This paper reports that a simple chemical vapour deposition method has been adopted to fabricate large scale, high density boron nanocones with thermal evaporation of B/B2O3 powders precursors in an Ar/H2 gas mixture ...This paper reports that a simple chemical vapour deposition method has been adopted to fabricate large scale, high density boron nanocones with thermal evaporation of B/B2O3 powders precursors in an Ar/H2 gas mixture at the synthesis temperature of 1000-1200℃. The lengths of boron nanocones are several micrometres, and the diameters of nanocone tops are in a range of 50-100 nm. transmission electron microscopy and selected area electron diffraction indicate that the nanocones are single crystalline α-tetragonal boron. The vapour liquid solid mechanism is the main formation mechanism of boron nanocones. One broad photolumineseence emission peak at the central wavelength of about 650 nm is observed under the 532 nm light excitation. Boron nanocones with good photoluminescence properties are promising candidates for applications in optical emitting devices.展开更多
Cubic boron nitride thin films were deposited on silicon substrates by low-pressure inductively coupled plasmaenhanced chemical vapour deposition. It was found that the introduction of 02 into the deposition system su...Cubic boron nitride thin films were deposited on silicon substrates by low-pressure inductively coupled plasmaenhanced chemical vapour deposition. It was found that the introduction of 02 into the deposition system suppresses both nucleation and growth of cubic boron nitride. At a B2H6 concentration of 2.5% during film deposition, the critical O2 concentration allowed for the nucleation of cubic boron nitride was found to be less than 1.4%, while that for the growth of cubic boron nitride was higher than 2.1%. Moreover, the infrared absorption peak observed at around 1230- 1280 cm^-1, frequently detected for cubic boron nitride films prepared using non-ultrahigh vacuum systems, appears to be due to the absorption of boron oxide, a contaminant formed as a result of the oxygen impurity. Therefore, the existence of trace oxygen contamination in boron nitride films can be evaluated qualitatively by this infrared absorption peak.展开更多
The photoluminescence （PL） properties of Eu-implanted GaN thin films are studied. The experimental results show that the PL intensity is seriously affected by ion implantation conditions. The PL efficiency increases...The photoluminescence （PL） properties of Eu-implanted GaN thin films are studied. The experimental results show that the PL intensity is seriously affected by ion implantation conditions. The PL efficiency increases exponentially with annealing temperature increasing up to a maximum temperature of 1050℃. Moreover, the PL intensity for the sample implanted along the channelling direction is nearly twice more than that observed from the sample implanted along the random direction. The thermal quenching of PL intensity from 10K to 300K for sample annealed at 1050℃ is only 42.7%.展开更多
Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature...Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature （LT）; （B） an A1N nucleation layer deposited at high temperature; or （C） an LT thin AIN nucleation layer with an AIN layer and an A1N/A1CaN superlattice both subsequently deposited at high temperature. The samples have been characterized by Xray diffraction （XRD）, atomic force microscopy and photoluminescence. The GaN layers grown using nucleation layers B and C show narrower XRD rocking curves than that using nucleation layer A, indicating a reduction in crystal defect density. Furthermore, the GaN layer grown using nucleation layer C exhibits a surface morphology with triangular defect pits eliminated completely. The improved optical property, corresponding to the enhanced crystal quality, is also confirmed by temperature-dependent and excitation power-dependent photoluminescence measurements.展开更多
A new electroluminescent material tris- [5-choloro-8-hydroxyquinoline] aluminum has been synthesized and characterized. Solution of this material AI（5-Clq）3 in toluene showed absorption maxima at 385 nm which was at...A new electroluminescent material tris- [5-choloro-8-hydroxyquinoline] aluminum has been synthesized and characterized. Solution of this material AI（5-Clq）3 in toluene showed absorption maxima at 385 nm which was attributed to the moderate energy （π-π＊） transitions of the aromatic rings. The photoluminescence spectrum of AI（5-Clq）3 in toluene solution showed a peak at 522 nm. This material shows thermal stability up to 400 ℃. The structure of the device is ITO/0.4 wt%F4-TCNQ doped α-NPD （35 nm） / AI（5-Clq）3 （30 nm） / BCP （6 nm）/ Alq3 （30 nm） / LiF （1 nm） / A1 （150 nm）. This device exhibited a luminescence peak at 585 nm （CIE coordinates, x = 0.39, y = 0.50）. The maximum luminescence of the device was 920 Cd/m2 at 25 V. The maximum current efficiency of OLED was 0.27 Cd/A at 20 V and maximum power efficiency was 0.04 lm/W at 18 V.展开更多
We have synthesized and characterized a new electroluminescent material, [8-hydroxyquinoline] bis[2,2＇bipyridine] aluminum. A solution of this material Al（Bpy）2q in toluene showed absorption maxima at 380 nm,which ...We have synthesized and characterized a new electroluminescent material, [8-hydroxyquinoline] bis[2,2＇bipyridine] aluminum. A solution of this material Al（Bpy）2q in toluene showed absorption maxima at 380 nm,which was attributed to the moderate energy（ π–π＊） transitions of the aromatic rings. The photoluminescence spectrum of Al（Bpy）_2q in the toluene solution showed a peak at 518 nm. This material shows thermal stability up to300 ℃. The structure of the device is ITO/F4-TCNQ（1 nm）/α-NPD（35 nm）/Al（Bpy）2q（35 nm）/ BCP（6 nm）/Alq3（28 nm）/Li F（1 nm）/Al（150 nm）. This device exhibited a luminescence peak at 515 nm（CIE coordinates, xD0.32,yD0.49）. The maximum luminescence of the device was 214 cd/m^2 at 21 V. The maximum current efficiency of OLED was 0.12 cd/A at 13 V and the maximum power efficiency was 0.03 lm/W at 10 V.展开更多
