Selective area heteroepitaxy of nano-AlGaN ultraviolet excitation sources for biofluorescence application

2007 ◽  
Vol 22 (4) ◽  
pp. 838-844 ◽  
Author(s):  
Vibhu Jindal ◽  
James R. Grandusky ◽  
Neeraj Tripathi ◽  
Fatemeh Shahedipour-Sandvik ◽  
Steven LeBoeuf ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ultraviolet Excitation ◽  
Selective Area ◽  
Cathodoluminescence Spectroscopy ◽  
Mask Material ◽  
Selection Of

We report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters including temperature, pressure, NH3 flow, total alkyl flow, and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant, which resulted in a high-quality pyramidal structure. As indicated by high-resolution x-ray diffraction and cathodoluminescence spectroscopy, the composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.

Selective Area Heteroepitaxy of Nano-AlGaN UV Excitation Sources for Biofluorescence Application

2006 ◽  
Vol 916 ◽  
Author(s):  
Vibhu Jindal ◽  
James Grandusky ◽  
Fatemeh Shahedipour-Sandvik ◽  
Steven LeBoeuf ◽  
Joleyn Balch ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Selective Area ◽  
Mask Material ◽  
Uv Excitation ◽  
Selection Of

AbstractWe report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters; including temperature, pressure, NH3 flow, total alkyl flow and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant which resulted in a high quality pyramidal structure. As indicated by high resolution x-ray diffraction (XRD) and cathodoluminescence (CL) spectroscopy, composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.

Lattice constant variation in GaN:Si layers grown by HVPE

2002 ◽  
Vol 743 ◽  
Author(s):  
A. Usikov ◽  
O. V. Kovalenkov ◽  
M. M. Mastro ◽  
D. V. Tsvetkov ◽  
A. I. Pechnikov ◽  
...  
Keyword(s):  
Defect Formation ◽  
Strain Relaxation ◽  
Growth Conditions ◽  
Optical And Electrical Properties ◽  
X Ray Diffraction ◽  
Proper Selection ◽  
X Ray ◽  
Lattice Constants ◽  
Si Doping ◽  
Selection Of

ABSTRACTThe structural, optical, and electrical properties of HVPE-grown GaN-on-sapphire templates were studied. The c and a lattice constants of the GaN layers were measured by x-ray diffraction. It was observed that the c and a lattice constants vary non-monotonically with Si-doping. The proper selection of Si-doping level and growth conditions resulted in controllable strain relaxation, and thus, influenced defect formation in GaN-on-sapphire templates. It was also observed that HVPE homoepitaxial GaN layers grown on the templates have better crystal quality and surface morphology than the initial templates.

Determination of growth parameters for atomic layer epitaxy using reflectance difference spectroscopy

1996 ◽  
Vol 74 (S1) ◽  
pp. 85-88 ◽  
Author(s):  
R. Arès ◽  
C. A. Tran ◽  
S. P. Watkins
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Gas Flows ◽  
Difference Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reflectance Difference Spectroscopy

Reflectance difference spectroscopy (RDS) has been used to monitor the anisotropy of the surface of InAs and GaAs grown by atomic layer epitaxy (ALE). Saturation of the RDS signal is observed when the surface is fully covered with one monolayer of the impinging surface species. This property is used to optimize the growth interruptions for the ALE cycle. Good correlation of the RDS saturation is observed with growth-rate measurements obtained by X-ray diffraction (XRD). When exposure times are sufficiently long for saturation to be observed in the RDS signal, a growth rate of one monolayer per cycle (1 ML/cycle) is achieved. In principle all the different growth parameters such as exposure and purge times as well as gas flows can be determined in a few cycles performed on a single substrate. Without RDS the same results would require several growth runs and time consuming X-ray characterization.

