• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.5
• /
• pp.475-479
• /
• 1999

Langasite ($La_{3}Ga_{5}SiO_{14}$) was found to have wide application as a promising piezoelectric material. It has high thermal stability of the frequency and large electromechanical coupling factor. For the further development of new compounds with langasite type structure, powders in the La-Al-Si-O system were synthesized by a modified Pechini process. The evolution of the crystalline phase during calcination was studied using TG-DTA, XRD and TEM for the precursor powders. Decomposition proceeded via dehydration and removal of excess solvents at low temperatures ($T<500^{\circ}C$), followed by the crystallization of lanthanum aluminum silicate ($T>800^{\circ}C$) and phase transformation to $LaAlO_{3}$ phase ($T>1200^{\circ}C$). Transmission electron microscopy (TEM) of the calcined powders showed diffuse hollow rings corresponding to an amorphous phase at $800^{\circ}C$ and clear diffraction patterns corresponding to a crystalline phase from the P321 space group ($T<1200^{\circ}C$) and the R3m ($T<1200^{\circ}C$).

• Transactions of Materials Processing
• /
• v.18 no.7
• /
• pp.544-549
• /
• 2009

This study aimed to elucidate the deformation mechanism during low-temperature superplasticity of fine-grained Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy in the context of constitutive equation. For this purpose, initial coarse equiaxed microstructure was refined to $2.2{\mu}m$ via dynamic globularization. Globularized microstructure exhibited large superplastic elongations(434-826%) at temperatures of $650-750^{\circ}C$ and strain rate of $10^{-4}s^{-1}$. It was found that the main deformation mechanism of fine-grained material was grain boundary sliding accommodated by dislocation motion with both stress exponent (n) and grain size exponent (p) values of 2. When the alpha grain size, not sub-grain size, was considered to be an effective grain size, the apparent activation energy for low-temperature superplasticity of the present alloy(169kJ/mol) was closed to that of Ti-6Al-4V alloy(160kJ/mol).

• Journal of the Korean Physical Society
• /
• v.73 no.12
• /
• pp.1895-1898
• /
• 2018

The mechanical properties of Al, Ti, Fe, and Cu metals p-type Si, and n-type Si were investigated by using coincidence Doppler broadening (CDB) positron annihilation spectroscopy. The samples in this experiment were irradiated by using X-rays at generating powers for up to 9 kW. The data taken after the irradiation showed all the characteristic features predicted from defects with vacancies. The S parameter values of the metals were generally less than those of semiconductors such as p-type Si and n-type Si. The relationship between n-type Si and p-type Si were more affected when n-type Si rather than p-type Si was irradiated with X-rays.

• Membrane Journal
• /
• v.17 no.3
• /
• pp.254-268
• /
• 2007

Sodium type faujasite(FAU) zeolite layers with diverse materials characteristics(Si/Al ratio, thickness, and structural discontinuity) were hydrothermally grown on a porous $\alpha-Al_2O_3$ tube, and then the $CO_2/N_2$ separation was evaluated at $30^{\circ}C$ for an equimolar mixture of $CO_2$ and $N_2$. Among hydrothermal conditions, $SiO_2$ content in hydrothermal solution seriously affected materials characteristics: with an increment in the $SiO_2$ content, Si/Al ratio, thickness, and structural discontinuity of grown FAU zeolite layer simultaneously increased. The present study reveals that structural discontinuity(intercrystalline voids due to an incomplete densification and cracks induced by GIS Na-P1 phase) is the most important variable affecting the $CO_2/N_2$ separation. Also, it was suggested that the $CO_2$ desorption in permeate side be the rate-determining(slowest) step in the overall $CO_2$ permeation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.232-232
• /
• 2010

Simulation Program (AFORS-HET 2.4.1) was used, include the basic structure of crystalline silicon thin film as above, under the intrinsic a-Si:H films bonded symmetrical structure (Symmetrical structure) were used. The structure of ITO, a-Si p-type, intrinsic a-Si, c-Si, intrinsic a-Si, a-Si n-type, metal (Al) layer has one of the seven. When thickness for each layer was given the change, the changes of a-Si p-type layer and the intrinsic a-Si layer on top had an impact on efficiency. Efficiency ratio of p-type a-Si:H layer thickness was sensitive to, especially a-Si: H layer thickness is increased in a rapid decrease in Jsc and FF, and efficiency was also decreased.