基金Project supported in part by the National 863 (Grant No 2007AA03Z305)973 (Grant No 2007CB935503) Projects+1 种基金the National Science Foundation of China (Grant Nos U0734003 and 60571045)China Postdoctoral Science Foundation
文摘This paper reports that a simple chemical vapour deposition method has been adopted to fabricate large scale, high density boron nanocones with thermal evaporation of B/B2O3 powders precursors in an Ar/H2 gas mixture at the synthesis temperature of 1000-1200℃. The lengths of boron nanocones are several micrometres, and the diameters of nanocone tops are in a range of 50-100 nm. transmission electron microscopy and selected area electron diffraction indicate that the nanocones are single crystalline α-tetragonal boron. The vapour liquid solid mechanism is the main formation mechanism of boron nanocones. One broad photolumineseence emission peak at the central wavelength of about 650 nm is observed under the 532 nm light excitation. Boron nanocones with good photoluminescence properties are promising candidates for applications in optical emitting devices.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50772096)the Educational Department of Zhejiang Province, China (Grant No. 20061365)
文摘Cubic boron nitride thin films were deposited on silicon substrates by low-pressure inductively coupled plasmaenhanced chemical vapour deposition. It was found that the introduction of 02 into the deposition system suppresses both nucleation and growth of cubic boron nitride. At a B2H6 concentration of 2.5% during film deposition, the critical O2 concentration allowed for the nucleation of cubic boron nitride was found to be less than 1.4%, while that for the growth of cubic boron nitride was higher than 2.1%. Moreover, the infrared absorption peak observed at around 1230- 1280 cm^-1, frequently detected for cubic boron nitride films prepared using non-ultrahigh vacuum systems, appears to be due to the absorption of boron oxide, a contaminant formed as a result of the oxygen impurity. Therefore, the existence of trace oxygen contamination in boron nitride films can be evaluated qualitatively by this infrared absorption peak.
文摘The photoluminescence （PL） properties of Eu-implanted GaN thin films are studied. The experimental results show that the PL intensity is seriously affected by ion implantation conditions. The PL efficiency increases exponentially with annealing temperature increasing up to a maximum temperature of 1050℃. Moreover, the PL intensity for the sample implanted along the channelling direction is nearly twice more than that observed from the sample implanted along the random direction. The thermal quenching of PL intensity from 10K to 300K for sample annealed at 1050℃ is only 42.7%.
基金Project supported by the National Key Science & Technology Major Project of the Ministry of Science and Technology of China(Grant No. 2008ZX01002-002)the Major Program and the Key Program of the National Natural Science Foundation of China(Grant Nos. 60890191 and 60736033)
文摘Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature （LT）; （B） an A1N nucleation layer deposited at high temperature; or （C） an LT thin AIN nucleation layer with an AIN layer and an A1N/A1CaN superlattice both subsequently deposited at high temperature. The samples have been characterized by Xray diffraction （XRD）, atomic force microscopy and photoluminescence. The GaN layers grown using nucleation layers B and C show narrower XRD rocking curves than that using nucleation layer A, indicating a reduction in crystal defect density. Furthermore, the GaN layer grown using nucleation layer C exhibits a surface morphology with triangular defect pits eliminated completely. The improved optical property, corresponding to the enhanced crystal quality, is also confirmed by temperature-dependent and excitation power-dependent photoluminescence measurements.
文摘A new electroluminescent material tris- [5-choloro-8-hydroxyquinoline] aluminum has been synthesized and characterized. Solution of this material AI（5-Clq）3 in toluene showed absorption maxima at 385 nm which was attributed to the moderate energy （π-π＊） transitions of the aromatic rings. The photoluminescence spectrum of AI（5-Clq）3 in toluene solution showed a peak at 522 nm. This material shows thermal stability up to 400 ℃. The structure of the device is ITO/0.4 wt%F4-TCNQ doped α-NPD （35 nm） / AI（5-Clq）3 （30 nm） / BCP （6 nm）/ Alq3 （30 nm） / LiF （1 nm） / A1 （150 nm）. This device exhibited a luminescence peak at 585 nm （CIE coordinates, x = 0.39, y = 0.50）. The maximum luminescence of the device was 920 Cd/m2 at 25 V. The maximum current efficiency of OLED was 0.27 Cd/A at 20 V and maximum power efficiency was 0.04 lm/W at 18 V.
文摘We have synthesized and characterized a new electroluminescent material, [8-hydroxyquinoline] bis[2,2＇bipyridine] aluminum. A solution of this material Al（Bpy）2q in toluene showed absorption maxima at 380 nm,which was attributed to the moderate energy（ π–π＊） transitions of the aromatic rings. The photoluminescence spectrum of Al（Bpy）_2q in the toluene solution showed a peak at 518 nm. This material shows thermal stability up to300 ℃. The structure of the device is ITO/F4-TCNQ（1 nm）/α-NPD（35 nm）/Al（Bpy）2q（35 nm）/ BCP（6 nm）/Alq3（28 nm）/Li F（1 nm）/Al（150 nm）. This device exhibited a luminescence peak at 515 nm（CIE coordinates, xD0.32,yD0.49）. The maximum luminescence of the device was 214 cd/m^2 at 21 V. The maximum current efficiency of OLED was 0.12 cd/A at 13 V and the maximum power efficiency was 0.03 lm/W at 10 V.
