Ultra-Smooth ZnO Buffer Layers on (001) Sapphire

1997 ◽  
Vol 482 ◽  
Author(s):  
A. J. Drehman ◽  
S.-Q. Wang ◽  
P. W. Yip
Keyword(s):  
Buffer Layers ◽  
Zno Films ◽  
Potential Candidate ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Electrical Resistivities

AbstractUsing off-axis reactive rf sputtering, we have grown extremely smooth, nearly epitaxial, (001) oriented ZnO films on c-axis sapphire substrates. Atomic Force Microscopy was used to determine that these films are extremely smooth, having an rms roughness of only a few tenths of a nanometer. Based on high resolution x-ray diffraction (HXRD), the ZnO is highly oriented, with a rocking curve width of less than 400 arc seconds for the (006) diffraction peak, and only somewhat larger for the (112) reflection. HXRD Phi scans show that the ZnO (112) reflection is rotated in the a-b plane by 30 degrees from the sapphire (113) direction. These two measurements indicate excellent in-plane orientation. We are investigating the use of these buffer layers for subsequent GaN growth. Electrical resistivities of the films exceeded 100 kΩ-cm making ZnO a potential candidate as an insulating buffer layer.

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.

scholarly journals Dielectric Function of AlN Grown on Si (111) by MBE

1999 ◽  
Vol 572 ◽  
Author(s):  
Stefan Zollner ◽  
Atul Konkar ◽  
R. B. Gregory ◽  
S. R. Wilson ◽  
S. A. Nikishin ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Buffer Layers ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Growth Morphology ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dimensional Growth ◽  
Peak Widths

ABSTRACTWe measured the ellipsometric response from 0.7–5.4 eV of c-axis oriented AlN on Si (111) grown by molecular beam epitaxy. We determine the film thicknesses and find that for our AlN the refractive index is about 5–10% lower than in bulk AlN single crystals. Most likely, this discrepancy is due to a low film density (compared to bulk AlN), based on measurements using Rutherford backscattering. The films were also characterized using atomic force microscopy and x-ray diffraction to study the growth morphology. We find that AlN can be grown on Si (111) without buffer layers resulting in truely two-dimensional growth, low surface roughness, and relatively narrow x-ray peak widths.

Investigation Of Nucleation And Initial Stage Of Gan Growth By Atomic Force Microscopy And X-Ray Diffraction

1997 ◽  
Vol 482 ◽  
Author(s):  
P. W. Yip ◽  
S.-Q. Wang ◽  
A. J. Drehman ◽  
L. D. Zhu ◽  
P. E. Norris
Keyword(s):  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Deposition Temperature ◽  
Yellow Luminescence ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Initial Stage

AbstractThe nucleation and initial stage of GaN growth on sapphire was investigated by atomic force microscopy, X-ray diffraction and photoluminescence. A 15 to 30 nm thick GaN buffer layer deposited at proper conditions was extremely smooth and nearly amorphous. Proper post deposition annealing resulted in the buffer crystallized. The buffer layer deposition temperature, thickness and annealing time and temperature must be coordinated. Low deposition temperature and/or insufficient annealing of the buffer results in a GaN wafer which has fine spiking surface morphology with an RMS of 3.4 nm for 1.4 μm wafer, strong yellow luminescence and wide xray rocking curve FWHM. High deposition temperature, longer crystallization time, and a low growth rate results in a wafer which exhibits strong band edge luminescence without noticeable yellow luminescence, and a narrow (002) diffraction rocking curve. However, the surface morphology exhibits well developed hexagonal feature with RMS roughness of 14.3 nm for a 570 nm thick layer. X-ray rocking curve analysis revealed buffer crystallization, domain coalescence and alignment process. The FWHM of the ω–scan of GaN (101) diffraction was 1700–2000 arc seconds for 200–1400 nm wafers which indicates that the twist of the domains is not changing much with the growth.

