DH Baek - Academia.edu (original) (raw)
Papers by DH Baek
Applied Physics A Solids and Surfaces, 1994
We have investigated vibrational properties of silicon-nitride films, SiN x (0.3 < x < 1.33), pro... more We have investigated vibrational properties of silicon-nitride films, SiN x (0.3 < x < 1.33), produced by a non-thermal method using high-resolution electron energy loss spectroscopy. The results, based on a continuous random network model assuming a planar XY 3 vibrational bond unit, show that the SiN bonds in the films closely resemble those in typical thermal silicon nitride although nitrogens occupy some metastable binding sites. We estimate force constants of the restoring forces for a Si3N bond unit, which tend to increase gradually with increasing nitrogen content x. In particular, the central force constant k 1 for the in-plane stretching mode of silicon atoms varies with x in the range 297 < k < 331 N/M, larger than the theoretical value for a nitrogen atom imbedded in a pure Si crystal.
Physical Review B, 1992
The local atomic-bond structures in amorphous Si02 films prepared by a nonthermal method have bee... more The local atomic-bond structures in amorphous Si02 films prepared by a nonthermal method have been investigated by electron-energy-loss spectroscopy (EELS). The method utilizes oxygen ions of energy below 600 eV impinging on Si(100) surfaces at room temperature. The results, based on an augmented-central-force model, reveal that the Si-0 bond nature in the films strongly resembles a typical thermal SiO& glass. The contribution of noncentral forces to the local Si-0 bonding, in terms of the ratio of noncentral-to-central force constants P/a, is estimated by reducing the low-frequency EELS vibrational band (%co 80 meV). The ratio is found to be rather temperature insensitive but increases with film thickness, in the range 0. 13 (p/a (0.19. We also observe thermally activated migration of oxygen atoms in the films with an activation energy barrier of about 0.22 eV.
Physical Review Letters, 1992
We report results of an angle-resolved photoemission study to elucidate the driving mechanism of ... more We report results of an angle-resolved photoemission study to elucidate the driving mechanism of the Mo(001) surface reconstruction. We find, for the first time, a remarkable change of the shapes of Fermi contours upon cooling, which reveals a significant nesting at kt =0.65 A ', extended 0.30 A ' perpendicular to the Z axis. The results suggest that the reconstruction should occur essentially by Peierls-type 2kF instabilities with significant matrix element effects.
Physical Review B
We have investigated the critical behavior of a two-dimensional phase transition of the p(2X 1) o... more We have investigated the critical behavior of a two-dimensional phase transition of the p(2X 1) oxygen overlayer on a W(110) surface, using high-resolution low-energy-electron diffraction (LEED). The temperature dependence of a characteristic (20) LEED spot of the p(2X1) structure reveals a powerlaw divergence for the susceptibility and correlation length of the critical scattering near the transition temperature of 709 K. Two independent exponents estimated from line-shape analyses are P=0. 19+0.05 and y =1.48+0.34 for T(T"showing significant deviations from those of the twodimensional (2D) Ising model. Other exponents estimated by the scaling relations agree qualitatively with experimental values. We further observe that the exponent g near T, also shows large deviation from the theoretical value. We find that these nonuniversal values for the exponents are consistent with the 2D XY model with cubic anisotropy.
Physical review. B, Condensed matter, Jan 15, 1994
We report results of a combined study of in situ x-ray-photoemission spectroscopy (XPS) and lowen... more We report results of a combined study of in situ x-ray-photoemission spectroscopy (XPS) and lowenergy-electron difFraction (LEED) for silicon nitride films fabricated at room temperature. A variety of nitride films of SiN"(0.2 &x~1 .33) were formed by bombarding low-energy nitrogen ions (E 600 eV) onto a Si(001) surface without thermal treatment. The results reveal that the SiN bond nature in the ion-deposited layers (IDL s), derived from the characteristic XPS spectra, strongly resembles that of a typical thermally prepared silicon nitride, P-Si,N4. We find the chemical shift per SiN bond to be 0.62 eV, and a shift of Fermi level due to nitridation less than 0.1 eV. We estimate the thickness of the unannealed IDL's to be less than 18 A. Upon annealing an IDL, progressive changes of XPS peaks and LEED patterns suggest that nitrogen atoms migrate from initial metastable defect sites to thermally stable sites, and tend to coalesce to form locally ordered microcrystallites. The thermal activation energy barrier in an IDL of E =400 eV, x =1.33 is found to be about 0.21 eV, in agreement with theoretical predictions.
Journal of Applied Physics, 1991
By impinging a beam of O+2 ions of energy 150 eV<E<1 keV on a Si(100) surface, we produced ... more By impinging a beam of O+2 ions of energy 150 eV<E<1 keV on a Si(100) surface, we produced oxide films of varying thickness at room temperature. We find that the Si—O bond features of the films are quite similar to those of a thermally prepared vitreous SiO2 glass. We further observe that an intermediate range order in the form of n-member ring clusters with n=4 and n=6 exists in the resulting films.
