5-1.85{\times}10^6$, subthreshold = 0.733.1.13 V/decade), indicating that the use of Ti-rich($Ti{\geq}60at.%$) alloy underlayer effectively passivated the Cu surface as a result of the formation of $TiO_2$ on the Cu grain boundaries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.594-599
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• 2005

In this paper, we report the properties of Mo metal employed as PMOS gate electrode. Mo on $SiO_2$ was observed to be stable up to $900^{\circ}C$ by analyzing the Interface with XRD. C-V measurement was performed on the fabricated MOS capacitor with Mo Bate on $SiO_2$. The stability of EOT and work-function was verified by comparing the C-V curves measured before and after annealing at 600, 700, 800, and $900^{\circ}C$. C-V hysteresis curve was performed to identify the effect of fired charge. Gate-injection and substrate-injection of carrier were performed to study the characteristics of $Mo-SiO_2$ and $SiO_2-Si$ interface. Sheet resistance of Mo metal gate obtained from 4-point probe was less than $10\;\Omega\Box$ that was much lower than that of polysilicon.