• Advances in nano research
• /
• v.10 no.1
• /
• pp.91-99
• /
• 2021

Silicene is an emerging two-dimensional (2D) semiconductor material which has been envisaged to be compatible with conventional silicon technology. This paper presents a theoretical study of uniformly doped silicene with aluminium (AlSi3) Field-Effect Transistor (FET) along with the benchmark of device performance metrics with other 2D materials. The simulations are carried out by employing nearest neighbour tight-binding approach and top-of-the-barrier ballistic nanotransistor model. Further investigations on the effects of the operating temperature and oxide thickness to the device performance metrics of AlSi3 FET are also discussed. The simulation results demonstrate that the proposed AlSi3 FET can achieve on-to-off current ratio up to the order of seven and subthreshold swing of 67.6 mV/dec within the ballistic performance limit at room temperature. The simulation results of AlSi3 FET are benchmarked with FETs based on other competitive 2D materials such as silicene, graphene, phosphorene and molybdenum disulphide.

• Proceedings of the Korean Ceranic Society Conference
• /
• 1986.12a
• /
• pp.287-304
• /
• 1986

High quality monocrystalline $\beta$-SiC thin films were grown via two-step process of conversion of the Si(100) surface by reaction with $C_2H_4$ and the subsequent chemical vapor deposition (CVD) at $1360^{\circ}C$ and 1 atm total pressure. Four dopants, B and Al and p-type, and N and P for n-type, were also incorporated into monocrystalline $\beta$-SiC thin films during the CVD growth process. IR and Raman spectroscopies were used to evaluate the quality of the undoped $\beta$-SiC thin films and to investigate the effects of dopants on the structure of the doped $\beta$-SiC thin films. The changes in the shape of IR and Raman spectra of the doped thin films due to dopants were observed. But the XTEM micrographs except for the B-doped and annealed films showed the same density and distribution of stacking faults and dislocations as was seen in the undoped samples, The IR and Raman spectra of the B-doped and annealed films showed the broad and weak bands and one extra peak at the 850 $cm^{-1}$ respectively. The SAD pattern and XTEM micrograph of the B-doped and annealed film provided the evidence for twinning.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.70-73
• /
• 2001

MFIS(Metal-ferroelectric-insulator- semiconductor) structures using silicon oxynitride(SiON) buffer layers were fabricatied and demonstrated nonvolatile memory operations. Oxynitride(SiON) films have been formed on p-Si(100) by RTP(rapid thermal process) in O$_2$+N$_2$ ambient at 1100$^{\circ}C$. The gate leakage current density of Al/SiON/Si(100) capacitor was about the order of 10$\^$-8/ A/cm$^2$ at the range of ${\pm}$ 2.5 MV/cm. The C-V characteristics of Al/LiNbO$_3$/SiON/Si(100) capacitor showed a hysteresis loop due to the ferroelectric nature of the LiNbO$_3$ thin films. Typical dielectric constant value of LiNbO$_3$ film of MFIS device was about 24. The memory window width was about 1.2V at the electric field of ${\pm}$300 kV/cm ranges.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.6
• /
• pp.575-579
• /
• 2008

Al-doped p-type ZnO films were fabricated on n-Si (100) and homo-buffer layers in pure oxygen at $450^{\circ}C$ of by RF magnetron sputtering. Target was ZnO ceramic mixed with 2 wt% $Al_2O_3$. XRD spectra show that the Al-doped ZnO thin films have ZnO crystal structure and homo-buffer layers are beneficial to Al-doped ZnO films to grow along c-axis. Hall Effect experiments with Van der Pauw configuration show that p-type carrier concentrations are ranged from $1.66{\times}10^{16}$ to $4.04{\times}10^{18}\;cm^{-3}$, mobilities from 0.194 to $2.3\;cm^2V^{-1}s^{-1}$ and resistivities from 7.97 to $18.4\;{\Omega}cm$. p-type sample has density of $5.40\;cm^{-3}$ which is smaller than theoretically calculated value of $5.67\;cm^{-3}$. XPS spectra show that Ols has O-O and Zn-O structures and Al2p has only Al-O structure. P-ZnO:Al/n-ZnO:Al junctions were fabricated by magnetron sputtering. V-I curves show that the p-n junctions have rectifying characteristics.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.10a
• /
• pp.14-14
• /
• 2011

AlInN has been studied extensively over the past few years due to its interesting material properties that are not present in other ternary nitrides. However, basic material study of AlInN has not been reported as much compared to device applications due to the difficulty in the growth. We have performed the material studies from various aspects. A secondary ion mass spectrometry (SIMS) has shown high oxygen content above $1{\times}10^{18}\;cm^{-3}$ with its insensitivity to the growth conditions. While the free carrier concentration observed by the capacitance-voltage (C-V) measurements was about $3{\times}10^{17}\;cm^{-3}$, the activation energy measured by temperature dependent C-V was only about 4 meV. Si doped AlInN (Si level ${\sim}2{\times}10^{18}\;cm^{-3}$) showed almost no carrier freeze-out at carrier density of $1{\times}10^{18}\;cm^{-3}$. More studies were carried out with a transmission electron microscopy, time-resolved photoluminescence and other analytical techniques to understand the results from SIMS and C-V studies. In this report, we will discuss the possible correlations between the abnormal characteristics in AlInN.