Kyungjoon Baek - Academia.edu (original) (raw)
Papers by Kyungjoon Baek
Journal of the Korean Physical Society, 2010
Novel ZnWO 4 thin films were achieved by annealing sandwich WO 3 /ZnO/WO 3 (WZW) heterolayer that... more Novel ZnWO 4 thin films were achieved by annealing sandwich WO 3 /ZnO/WO 3 (WZW) heterolayer that were deposited on clean fused silica substrates by RF magnetron sputtering technique. The crystal structures, surface morphologies and photoluminescence (PL) properties of the annealed WZW heterolayers were characterized by x-ray diffraction (XRD), Raman, scanning electron microscopy (SEM) and PL measurements. The XRD and Raman patterns show that the ZnWO 4 thin films formed from WZW heterolayers possess the monoclinic wolframite structure with a preferential orientation along the a-axis. The annealing temperature of WZW heterolayer plays a vital role in determining the crystallization, surface morphologies and PL properties of the formed ZnWO 4 films. The SEM graphs and PL spectra indicate that the annealing treatment at about 750°C for 30min is very effective for deposited WZW heterolayer to form the flat ZnWO 4 thin film with the regular nanometer grains (200-400 nm) and the strongest PL emission near about 495 nm, while further increasing annealing temperature to 850°C leads to a rough surface and weakened PL intensity. The PL spectra from all the annealed WZW films display a broad and asymmetrical shape and are depend on the excitation wavelengths in the range of 240-290 nm as well as annealing temperature. The related PL mechanisms were analyzed and discussed according to the excitation spectra monitored at 410 nm and 495 nm, respectively. It is suggested that the coexistence of the ZnWO 4 and ZnO excitation bands in the film should be responsible for the evolving of PL shapes with the excitation wavelengths. Finally, the average PL decay time of the formed ZnWO 4 film was determined to be about 22μs by time-resolving the three intrinsic emissions of the ZnWO 4 crystallites. This work illustrates that magnetron sputtering is an effective technique to prepare the fluorescing ZnWO 4 film.
Journal of Materials Science, Jul 1, 2010
A novel red-emitting phosphor NaY 9 (SiO 4) 6 O 2 :Sm 3+ (NYS:Sm 3+) was synthesized and the X-ra... more A novel red-emitting phosphor NaY 9 (SiO 4) 6 O 2 :Sm 3+ (NYS:Sm 3+) was synthesized and the X-ray diffraction and high-resolution TEM testified that the NYS compound belongs to the apatite structure which crystallized in a hexagonal unit cell with space group P6 3 /m. The novel phosphor boasts of such three advantageous properties as perfect compatible match with the commercial UV chips, 73.2% quantum efficiency and 90.9% thermal stability at 150 °C. Details are as follows. NYS:Sm 3+ phosphor showed obvious absorption in the UV regions centered at 407 nm, which can be perfectly compatible with the commercial UV chips. The property investigations showed that NYS:Sm 3+ phosphor emitted reddish emission with CIE coordination of (0.563, 0.417). The optimum quenching concentration of Sm 3+ in NYS phosphor was about 10%mol, and the corresponding concentration quenching mechanism was verified to be the electric dipole-dipole interaction. Upon excitation at 407 nm, the compositionoptimized NYS:0.10Sm 3+ exhibited a high quantum efficiency of 73.2%, and its luminescence intensity at 150 °C decreased simply to 90.9% of the initial value at room temperature. All of the results indicated that NYS:Sm 3+ is a promising candidate as a reddish-emitting UV convertible phosphor for application in white light emitting diodes (w-LEDs). In the past decades, solid-state lighting technology has become commercially available with the advent of high performance w-LEDs, which represents a rapid evolution of new lighting systems designed to deliver improved illumination as well as new lighting features such as being environmentally friendly, offering long lifetime, enhancing energy-saving, and producing high luminous efficiency 1-5. Presently, the commercial phosphor-converted w-LEDs use yellow-emitting (YAG:Ce 3+) phosphor coated on a blue In-doped GaN chip or couple three red-, blue-and green-, (RGB tricolor) phosphors with near-ultraviolent (n-UV) chips 6-8. However, this method faces problems of low color rendering index (CRI) and a high correlated color temperature (CCT) due to the deficiency of sufficient red spectral component. Therefore, it is necessary to explore alternative red or reddish phosphors which can be effectively excited in the UV range with excellent chemical stability 9-13. Selection of suitable host material is also an important factor for the preparation of luminescent materials for different applications. Compounds with oxy-apatite structure have been intensively studied owing to their excellent chemical and physical stabilities 14-17. It is well known that oxy-apatite structure belongs to the hexagonal symmetrical system (space group of P6 3 /m) with a general chemical formula as A 10 [MO 4 ] 6 O 2 , in which A is a cation (Na + , Ca 2+ , Y 3+ , La 3+ , etc.), while MO 4 is an anionic group (PO 4 , SiO 4 , GeO 4 , etc.) 18-21. As an important
