AlN film is deposited on a nanorod ZnO template by metalorganic chemical vapor deposition. Scanning electron microscopy measurements reveal that this film forms a lying nanorod surface. The grazing incidence X- ray di...AlN film is deposited on a nanorod ZnO template by metalorganic chemical vapor deposition. Scanning electron microscopy measurements reveal that this film forms a lying nanorod surface. The grazing incidence X- ray diffraction further proves that it is entirely a wurtzite AIN structure, and the average size of the crystallite grains is about 12nm,which is near the ZnO nanorod diameter （30nm）. This means that the nanorod ZnO template can restrict the AlN lateral overgrowth. Additionally, by etching the ZnO template with H2 at high temperatures,we directly achieve epitaxial lift-off during the growth process. Eventually, free-standing AlN nanocrystals are achieved,and the undamaged area is near 1cm × 1cm. We define the growth mechanism as a ＂grow-etch- merge＂ process.展开更多
ZnO films prepared at different temperatures and annealed at 900^o C in oxygen are studied by photoluminescence （PL） and x-ray photoelectron spectroscopy （XPS）. It is observed that in the PL of the as-grown films ...ZnO films prepared at different temperatures and annealed at 900^o C in oxygen are studied by photoluminescence （PL） and x-ray photoelectron spectroscopy （XPS）. It is observed that in the PL of the as-grown films the green luminescence （GL） and the yellow luminescence （YL） are related, and after annealing the GL is restrained and the YL is enhanced. The 0 ls XPS results also show the coexistence of oxygen vacancy （Vo） and interstitial oxygen （Oi） before annealing and the quenching of the Vo after annealing. By combining the two results it is deduced that the GL and YL are related to the Vo and Oi defects, respectively.展开更多
We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were de...We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were deposited on nitrided sapphire, low-temperature InN （LT-InN） and high-temperature GaN （HT-GaN）, respectively. The InN layer grown directly on nitrided sapphire owns the narrowest x-ray diffraction rocking curve （XRC） width of 300 aresee among the three samples, and demonstrates a two-dimensional （2D） step-flow-like lateral growth mode, which is much different from the three-dimensional （3D） pillar-like growth mode of LT-InN and HT-GaN buffered samples. It seems that mismatch tensile strain is helpful for the lateral epitaxy of InN film, whereas compressive strain promotes the vertical growth of InN films.展开更多
Employing the metal-organic chemical vapour deposition （MOCVD） technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux （BDF...Employing the metal-organic chemical vapour deposition （MOCVD） technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux （BDF） and the carrier gas flux of oxygen （OCGF）. The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction （XRD） and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 20 locations of ZnQ （002） face in the XRD patterns and the E2 （high） locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopy results show all the samples have a sharp ultraviolet luminescent band without any defects-related emission. Upon the experiments a possible growth mechanism is proposed.展开更多
The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of ba...The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain.展开更多
Semi-polar ZnO (1011) epitaxial films are demonstrated using a methanol oxidant by metalorganic chemical vapor deposition on Si (111) substrates at 500℃.X-ray (O) scanning indicates that there are six kinds of in-pla...Semi-polar ZnO (1011) epitaxial films are demonstrated using a methanol oxidant by metalorganic chemical vapor deposition on Si (111) substrates at 500℃.X-ray (O) scanning indicates that there are six kinds of in-plane domain growths,with the ZnO [1012] parallel to the Si (11(2)〉 direction families.The crystallographic orientation of ZnO is supposed to be caused by surface passivation.The methanol,as a polar molecule,may be adsorbed on the Si (111) surface to form a passivation layer,which inhibits the (0001) ZnO plane deposition on the substrate surface,and as a result the ZnO (1011) plane becomes preferred.The optical properties,examined by a roomtemperature photoluminescence spectrum,exhibit a strong near-band-edge emission peak at 379nm,indicating that the (1011) ZnO film has good crystal quality.These results are significant for research into and for the applications of semi-polar ZnO films.展开更多
