Nondestructive Characterization of GaN Films Grown at Low and High Temperatures

1999 ◽  
Vol 591 ◽  
Author(s):  
C.H. Yana ◽  
H.W. Yao ◽  
J.M. Van Hove ◽  
A.M. Wowchak ◽  
P.P. Chow ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Temperatures ◽  
Sapphire Substrates ◽  
Wurtzite Crystal Structure ◽  
Phonon Spectra ◽  
Scattering Geometry ◽  
Back Scattering ◽  
Nondestructive Characterization

ABSTRACTGaN films grown on GaAs and sapphire substrates by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) at both low and high temperatures (LT and HT) were characterized by Raman scattering and variable angle spectroscopic ellipsometry (VASE). Optical phonon spectra of GaN films are obtained through back-scattering geometry. Crystal quality of these films was qualitatively examined using phonon line-width. Phonon spectra showed that the HT GaN has wurtzite crystal structure, while LT GaN and GaN/GaAs have cubic-like structures. Thickness nonuniformity and defect-related absorption can be characterized by pseudo dielectric functions directly. Surface roughness also can be determined by using an effective-medium approximation (EMA) over-layer in a VASE analysis. Anisotropic optical constants of GaN, both ordinary and extraordinary, were obtained in the spectral range of 0.75 to 6.5 eV with the consideration of surface roughness, through the small and large angles of incidence, respectively. The film thickness of the GaN was accurately determined via the analysis as well.

scholarly journals Ultra-thin films for plasmonics: a technology overview

2015 ◽  
Vol 4 (3) ◽  
Author(s):  
Radu Malureanu ◽  
Andrei Lavrinenko
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Support Surface ◽  
New Materials ◽  
Infra Red ◽  
Plasmon Polaritons ◽  
Plasmon Propagation ◽  
Made In

AbstractUltra-thin films with low surface roughness that support surface plasmon-polaritons in the infra-red and visible ranges are needed in order to improve the performance of devices based on the manipulation of plasmon propagation. Increasing amount of efforts is made in order not only to improve the quality of the deposited layers but also to diminish their thickness and to find new materials that could be used in this field. In this review, we consider various thin films used in the field of plasmonics and metamaterials in the visible and IR range. We focus our presentation on technological issues of their deposition and reported characterization of film plasmonic performance.

Growth of (0001) ZnO Thin Films on Sapphire

1996 ◽  
Vol 449 ◽  
Author(s):  
A. J. Drehman ◽  
P. W. Yip
Keyword(s):  
Surface Roughness ◽  
Buffer Layers ◽  
Zno Films ◽  
X Ray Diffraction ◽  
Axis Orientation ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force

ABSTRACTUsing reactive rf sputtering, we have grown (0001) oriented ZnO films in situ on heated c-axis sapphire substrates, that are promising, particularly in terms of surface roughness, as buffer layers for the subsequent epitaxial growth of III-V nitride films. We compare the effects of on-axis and off-axis sputter geometries on the film epitaxy and smoothness. We also examined the effect of substrate temperature on the growth and smoothness and quality of the film. X-ray diffraction was used to verify the hexagonal ZnO phase, its c-axis orientation and, qualitatively, the degree of its epitaxy. Atomic Force Microscopy (AFM) was used to determine the ZnO growth morphology and roughness. Our best films, obtained by off-axis sputter deposition, have a surface roughness of less than 1 nm.

Micro-Quality Control on Ultra-Precision Machining of Sapphire Substrates

2010 ◽  
Vol 102-104 ◽  
pp. 738-741
Author(s):  
Hai Zhou ◽  
Li Gang Bai ◽  
Dai Pin Wang
Keyword(s):  
Surface Roughness ◽  
Ph Value ◽  
Diamond Wheel ◽  
Precision Machining ◽  
New Approach ◽  
Sapphire Substrates ◽  
Ductile Mode ◽  
Ultra Precision ◽  
Main Factors

This paper proposed a new approach to control the micro-quality of sapphire substrate, in order to grow GaN on substrate. The main factors that influence macro-quality are the method of slicing, grinding and polishing. Thread speed of slicing is less than 0.5m/s. Ductile mode grinding of substrate is achieved by #3000 diamond wheel and feed of 1μm/r. The suitable polishing conditions are that the SiO2 grain size is less than 10nm, the concentration SiO2 is 3％, pH value of polishing liquid is 10.5 and polishing stress is 190Pa. The undamaged substrates have been obtained steadily. The surface roughness RMS is less than 0.4 nm.

scholarly journals Raman characterization of the optical phonons in AlxGa1−xN layers grown by MBE and MOCVD