2015 IEEE International Electron Devices Meeting (IEDM), 2015
We report novel nanoscale synapse and neuron devices for ultra-high density neuromorphic system. ... more We report novel nanoscale synapse and neuron devices for ultra-high density neuromorphic system. By adopting a Mo electrode, the redox reaction at Mo/Pr 0.7 Ca 0.3 MnO 3 (PCMO) interface was controlled which in turn significantly improve synapse characteristics such as switching uniformity, disturbance, retention and multi-level data storage under identical pulse condition. Furthermore, The NbO 2 based Insulator-Metal Transition (IMT) oscillator was developed for neuron application. Finally, we have experimentally confirmed the realization of pattern recognition with high accuracy using the 11k-bit Mo/PCMO synapse array and NbO 2 oscillator neuron.
Journal of the Korean Physical Society, 2011
Nanoscale Advances, 2020
Void formation and migration that drive the device failure of Ge2Sb2Te5 (GST)-based practical dev... more Void formation and migration that drive the device failure of Ge2Sb2Te5 (GST)-based practical devices were revealed via in situ TEM.
Advanced materials (Deerfield Beach, Fla.), 2017
Creation of nanometer-scale conductive filaments in resistive switching devices makes them appeal... more Creation of nanometer-scale conductive filaments in resistive switching devices makes them appealing for advanced electrical applications. While in situ electrical probing transmission electron microscopy promotes fundamental investigations of how the conductive filament comes into existence, it does not provide proof-of-principle observations for the filament growth. Here, using advanced microscopy techniques, electrical, 3D compositional, and structural information of the switching-induced conductive filament are described. It is found that during in situ probing microscopy of a Ag/TiO2 /Pt device showing both memory- and threshold-switching characteristics, a crystalline Ag-doped TiO2 forms at vacant sites on the device surface and acts as the conductive filament. More importantly, change in filament morphology varying with applied compliance currents determines the underlying switching mechanisms that govern either memory or threshold response. When focusing more on threshold sw...
Physica E Low Dimentional Systems and Nanostructures, 2011
... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them w... more ... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them with SnO 2 . The blue emission is further enhanced by annealing in a reducing atmosphere whereas it is slightly degraded by annealing in an oxidative ... [7] J. Jun, C. Jin, H. Kim, J ...
Cryst Res Tech, 2010
Ga 2 O 3 /SnO 2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then... more Ga 2 O 3 /SnO 2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO 2 . Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga 2 O 3 cores and the SnO 2 shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO 2 shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H 2 /N 2 atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H 2 /N 2 annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere.
J Mater Sci Mater Electron, 2010
TiO 2 -sheathed Ga 2 O 3 one-dimensional (1D) nanostructures were synthesized by thermal evaporat... more TiO 2 -sheathed Ga 2 O 3 one-dimensional (1D) nanostructures were synthesized by thermal evaporation of GaN powders and then sputter-deposition of TiO 2 . Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga 2 O 3 cores are of a single crystal nature with a monoclinic structure while the TiO 2 shells are amorphous. Photoluminescence (PL) emission is slightly decreased in intensity by TiO 2 coating, but it is significantly increased by thermal annealing in an oxygen atmosphere. The emission peak is also shifted from *500 to *550 nm by oxygen annealing. The increase in the green emission is due to the increase in the concentration of the Ga vacancies in the cores by the inflow of oxygen during oxygen annealing. On the other hand, annealing in a nitrogen atmosphere leads to a red shift of the emission to *700 nm originating from nitrogen doping.
