Browsing by Author "Chueh, YL"

Now showing 1 - 8 of 8

Analysis of silicon nanocrystals in silicon-rich SiO2 synthesized by CO2 laser annealing - art. no. 602020
(2005)
Lin, CJ
;
Lin, GR
;
Chueh, YL
;
Chou, LJ
;
光電工程學系
The localized synthesis of 4.2-5.6 nm-Si nanocrystals (nc-Si) in Si-rich SiO2 (SRSO) by CO, laser annealing at laser intensity of below ablation-threshold (6 kW/cm(2)) is demonstrated. Since the SRSO exhibits a high absorption coefficient of up to 0.102 cm(-1) at wavelength of 10.6 mu m, a direct-writing CO, laser annealing system with focusing spot 2 size of 0.2 mm(2) is used to locally anneal the SRSO and precipitate the nc-Si. A thermophysical model reveals that the surface temperature of SRSO ranging from 130 degrees C to 3350 degrees C is achieved by varying the laser power densities from 1.5 to 13.5 kW/cm(2). The CO2 laser-ablation-threshold power density is about 6 kW/cm(2). corresponding to the optimized annealing temperature 1285 degrees C at the ablation threshold. The CO2 laser annealing is capable of the precise control on power density and spot size, which benefits from the in-situ and localized annealing temperature control of SRSO film, and also prevents from the eternal damage of the other electronic devices nearby the annealing site. The nc-Si dependent photoluminescence (PL) were observed at 806 nm or longer, whereas the laser-ablation damaged SRSO film exhibits significant blue PL at 410 nm due to the oxygen-related structural defects. The refractive index of the laser-treated SRSO film is increasing from 1.57 to 2.31 as the laser intensity increases from 1.5 to 6.0 kW/cm(2) which is mainly attributed to the increasing density of nc-Si embedded in SRSO. High resolution transmission electron microscopy (HRTEM) analysis reveals that the average size of nc-Si embedded in SRSO film is about 5.3 nm, which correlates well with the theoretical prediction of a corresponding PL at 806 nm. The HRTEM estimated square density of the nc-Si in SRSO film under the laser intensity of 6 kW/cm(2) is about 10(18) cm(-3).
Anomalous electrical performance of nanoscaled interfacial oxides for bonded n-GaAs wafers
(2006-03-13)
Hao, OY
;
Wu, YCS
;
Chiou, HH
;
Liu, CC
;
Cheng, JH
Electrical performance was found to be closely related to the variation of nanosized interface morphology in previous studies. This work investigated in detail the microstructural development of in- and anti-phase bonded interfaces for n-type (100) GaAs wafers treated at 500, 600, 700 and 850 degrees C. The interfacial energy of anti-phase bonding is higher than that of in-phase bonding based on the first-principles calculations. The higher interface energy tends to stabilize the interfacial oxide layer. The continuous interfacial oxide layer observed below 700 degrees C can deteriorate the electrical property due to its insulating property. However, the existence of nanoscaled oxide at anti-phase bonded interfaces can improve the electrical conductivity at 700 degrees C. This is due to the suppression of the evaporation of As atom by the interfacial nanoscaled oxides based on the analysis of autocorrelation function and energy dispersive x-ray spectroscopy. (c) 2006 American Institute of Physics.
CO2 laser annealing synthesis of silicon nanocrystals buried in Si-rich SiO2
(2005)
Lin, CJ
;
Chueh, YL
;
Chou, LJ
;
Kuo, HC
;
Lin, GR
Localized synthesis of 3-8 nm Si nanocrystals (nc-Si) in PECVD-grown Si-rich SiO2 (SRSO) film is demonstrated using CO2 laser annealing at an intensity below the ablation-threshold (6.0 kW/cm(2)). At an optimized surface temperature of 1285 degrees C, the precipitated nc-Si in CO2-laser-annealed SRSO film results in near-infrared photoluminescence (PL) at 806 ran, whereas the ablation damage induced at higher laser intensities as well as temperatures results in blue PL at 410 nm related to structural defects. The refractive index of the laser-annealed SRSO at 633 nm increases from 1.57 to 2.31 as the laser intensity increases from 1.5 to 6.0 kW/cm(2). Transmission electron microscopy analysis reveals that the average size and volume density of Si nanocrystals embedded in the SRSO film are about 6 nm and 4.5 x 10(16) cm(-3), respectively. The CO2 laser annealing with controlled intensity and spot size can potentially accomplish in-situ, localized annealing of the SRSO film without causing irreversible damage to nearby electronics.