1997 ◽  
Vol 2 ◽  
Author(s):  
A. Cros ◽  
H. Angerer ◽  
R. Handschuh ◽  
O. Ambacher ◽  
M. Stutzmann
Keyword(s):  
Phonon Mode ◽  
Aluminum Content ◽  
Composition Range ◽  
Theoretical Calculations ◽  
Phonon Modes ◽  
Sapphire Substrates ◽  
Mode Behavior ◽  
Raman Characterization

We present the results of Raman measurements performed on AlxGa1−xN layers grown by MBE and MOCVD. The films were deposited on (0001) c-sapphire substrates, and the aluminum content covered the whole composition range for x from 0 (GaN) to 1 (AlN). It is shown that the energies of both A1(TO) and A1(LO) phonon modes smoothly increase with increasing x, indicating a one-mode behavior. The E2 phonon mode, however, presents a different behavior. Its energy increases very slowly with aluminum content and, for x≈0.4, a new phonon mode shows up which is shifted to higher energies by 50 cm−1. This new line leads to the E2 AlN mode for increasing aluminum content. The linewidths and intensities of these modes strongly depend on composition. These results are compared with recent theoretical calculations. Finally, the Raman selection rules in the MBE and MOCVD samples are compared and conclusions about the quality of the layers are drawn.

Grinding Performance Evaluation of the Developed Chemo-Mechanical Grinding (CMG) Tools for Sapphire Substrate

2012 ◽  
Vol 565 ◽  
pp. 105-110 ◽  
Author(s):  
Zhi Gang Dong ◽  
Shang Gao ◽  
P. Zhou ◽  
Ren Ke Kang ◽  
Dong Ming Guo
Keyword(s):  
Surface Roughness ◽  
Performance Evaluation ◽  
Surface Quality ◽  
Sapphire Substrate ◽  
Physicochemical Characteristics ◽  
Diamond Wheel ◽  
Mechanical Grinding ◽  
Sapphire Substrates ◽  
Grinding Performance

In order to improve the surface quality of sapphire substrates ground by diamond wheel, the chemo-mechanical grinding (CMG) tools for sapphire grinding was investigated in this paper. According to the processing principle of CMG, three CMG tools with different abrasives of SiO2, Fe2O3 and MgO were developed respectively. The compositions of the CMG tools were designed and optimized based on the physicochemical characteristics of sapphire. The grinding experiments were performed with the developed CMG tools and the grinding performance of three kind of tools were evaluated by comparing the surface roughness and the MRR of sapphire. The experiment results show that the grinding performance of SiO2 CMG tool was worst. The surface roughness and MRR corresponding to SiO2 CMG tool were all significantly poorer than Fe2O3 and MgO CMG tools. The highest MRR could be obtained by Fe2O3 CMG tool, but the best surface quality was obtained by MgO CMG tool.

scholarly journals The Influence of Angstrom-Scale Roughness on the Laser-Induced Damage Threshold of Single-Crystal ZnGeP2

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 83
Author(s):  
Nikolai Yudin ◽  
Andrei Khudoley ◽  
Mikhail Zinoviev ◽  
Sergey Podzvalov ◽  
Elena Slyunko ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Magnetic Particles ◽  
Damage Threshold ◽  
Structural Defects ◽  
Physical Limitations ◽  
Laser Induced Damage ◽  
Crystal Volume

Magnetorheological processing was applied to polish the working surfaces of single-crystal ZnGeP2, in which a non-aqueous liquid with the magnetic particles of carbonyl iron with the addition of nanodiamonds was used. Samples of a single-crystal ZnGeP2 with an Angstrom level of surface roughness were received. The use of magnetorheological polish allowed the more accurate characterization of the possible structural defects that emerged on the surface of a single crystal and had a size of ~0.5–1.5 μm. The laser-induced damage threshold (LIDT) value at the indicated orders of magnitude of the surface roughness parameters was determined not by the quality of polishing, but by the number of point depressions caused by the physical limitations of the structural configuration of the crystal volume. These results are in good agreement with the assumption made about a significant effect of the concentration of dislocations in a ZnGeP2 crystal on LIDT.

