Formation and Characterization of Oxides on GaN surfaces

2000 ◽  
Vol 622 ◽  
Author(s):  
D. Mistele ◽  
T. Rotter ◽  
F. Fedler ◽  
H. Klausing ◽  
O.K. Semchinova ◽  
...  
Keyword(s):  
Saturated Calomel Electrode ◽  
Depth Profiling ◽  
Amorphous State ◽  
Theoretical Work ◽  
Oxide Thickness ◽  
X Ray Diffraction ◽  
Oxide Layers ◽  
Voltage Range ◽  
Polar Surfaces

ABSTRACTWe characterized oxides formed directly on n-GaN surfaces. The methods used for oxide layer formation were both photoanodic oxidation and thermal oxidation. The photoanodic oxidation took place in aqueous solutions of potassium hydroxide with pH values lower than 13. Homogenous oxide films were obtained in the voltage range from -0.6 V to 0.4 V vs the saturated calomel electrode (SCE). The characterization of the oxide layers was performed primarily by Auger electron spectroscopy (AES). First the surface chemistry was determined, proving that Ga-oxide is formed with an attributed stoichiometry of Ga2O3. Secondly, depth profiling shows the oxide thickness to be dependent on the photoanodic voltage and oxidation time. Complementary X-ray diffraction (XRD) studies suggest an amorphous state of the formed layers. Annealing GaN in O2-atmospheres above 900°C also lead to surfaces fully covered with gallium oxide. We found that N-polar surfaces oxidize faster than Ga-polar surfaces, which is in agreement to the theoretical work of Zywietz et al [1]. Furthermore, we report on the electrical properties of the anodized oxide layers by analyzing MOS structures.

scholarly journals Formation of Nanoporous Mixed Aluminum-Iron Oxides by Self-Organized Anodizing of FeAl3 Intermetallic Alloy

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2299 ◽  
Author(s):  
Paulina Chilimoniuk ◽  
Marta Michalska-Domańska ◽  
Tomasz Czujko
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Anodic Oxide ◽  
Oxide Thickness ◽  
Structural Features ◽  
Intermetallic Alloy ◽  
Oxide Mixture ◽  
Oxide Layers ◽  
Voltage Range ◽  
Interpore Distance

Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy were prepared by two-step anodization in 20 wt% H2SO4 at 0 °C. The voltage range was 10.0–22.5 V with a step of 2.5 V. The structural and morphological characterizations of the received anodic oxide layers were performed by field emission scanning electron microscopy (FE-SEM). Therefore, the formed anodic oxide was found to be highly porous with a high surface area, as indicated by the FE-SEM studies. It has been shown that the morphology of fabricated nanoporous oxide layers is strongly affected by the anodization potential. The oxide growth rate first increased slowly (from 0.010 μm/s for 10 V to 0.02 μm/s for 15 V) and then very rapidly (from 0.04 μm/s for 17.5 V up to 0.13 μm/s for 22.5 V). The same trend was observed for the change in the oxide thickness. Moreover, for all investigated anodizing voltages, the structural features of the anodic oxide layers, such as the pore diameter and interpore distance, increased with increasing anodizing potential. The obtained anodic oxide layer was identified as a crystalline FeAl2O4, Fe2O3 and Al2O3 oxide mixture.

Characterization of Structural Defects in Germanium Epitaxially Grown on Nano-Structured Silicon

2011 ◽  
Vol 178-179 ◽  
pp. 43-49 ◽  
Author(s):  
Peter Zaumseil ◽  
Yuji Yamamoto ◽  
Joachim Bauer ◽  
Markus Andreas Schubert ◽  
Jana Matejova ◽  
...  
Keyword(s):  
Oxide Thickness ◽  
Growth Conditions ◽  
Structural Defects ◽  
Misfit Dislocations ◽  
Strain Partitioning ◽  
X Ray Diffraction ◽  
Reduced Pressure ◽  
Periodic Arrays ◽  
Transmission Electron