Effects of N2O fluence on the PECVD-grown Si-rich SiOx with buried Si nanocrystals
(2005)
Lin, CJ
;
Kuo, HC
;
Chen, CY
;
Chueh, YL
;
Chou, LJ
The optimized N2O fluence is demonstrated for plasma enhanced chemical vapor deposition (PECVD) of Si-rich substoichiometric silicon oxide (SiOx) films with buried Si nanocrystals. Strong room-temperature photoluminescence (PL) at 550-870 rim has been observed in SiOx films grown by PECVD under a constant SiH4 fluence of 20 sccm with an N2O fluence varying from 105 sccm to 130 sccm. A 22-nm-redshift in the central PL wavelength has been detected after annealing from 15 min to 180 min. The maximum PL irradiance is observed from the SiOx film grown at the optimal N2O fluence of 120 sccm after annealing for 30 minutes. Larger N2O fluence or longer annealing time leads to a PL band that is blue-shifted by 65 nm and 20 nm, respectively. Such a blue shift is attributed to shrinkage in the size of the Si nanocrystals with the participation of oxygen atoms from N2O incorporated within the SiOx matrix. The (220)-oriented Si nanocrystals exhibit radii ranging from 4.4 nm to 5.0 nm as determined by transmission electron microscopy (TEM). The luminescent lifetime lengthens to 52 mu s as the nc-Si size increase to > 4 nm. Optimal annealing times for SiOx films prepared at different N2O fluences are also reported. A longer annealing process results in a stronger oxidation effect in SiOx films prepared at higher N2O fluences, yielding a lower PL irradiance at shorter wavelengths. In contrast, larger Si nanocrystals can be precipitated when the N2O fluence becomes lower; however, such a SiOx film usually exhibits weaker PL at longer wavelength due to a lower nc-Si density. These results indicate that a N2O/SiH4 fluence ratio of 6:1 is the optimized PECVD growth condition for the Si-rich SiO2 wherein dense Si nanocrystals are obtained after annealing.
Improved near-infrared luminescence of si-rich SiO2 with buried Si nanocrystals grown by PECVD at optimized N2O fluence
(2005)
Chen, CY
;
Lin, CJ
;
Kuo, HC
;
Lin, GR
;
Chueh, YL
The optimized N2O fluence for plasma enhanced chemical vapor deposition (PECVD) growing silicon-rich substoichiometric silicon oxide (SiOx) with buried Si nanocrystals is demonstrated. Strong room-temperature photoluminescence (PL) at 550-870 nm has been observed in SiOx thin films grown by PECVD with N2O fluence varying from 105 to 130 sccm. After annealing from 15 to 180 min, a 22-nm-redshift of the PL has been detected. The maximum PL intensity is observed for the 30-min annealed SiOx growing at N2O fluence at 120 sccm. Larger N2O fluence and longer annealing time causes a PL blueshift by 65 nm and 20 nm, respectively. Such a blueshift is attributed to shrinkage in the size of the Si nanocrystals under the participation of dissolved oxygen atoms from N2O. The (220)-oriented Si nanocrystals with radius ranging from 4.4 to 5.0 nm are determined. The luminescent lifetimes lengthens from 20 mu s to 52 mu s as the nc-Si size extends from 4.0 to 4.2 run. Optimal annealing times for SiOx preparing at different N2O fluences and an optimum N2O fluence of 120 sccm are reported. Serious oxidation effect at larger N2O fluence condition is observed, providing smaller PL intensity at shorter wavelengths. In contrast, the larger size nc-Si will be precipitated when N2O fluence becomes smaller, leading to a weaker PL at longer wavelength. These results provide the optimized growth condition for the Si-rich SiO2 with buried Si nanocrystals.