Solid State Commun, 2010
CuO-core/ SnO 2-shell one-dimensional nanostructures have been fabricated by thermal oxidation of... more CuO-core/ SnO 2-shell one-dimensional nanostructures have been fabricated by thermal oxidation of a copper foil and then atomic layer deposition of SnO 2. The structure and optical properties of the nanostructures have been investigated by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence (PL) spectroscopy, and energy-dispersive X-ray analysis techniques. The nanostructures are found to have the form of nanorods, with the diameter of the CuO cores being in the range from a few tens to a few hundreds of nanometers, the thickness of the SnO 2 shells being ˜15 nm, and with a length of a few tens of micrometers. The CuO cores and the SnO 2 shells of the as-synthesized nanorods have crystalline monoclinic CuO and amorphous SnO 2 structures, respectively, but the SnO 2 shells are found to crystallize to tetragonal SnO 2 on thermal annealing. The PL emission intensity of the CuO nanorods has been slightly increased by SnO 2 coating. The PL emission of the SnO 2-coated CuO nanorods is somewhat increased and the emission peak position is red-shifted from 550 to 580 nm by annealing in a reducing atmosphere. On the other hand, the PL emission is significantly increased and the emission peak position is shifted from 550 nm further to around 595 nm by annealing in an oxidative atmosphere. In addition, the origins of the PL enhancements in the nanorods by coating and annealing are discussed.
J Mater Sci, 2010
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Journal- Korean Physical Society
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Journal of Materials Science, 2010
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Physica E: Low-dimensional Systems and Nanostructures, 2011
... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them w... more ... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them with SnO 2 . The blue emission is further enhanced by annealing in a reducing atmosphere whereas it is slightly degraded by annealing in an oxidative ... [7] J. Jun, C. Jin, H. Kim, J ...
Solid State Communications, 2010
CuO-core/SnO 2 -shell one-dimensional nanostructures have been fabricated by thermal oxidation of... more CuO-core/SnO 2 -shell one-dimensional nanostructures have been fabricated by thermal oxidation of a copper foil and then atomic layer deposition of SnO 2 . The structure and optical properties of the nanostructures have been investigated by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence (PL) spectroscopy, and energy-dispersive X-ray analysis techniques. The nanostructures are found to have the form of nanorods, with the diameter of the CuO cores being in the range from a few tens to a few hundreds of nanometers, the thickness of the SnO 2 shells being ∼15 nm, and with a length of a few tens of micrometers. The CuO cores and the SnO 2 shells of the as-synthesized nanorods have crystalline monoclinic CuO and amorphous SnO 2 structures, respectively, but the SnO 2 shells are found to crystallize to tetragonal SnO 2 on thermal annealing. The PL emission intensity of the CuO nanorods has been slightly increased by SnO 2 coating. The PL emission of the SnO 2 -coated CuO nanorods is somewhat increased and the emission peak position is red-shifted from 550 to 580 nm by annealing in a reducing atmosphere. On the other hand, the PL emission is significantly increased and the emission peak position is shifted from 550 nm further to around 595 nm by annealing in an oxidative atmosphere. In addition, the origins of the PL enhancements in the nanorods by coating and annealing are discussed.