Selective epitaxial growth of germanium (Ge) on nano-structured Si(001) wafers is studied to evaluate the applicability of the nano-heteroepitaxy (NHE) approach on Ge-Si system. Based on a gate spacer technology established in advanced silicon microelectronics periodic arrays of nano-scaled Si islands are prepared, where Ge is deposited on top by reduced pressure CVD. The spacing of these structures is 360 nm. The structural perfection of the deposited Ge is investigated by transmission electron microscopy and X-ray diffraction. It is found that SiO2used as masking material is responsible for the suppression of the desired strain partitioning effect according to NHE. Even for 10 nm oxide thickness, the lattice of Ge layers deposited on Si nano-islands relaxes completely by generation of misfit dislocations at the interface. The occurrence of additional structural defects like stacking faults and micro twins can be controlled by suited growth conditions.

Depth Sensitive Imaging of Defects in Epilayers and Single Crystals Using White Beam Synchrotron Radiation Topography in Grazing Bragg-Laue Geometry.

1989 ◽  
Vol 163 ◽  
Author(s):  
M. Dudley ◽  
G.-D. Yao ◽  
J. Wu ◽  
H.-Y. Liu
Keyword(s):  
Penetration Depth ◽  
Depth Profiling ◽  
X Rays ◽  
X Ray Diffraction ◽  
General Applicability ◽  
Advantages And Disadvantages ◽  
White Beam ◽  
Diffraction Geometry ◽  
Topographic Imaging

AbstractThe technique of Synchrotron White Beam topographic imaging in grazing Bragg-Laue geometries has been developed at the Stony Brook synchrotron topography station at the NSLS. This technique enables imaging of defects in subsurface regions of thickness which can range from hundreds of Angstroms to hundreds of microns as determined by the penetration depth of the X-rays. This penetration depth, which is shown to be determined by the kinematical theory of X-ray diffraction, can be conveniently varied, in a controlled manner, by simple manipulation of the diffraction geometry, thereby enabling a depth profiling of the defect content.The fundamentals of the technique are described, and its advantages and disadvantages compared to existing techniques are discussed in detail. Examples of application of the technique in the characterization of defects in thin epitaxial films of GaAs on Si, are given, and the general applicability of the technique is discussed.

Fabrication and Characterization of Metal-Ferroelectric-Gan Structures

1999 ◽  
Vol 595 ◽  
Author(s):  
W.P. Li ◽  
R. Zhang ◽  
J. Yin ◽  
X.H. Liu ◽  
Y.G. Zhou ◽  
...  
Keyword(s):  
High Frequency ◽  
High Dielectric Constant ◽  
Oxide Thickness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Active Layers ◽  
Pzt Films ◽  
High Dielectric ◽  
Mos Structures

AbstractGaN-based metal-ferroelectric-semiconductor (MFS) structure has been fabricated by using ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) instead of conventional oxides as gate insulators. The GaN and PZT films in the MFS structures have been characterized by various methods such as photoluminescence (PL), wide-angle X-ray diffraction (XRD) and high-resolution X-ray diffraction (HRXRD). The Electric properties of GaN MFS structure with different oxide thickness have been characterized by high-frequency C-V measurement. When the PZT films are as thick as 1 µm, the GaN active layers can approach inversion under the bias of 15V, which can not be observed in the traditional GaN MOS structures. When the PZT films are about 100 nm, the MFS structures can approach inversion just under 5V. All the marked improvements of C-V behaviors in GaN MFS structures are mainly attributed to the high dielectric constant and large polarization of the ferroelectric gate oxide.