Oxygen defect and Si nanocrystal dependent white-light and near-infrared electroluminescence of Si-implanted and plasma-enhanced chemical-vapor deposition-grown Si-rich SiO2
(2005-05-01)
Lin, GR
;
Lin, CJ
;
Lin, CK
;
Chou, LJ
;
Chueh, YL
The mechanisms for silicon (Si) defect and nanocrystal related white and near-infrared electroluminescences (ELs) of Si-rich SiO2 films synthesized by Si-ion implantation and plasma-enhanced chemical-vapor deposition (PECVD) are investigated. The strong photoluminescence (PL) of Si-ion-implanted SiO2 (SiO2:Si+) at 415-455 nm contributed by weak-oxygen bond and neutral oxygen vacancy defects is observed after 1100 degrees C annealing for 180 min. The white-light EL of a reverse-biased SiO2:Si+ metal-oxide-semiconductor (MOS) diode with a turn-on voltage of 3.3 V originates from the minority-carrier tunneling and recombination in the defect states of SiO2:Si+, which exhibits maximum EL power of 120 nW at bias of 15 V with a power-current slope of 2.2 mu W/A. The precipitation of nanocrystallite silicon (nc-Si) in SiO2:Si+ is less pronounced due to relatively small excess Si density. In contrast, the 4-nm nc-Si contributed to PL and EL at about 760 nm is precipitated in the PECVD-grown Si-rich SiOx film after annealing at 1100 degrees C for 30 min. The indium-tin-oxide/Si-rich SiOx/p-Si/Al metal oxide semiconductor (MOS) diode is highly resistive with turn-on voltage and power-current (P-I) slope of 86 V and 0.7 mW/A, respectively. The decomposed EL peaks at 625 and 768 nm are contributed by the bias-dependent cold-carrier tunneling between the excited states in adjacent nc-Si quantum dots. (C) 2005 American Institute of Physics.
Photoluminescence of plasma enhanced chemical vapor deposition amorphous silicon oxide with silicon nanocrystals grown at different fluence ratios and substrate temperatures
(2006-02-01)
Lin, CJ
;
Lin, CK
;
Chang, CW
;
Chueh, YL
;
Kuo, HC
Near-infrared photolummescent dynamics of thermally annealed Si-rich SiOx, films grown by plasma enhanced chemical vapor deposition at different substrate temperatures and N2O/SiH4 fluence ratios are studied. The size of nanocrystallite Si (nc-Si) critically depends on the density of oxygen atoms in a Si-rich layer when the N2O/SiH4 ratio is smaller than 4; that is, it significantly increases at low N2O/SiH4 ratios. Deposition at a high N2O/SiH4 ratio strongly reduces the density of nc-Si and degrades the luminescence at 700-800 mn since the density of oxygen atoms is sufficient in the reaction of nc-Si with silicon atoms and formation of a stoichiometriC SiO2 matrix. Under a high RF power condition, the increasing substrate temperature usually inhibits the precipitation of nc-Si since high-temperature growth facilitates stochiometric SiO2 deposition. The disappearance of visible PL reveals the complete regrowth of a stoichiometric SiO2 matrix around a nanocrystallite Si cluster after annealing. The results of the transient luminescent analysis of Si-rich SiOx samples corroborate well with the observed values and reveal a lifetime of 43 mu s under an optimized nc-Si precipitation condition of 1100 degrees C annealing for 3 h.
Synthesis of silicon nanocrystals in silicon-rich SiO2 by rapid CO2 laser annealing
(2005)
Lin, CJ
;
Lin, GR
;
Chueh, YL
;
Chou, LJ
;
光電工程學系
Localized synthesis of 4.2-5.6 nm Si nanocrystals (nc-Si) in plasma enhanced chemical vapor deposition-grown Si-rich SiOx (x = 1.25) (SRSO) layer is demonstrated using a CO2 laser annealing at intensity of 6.0 kW/cm(2). At an optimized surface temperature of 1285 C, the precipitated nc-Si in annealed SRSO results in near-infrared photoluminescence at 806 nm. The refractive index of the laser-annealed SRSO at 633 nm increases from 1.57 to 2.31 as the laser intensity increases from 1.5 to 6.0 kW/cm(2). Transmission electron microscopy analysis reveals that the average size and volume density of nc-Si embedded in the SRSO layer are about 5.2 nm and 1.08 x 10(18) cm(-3). (c) 2005 The Electrochemical Society.