White beam X-ray Diffraction Topography (WBXDT) Studies of Bridgman Grown CdZnTe Crystals

2015 ◽  
Vol 1792 ◽  
Author(s):  
Stephen Babalola ◽  
Samuel Uba ◽  
Anwar Hossain ◽  
Giuseppe Camarda ◽  
Ralph James ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Charge Trapping ◽  
Radiation Detectors ◽  
Growth Conditions ◽  
High Energy ◽  
Infrared Transmission ◽  
X Ray Diffraction ◽  
Large Area ◽  
X Ray ◽  
White Beam

ABSTRACTCZT is a semiconductor material that promises to be a good candidate for uncooled gamma radiation detectors. However, to date, we are yet to overcome the technological difficulties in production of large size, defect-free CZT crystals. The most common problem is accumulation of Tellurium precipitates as microscopic inclusions. These inclusions influence the charge collection through charge trapping and electric field distortion. We employed high energy transmission X-ray diffraction techniques to study the quality of the CdZnTe crystals grown by Bridgman Technique. Crystallinity and defects within two different growth set-ups, i.e. with and without choked seeding, were compared by imaging the crystal orientation topography with white beam X-ray diffraction topography (WBXDT). The X-ray diffraction topography results show high correlation with large-area infrared transmission images of the crystals. Grain boundaries that are highly decorated with Te inclusions are observed. Characteristic Te inclusion arrangements as a result of growth conditions are discussed. We also measured the electronic properties of the detectors fabricated from ingots grown using two Bridgman processes, and observed a reduction in electrical resistivity of choked-seeding-grown CdZnTe crystals. Our results show that although choked seeding technique holds a promise in the realization of high quality mono-crystalline CdZnTe, current growth parameters must be improved to obtain defect-free crystals. These results are helpful to attain optimal seeding process for Bridgman-growth of large single crystals of CdZnTe.

Study on TlBr Single Crystal Growth Using Improved Electro Dynamic Gradient Method

2011 ◽  
Vol 415-417 ◽  
pp. 1979-1982
Author(s):  
Zhi Ping Zheng ◽  
Jing Wang ◽  
Lin Quan ◽  
Shu Ping Gong ◽  
Dong Xiang Zhou
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Electrical Properties ◽  
Temperature Gradient ◽  
Growth Conditions ◽  
Single Crystal Growth ◽  
Optical And Electrical Properties ◽  
X Ray Diffraction ◽  
X Ray

Electro Dynamic Gradient (EDG) method was utilized for TlBr crystal growth in this paper. The influence of crystal growth conditions such as temperature gradient and growth rate on optical and electrical properties of grown TlBr crystals was investigated. The quality of TlBr crystals was characterized by infrared (IR) transmittance spectrum, X-ray diffraction, and I-V measurements.

AIN/GaN and AIGaN/GaN Heterostructures Grown by HVPE on SiC Substrates

1997 ◽  
Vol 482 ◽  
Author(s):  
Yu. V. Melnik ◽  
A. E. Nikolaev ◽  
S. I. Stepanov ◽  
A. S. Zubrilov ◽  
I. P. Nikitina ◽  
...  
Keyword(s):  
Growth Rate ◽  
Electron Beam ◽  
Vapor Phase ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Hydride Vapor Phase Epitaxy ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
X Ray ◽  
Micro Analysis

AbstractGaN, AIN and AIGaN layers were grown by hydride vapor phase epitaxy. 6H-SiC wafers were used as substrates. Properties of AIN/GaN and AIGaN/GaN structures were investigated. AIGaN growth rate was about 1 μm/min. The thickness of the AIGaN layers ranged from 0.5 to 5 μm. The AIN concentration in AIGaN layers was varied from 9 to 67 mol. %. Samples were characterised by electron beam micro analysis, Auger electron spectroscopy, X-ray diffraction and cathodoluminescence.Electrical measurements performed on AIGaN/GaN/SiC samples indicated that undoped AIGaN layers are conducting at least up to 50 mol. % of AIN.

scholarly journals Influence of the growth parameters of TiO2 thin films deposited by the MOCVD method