We investigate effects of nitridation on AlN morphology, structural properties and stress. It is found that 3min nitridation can prominently improve AlN crystal structure, and slightly smooth the surface morphology. H...We investigate effects of nitridation on AlN morphology, structural properties and stress. It is found that 3min nitridation can prominently improve AlN crystal structure, and slightly smooth the surface morphology. However, 10min nitridation degrades out-of-plane crystal structure and surface morphology instead. Additionally, 3-min nitridation introduces more tensile stress （1.5 GPa） in AlN films, which can be attributed to the weaker islands 2D coalescent. Nitridation for lOmin can introduce more defects, or even forms polycrystallinity interlayer, which relaxes the stress. Thus, the stress in AlN with 10 min nitridation decreases to -0.2 GPa compressive stress.展开更多
Aluminium nitride （AIN） films grown with dimethylethylamine Mane （DMEAA） are compared with the ones grown with trimethylaluminium （TMA）. In the high-resolution x-ray diffraction Ω scans, the full width at half ...Aluminium nitride （AIN） films grown with dimethylethylamine Mane （DMEAA） are compared with the ones grown with trimethylaluminium （TMA）. In the high-resolution x-ray diffraction Ω scans, the full width at half maximum （FWHM） of （0002） AIN films grown with DMEAA is about 0.70 deg, while the FWHM of （0002） AIN films grown with TMA is only 0.11 deg. The surface morphologies of the films are different, and the rms roughnesses of the surface are approximately identical. The rms roughness of AIN films grown with DMEAA is 47.4nm, and grown with TMA is 69.4nm. Although using DMEAA as the aluminium precursor cannot improve the AIN crystal quality, AIN growth can be reached at low temperature of 673 K. Thus, DMEAA is an alternative aluminium precursor to deposit AIN film at low growth temperatures.展开更多
基金Project supported by the National Natural Science Foundation of China(No.60506002,60776015)the Special Funds for MajorState Basic Research Project (973) of China(No.2006CB604907)the 863 High Technology R &D Program of China(No.2007AA03Z402,2007AA03Z451)
文摘AlN film is deposited on a nanorod ZnO template by metalorganic chemical vapor deposition. Scanning electron microscopy measurements reveal that this film forms a lying nanorod surface. The grazing incidence X- ray diffraction further proves that it is entirely a wurtzite AIN structure, and the average size of the crystallite grains is about 12nm,which is near the ZnO nanorod diameter （30nm）. This means that the nanorod ZnO template can restrict the AlN lateral overgrowth. Additionally, by etching the ZnO template with H2 at high temperatures,we directly achieve epitaxial lift-off during the growth process. Eventually, free-standing AlN nanocrystals are achieved,and the undamaged area is near 1cm × 1cm. We define the growth mechanism as a ＂grow-etch- merge＂ process.
基金Supported by the Special Funds for Major State Basic Research Programme of China under No 2006CB604907, and the National Natural Science Foundation of China under Grant No 60506002.
文摘ZnO films prepared at different temperatures and annealed at 900^o C in oxygen are studied by photoluminescence （PL） and x-ray photoelectron spectroscopy （XPS）. It is observed that in the PL of the as-grown films the green luminescence （GL） and the yellow luminescence （YL） are related, and after annealing the GL is restrained and the YL is enhanced. The 0 ls XPS results also show the coexistence of oxygen vacancy （Vo） and interstitial oxygen （Oi） before annealing and the quenching of the Vo after annealing. By combining the two results it is deduced that the GL and YL are related to the Vo and Oi defects, respectively.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60506002 and 60776015, the Special Funds for Major State Basic Research Project of China No 2006CB604907, and National High-Tech R＆D Programme of China under Grant Nos 2007AA03Z402 and 2007AA03Z451.