Materials Science and Engineering: B, 2010
Influence of the thermal annealing atmosphere and the ZnO layer thickness on the photoluminescenc... more Influence of the thermal annealing atmosphere and the ZnO layer thickness on the photoluminescence properties of ZnS-core/ZnO-shell one-dimensional (1D) radial heterostructures was investigated. ZnS nanowires were synthesized by thermal evaporation of ZnS powders and then coated with ZnO by using the sputter-deposition technique to form the nanostructures. TEM and XRD analysis results reveal that a crystalline ZnS phase with a
Journal of the Korean Physical Society, 2010
Novel ZnWO 4 thin films were achieved by annealing sandwich WO 3 /ZnO/WO 3 (WZW) heterolayer that... more Novel ZnWO 4 thin films were achieved by annealing sandwich WO 3 /ZnO/WO 3 (WZW) heterolayer that were deposited on clean fused silica substrates by RF magnetron sputtering technique. The crystal structures, surface morphologies and photoluminescence (PL) properties of the annealed WZW heterolayers were characterized by x-ray diffraction (XRD), Raman, scanning electron microscopy (SEM) and PL measurements. The XRD and Raman patterns show that the ZnWO 4 thin films formed from WZW heterolayers possess the monoclinic wolframite structure with a preferential orientation along the a-axis. The annealing temperature of WZW heterolayer plays a vital role in determining the crystallization, surface morphologies and PL properties of the formed ZnWO 4 films. The SEM graphs and PL spectra indicate that the annealing treatment at about 750°C for 30min is very effective for deposited WZW heterolayer to form the flat ZnWO 4 thin film with the regular nanometer grains (200-400 nm) and the strongest PL emission near about 495 nm, while further increasing annealing temperature to 850°C leads to a rough surface and weakened PL intensity. The PL spectra from all the annealed WZW films display a broad and asymmetrical shape and are depend on the excitation wavelengths in the range of 240-290 nm as well as annealing temperature. The related PL mechanisms were analyzed and discussed according to the excitation spectra monitored at 410 nm and 495 nm, respectively. It is suggested that the coexistence of the ZnWO 4 and ZnO excitation bands in the film should be responsible for the evolving of PL shapes with the excitation wavelengths. Finally, the average PL decay time of the formed ZnWO 4 film was determined to be about 22μs by time-resolving the three intrinsic emissions of the ZnWO 4 crystallites. This work illustrates that magnetron sputtering is an effective technique to prepare the fluorescing ZnWO 4 film.
Journal of Materials Science, Jul 1, 2010
A novel red-emitting phosphor NaY 9 (SiO 4) 6 O 2 :Sm 3+ (NYS:Sm 3+) was synthesized and the X-ra... more A novel red-emitting phosphor NaY 9 (SiO 4) 6 O 2 :Sm 3+ (NYS:Sm 3+) was synthesized and the X-ray diffraction and high-resolution TEM testified that the NYS compound belongs to the apatite structure which crystallized in a hexagonal unit cell with space group P6 3 /m. The novel phosphor boasts of such three advantageous properties as perfect compatible match with the commercial UV chips, 73.2% quantum efficiency and 90.9% thermal stability at 150 °C. Details are as follows. NYS:Sm 3+ phosphor showed obvious absorption in the UV regions centered at 407 nm, which can be perfectly compatible with the commercial UV chips. The property investigations showed that NYS:Sm 3+ phosphor emitted reddish emission with CIE coordination of (0.563, 0.417). The optimum quenching concentration of Sm 3+ in NYS phosphor was about 10%mol, and the corresponding concentration quenching mechanism was verified to be the electric dipole-dipole interaction. Upon excitation at 407 nm, the compositionoptimized NYS:0.10Sm 3+ exhibited a high quantum efficiency of 73.2%, and its luminescence intensity at 150 °C decreased simply to 90.9% of the initial value at room temperature. All of the results indicated that NYS:Sm 3+ is a promising candidate as a reddish-emitting UV convertible phosphor for application in white light emitting diodes (w-LEDs). In the past decades, solid-state lighting technology has become commercially available with the advent of high performance w-LEDs, which represents a rapid evolution of new lighting systems designed to deliver improved illumination as well as new lighting features such as being environmentally friendly, offering long lifetime, enhancing energy-saving, and producing high luminous efficiency 1-5. Presently, the commercial phosphor-converted w-LEDs use yellow-emitting (YAG:Ce 3+) phosphor coated on a blue In-doped GaN chip or couple three red-, blue-and green-, (RGB tricolor) phosphors with near-ultraviolent (n-UV) chips 6-8. However, this method faces problems of low color rendering index (CRI) and a high correlated color temperature (CCT) due to the deficiency of sufficient red spectral