Applied Physics A Solids and Surfaces, 1994
We have investigated vibrational properties of silicon-nitride films, SiN x (0.3 < x < 1.33), pro... more We have investigated vibrational properties of silicon-nitride films, SiN x (0.3 < x < 1.33), produced by a non-thermal method using high-resolution electron energy loss spectroscopy. The results, based on a continuous random network model assuming a planar XY 3 vibrational bond unit, show that the SiN bonds in the films closely resemble those in typical thermal silicon nitride although nitrogens occupy some metastable binding sites. We estimate force constants of the restoring forces for a Si3N bond unit, which tend to increase gradually with increasing nitrogen content x. In particular, the central force constant k 1 for the in-plane stretching mode of silicon atoms varies with x in the range 297 < k < 331 N/M, larger than the theoretical value for a nitrogen atom imbedded in a pure Si crystal.
Physical Review B, 1992
The local atomic-bond structures in amorphous Si02 films prepared by a nonthermal method have bee... more The local atomic-bond structures in amorphous Si02 films prepared by a nonthermal method have been investigated by electron-energy-loss spectroscopy (EELS). The method utilizes oxygen ions of energy below 600 eV impinging on Si(100) surfaces at room temperature. The results, based on an augmented-central-force model, reveal that the Si-0 bond nature in the films strongly resembles a typical thermal SiO& glass. The contribution of noncentral forces to the local Si-0 bonding, in terms of the ratio of noncentral-to-central force constants P/a, is estimated by reducing the low-frequency EELS vibrational band (%co 80 meV). The ratio is found to be rather temperature insensitive but increases with film thickness, in the range 0. 13 (p/a (0.19. We also observe thermally activated migration of oxygen atoms in the films with an activation energy barrier of about 0.22 eV.
Physical Review Letters, 1992
We report results of an angle-resolved photoemission study to elucidate the driving mechanism of ... more We report results of an angle-resolved photoemission study to elucidate the driving mechanism of the Mo(001) surface reconstruction. We find, for the first time, a remarkable change of the shapes of Fermi contours upon cooling, which reveals a significant nesting at kt =0.65 A ', extended 0.30 A ' perpendicular to the Z axis. The results suggest that the reconstruction should occur essentially by Peierls-type 2kF instabilities with significant matrix element effects.
Physical Review B
We have investigated the critical behavior of a two-dimensional phase transition of the p(2X 1) o... more We have investigated the critical behavior of a two-dimensional phase transition of the p(2X 1) oxygen overlayer on a W(110) surface, using high-resolution low-energy-electron diffraction (LEED). The temperature dependence of a characteristic (20) LEED spot of the p(2X1) structure reveals a powerlaw divergence for the susceptibility and correlation length of the critical scattering near the transition temperature of 709 K. Two independent exponents estimated from line-shape analyses are P=0. 19+0.05 and y =1.48+0.34 for T(T"showing significant deviations from those of the twodimensional (2D) Ising model. Other exponents estimated by the scaling relations agree qualitatively with experimental values. We further observe that the exponent g near T, also shows large deviation from the theoretical value. We find that these nonuniversal values for the exponents are consistent with the 2D XY model with cubic anisotropy.
Physical review. B, Condensed matter, Jan 15, 1994
We report results of a combined study of in situ x-ray-photoemission spectroscopy (XPS) and lowen... more We report results of a combined study of in situ x-ray-photoemission spectroscopy (XPS) and lowenergy-electron difFraction (LEED) for silicon nitride films fabricated at room temperature. A variety of nitride films of SiN"(0.2 &x~1 .33) were formed by bombarding low-energy nitrogen ions (E 600 eV) onto a Si(001) surface without thermal treatment. The results reveal that the SiN bond nature in the ion-deposited layers (IDL s), derived from the characteristic XPS spectra, strongly resembles that of a typical thermally prepared silicon nitride, P-Si,N4. We find the chemical shift per SiN bond to be 0.62 eV, and a shift of Fermi level due to nitridation less than 0.1 eV. We estimate the thickness of the unannealed IDL's to be less than 18 A. Upon annealing an IDL, progressive changes of XPS peaks and LEED patterns suggest that nitrogen atoms migrate from initial metastable defect sites to thermally stable sites, and tend to coalesce to form locally ordered microcrystallites. The thermal activation energy barrier in an IDL of E =400 eV, x =1.33 is found to be about 0.21 eV, in agreement with theoretical predictions.
Journal of Applied Physics, 1991
By impinging a beam of O+2 ions of energy 150 eV<E<1 keV on a Si(100) surface, we produced ... more By impinging a beam of O+2 ions of energy 150 eV<E<1 keV on a Si(100) surface, we produced oxide films of varying thickness at room temperature. We find that the Si—O bond features of the films are quite similar to those of a thermally prepared vitreous SiO2 glass. We further observe that an intermediate range order in the form of n-member ring clusters with n=4 and n=6 exists in the resulting films.