Comparison of the Microstructure of AlN Films Grown by MOCVD and by PLD on Sapphire Substrates

1996 ◽  
Vol 449 ◽  
Author(s):  
Yun-Xin Li ◽  
Lourdes Salamanca-Riba ◽  
V. Talyan ◽  
T. Venkatesan ◽  
C. Wongchigul ◽  
...  
Keyword(s):  
Low Density ◽  
Full Width ◽  
High Crystalline Quality ◽  
Rocking Curve ◽  
X Ray ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Film Substrate ◽  
Microscopy Images

ABSTRACT(0001) aluminium nitride thin films were grown epitaxially on (0001) Sapphire substrates by MOCVD at 1200° C and PLD at 800° C. Both films have the same epitaxial growth relationship: (0001)AlN//(0001)Sap, and the same in-plane relationship which shows a 30° rotation between A1N and Sapphire: [ 12 10]AlN//[0 110]Sap and [10 10]AlN //[ 2110]Sap. The full width at half maximum (FWHM) of x-ray rocking curve of the MOCVD A1N film was 0.16° and PLD A1N film was 0.2°. Films grown by both MOCVD and PLD showed high crystalline quality. HRTEM images showed that these films are single crystalline with very low density of defects.Dislocations in the film parallel to the film / substrate interface were observed in both A1N films. Atomic force microscopy images showed that the MOCVD films have flatter and larger terraces than the PLD films. The PLD technique for A1N growth needs to be improved further. But both films have a surface roughness of approximately 100nm.

Growth and Characterization of AlN and GaN Thin Films Deposited on Si(111) Substrates Containing a Very Thin Al Layer

2003 ◽  
Vol 798 ◽  
Author(s):  
Zachary J. Reitmeier ◽  
Robert F. Davis
Keyword(s):  
Flow Time ◽  
Buffer Layers ◽  
Nucleation Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Aln Buffer ◽  
Peak Widths

ABSTRACTAlN films and GaN films with AlN buffer layers were deposited via metalorganic vapor phase epitaxy on Si(111) substrates previously exposed to trimethylaluminum for increasing times. Atomic force microscopy (AFM) was used to determine the influence of Al pre-flow time on the nucleation and surface morphology of the AlN and GaN films. When preceded by a 10 second Al pre-flow, AlN films feature an increased and more uniform nucleation density as compared to films deposited without Al pre-flows. Ten second Al pre-flows were also found to result in a reduction of the RMS roughness for 100 nm thick AlN films from 3.6 nm to 1.0 nm. AFM of 0.5 μm thick GaN films deposited on AlN buffers with varying pre-flow times showed reduced roughness and decreased pit density when using Al pre-flows of 10 or 20 seconds. High resolution x-ray diffraction of the GaN films showed a reduction in the average full-width halfmaximum (FWHM) of the GaN (00.2) reflection from 1076 arcsec to 914 arcsec when the AlN buffer layer was initiated with a 10 second Al pre-flow. Increasing the pre-flow time to 20 seconds and 30 seconds resulted in average (00.2) FWHM values of 925 arcsec and 928 arcsec, respectively. Similar behavior of the peak widths was observed for the (30.2) and (10.3) reflections when the pre-flow times were varied from 0 to 30 seconds.

BaTiO3 Waveguides on MgO Buffered-Sapphire Single Crystals

1999 ◽  
Vol 597 ◽  
Author(s):  
Judit G. Lisoni ◽  
M. Siegert ◽  
C. H. Lei ◽  
C. L. Jia ◽  
J. Schubert ◽  
...  
Keyword(s):  
Optical Waveguides ◽  
Ferroelectric Thin Film ◽  
X Ray Diffraction ◽  
Epitaxial Relationship ◽  
Rocking Curve ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Good Crystalline Quality

AbstractWithin our program to develop ferroelectric thin film optical waveguides, we have studied the growth of epitaxial waveguides BaTiO3 on r-plane sapphire substrates with a MgO buffer layer. The films were prepared by pulsed laser deposition (PLD). Their structural properties were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Rutherford backscattering (RBS) in random and channeling (RBS-c) configuration and atomic force microscopy (AFM). They displayed good crystalline quality, characterized by an RBS-c minimum yield of about 4–6%, a full width at half maximum (FWHM) of the XRD rocking curve measurement of the BaTiO3(200) reflection of 0.32° and a rms roughness of 1.2 nm in a film of ∼ 1.0 μm thickness. The epitaxial relationship was found to be BaTiO3(100) // MgO(100) // A12O3(1102). The refractive index, the birefringence and the optical losses have been measured.