文摘We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy （MOVPE） method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were deposited on nitrided sapphire, low-temperature InN （LT-InN） and high-temperature GaN （HT-GaN）, respectively. The InN layer grown directly on nitrided sapphire owns the narrowest x-ray diffraction rocking curve （XRC） width of 300 aresee among the three samples, and demonstrates a two-dimensional （2D） step-flow-like lateral growth mode, which is much different from the three-dimensional （3D） pillar-like growth mode of LT-InN and HT-GaN buffered samples. It seems that mismatch tensile strain is helpful for the lateral epitaxy of InN film, whereas compressive strain promotes the vertical growth of InN films.
基金Supported by the National High-Tech Research and Development Programme of China under Grant Nos 2007AA03Z402 and 2007AA03Z451, the National Basic Research Programme of China under Grant No 2006CB604907, and the National Natural Science Foundation of China under Grant Nos 60506002 and 60776015.
文摘Employing the metal-organic chemical vapour deposition （MOCVD） technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux （BDF） and the carrier gas flux of oxygen （OCGF）. The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction （XRD） and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 20 locations of ZnQ （002） face in the XRD patterns and the E2 （high） locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopy results show all the samples have a sharp ultraviolet luminescent band without any defects-related emission. Upon the experiments a possible growth mechanism is proposed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.91233111,61274041,11275228,61006004,and 61076001)the Special Funds for Major State Basic Research Project (973 Program) of China (Grant No.2012CB619305)+1 种基金the 863 High Technology R&D Program of China (Grant No.2011AA03A101)the Special Fund for LED Industrial Development of Guangdong Province of China (Grant No.2012A080302003)
文摘The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain.
基金Supported by the National Science Foundation of China under Grant Nos 61006004,60976008 and 10979507the National Basic Research Program of China under Grant No A000091109-05the National High-Technology R&D Program of China under Grant No 2011AA03A101.
文摘Semi-polar ZnO (1011) epitaxial films are demonstrated using a methanol oxidant by metalorganic chemical vapor deposition on Si (111) substrates at 500℃.X-ray (O) scanning indicates that there are six kinds of in-plane domain growths,with the ZnO [1012] parallel to the Si (11(2)〉 direction families.The crystallographic orientation of ZnO is supposed to be caused by surface passivation.The methanol,as a polar molecule,may be adsorbed on the Si (111) surface to form a passivation layer,which inhibits the (0001) ZnO plane deposition on the substrate surface,and as a result the ZnO (1011) plane becomes preferred.The optical properties,examined by a roomtemperature photoluminescence spectrum,exhibit a strong near-band-edge emission peak at 379nm,indicating that the (1011) ZnO film has good crystal quality.These results are significant for research into and for the applications of semi-polar ZnO films.
基金Supported by the National Natural Science Foundation of China under Grant No 60376013
文摘We investigate effects of nitridation on AlN morphology, structural properties and stress. It is found that 3min nitridation can prominently improve AlN crystal structure, and slightly smooth the surface morphology. However, 10min nitridation degrades out-of-plane crystal structure and surface morphology instead. Additionally, 3-min nitridation introduces more tensile stress （1.5 GPa） in AlN films, which can be attributed to the weaker islands 2D coalescent. Nitridation for lOmin can introduce more defects, or even forms polycrystallinity interlayer, which relaxes the stress. Thus, the stress in AlN with 10 min nitridation decreases to -0.2 GPa compressive stress.
基金Supported by the National Natural Science Foundation of China under Grant No 60376013.
文摘Aluminium nitride （AIN） films grown with dimethylethylamine Mane （DMEAA） are compared with the ones grown with trimethylaluminium （TMA）. In the high-resolution x-ray diffraction Ω scans, the full width at half maximum （FWHM） of （0002） AIN films grown with DMEAA is about 0.70 deg, while the FWHM of （0002） AIN films grown with TMA is only 0.11 deg. The surface morphologies of the films are different, and the rms roughnesses of the surface are approximately identical. The rms roughness of AIN films grown with DMEAA is 47.4nm, and grown with TMA is 69.4nm. Although using DMEAA as the aluminium precursor cannot improve the AIN crystal quality, AIN growth can be reached at low temperature of 673 K. Thus, DMEAA is an alternative aluminium precursor to deposit AIN film at low growth temperatures.