component. Therefore, it is necessary to explore alternative red or reddish phosphors which can be effectively excited in the UV range with excellent chemical stability 9-13. Selection of suitable host material is also an important factor for the preparation of luminescent materials for different applications. Compounds with oxy-apatite structure have been intensively studied owing to their excellent chemical and physical stabilities 14-17. It is well known that oxy-apatite structure belongs to the hexagonal symmetrical system (space group of P6 3 /m) with a general chemical formula as A 10 [MO 4 ] 6 O 2 , in which A is a cation (Na + , Ca 2+ , Y 3+ , La 3+ , etc.), while MO 4 is an anionic group (PO 4 , SiO 4 , GeO 4 , etc.) 18-21. As an important
2015 IEEE International Electron Devices Meeting (IEDM), 2015
We report novel nanoscale synapse and neuron devices for ultra-high density neuromorphic system. ... more We report novel nanoscale synapse and neuron devices for ultra-high density neuromorphic system. By adopting a Mo electrode, the redox reaction at Mo/Pr 0.7 Ca 0.3 MnO 3 (PCMO) interface was controlled which in turn significantly improve synapse characteristics such as switching uniformity, disturbance, retention and multi-level data storage under identical pulse condition. Furthermore, The NbO 2 based Insulator-Metal Transition (IMT) oscillator was developed for neuron application. Finally, we have experimentally confirmed the realization of pattern recognition with high accuracy using the 11k-bit Mo/PCMO synapse array and NbO 2 oscillator neuron.
Journal of the Korean Physical Society, 2011
Nanoscale Advances, 2020
Void formation and migration that drive the device failure of Ge2Sb2Te5 (GST)-based practical dev... more Void formation and migration that drive the device failure of Ge2Sb2Te5 (GST)-based practical devices were revealed via in situ TEM.
Advanced materials (Deerfield Beach, Fla.), 2017
Creation of nanometer-scale conductive filaments in resistive switching devices makes them appeal... more Creation of nanometer-scale conductive filaments in resistive switching devices makes them appealing for advanced electrical applications. While in situ electrical probing transmission electron microscopy promotes fundamental investigations of how the conductive filament comes into existence, it does not provide proof-of-principle observations for the filament growth. Here, using advanced microscopy techniques, electrical, 3D compositional, and structural information of the switching-induced conductive filament are described. It is found that during in situ probing microscopy of a Ag/TiO2 /Pt device showing both memory- and threshold-switching characteristics, a crystalline Ag-doped TiO2 forms at vacant sites on the device surface and acts as the conductive filament. More importantly, change in filament morphology varying with applied compliance currents determines the underlying switching mechanisms that govern either memory or threshold response. When focusing more on threshold sw...
Physica E Low Dimentional Systems and Nanostructures, 2011
... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them w... more ... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them with SnO 2 . The blue emission is further enhanced by annealing in a reducing atmosphere whereas it is slightly degraded by annealing in an oxidative ... [7] J. Jun, C. Jin, H. Kim, J ...
Cryst Res Tech, 2010
Ga 2 O 3 /SnO 2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then... more Ga 2 O 3 /SnO 2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO 2 . Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga 2 O 3 cores and the SnO 2 shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO 2 shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H 2 /N 2 atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H 2 /N 2 annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere.
J Mater Sci Mater Electron, 2010
TiO 2 -sheathed Ga 2 O 3 one-dimensional (1D) nanostructures were synthesized by thermal evaporat... more TiO 2 -sheathed Ga 2 O 3 one-dimensional (1D) nanostructures were synthesized by thermal evaporation of GaN powders and then sputter-deposition of TiO 2 . Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga 2 O 3 cores are of a single crystal nature with a monoclinic structure while the TiO 2 shells are amorphous. Photoluminescence (PL) emission is slightly decreased in intensity by TiO 2 coating, but it is significantly increased by thermal annealing in an oxygen atmosphere. The emission peak is also shifted from *500 to *550 nm by oxygen annealing. The increase in the green emission is due to the increase in the concentration of the Ga vacancies in the cores by the inflow of oxygen during oxygen annealing. On the other hand, annealing in a nitrogen atmosphere leads to a red shift of the emission to *700 nm originating from nitrogen doping.