Cerâmica ◽  
2002 ◽  
Vol 48 (305) ◽  
pp. 38-42 ◽  
Author(s):  
M. I. B. Bernardi ◽  
E. J. H. Lee ◽  
P. N. Lisboa-Filho ◽  
E. R. Leite ◽  
E. Longo ◽  
...  
Keyword(s):  
Thin Films ◽  
Growth Parameters ◽  
Structural Characteristics ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Tio2 Thin Films ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Deposition Parameters

The synthesis of TiO2 thin films was carried out by the Organometallic Chemical Vapor Deposition (MOCVD) method. The influence of deposition parameters used during growth on the final structural characteristics was studied. A combination of the following experimental parameters was studied: temperature of the organometallic bath, deposition time, and temperature and substrate type. The high influence of those parameters on the final thin film microstructure was analyzed by scanning electron microscopy with electron dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction.

Synchrotron white beam x-ray topography (SWBXT) and high resolution triple axis diffraction studies on AlN layers grown on 4H- and 6H-SiC seeds

2004 ◽  
Vol 831 ◽  
Author(s):  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Rafael Dalmau ◽  
Raoul Schlesser ◽  
Zlatko Sitar
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Large Diameter ◽  
Laser Diodes ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
White Beam ◽  
Strain Data ◽  
Growth Experiments

ABSTRACTFor nitride based devices such as LEDs, high power FETs and laser diodes, single crystal substrates of AlN are highly desirable. While the sublimation technique is suitable for growing bulk AlN crystals, appropriate seeds are also necessary for growing large diameter oriented boules. 4H- and 6H-SiC substrates which are readily available commercially can potentially be implemented as seeds for bulk AlN growth. However, issues regarding SiC decomposition at high temperatures, thermal expansion mismatch, single crystal growth, etc. need to be addressed. Towards this end, a series of growth experiments have been carried out in a resistively heated reactor using on and off-axis 4H- and 6H-SiC substrates as seeds for AlN growth from the vapor phase. Several hundred microns thick AlN layers have been grown under different growth conditions. Synchrotron white beam x-ray topography (SWBXT) has been used to map the defect distribution in the grown layers and high resolution triple axis x-ray diffraction (HRTXD) experiments were carried out to record reciprocal space maps from which tilt, mismatch and strain data can be obtained. These results are analyzed with respect to the growth conditions in order to gain a better understanding of this growth process.

Magnetic and Optical Properties of Eu-doped GaN

2006 ◽  
Vol 955 ◽  
Author(s):  
Jennifer Hite ◽  
G T Thaler ◽  
J H Park ◽  
A J Steckl ◽  
C R Abernathy ◽  
...  
Keyword(s):  
Saturation Magnetization ◽  
Room Temperature Ferromagnetism ◽  
Inverse Correlation ◽  
Absolute Intensity ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
Cell Temperature ◽  
X Ray ◽  
Pl Intensity ◽  
The Eu

ABSTRACTGaN films were doped with Eu to a concentration of ∼0.12 at. % during growth at 800°C by molecular beam epitaxy, with the Eu cell temperature held constant at 470°C. All samples were post-annealed at 675°C. The films exhibited strong photoluminescence (PL) in the red (622 nm) whose absolute intensity was a function of the Ga flux during growth, which ranged from 3-5.4×10−7 Torr. The maximum PL intensity was obtained at a Ga flux of 3.6×10−7 Torr. The samples showed room temperature ferromagnetism with saturation magnetization of ∼0.1-0.45 emu/cm3, consistent with past reports where the Eu was found to be predominantly occupying substitutional Ga sites. There was an inverse correlation between the PL intensity and the saturation magnetization in the films. X-ray diffraction showed the presence of EuGa phases under all of our growth conditions but these cannot account for the observed magnetic properties.

scholarly journals Solidified Fillings of Nanopores

2005 ◽  
Vol 876 ◽  
Author(s):  
Patrick Huber ◽  
Klaus Knorr
Keyword(s):  
Pore Diameter ◽  
Stacking Faults ◽  
Pore Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medium Length ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Diffraction Patterns ◽  
Selection Of

AbstractWe present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

Sign in / Sign up

Export Citation Format

Share Document