Epitaxial Batio3 and Knbo3 Thin Films On Various Substrates for Optical Waveguide Applications

1996 ◽  
Vol 441 ◽  
Author(s):  
L. Beckers ◽  
W. Zander ◽  
J. Schubert ◽  
P. Leinenbach ◽  
Ch. Buchal ◽  
...  
Keyword(s):  
Optical Materials ◽  
Rutherford Backscattering Spectrometry ◽  
X Ray Diffraction ◽  
Crystalline Perfection ◽  
Rocking Curve ◽  
X Ray ◽  
Flat Surfaces ◽  
Force Microscopy ◽  
Atomic Force ◽  
Yield Values

AbstractTechnologically interesting optical materials such as BaTiO3 and KnbO3 are difficult to grow as single crystals of large dimensions. Thin film techniques can overcome this problem by synthesizing these materials on commercially available substrates. We demonstrate the deposition of single crystalline BaTiO3 and KnbO3 on MgO, SrTiO3 and buffered MgO substrates by Pulsed Laser Deposition (PLD). The samples are characterized by Rutherford Backscattering Spectrometry / Channeling (RBS/C), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM). We found excellent crystalline quality, confirmed by RBS/C minimum yield values of 2 % and a FWHM of 0.36° of the BaTiO3(002) rocking curve. Even films of a few microns thickness have been grown without loss of crystalline perfection, and all films show very flat surfaces. The RMS roughness of a 950 nm BaTiO3 film was found to be 1.1 nm.

A Study of the Effect of Growth Rate and Annealing on GaN Buffer Layers on Sapphire

1995 ◽  
Vol 395 ◽  
Author(s):  
J.C. Ramer ◽  
K. Zheng ◽  
C.F. Kranenberg ◽  
M. Banas ◽  
S.D Hersee
Keyword(s):  
Growth Rate ◽  
Buffer Layer ◽  
Layer Growth ◽  
Buffer Layers ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Gan Buffer Layer

ABSTRACTUsing atomic force microscopy (AFM) and X-ray diffraction (XRD) we have determined that on [0001] oriented sapphire, the GaN buffer layer shows a degree of crystallinity that is dependent on growth rate. Annealing studies show evolution of the crystallinity and the emergence of a preferred orientation. Also, substrate orientation is found to influence the buffer layer crystallinity. Based on this work and previous results, we propose that the GaN buffer layer growth can be described by the Stranski-Krastanov growth process.

Investigations of ZnO Nanorod Films Grown by Hydrothermal Method for Ethanol Gas Sensor

2020 ◽  
Vol 19 (03) ◽  
pp. 1950022
Author(s):  
S. Jainulabdeen ◽  
C. Gopinathan ◽  
A. Mumtaz Parveen ◽  
K. Mahalakshmi ◽  
K. Jeyadheepan ◽  
...  
Keyword(s):  
Growth Mechanism ◽  
Grazing Incidence ◽  
Growth Time ◽  
Zno Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Ethanol Sensing ◽  
Zno Rods

Rod-structured ZnO has grown hydrothermally on the seed layer by varying growth time. The growth mechanism of rod-structured ZnO thin films is studied extensively with the help of characterizing tools. The preferred orientation and c/a ratio are studied with Grazing Incidence X-ray diffraction (GIXRD). The growth mechanism of ZnO rod structure is studied in detailed manner with Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The optical absorption and emission properties of ZnO rods are studied with respect to growth morphology. Ethanol sensing measurements are carried out at room temperature (RT). The nanostructured ZnO films show good response and sensitivity to ethanol gas at RT.

HVPE and MOVPE GaN Growth on Slightly Misoriented Sapphire Substrates

1999 ◽  
Vol 595 ◽  
Author(s):  
Olivier Parillaud ◽  
Volker Wagner ◽  
Hans-Jörg Bühlmann ◽  
François Lelarge ◽  
Marc Ilegems
Keyword(s):  
Substrate Surface ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Step Flow ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Step Flow Growth ◽  
Gan Buffer Layer

AbstractWe present preliminary results on gallium nitride growth by HVPE on C-plane sapphire with 2, 4 and 6 degrees misorientation towards M and A directions. A nucleation GaN buffer layer is deposited prior the growth by MOVPE. Surface morphology and growth rates are compared with those obtained on exact C-plane oriented sapphire, for various growth conditions. As expected, the steps already present on the substrate surface help to initiate a directed step-flow growth mode. The large hillocks, which are typical for HVPE GaN layers on (0001) sapphire planes, are replaced by more or less parallel macro-steps. The width and height of these steps, due to step bunching effect, depend directly on the angle of misorientation and on the growth conditions, and are clearly visible by optical or scanning electron microscopy. Atomic force microscopy and X-ray diffraction measurements have been carried out to quantify the surface roughness and crystal quality.

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