Microstructural Characterization of Ba2YCu3O7 Films Produced by Co-Evaporation

1987 ◽  
Vol 99 ◽  
Author(s):  
G. J. Fisanick ◽  
P. Mankeewicht ◽  
W. Skocpolt ◽  
R. E. Howardt ◽  
A. Dayem ◽  
...  
Keyword(s):  
Plane Surface ◽  
Depth Profiling ◽  
Microstructural Characterization ◽  
Areal Density ◽  
Oxygen Stoichiometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Annealing Conditions ◽  
Auger Microscopy

ABSTRACTBa2YCu3O7 films produced by co-evaporation of BaF2, Cu and Y onto <100> S1TiO3 substrates in an O2 ambient followed by post-annealing were analyzed using RBS, X-ray diffraction and Auger microscopy. These films exhibit Tc's (R=0) of =90K and a best Jc of > 1.0×106 A/cm2 at 81K for a =2500A thick film. RBS and Auger depth profiling limit the level of F present in the post-annealed films to <5 at. %, although F is evident in the as-deposited material. RBS channeling experiments yield a Xmin=31%, demonstrating the epitaxial quality of the films. X-ray diffraction shows that the films are predominantly oriented with c-axis perpendicular to the substrate, with narrow mosaic spread in-plane. A small portion of the film is in the form of needles oriented with a-axis perpendicular to the substrate, whose areal density is dependent on annealing conditions and local film stoichiometry. Scanning Auger microscopy confirms that the needles and c-axis plateaus have the same metal and oxygen stoichiometry. Also present in the film are insulating balls which appear to nucleate terraces in the c-axis perpendicular structure. Scanning Auger shows that these features are also close to the metals stoichiometry, but are C rich compared to the needles. The plateaus are covered with =11 times more C than the needles, indicating that the basal plane surface is highly reactive. Auger depth profiling and RBS show little evidence for interdiffusion.

Preparation and Characterization of Cu2ZnSnSe4 Thin Films by Selenization of Electrodeposited Metal Precursors

2011 ◽  
Vol 685 ◽  
pp. 105-109 ◽  
Author(s):  
Ji Li ◽  
Zhong Wei Zhang ◽  
Yang Ou ◽  
Wei Feng Liu ◽  
Guo Shun Jiang ◽  
...  
Keyword(s):  
Thin Films ◽  
Energy Dispersive Spectrometry ◽  
Saturated Calomel Electrode ◽  
Elemental Selenium ◽  
X Ray Diffraction ◽  
Glass Substrates ◽  
Metal Precursors ◽  
Different Temperatures ◽  
Electrodeposited Metal

Cu2ZnSnSe4thin films were prepared by selenization of electrodeposited Cu-Zn-Sn precursors. The Cu-Zn-Sn precursors were electrodeposited on the Mo-coated glass substrates from an electrolyte containing copper sulfate, zinc sulfate, tin (II) sulfate at a fixed potential between -1.2V and -1.25V vs. saturated calomel electrode, then the Cu2ZnSnSe4thin films were obtained by selenizing Cu-Zn-Sn precursors in elemental selenium atmosphere at different temperatures. The structure, composition and optical properties of the films were investigated by X-ray diffraction, Energy dispersive spectrometry and UV-VIS absorption spectroscopy. The CZTSe films have a stannite structure and an optical band-gap about 1.6 eV which is suitable for fabricating solar cells.

Si diffusion coating on steels by SiH4/H2 treatment for high temperature oxidation protection

1990 ◽  
Vol 5 (1) ◽  
pp. 74-82 ◽  
Author(s):  
A. L. Cabrera ◽  
J. F. Kirner ◽  
R. Pierantozzi
Keyword(s):  
High Temperatures ◽  
Diffusion Coating ◽  
Depth Profiling ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
Diffusion Coatings ◽  
Composition And Structure

The reaction of SiH4/H2 mixtures with iron and steels was studied at a total pressure of 1 atm and temperatures above 500 °C. When the amount of water vapor in the gas mixture is carefully controlled, a metal silicide diffusion coating forms at low temperatures (below 900°C). Composition and structure of the Si diffusion coatings were determined with Auger depth profiling and x-ray diffraction. Kinetics of the surface reaction between SiH4, and the metal substrate as well as the behavior of these films in severe environments at high temperatures were studied by a microgravimetric technique. Characterization of these Si coatings on iron, low carbon steel (1010), 9% Cr/1% Mo steel (alloy A182F9), and stainless steels (310) and their applications to reduce oxidation, nitriding, or coking at high temperatures or corrosion in mineral acids are described.

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