Solid State Commun, 2010
CuO-core/ SnO 2-shell one-dimensional nanostructures have been fabricated by thermal oxidation of... more CuO-core/ SnO 2-shell one-dimensional nanostructures have been fabricated by thermal oxidation of a copper foil and then atomic layer deposition of SnO 2. The structure and optical properties of the nanostructures have been investigated by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence (PL) spectroscopy, and energy-dispersive X-ray analysis techniques. The nanostructures are found to have the form of nanorods, with the diameter of the CuO cores being in the range from a few tens to a few hundreds of nanometers, the thickness of the SnO 2 shells being ˜15 nm, and with a length of a few tens of micrometers. The CuO cores and the SnO 2 shells of the as-synthesized nanorods have crystalline monoclinic CuO and amorphous SnO 2 structures, respectively, but the SnO 2 shells are found to crystallize to tetragonal SnO 2 on thermal annealing. The PL emission intensity of the CuO nanorods has been slightly increased by SnO 2 coating. The PL emission of the SnO 2-coated CuO nanorods is somewhat increased and the emission peak position is red-shifted from 550 to 580 nm by annealing in a reducing atmosphere. On the other hand, the PL emission is significantly increased and the emission peak position is shifted from 550 nm further to around 595 nm by annealing in an oxidative atmosphere. In addition, the origins of the PL enhancements in the nanorods by coating and annealing are discussed.
J Mater Sci, 2010
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Journal- Korean Physical Society
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Journal of Materials Science, 2010
Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO... more Influence of the thermal annealing atmosphere on the photoluminescence properties of ZnS-core/SnO2-shell coaxial nanowires was investigated. ZnS nanowires were synthesized by a two-step process: the thermal evaporation of ZnS powders and the atomic layer deposition of SnO2. Transmission electron microscopy and X-ray diffraction analyses reveal that two crystalline ZnS phases: one with a zinc blende structure and the other with
Physica E: Low-dimensional Systems and Nanostructures, 2011
... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them w... more ... The blue emission of the TeO 2 nanowires is slighly enhanced in intensity by sheathing them with SnO 2 . The blue emission is further enhanced by annealing in a reducing atmosphere whereas it is slightly degraded by annealing in an oxidative ... [7] J. Jun, C. Jin, H. Kim, J ...
Solid State Communications, 2010
CuO-core/SnO 2 -shell one-dimensional nanostructures have been fabricated by thermal oxidation of... more CuO-core/SnO 2 -shell one-dimensional nanostructures have been fabricated by thermal oxidation of a copper foil and then atomic layer deposition of SnO 2 . The structure and optical properties of the nanostructures have been investigated by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence (PL) spectroscopy, and energy-dispersive X-ray analysis techniques. The nanostructures are found to have the form of nanorods, with the diameter of the CuO cores being in the range from a few tens to a few hundreds of nanometers, the thickness of the SnO 2 shells being ∼15 nm, and with a length of a few tens of micrometers. The CuO cores and the SnO 2 shells of the as-synthesized nanorods have crystalline monoclinic CuO and amorphous SnO 2 structures, respectively, but the SnO 2 shells are found to crystallize to tetragonal SnO 2 on thermal annealing. The PL emission intensity of the CuO nanorods has been slightly increased by SnO 2 coating. The PL emission of the SnO 2 -coated CuO nanorods is somewhat increased and the emission peak position is red-shifted from 550 to 580 nm by annealing in a reducing atmosphere. On the other hand, the PL emission is significantly increased and the emission peak position is shifted from 550 nm further to around 595 nm by annealing in an oxidative atmosphere. In addition, the origins of the PL enhancements in the nanorods by coating and annealing are discussed.
Materials Science and Engineering: B, 2010
Influence of the thermal annealing atmosphere and the ZnO layer thickness on the photoluminescenc... more Influence of the thermal annealing atmosphere and the ZnO layer thickness on the photoluminescence properties of ZnS-core/ZnO-shell one-dimensional (1D) radial heterostructures was investigated. ZnS nanowires were synthesized by thermal evaporation of ZnS powders and then coated with ZnO by using the sputter-deposition technique to form the nanostructures. TEM and XRD analysis results reveal that a crystalline ZnS phase with a