Surface Morphology Improvement and Repeatable Doping Characterization of 4H-SiC Epitaxy Grown on 4° Off-Axis 4H-SiC Wafers

2009 ◽  
Vol 615-617 ◽  
pp. 423-426 ◽  
Author(s):  
Swapna G. Sunkari ◽  
Hrishikesh Das ◽  
Carl Hoff ◽  
Yaroslav Koshka ◽  
Janna R. B. Casady ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Surface ◽  
Process Conditions ◽  
Power Devices ◽  
Low Loss ◽  
High Surface Quality ◽  
Non Destructive ◽  
Koh Etching

4H Silicon Carbide (4H-SiC) has a great potential for low-loss power devices due to its superior electrical properties. However, the increase in demand for the power devices requires high quality SiC substrates and epitaxial layers. Mercury probe Capacitance Voltage (Hg CV) measurement is a well known procedure to characterize epi layers grown on SiC substrates, due to its non-destructive technique. However, careful calibration of the tool is very important for repeatable and accurate measurements. Here we present very close repeatability of Hg CV within 2.4% (standard deviation 0.7%), between different Solid State Measurements (SSM) setups compared with Ni Schottky (NiS) CV. In addition to growing uniformly doped epi layers, high surface quality of the epi layer is also needed for improved device performance. Improved process conditions resulted in a smooth epi with a surface roughness Ra 1.2 nm for a 6 µm thick epi layer. Molten Potassium Hydroxide (KOH) etching analysis also revealed a significant correlation between the surface roughness and epi defects.

Characterization of Topography of Cut Surface Based on Theoretical Roughness Indexes

2011 ◽  
Vol 496 ◽  
pp. 194-199 ◽  
Author(s):  
Csaba Felhő ◽  
János Kundrák
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Tribological Properties ◽  
Significant Influence ◽  
Machined Surface ◽  
Edge Geometry ◽  
Mathematical Relation ◽  
Cut Surface

The microgeometry of cut surfaces is one important characteristic of surface quality, since it has significant influence on the tribological properties of working surfaces. In addition to the ability to plan the economical effectiveness of cutting and the accuracy of workpieces the ability to plan the quality of machined surfaces has also emphasized importance. This is why the predictability of surface roughness in planning of technological processes is more and more important. More and more opportunities presenting themselves and one of these is the estimation of the expected value of roughness of the machined surface on the basis of the theoretical value of roughness. The paper focuses on the introduction of a method to describe a mathematical relation between the theoretical and the measured roughness indexes in cutting with tools having defined edge geometry, thus the planning may be more accurate.

Optimization of x-ray Techniques for Nondestructive Characterization of Single Crystal Turbine Blades

1999 ◽  
Vol 591 ◽  
Author(s):  
J.M. Winter ◽  
K.G. Lipetzky ◽  
R.E. Green
Keyword(s):  
Single Crystal ◽  
Turbine Blades ◽  
Crystalline Perfection ◽  
X Ray ◽  
Diffraction Imaging ◽  
Nickel Based Alloy ◽  
Beam Transmission ◽  
Nondestructive Characterization

ABSTRACTThis paper describes nondestructive x-ray characterization techniques which detect macroscopic and microscopic defects, determine the overall crystallographic perfection, and detect any unwanted secondary crystals both on the external surface as well as in the interior of single crystal blades. The method of Asymmetric Crystal Topography for diffraction imaging the surfaces of single crystal turbine blades and the method of White Beam Transmission Topography for diffraction imaging through the thickness of single crystal turbine blades are both discussed and illustrated with representive diffraction images (topographs). It is clear that the images gained from these methods have a capability for providing information about the details of crystalline perfection (or lack thereof) in nickel-based alloy single crystal turbine blades. Such information can provide considerable leverage for the crystal grower to help in adjusting processing variables to enhance quality of a critical product. And the same methods of topography can conceiveably provide tools for evaluating the finished product in a way which has not been available to date.

scholarly journals Microstructural Characterization of High Indium-Composition InXGa1−XN Epilayers Grown on c-Plane Sapphire Substrates

2013 ◽  
Vol 19 (S5) ◽  
pp. 145-148 ◽  
Author(s):  
Myoungho Jeong ◽  
Hyo Sung Lee ◽  
Seok Kyu Han ◽  
Eun-Jung-Shin ◽  
Soon-Ku Hong ◽  
...  
Keyword(s):  
Green Light ◽  
Microstructural Characterization ◽  
Misfit Strain ◽  
Ingan Layer ◽  
Light Emitting ◽  
Composition Modulation ◽  
Sapphire Substrates ◽  
Crystallographic Planes

AbstractThe growth of high-quality indium (In)-rich InXGa1−XN alloys is technologically important for applications to attain highly efficient green light-emitting diodes and solar cells. However, phase separation and composition modulation in In-rich InXGa1−XN alloys are inevitable phenomena that degrade the crystal quality of In-rich InXGa1−XN layers. Composition modulations were observed in the In-rich InXGa1−XN layers with various In compositions. The In composition modulation in the InXGa1−XN alloys formed in samples with In compositions exceeding 47%. The misfit strain between the InGaN layer and the GaN buffer retarded the composition modulation, which resulted in the formation of modulated regions 100 nm above the In0.67Ga0.33N/GaN interface. The composition modulations were formed on the specific crystallographic planes of both the {0001} and {0114} planes of InGaN.

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